Housing Reports >> Summaries

Brief summary of each of the housing reports published on WHE website is listed below:

Report # 1 : Confined Block Masonry House by Virginia I. Rodriguez, Maria I. Yacante, Sergio Reiloba Housing Type: Confined Masonry Building     Country: ARGENTINA This is typically a one-or two-story residential building of detached or semi-detached construction, generally found in the urban areas of San Juan and Mendoza, and less frequently in the rural areas. The walls are made of concrete block masonry with reinforced concrete columns and beams that tie the walls together and provide strength for the building. One of the main structural deficiencies for this construction type lies in the widely different wall densities in the two orthogonal directions. This deficiency may be eliminated with appropriate architectural design. This construction type is otherwise expected to demonstrate good seismic performance.

Report # 2 : Traditional Adobe House with Reinforcement by Virginia I. Rodriguez, Maria I. Yacante, Sergio Reiloba Housing Type: Adobe / Earthen House     Country: ARGENTINA This construction type is a single-family house. In general, it is a single-storey building, an isolated construction found in the rural areas of San Juan and Mendoza. The traditional adobe block masonry walls are reinforced with foundations and plinth structure, which provide structural strength. A deficiency in this type of construction is that the adobe blocks deteriorate due to prolonged exposure to humidity.

Report # 3 : Steel Frame Buildings with Shear Walls by Elias Arze-L. Housing Type: Steel Structural Wall Building     Country: CHILE These buildings are modern steel composite structures ranging from 3 to 24 stories. The buildings have a rigid steel frame with floor diaphragms made of post-tensioned concrete slabs or composite steel decking, with or without a concrete slab covering. Additional lateral force-resisting elements are added to the steel moment-resisting frame to stiffen the structure and enhance the seismic performance. These elements are steel #X# or concentric braces and reinforced concrete shear walls. The seismic performance for these composite structures is very good. Most of these buildings are used as apartments or offices.

Report # 4 : Concrete Shear Wall Buildings by Ofelia Moroni, Cristian Gomez Housing Type: RC Structural Wall Building     Country: CHILE This housing type is mainly characterized by reinforced concrete shear walls that are built in both directions along the entire height. Some of the walls may be perforated with openings (coupled walls). These buildings are multiple housing units and are found in the major urban areas in Chile. Stiffness and mass distribution are regular and most of them may have a symmetry axis in at least one direction of the plan. In general, these buildings are quite stiff because they must resist a base shear of 5-6.7% (depending on the seismic zone) and the story drift must be equal to or less than 0.002. Seismic performance is very good, strength and stiffness are controlled, and torsional effects are minimal. The buildings may have one or two basement floors. Problems that may appear in the future include reduction in the wall density, introduction of soft floor, or torsional effects.

Report # 5 : Reinforced Clay/Concrete Block Masonry Building by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza Housing Type: Reinforced Masonry Building     Country: CHILE This is a rather recent construction practice followed since 1970, and it has been widely used for dwellings and up to 4-story-high apartment buildings. Buildings of this type can be found both in urban and rural areas of Chile. The main load-bearing elements are masonry walls reinforced with vertical steel reinforcement bars and placed in the hollow cores of clay masonry units (hollow clay tiles) or concrete blocks. Horizontal reinforcement bars are placed in horizontal bed joints. Masonry shear walls are tied together at floor levels by means of reinforced concrete beams in a regular structural layout. Stiffness distribution both in plan and elevation is uniform. Prior to 1986, there was no seismic design code for this structural type. During the March 3, 1985 Llolleo earthquake, performance of buildings of this type was rather poor, mainly due to construction problems, such as partial grouting in the hollow cores with reinforcement, poor quality of the mortar, and lack of horizontal reinforcement. Following the earthquake, the Chilean Design Code NCh1928 code was published based on the U.S. Uniform Building Code (UBC-1979) and on the seismic performance of this construction type reported in previous earthquakes. Since 1993, when the last version of NCh1928 was published, and more restricted requirements were enforced, the use of this type of construction has been less frequent, in part because of economic reasons.

Report # 6 : Concrete Frame and Shear Wall Building by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza Housing Type: RC Moment Frame Building     Country: CHILE Buildings of this type are used mainly for offices or hotels, and they are found in large cities throughout the country. At the present time this building type represents about 15-20% of the high-rise building stock in Chile (building with more than 10 stories). The structural system consists of reinforced concrete frames and shear walls. The walls are typically located around the staircases and the elevators, while the frames may be uniformly distributed in plan or at the perimeter only. Most of the lateral load-bearing elements exist along the full building height in the elevation and in both directions of the building plan. In some buildings the walls are perforated with openings and coupled with lintel beams. Some buildings of this type have one or more basement floors. In general, these buildings are quite stiff. Seismic performance is very good, strength and stiffness are controlled, and torsion effects are minimal. Problems that may occur in the future are related to the reduction in the wall density, and introduction of soft-story or torsional effects.

Report # 7 : Confined block masonry building by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza Housing Type: Confined Masonry Building     Country: CHILE This construction practice started during the 1940s after the 1939 earthquake that struck the mid-southern region of Chile. It is mainly used for dwellings and apartment buildings up to four stories high. Buildings of this type are found in all regions of Chile. This is a confined masonry construction, consisting of load-bearing unreinforced masonry walls (commonly made of clay units or concrete blocks) confined with cast-in-place reinforced-concrete, vertical tie-columns. these tie-columns are built at regular intervals and are connected with reinforced concrete tie- beams cast after the masonry walls have been constructed. Tie-columns and tie-beams prevent damage due to out-of-plane bending effects and improve wall ductility. Floor systems generally consist of cast-in-place reinforced slabs with a thickness between 100 to 120 mm. Confined masonry walls have limited shear strength and ductility compared to reinforced concrete walls. Nevertheless, typical buildings of this type have good earthquake resistance, because they have high wall densities and because wall layouts are symmetric and regular, both in plan and elevation. Their seismic behavior has been satisfactory, particularly in one- or two-story-high buildings during strong earthquakes [Monge, 1969].

Report # 8 : Buildings with hybrid masonry walls by Ofelia Moroni, Cristian Gomez, Maximiliano Astroza Housing Type: Confined Masonry Building     Country: CHILE This housing type represents a common multi-family urban construction in Chile. Practice of this construction "mainly used for dwellings and for up to 4-story apartment buildings" began in the 1980s. The main load-bearing system consists of masonry walls in the transverse direction and reinforced concrete walls in the longitudinal direction. In some cases, longitudinal walls are of reinforced masonry construction (instead of concrete construction). Masonry walls in the transverse direction are usually confined with concrete posts at the ends (such as is found in confined masonry construction). Buildings are usually regular in plan and in elevation. The seismic design code does not address this building type. However, the Chilean Ministry of Housing has issued specifications for 1- and 2-story dwellings, which have mainly been followed in the design (even in taller buildings of this type). Performance in the 1985 Llolleo earthquake was rather poor, with most buildings experiencing structural damage.

Report # 9 : Multistory base-isolated brick masonry building with reinforced concrete floors and roof by Fu L. Zhou, Zhong G. Xu, Wen G. Liu Housing Type: Seismic Protection Systems     Country: CHINA This is typically a 5- to 8-story building with commercial enterprises on the ground floor and residences above. Brick masonry buildings have been used in China for thousands of years. This construction practice possesses the advantage of easy manufacture and low cost; however, the brittleness of the brick masonry material combined with weak seismic resistance induces severe damage or collapse of buildings and causes thousands of deaths during an earthquake. Since 1990, base-isolated brick masonry buildings with reinforced concrete floors/roof have been used more widely in China. The base-isolated building consists of an isolation system (laminated rubber isolation devices) superstructure and substructure. The base-isolation system is located on top of the walls or columns in the basement or at the ground floor level of a building without a basement. The superstructure consists of conventional multi-story brick masonry walls and reinforced concrete floors/roof. The substructure is part of the building beneath the isolation system and consists of the basement and the foundation structure. The base-isolated masonry structure results in an increase in seismic safety by a factor of 4-12 times as compared to that of a non-isolation masonry structure. The high seismic resistance of the base isolation structure house has been proven by shake table tests and in many actual earthquake events in China and other countries. The wide usage of base isolation technology indicates that the era of strong earthquake-proof buildings is coming in China.

Report # 10 : Non-engineered Unreinforced Brick Masonry Building by Luis G. Mej Housing Type: Unreinforced Masonry Building     Country: COLOMBIA This type of housing is typically constructed in urban and rural areas in the interior of Colombia. This type of construction is especially widespread in the following provinces of the Andean region of Colombia: Antioquia, Caldas, Risaralda, Quindio, Tolima and Valle, where it constitutes approximately 60% of the housing stock. It is used exclusively as residential housing. This construction is very vulnerable to earthquake effects due to its brittle behavior. It has demonstrated poor seismic performance in several Colombian earthquakes.

Report # 11 : Gravity Concrete Frame Buildings (Predating Seismic Codes) by Luis G. Mej Housing Type: RC Moment Frame Building     Country: COLOMBIA This is typical multi-family housing construction found in urban areas of Colombia that predates seismic codes. This housing type is widely used and represents 60% of the existing housing stock. At the present time, poor people occupy buildings of this type. This construction is rather vulnerable to seismic effects due to a limited amount of transverse reinforcement (ties); this is especially true for columns. This structural system is very flexible when subjected to lateral seismic loads. The quality of materials and workmanship is typically rather poor. In many cases, buildings of this type are constructed on a very steep terrain; soil condition is often rather poor.

Report # 12 : Clay brick/concrete block masonry walls with concrete floors (predating seismic codes or with a few seismic features) by Luis G. Mej Housing Type: Unreinforced Masonry Building     Country: COLOMBIA Typical multi-family housing construction found in urban areas of Colombia. It is a modern construction practice and represents approximately 50% of the housing stock for medium-rise (4- to 6-story high) buildings constructed in the last 25 years. This type of construction generally predates seismic codes; however, some buildings of this type were constructed after the first edition of the Colombian Seismic Code was issued in 1984. This type of construction can be found either on flat or on sloped terrain; vertical stiffness irregularity in the sloped terrain conditions may introduce additional unfavorable effects. Due to poor construction practices and poor detailing of the reinforcement, this construction is considered to be very vulnerable to earthquake effects.

Report # 13 : Gravity-Designed Reinforced Concrete Frame Buildings with Unreinforced Masonry Infill Walls by V. Levtchitch Housing Type: RC Moment Frame Building     Country: CYPRUS This type of concrete apartment building was widely constructed after the 1974 Turkish invasion in order to accommodate approximately 200,000 refugees. Typically, these buildings are low-rise (up to 5 stories) apartment blocks. As a rule, architectural considerations prevail over structural requirements. Very often columns are located irregularly and do not form a definite grid. Soft ground stories are used for car-parks (garages) and shops. Staircases and lift (elevator) shafts are not located symmetrically. The vulnerability of these buildings should be very high when the inherent seismic deficiencies of this structural type (design mistakes, construction faults, unavoidable aging, lack of maintenance, accumulation of minor damage from previous earthquakes, deterioration of the concrete and corrosion of the reinforcing bars) are taken into account. But against all odds the majority of these buildings have stood well in numerous small earthquakes and exhibited rather good performance under the peak ground accelerations of up to 0.15g (the maximum expected in Cyprus). Damage and destruction have been very selective depending on the local soil conditions and periods of natural vibration.

Report # 14 : Vivienda de Adobe (Adobe house) by Manuel A. Lopez M., Julian Bommer, Gilda Benavidez Housing Type: Adobe / Earthen House     Country: EL SALVADOR This housing type can be found in rural and urban areas. Rural: Adobe houses are generally small structures, 5 x 6 m in the plan, having load-resistant walls made of adobe bricks between 0.3 and 0.5 m thick. Usually, they are single-family (5-person) houses. Wood planks that support metal sheets covered by tiles sometimes constitute the roof. In some cases, the roof can be a thatched roof supported on wood purlins. Urban: Adobe houses are much bigger in urban areas than in rural areas. They are one-floor structures and their plans are 15 x 30 m or larger. The wall thickness can easily reach 1 m and wall height can reach 3 m or more. In both the cases mentioned above, the adobe housing type has performed badly in earthquakes. Its heavy roof sometimes can be its biggest weakness and its unreinforced walls make this house vulnerable to earthquake effects.

Report # 15 : Multistory reinforced concrete frame building by T. P. Tassios, Kostas Syrmakezis Housing Type: RC Moment Frame Building     Country: GREECE These buildings represent a typical multi-family residential construction, mainly found in the Greek suburbs. This housing type is very common and constitutes approximately 30% of the entire housing stock in Greece. Buildings are generally medium-rise, typically 4 to 5 stories high. The main lateral load-resisting structure is a dual system, consisting of reinforced concrete columns and shear walls. A relatively small-sized reinforced concrete core is usually present and serves as an elevator shaft. The roof and floor structures consist of rigid concrete slabs supported by the beams. Seismic performance of these buildings is generally good, provided that the seismic design takes into account the soft ground floor effects, e.g., by installing strong RC shear walls. Failure of the soft ground floor is the most common type of damage for this type of structure. Some buildings of this type were damaged in the 1999 Athens earthquake.

Report # 16 : Load-bearing stone masonry building by T. P. Tassios, Kostas Syrmakezis Housing Type: Stone Masonry House     Country: GREECE These buildings are mainly found in the historical centers of Greek cities and provinces. The main load-bearing structure consists of stone masonry walls. The walls are built using local field stones and lime mortar. The floors and roof are of timber construction. The seismic performance is generally poor. Diagonal cracking at the horizontal and vertical joints are the common type of damage.

Report # 17 : Reinforced concrete frame building with an independent vertical extension by Vlasis Koumousis Housing Type: RC Moment Frame Building     Country: GREECE This is a typical residential construction found in the suburbs of large Greek cities and in smaller towns. Buildings are three stories with a warehouse on the ground floor level, and typically, two apartments on the upper floor levels. The peculiarity of this building type is that it consists of two independent structures built over a period of 20 years. The two lower stories were constructed in the 1960s as a reinforced concrete frame structure, without provisions for vertical extension. In the 1980s, an additional floor was built on top of the existing structure and an independent elevator core and staircase added to expand the building horizontally. Columns and shear walls at the perimeter of the 1980 portion of the building were built on separate footings, whereas the interior columns and shear walls were constructed by drilling openings through the slabs of the 1960 portion in order to achieve continuity from the top floor down to the new foundations. Floor structure for the 1980 portion was constructed at an elevation 400 mm higher when compared to the roof level of the 1960 portion. The entire layout results in a tight connection of the new and the old structure. Due to the anomalous position of the channel-shaped elevator shaft, seismic response of this structure is characterized with significant torsional vibrations in the newer 1980 section, thus resulting in excessive lateral displacements in the 1960 structure. Some buildings of this type were damaged in the 1999 Athens earthquake and were strengthened after the earthquake.

Report # 18 : Rubble stone masonry walls with timber frame and timber roof by Svetlana N. Brzev, Marjorie Greene, Ravi Sinha Housing Type: Stone Masonry House     Country: INDIA This typical rural construction in central, southern, and northern India houses millions of people. It is cheap to construct using field stones and boulders, but extremely vulnerable in earthquakes because of its heavy roofs and poorly constructed walls. The load-bearing structure is a traditional timber frame system, known as 'khan'. It is a complete frame with timber posts spanned at about 2.6 m. Thick stone walls (typical thickness 600 mm - 1.2 m) provide enclosure and partial support to the roof. Walls are either supported by strip footings of uncoursed rubble masonry or are without any footings at all. The roof structure consists of timber planks and joists. To help keep the interiors cooler during hot summer months (peak temperatures exceeding 40°C.), a 500-800 mm thick mud overlay covers the top the roof. This construction type is considered to be very vulnerable to earthquake effects. Many buildings of this type were damaged or collapsed in the 1993 Killari (Maharashtra) earthquake (M 6.4) with over 8,000 deaths.

Report # 19 : Reinforced concrete frame building with masonry infill walls designed for gravity loads by Kishor S. Jaiswal, Ravi Sinha, Alok Goyal Housing Type: RC Moment Frame Building     Country: INDIA The construction of reinforced concrete buildings with brick masonry infill walls has been a very common practice in urban India for the last 25 years. Most of this construction has been designed for gravity loads only, in violation of the Code of Indian Standards for earthquake-resistant design. These buildings performed very poorly during the Bhuj earthquake of January 2001 and several thousand buildings collapsed. The collapse was not limited to the epicentral region. The seismic vulnerability of this construction is clearly demonstrated by the collapse of about 75 RCC frame buildings and damage to several thousand others in and around Ahmedabad, which is over 250 km from the epicenter.

Report # 20 : Unreinforced brick masonry walls in mud mortar with flat timber roof by Amir Ali Khan, Khalid Moin Housing Type: Unreinforced Masonry Building     Country: INDIA This is a traditional construction practice prevalent both in the urban and rural areas of northern India, particularly in the western part of the Uttar Pardesh state. According to the 1991 Indian census, this construction constitutes about 17% of the total national housing stock and about 31% of the U.P. housing stock. Typically, this is a single-story construction. The main load-bearing elements are unreinforced brick masonry walls in mud mortar built without any seismic provisions. The roof structure consists of timber beams supported by the walls. Clay tiles or bricks are laid atop the beams; finally, mud overlay is placed on top of the tiles for the thermal protection and to prevent leakage. The main seismic deficiencies are heavy roofs and low-strength masonry walls, which render the building rather vulnerable to seismic effects.

Report # 21 : Unreinforced brick masonry building with reinforced concrete roof slab by Ravi Sinha, Svetlana N. Brzev Housing Type: Unreinforced Masonry Building     Country: INDIA Typical rural and urban construction in western and southern India. This construction is widely prevalent among the middle-class population in urban areas and has become popular in rural areas in the last 30 years. Brick masonry walls in cement mortar function as the main load-bearing element. The roof structure is a cast-in-situ reinforced concrete slab. If constructed without seismic features, buildings of this type are vulnerable to earthquake effects. They exhibited rather poor performance during the Koyna (1967), Killari (1993), Jabalpur (1997), and Bhuj (2001) earthquakes in India.

Report # 22 : Unreinforced brick masonry walls with pitched clay tile roof by Amit Kumar Housing Type: Unreinforced Masonry Building     Country: INDIA This is a traditional construction practice followed in India for centuries. Buildings of this construction type are used for residential, commercial, and public purposes throughout India, especially in the northern and central parts, where good quality soil for brick production is widely available. This is a single-story construction used both in rural and urban areas. The walls are constructed using clay bricks laid in mud, brick-lime or cement/sand mortar. The roof does not behave as a rigid diaphragm. These buildings are built without any seismic provisions and are considered to be moderately-to-highly vulnerable to earthquake effects.

Report # 23 : Rural mud house with pitched roof by Amit Kumar Housing Type: Adobe / Earthen House     Country: INDIA This is a typical rural construction found throughout India, except in the high rainfall areas in the northeastern part of the country. It is a single-family house, mainly occupied by the poorer segment of the population. The main load-bearing system consists of mud walls, which carry the roof load. In some cases wooden posts are provided at the wall corners and at intermediate locations. The wooden posts and walls are not structurally integrated, and therefore the loads are shared by the walls and the frame. There are very few openings (doors and windows) in these buildings. In rural areas there are usually no windows at all. In general, this type of construction is built by the owners and local unskilled masons and the craftsmanship is very poor. This building type is classified as grade-A (most vulnerable) per the IAEE building classification and IS Code 1893:1984. This is a low-strength masonry construction and it is considered extremely vulnerable to seismic forces.

Report # 24 : Unreinforced clay brick masonry house by Sugeng Wijanto Housing Type: Unreinforced Masonry Building     Country: INDONESIA Unreinforced clay brick masonry (UCB) housing construction is still often found in rural areas of Indonesia. This is a single-story building and the main load-bearing structure in these buildings consists of brick masonry walls built in cement mortar and a timber roof structure. This is non-engineered construction built following the traditional construction practice, without any input by architects or building experts. Builders follow a pattern by observing the behavior of typical buildings in the surrounding area. Buildings of this type typically experience severe damage or collapse in the earthquakes in Indonesia.

Report # 25 : Steel frame with semi-rigid "Khorjini" connections and jack arch roof "Taagh-e-Zarbi". by Arzhang Alimoradi Housing Type: Steel Moment Frame Building     Country: IRAN This is a common type of urban/rural construction in many parts of Iran. It is widely used in the cities as a popular structural system for low-rise residential buildings because of the ease of construction and of erecting the frame. Buildings of this type are up to 5 stories high, with a height/width aspect ratio on the order of 1.5. This system consists of a special kind of steel framing with heavy brick infills as partitions. Roof girders are connected to the supporting columns by means of semi-rigid connections. Diaphragms may range from flexible to rigid depending on the detailing and the construction quality. The structure is extremely heavy because of the brick infills between the roof beams. The roof is constructed in the form of a shallow arch called a 'jack arch'. Roofs, ceilings, and floors constructed in this way contributed to building failures and to an unusually high death toll in many recent earthquakes in Iran. As many as half the buildings completed in the early 1970s in Iran had jack arches. In a jack arch system, steel beams or a reinforced concrete joist system span the distance between the main girders across the length of the building. An arch made of small bricks connect the beams. Each arch rises only about ten centimeters. The 'valleys' of this wave-like surface are filled with mortar. The completed ceiling, roof, or floor is thick and heavy. Frequently the steel support beams are not tied together properly or are left untied (From: http://www.johnmartin.com/eqshow/647014_00.htm). Seismic vulnerability of this system is observed as medium to high. The dynamic behavior of the system in the two main perpendicular directions of the building plan differs significantly because of the differences in the stiffness and configuration of the connections in these two directions. Furthermore, 'X' bracings are usually used in the weak direction which further magnifies the non-uniform behavior of the structural system.

Report # 26 : Semi-rigid steel frame with "Khorjinee" connections by Behrokh H. Hashemi, Mohsen G. Ashtiany Housing Type: Steel Braced Frame Building     Country: IRAN This housing type is commonly used for low-rise building construction in Iran, mainly for family apartment buildings. This structure is characterized with a special type of semi-rigid beam-to-column connection called "Khorjinee connection." This connection consists of a pair of continuous beams spanning over several columns and connected to the column sides by means of angle sections. Beam and column are welded to the angle section. A major problem with the Khorjinee connection is that it is very difficult to improve the rigidity of the connection in the weak direction (the direction perpendicular to the connection) since the crossed beams are connected to the web of Khorjinee beams. Thus, in the weak direction of the frames, the connections are considered as pinned (hinges) and the bracing is used to resist seismic loads. However, in the Khorjinee direction, since the possibility of using the bracing is very limited, the frame is considered a rigid structure. Also, out-of-plane partial beam-to-column transfer of bending moment and early onset of failure in the angles are the most likely causes of failure for a building subjected to lateral earthquake loads. These buildings are vulnerable in earthquakes (e.g., 1990 Manjil earthquake).

Report # 27 : Confined brick masonry building with concrete tie columns and beams by Behrokh H. Hashemi, Faramarz Alemi, Mohsen G. Ashtiany Housing Type: Confined Masonry Building     Country: IRAN This is a typical confined brick masonry housing construction common in rural areas of Iran. This building type is often used as a single-family house. Brick masonry shear walls confined with concrete tie columns and beams provide earthquake resistance in both directions. This building type is expected to have good seismic performance.

Report # 28 : Single-family stone masonry house by Dina D'Ayala, Elena Speranza Housing Type: Stone Masonry House     Country: ITALY These buildings form the historic centers of most hilltop villages and towns in central Italy. They are arranged in long terraced clusters. Hillside dwellings have common walls and a variable number of stories (up to 2 or 3). Buildings situated in the valley usually have 4 or 5, with a maximum of 6, stories. The typical house is usually formed by one or two masonry cells, depending on the depth of the block, and with a staircase (usually but not necessarily) running along the common wall. The masonry is made of roughly squared stone blocks set in lime mortar, and the walls are made of two leaves with a rubble core at the base, tapering at the upper floors. Limestone is used for the blocks, while a particular type of tuffa stone is used for the lintels above the openings. At the ground level there are sometimes vaulted structures. The upper stories were originally spanned by timber beams, with joist and timber boards covered by tiles. The roof structure is usually original and made of timber trusses. In the recent past, many of the original floors have been replaced either with iron 'I' beams and jack arches (renovations occurring before World War II), or during the last fifty years, with weakly reinforced concrete slabs. Other alterations include vertical extensions, the closing and opening of windows, and introduction of hygienic services. A high proportion of these houses exhibit the traditional iron ties introduced in the 18th century to tie together the orthogonal walls and floors for better seismic performance. After the introduction of modern seismic codes in the 1980s, many buildings have undergone further strengthening through the use of RC ring beams and concrete jacketing of walls.

Report # 29 : Single-family historic brick masonry house (Casa unifamiliare in centro storico, Centro Italia) by Dina D'Ayala, Elena Speranza, Francesco D'Ercole Housing Type: Unreinforced Masonry Building     Country: ITALY This single-family housing type, found throughout the Central Italy (Centro Italia) mainly in hill towns and small cities, is typically built on sloped terrain. A typical house is 3 stories high, built between two adjacent buildings with which it shares common walls. The main facade of the house faces a narrow road. The ground floor level (perforated with openings on one side only) is used for storage, while the other two stories are used for residential purposes. Typical buildings of this type are approximately 3 m wide and 9 m long. The building height on the front side is on the order of 4.5 m, whereas the height on the rear side is larger (close to 5 m). All the walls are made of unreinforced brick masonry in lime mortar, while the floor structures are vaults at the ground floor level, and timber floor structures at the higher levels. The roof is made of timber and is double-pitched, sloping down towards the front and rear walls. Buildings of this type are expected to demonstrate rather good seismic performance, mostly due to their modest height. Problems related to seismic performance might be caused by the adjacent buildings (typically one story higher). Seismic strengthening techniques for buildings of this type are well established and strengthening of some buildings has been done after the recent earthquake.

Report # 30 : Reinforced concrete frame building by Maurizio Leggeri, Giuseppe Lacava, Eugenio Viola Housing Type: RC Moment Frame Building     Country: ITALY This building type is commonly used for multifamily housing in urban areas of Italy and is particularly common in the region of Potenza (Basilicata). Prior to 1981, this region was not included in the official seismic zonation map of Italy, in spite of the historical evidence. However, after the major earthquake of November 1980, the entire Potenza province was recognized as a seismically prone area. Consequently, seismic considerations were not taken into account for in the building design projects predating the 1980 earthquake. The main load-bearing structure is reinforced concrete frame with masonry infill walls. Many buildings of this type were strengthened using the financial assistance provided by the government. The upgrade typically consists of installing new shear walls and L-shaped columns, and strengthening the foundation.

Report # 31 : Brick masonry farmhouse with a "dead door" by Agostino Goretti, Daniela Malvolti, Simona Papa Housing Type: Unreinforced Masonry Building     Country: ITALY This is a single-family farmhouse construction, found throughout the Padania plain (Reggio Emilia Province). This housing type accounts for approximately 20% of the entire housing stock in the Reggio Emilia municipality. This building practice is no longer followed. Most of the existing buildings were built in the 19th and 20th centuries. The residential and agricultural sections of the house are separated by a central area closed at one end and hence called a "dead door." The residential section usually has two floors (typical story height 2.5 - 3.0 m) and a sloping roof. The agricultural portion, usually larger than the residential section, also has two floor levels. The first-floor height is on the order of 2.5 - 3.0 m whereas the second-story floor height ranges from 5.0 - 9.0 m. As a result, the roof in the agricultural section of the building is at a higher level than that of the residential. The first floor is used as a cow shed and the second as a hayloft. The load-bearing structure consists of brick masonry walls in lime mortar. The walls are characterized by variable thickness, decreasing from 280 mm at the first-floor level to 150 mm at the second-floor level. There are brick masonry columns in the interior of the agricultural section at the second-floor level. The buttresses can be found in the exterior brick masonry walls. Both the residential and agricultural sections have wooden floors; there are vaulted floors in the central area. In some cases, composite floors made of steel beams and perforated bricks can be found. Although the building plan is very regular, the seismic performance of this building type is rather poor due to the vertical irregularity (offset of the floors in the residential and agricultural sections), the absence of connections between walls and between the walls and floors, the thrusting of the roof, and the deterioration of materials.

Report # 32 : Prefabricated large panel concrete buildings with two interior longitudinal walls. by Igor E. Itskov, Ashimbayev M. Umarbayevich, Nikolai B. Chernov Housing Type: RC Structural Wall Building     Country: KAZAKHSTAN This is a typical urban residential construction type commonly found in the southern part of Kazakhstan. Typical buildings of this type are 5- or 9-stories high. This is a prefabricated large panel construction typical for the post-Soviet Union. Large panel buildings with two interior longitudinal walls (as described in this contribution) were developed in Kazakhstan and were specifically designed for the areas of high seismic hazard (intensity 9 and higher per MSK scale). It is considered that this building type (with two interior longitudinal walls) is superior as compared to other large panel building types (usually characterized with one longitudinal wall only) in terms of seismic resistance. The load-bearing system consists of precast reinforced concrete walls and floor panels. All precast members are joined in a box-type structure by means of panel joints. Facade walls are usually made of 2 exterior layers of low-strength lightweight (ceramsite) concrete with good thermal insulation properties and the interior layer of normal-weight concrete. Large panel buildings are generally well-known for their good seismic resistance, which is mainly due to the large rigidity and high degree of redundancy. The fundamental period of vibration for a 9-story building of this type is approximately 0.35-0.4 sec. Large panel buildings of a similar construction (with one longitudinal interior wall) existed in Armenia at the time of the 1988 Spitak earthquake and they remained undamaged, whereas other precast construction types (mainly concrete frame construction) had suffered significant damage and/or collapse. Although the buildings of this type have not been exposed to major damaging earthquakes in Kazakhstan as yet, their dynamic performance was evaluated by means of harmonic forced vibration tests simulating earthquake effects. The buildings subjected to these tests did not experience any damage.

Report # 33 : Precast reinforced concrete frame building with cruciform and linear-beam elements (Series 106) by Ulugbek T. Begaliev, Svetlana Uranova, V. Manukovskiy Housing Type: Precast Concrete Building     Country: KYRGYZSTAN Precast reinforced concrete frame buildings (series 106) were introduced in Kyrgyzstan around 1975. These apartment buildings are usually 9 stories high; less frequently they may be 12 stories. The fundamental period of vibrations is typically in the range of 0.65-0.85 sec. Series 106 was developed by the Kyrgyz Design Institute for construction in earthquake-prone areas. Several buildings of this type (about 15 in total) were built in the capital city Bishkek (design seismicity 8 on the MSK scale). The load-bearing structure consists of a precast reinforced concrete space frame and precast floor slabs. Partition walls are constructed using clay-brick masonry units or small concrete blocks. Buildings of this type have not yet been subjected to major earthquakes. These buildings are not considered to be highly vulnerable to earthquake effects, provided that the construction quality, particularly with reference to the joints, is satisfactory. It should be noted that precast frame buildings of a different type (Series 111) performed very poorly in the 1988 Spitak (Armenia) earthquake.

Report # 34 : Buildings with hollow clay tile load-bearing walls and precast concrete floor slabs by Ulugbek T. Begaliev, Svetlana Uranova Housing Type: Unreinforced Masonry Building     Country: KYRGYZSTAN Buildings of this type are characterized with load-bearing masonry walls and precast concrete floors. Typical buildings of this type are 3 to 4 stories high and they are characterized with two longitudinal walls and several cross walls. There are many existing buildings of this type in Kyrgyzstan, and most of them were constructed in the 1960s. This construction practice was banned after 1966, due to the code provisions that required restriction of the size of the cores in hollow clay tiles (blocks). The exterior walls are made of hollow clay masonry tiles (blocks). In some cases there are two wall wythes: the exterior wythe made of hollow clay tiles and the interior wythe made of solid clay bricks. The floor system consists of precast reinforced concrete hollow core slabs. Buildings of this type were built in the areas with high seismic design intensity (8, 9 and higher on the MSK scale). This building type is considered to be rather vulnerable to seismic effects.

Report # 35 : Traditional wood frame construction (yurta) by Ulugbek T. Begaliev, Svetlana Uranova Housing Type: Timber Building     Country: KYRGYZSTAN This type of building is the national traditional dwelling of the Kyrgyz people. It is a light portable construction. The bearing structure of a yurta is a special wood frame, consisting of wood poles. The wood frame is covered by felt tension cloth. The floors are traditionally covered with felt rugs (koshma). Yurtas can be easily disassembled and moved to new places. They are warm in winter and cool in the summer. The buildings have only one door and one opening in the roof. Yurtas are circular in plan. The diameter is usually 4 m#6 m. This type of building is used at the present time by shepherds, particularly during the summer, for celebrations and funerals, and as temporary buildings during extreme situations in Kyrgyzstan. The yurta is a very light structure, has a symmetrical plan, and has good seismic resistance.

Report # 36 : Single-family brick masonry house by Ulugbek T. Begaliev, Svetlana Uranova Housing Type: Confined Masonry Building     Country: KYRGYZSTAN This housing type represents a very popular single-family housing construction practice followed in Kyrgyzstan in the recent past. Approximately 80% buildings of this type, mostly those constructed after 1990, do not comply with the Building Code requirements. These are low-rise (1- to 2-story high) buildings with a complex plan and wall layout. The main load-bearing system consists of brick masonry walls in cement mortar partially confined with reinforced concrete posts and beams; columns are provided only at some wall corners and intersections. Rigid brick masonry walls have low load-carrying capacity. Wall thickness is either 380 mm or 510 mm. SNiP (Building Code) includes provisions for the horizontal wall reinforcement (welded wire mesh at the wall corners) and the provision of reinforced concrete columns at the wall corners. The floor system consists of precast reinforced concrete hollow-core slabs with typical slab panel dimensions of 5.86 m length X 1.2 m width. Reinforced concrete bond beam (belt) is constructed at the building perimeter at the floor level to provide the confinement and diaphragm action for seismic load effects. Complex building geometry and irregular wall distribution results in the significant torsional effects during earthquakes due to the eccentricity between the centre of mass and centre of stiffness. These buildings are located in the regions of high seismic hazard, which had experienced earthquakes of intensity VIII, IX or higher (per the MSK scale) in the past. This type of construction is expected to demonstrate poor seismic performance, due to the poor quality of masonry walls and complex layout resulting in torsional effects.

Report # 38 : Prefabricated concrete panel buildings with monolithic panel joints by Svetlana Uranova, Ulugbek T. Begaliev Housing Type: RC Structural Wall Building     Country: KYRGYZSTAN Prefabricated concrete panel building construction with monolithic panel joints has been practiced throughout the former Soviet Union (including Kyrgyzstan) since 1965. This type of prefabricated construction is known as seria 105. Apartment buildings of this type are usually 5-9 stories high. The foundations are made of cast in-situ reinforced concrete. Steel dowels are provided in the foundations to ensure anchorage of steel rebars located in the panels and in the panel joints. The load-bearing structure in large panel buildings consists of reinforced concrete panels combined to form a box-type rigid system by means of special joints. This building type is considered to be one of the most earthquake-resistant construction types in the former Soviet Union.

Report # 39 : Reinforced concrete frame buildings without beams (seria KUB). by Svetlana Uranova, Ulugbek T. Begaliev Housing Type: Precast Concrete Building     Country: KYRGYZSTAN Frame buildings without beams were introduced in the last decade of the Soviet Union (period 1980-1989) in some of the Soviet Republics: Kyrgyzstan, Tadjikistan, Caucasian region of Russia etc. This type of precast construction is known as seria KUB. This type of apartment buildings is usually 5-9 stories high; in some cases these buildings are 12 stories high. The load-bearing structure consists of precast reinforced concrete columns and slabs. Precast column elements are usually two stories high. Typically, column spans are equal to 6m. Precast slab elements are made of solid concrete without ribs, and the dimensions are: 3 m x 3 m X 0.16 m (length X width X thickness). Most buildings of this type have some kind of lateral load resisting elements, such as: cast-in-situ shear walls, or precast shear walls, or shear cross braces etc. All precast structural elements are combined in 3-D moment frame by means of a special joint system. Partitions are made of brick masonry or small concrete block masonry. This building type is considered to be very vulnerable in earthquakes. The seismic resistance of buildings of this type depends on the type of column-to-slab joints. Similar structures were damaged in the 1988 Spitak (Armenia) earthquake.

Report # 40 : Buildings with cast in-situ load-bearing reinforced concrete walls by Svetlana Uranova, Ulugbek T. Begaliev, V. Manukovskiy Housing Type: RC Structural Wall Building     Country: KYRGYZSTAN Buildings with cast-in-situ load-bearing reinforced concrete walls are widespread in many republics of the former Soviet Union. There are many such buildings in Kyrgyzstan in areas with a design seismicity of 8 and 9 on the MSK scale. The buildings with cast-in-situ walls are typically medium- to high-rise buildings (4-18 stories high; often 12-stories high). High-rise buildings of this type (9-18 stories high) have basements. The load-bearing structure consists of cast-in-situ reinforced concrete walls and precast reinforced concrete floor slabs. Floor slabs are either two-way solid slab structures, or, less often, hollow-core slabs. These buildings do not have any frame elements (columns and beams). Facade walls are usually made of lightweight (ceramsite) concrete. The buildings are supported by concrete strip or mat foundations. This building type is considered to be earthquake-resistant. Problems are mainly related to the quality of construction.

Report # 41 : Two-story unreinforced brick masonry building with wooden floors by Svetlana Uranova, Ulugbek T. Begaliev Housing Type: Unreinforced Masonry Building     Country: KYRGYZSTAN This is a non-engineered construction practiced in Kyrgyzstan from 1920 to 1957. The load-bearing structure consists of unreinforced brick masonry walls and wooden floor beams. Brick masonry walls are usually constructed of mud mortar. Walls are usually perforated with rather large door and window openings. The wall length between the adjacent cross walls is on the order of 9-10 m. Wooden floor elements (beams) are not tied together and they do not behave as diaphragms. Based on the performance in past earthquakes, this building type is considered to be highly vulnerable to seismic effects.

Report # 42 : Houses with mud walls and thatch roofs by Svetlana Uranova, Ulugbek T. Begaliev Housing Type: Adobe / Earthen House     Country: KYRGYZSTAN This building type is widespread in the rural areas of Kyrgyzstan, and also in some urban areas. It is a non-engineered construction. Due to its low cost, it is mainly used by poor people. Various building materials are used for this type of construction, e.g., clay and straw for the walls, wood for the roof structure, and stone for the foundations. In order to achieve adequate flexibility or plasticity, a small amount of clay is mixed with water. Straw is added to achieve an improved consistency. Small panel boards are used as formwork for casting mud walls. The walls are cast in lifts; a new lift is cast after the previous one has set. Windows and doors have wood lintels. Floors are made out of wood planks. Buildings of this type do not have any earthquake-resistant features and are considered to be highly vulnerable to seismic effects.

Report # 43 : Rural mud wall building (nyumba yo mata OR ndiwula) by Mauro Sassu, Ignasio Ngoma Housing Type: Adobe / Earthen House     Country: MALAWI This housing construction type is used only for residential purposes. The building technique consists of timber poles as the core or base with a mud smear (plaster) applied on both sides. The plan is circular (only one floor) and the roof is formed by grass thatch supported on timber poles and cross members. The circular shape of the plan and the light weight of the roof, combined with the wood skeleton or frame, ensure a good seismic response. The seismic vulnerability is increased by poor connections of the wood skeleton and by progressive damage to the natural components.

Report # 44 : Reinforced concrete frame building with timber roof by Azlan B. Adnan, Tuan N. Tuan Chik, Bahiah Baharudin Housing Type: RC Moment Frame Building     Country: MALAYSIA This housing type is commonly used for family housing and it is found in urban areas of Malaysia. Columns and beams are of reinforced concrete to provide structural strength. The roof consists of timber trusses. These houses are designed according to the British Code BS 8110 without seismic design considerations.

Report # 45 : Rammed earth house with pitched roof (Nyumba yo dinda OR Nyumba ya mdindo) by Mauro Sassu, Ignasio Ngoma Housing Type: Adobe / Earthen House     Country: MALAWI This type of construction is used for residences only. The building technique consists of in-situ ramming of moist soil in a carefully aligned/placed mold. The mold dimensions are between (250 - 300 mm) wide X (400 - 450 mm) long X (200 - 300 mm) height. The plan of the house is rectangular. The roof is either grass thatch or iron sheets supported on timber poles. This type is found in all three regions of Malawi. The strength of the wall is low and depends on the compacting effort applied. The expected seismic performance is poor. There are no vertical or horizontal reinforcements.

Report # 46 : Unburnt brick wall building with pitched roof (nyumba ya zidina) by Mauro Sassu, Ignasio Ngoma Housing Type: Adobe / Earthen House     Country: MALAWI This type of building is found both in urban and rural areas throughout Malawi. It is a construction type that is gaining popularity at the moment; it is estimated that it constitutes 45% of the country's housing stock. The thatched roof is supported by unburnt mud brick walls built in mud mortar. The walls are built on a stone platform raised above ground as a protection against floods. These buildings are built without any horizontal and vertical reinforcement. As a result, the strength of the building is very low and it is considered to be very vulnerable to earthquake effects. In the 1989 Salima earthquake (magnitude 6), 9 people died and over 50,000 people were left homeless. Many buildings of this type suffered extensive damage or collapsed.

Report # 47 : Traditional oval-shaped rural stone house by Yogeshwar K. Parajuli, Bijay K. Upadhyay Housing Type: Stone Masonry House     Country: NEPAL This is a typical rural construction concentrated in the central mid-mountain region, particularly in the Kaski, Syangja, Parbat, and Baglung districts. (The country is divided into 75 administrative districts.) These primarily residential buildings are basically loose-fitting, load-bearing structures, constructed of uncoursed rubble stone masonry walls and a timber structure for the floor and roof. Village artisans play a pivotal role in these owner-built buildings. Because of the loss of integrity during an event, they are expected to be extremely vulnerable from the effects of an earthquake.

Report # 48 : Reinforced concrete frame with infill walls designed for gravity loading by Jalal N. Al Dabbeek, Abdel H. W. Al-Jawhari Housing Type: RC Moment Frame Building     Country: PALESTINIAN TERRITORIES This building type is usually found in most cities of West Bank and less often in the Gaza Strip. The structural system consists of solid slabs (either one-way or two-way) with beams and columns. The columns are usually of rectangular cross-section. The beams may be either dropped (deep) or hidden. The infill walls in the external frames may consist of stone with plain concrete only, or stone with plain concrete and hollow block. Sometimes polystyrene of 2-cm thickness is added for isolation purposes. On the other hand, the internal infill walls consist only of concrete hollow blocks of 10 cm thickness but may be as thick as 15 or 20 cm. These walls are used and considered as partitions.

Report # 49 : Unreinforced concrete and masonry bearing wall construction (designed for gravity loads only) by Jalal N. Al Dabbeek, Abdel H. W. Al-Jawhari Housing Type: Stone Masonry House     Country: PALESTINIAN TERRITORIES This building type is usually found in most cities of the West Bank and less often in the Gaza Strip. It is a traditional, non-engineered, low-rise construction practice. The main lateral load-resisting system consists of bearing walls with unreinforced concrete strip foundation. The interior masonry walls consist of plain concrete (system #2) or two wythe stone masonry walls filled with plain concrete (system #1). The exterior bearing walls consist of stone masonry facing with a plain concrete backup. Wall thickness ranges from 400 to 500 mm (system #1) to 300-mm thickness in system #2. It is important to note that system #1 represents the old practice for bearing-wall construction while system #2 represents the new trend which was developed and used from the 1950s to the 1970s. This construction is not practiced at the present time.

Report # 50 : Confined masonry building by Cesar Loaiza F., Marcial Blondet Housing Type: Confined Masonry Building     Country: PERU This multifamily housing construction type has been the most commonly used in the urban areas of Peru during the last 35 years. Confined masonry buildings consist of load-bearing unreinforced clay masonry walls confined by cast-in-place reinforced concrete tie columns and beams. Tie columns are cast after the construction of the masonry walls is complete and they are connected to the tie beams. Confined masonry walls have limited shear strength and ductility; however, buildings of this type typically have a good seismic resistance.

Report # 51 : Confined masonry houses by Cesar Loaiza F., Marcial Blondet Housing Type: Confined Masonry Building     Country: PERU This is the most common single-family housing construction practice followed both in urban and rural areas of Peru in the last 45 years. Confined masonry buildings consist of load-bearing unreinforced masonry walls made of clay brick units, confined by cast-in-place reinforced concrete tie columns and beams. These buildings do not have a complete load path in both horizontal directions required for adequate lateral load resistance. However, in spite of that, typical houses may show a good seismic performance.

Report # 52 : Adobe house by Cesar Loaiza F., Marcial Blondet, Gianfranco Ottazzi Housing Type: Adobe / Earthen House     Country: PERU This is a traditional construction practice followed for over 200 years. Houses of this type can be found both in urban and rural areas in the coastal and highlands regions of Peru. Walls are made of adobe blocks laid in mud mortar. The roof structure is made of wood; it usually consists of timber beams with timber planks covered with a mud mortar overlay or with clay tiles or metal sheets. Houses of this type are mainly occupied by poor people. This construction is considered to be very vulnerable to earthquake effects.

Report # 53 : Small concrete block masonry walls with concrete floors and roofs by Mark Klyachko, Yuriy Gordeev, Freda Kolosova Housing Type: Unreinforced Masonry Building     Country: RUSSIAN FEDERATION This is a typical residential construction found both in urban and rural areas. It represents a construction practice followed in the former Soviet Union. Buildings of this type constitute 15 to 30% of the housing stock in seismically prone areas of Russia (Far East, Siberia, Baikal Lake Region, North Caucasus) and in CIS states (Central Asia, Armenia, Georgia, etc.). The main load-bearing system for lateral and gravity loads consists of concrete block masonry walls and concrete floor slabs. Seismic resistance is relatively good, provided that the welded block wall connections are present and well constructed.

Report # 54 : Large concrete block walls with reinforced concrete floors and roof (typical series: 1-306c, 1-307c, 114c) by Mark Klyachko, Yuriy Gordeev, Freda Kolosova Housing Type: Others     Country: RUSSIAN FEDERATION This is a typical residential construction found both in urban and rural areas. It represents a construction practice followed in the former Soviet Union. Buildings of this type constitute 15 to 30% of the housing stock in earthquake-prone areas of Russia (Far East, Siberia, Baikal Lake Region, North Caucasus) and CIS states (Central Asia, Armenia, Georgia, etc.). The main load bearing system for lateral and gravity loads consists of concrete block masonry walls and concrete floor slabs. Seismic resistance is relatively good, provided that the welded block wall connections are present and are well constructed.

Report # 55 : Large reinforced concrete panel buildings (Series 122, 135 and 1-464c) by Mark Klyachko, Igor Mortchikchin, Igor Nudga Housing Type: Precast Concrete Building     Country: RUSSIAN FEDERATION Large panel buildings represent one of the most common multifamily housing construction types (apartment buildings) in the former Soviet Union. Buildings of this type range from 4 to 9 stories high. This construction practice started in the 1960s and has been followed ever since. This contribution describes three different types (series) of large panel construction, known as seria 122, seria 135, and seria 1-464c. These three types (seria) are characterized by welded panel connections. The main vertical load-bearing elements, designed to carry both gravity and lateral loads, are precast reinforced concrete panels. Typically, buildings are of a regular plan and are characterized with only one interior load-bearing wall in the longitudinal direction and several walls in the transverse direction. Floor and roof structures are also made of precast reinforced concrete panels. Both wall and floor panels are of room dimensions, and the assembly of these structures consists of setting the panels in their final position and joining them in a box-type structure by means of welded joints. The methodology of achieving panel connections in large panel construction practice has significantly improved in the last 50 years. Seria 1-464c is among the first seria of large panel construction. Initially, panel joints in seria 1-464c were achieved by welding the steel elements projecting from the panels. Later on, welded joints were replaced with the monolithic joints. Seria 1-464c is characterized by a plan typical for large panel buildings with continuous walls and a typical span (2.7 m or 3.6 m) of cross walls (Figures 3C and 3D). Seria 122 is characterized by discontinuous façade walls in the longitudinal direction (Figure 3A). Seria 135 is characterized by a larger span of cross walls (6m) as compared to the other types (see figure 3B). Due to the large wall density, these buildings are rather rigid. Seismic resistance in this construction type is generally good, as these buildings have been exposed to several strong earthquakes in the former Soviet Union.

Report # 56 : Timber log building by Mark Klyachko, Andrey Benin, Janna Bogdanova Housing Type: Timber Building     Country: RUSSIAN FEDERATION This is a rural housing construction practice widespread in the forests of Russia. Buildings of this type are common for seismically prone areas of Russia (Far East, Siberia, Baikal Lake Region, North Caucasus). The load-bearing structure is made of wood. To construct the walls, timber logs are sawn horizontally in a square or circular cross section with special end joints (similar to dovetail joints). Buildings have timber roofs and fieldstone or concrete strip foundations. Typical seria 146-115-77 cm of 'Giprolesprom' for seismic regions is an example of this building type. Seismic performance of these buildings is good if the construction quality is adequate.

Report # 57 : Wood panel wall buildings (typical seria 181-115-77 cm of "Giprolesprom") by Mark Klyachko, Andrey Benin, Janna Bogdanova Housing Type: Timber Building     Country: RUSSIAN FEDERATION This is a rural housing construction practice widespread in the forested areas of Russia. Buildings of this type are common in seismically prone areas of Russia (Far East, Siberia, Baikal Lake Region). The load-bearing structure is made of wood panel walls. Buildings have timber roof and fieldstone or concrete strip foundations. Typical seria 181-115-77 cm of 'Giprolesprom' for seismic regions is an example of this building type. Seismic resistance is relatively high, provided that the quality of materials and the construction are satisfactory.

Report # 58 : Rubble-stone masonry house by Marjana Lutman, Miha Tomazevic Housing Type: Stone Masonry House     Country: SLOVENIA Rubble-stone masonry houses are still found throughout Slovenia. This housing type with its special history represents a typical, older residential building in the northwestern part of Slovenia. After their destruction during World War I, these houses were rebuilt, mostly with the recycled stone material from demolished buildings. Many houses of this type were subsequently damaged during the last two earthquakes in Slovenia (1976 Friuli and 1998 Bovec). In order to preserve the country's architectural heritage, about 66% of these houses were strengthened following these earthquakes.

Report # 59 : Reinforced concrete frame with concrete shear walls - dual system by Adel Awad, Hwaija Bassam, Isreb Talal Housing Type: RC Moment Frame Building     Country: SYRIAN ARAB REPUBLIC These buildings are characterized by a combination of shear walls and frames in both directions. The buildings are multiple housing units found in the main cities of Syria. The shear walls are often part of the elevator and service cores, whereas the frames are arranged in-plane, in conjunction with the walls, to support the floor system. Stiffness and mass distribution are irregular and the majority of buildings may experience soft-story or torsional problems. As a result, these buildings are expected to have only moderate seismic resistance.

Report # 60 : Moment resisting frame designed for gravity loads only by Adel Awad, Hwaija Bassam, Isreb Talal Housing Type: RC Moment Frame Building     Country: SYRIAN ARAB REPUBLIC These buildings are found in the main cities of Syria and represent modern construction practice followed in the last 50 years. The floor system is a two-way reinforced concrete slab, which spans between orthogonal sets of beams that transfer the load to the columns. The frames are designed to carry gravity loads only.

Report # 61 : Street front building with arcade at the first floor (pre-1970's construction) by George C. Yao, M. S. Sheu Housing Type: RC Moment Frame Building     Country: TAIWAN This building type is common in most Taiwanese cities and towns. It represents a construction practice that was followed before1970 and is no longer used. The main load-bearing structure consists of reinforced concrete frames designed for gravity loads only, with brick masonry infill walls. Brick walls were built before the concrete was poured thereby serving as a formwork for concrete. Buildings of pre-1970 construction were characterized with a better bond between the masonry and concrete as compared to the buildings of more recent construction, in which reinforced concrete frames serve as main load-bearing system for lateral and gravity loads. Buildings of this type are medium-rise (4 to 5 stories high). Usually, the first floor (typically 4 m high) is used for commercial purposes while the upper stories (typically 2 to 4 stories above, floor height 3 m) are used for storage and residences. Neighboring units of similar design are constructed together to form a shady corridor for pedestrians to walk in. The number of connected units varies from 6 to 10. These units may be connected in one row, or in an L shape, or in the U shape along the street block. There are several structural deficiencies characteristic for this construction: (1) the weak and soft first story because the commercial space demands a large opening at the street level; (2) typical building layout has walls in one direction only, perpendicular to the street. As a consequence, there are few earthquake-resisting elements in the other direction; (3) extra rooftop additions increase the load. Many buildings of this type collapsed in the 1999 Chi-Chi earthquake.

Report # 62 : Street front building with arcade at the first floor (contemporary construction) by George C. Yao, M. S. Sheu Housing Type: RC Moment Frame Building     Country: TAIWAN This building type is common in many Taiwanese cities and towns. The street-front buildings are medium-rise, reinforced concrete frames with infill brick masonry walls serving as partitions. Usually, the first floor (typically 4 m high) is used for commercial purposes while the upper stories (typically 2 to 4 stories above, floor height 3 m) are used for storage and residences. Neighboring units of similar design have been constructed together to form a corridor for pedestrians to walk in. Connected units vary in number from 6 to 10 and they may be built in a row, in an L shape, or in the U shape. There are several structural deficiencies associated with this building type: (1) the weak and soft first story can result from a large opening at the street level for commercial use; (2) a typical building layout has walls in one direction only, perpendicular to the street; as a consequence, there are few earthquake-resisting elements in the other direction; (3) extra rooftop additions increase loads. Also, building owners tend to reduce the number of columns for a wider storefront view. Many buildings of this type collapsed in the Chi-Chi earthquake of 1999.

Report # 63 : High-rise, reinforced concrete buildings with open space at the ground floor by Su C. Tung, George C. Yao Housing Type: RC Moment Frame Building     Country: TAIWAN This is an urban housing construction. Typically, these are 12-story apartment buildings with a parking area in the basement. The first and second floor are classified as Open Space (OS) and the ground floor is used by the residents for gardening and for leisure and social gatherings. The common features in these buildings are: (1) The two lower floors were designed for the OS with a net height of approximately 7.6 meters. (2) There are many walls above the third floor in both horizontal directions but very few walls on the OS except around the elevator shaft and the staircases. If the elevator is located at the corner of the building, torsional effect may be present. (3) Architects tend to design zigzag floor plans for these buildings in order to maximize view angle and natural lighting. (4) Very few columns were designed into these buildings in order to maximize the parking area on the basement level. The primary load-resisting system is reinforced concrete moment-resisting frame on a mat foundation. The fact that the partition walls are dense at the third floor and above, creates a soft-story configuration in the lateral load-resisting system. Many buildings of this type collapsed in the 1999 Chi-Chi earthquake due to the soft-story effect caused by the OS design.

Report # 64 : Reinforced concrete frame building with masonry infills by Polat Gulkan, Mark Aschheim, Robin Spence Housing Type: RC Moment Frame Building     Country: TURKEY Approximately 80 percent of Turkey's urban households live in mid-rise apartment blocks constructed of cast-in-situ, reinforced concrete with masonry infill. The vertical structure consists of columns 200-300 mm in thickness, longer in one direction than in the other, and designed to fit within the walls. Floor and roof slabs are of "filler slab" construction, with hollow clay or concrete tiles used to form the voids, and are usually supported by reinforced concrete beams. In some cases the framing is flat-slab construction. The reinforced concrete frame is infilled with hollow-tile or masonry-block walls which are rarely connected structurally to the frame. These buildings have not performed well in recent earthquakes because poor design and construction have resulted in insufficient lateral resistance in the framing system. In many cases, this has been coupled with an inappropriate building form. Notwithstanding the existence of earthquake-resistant design codes for more than 30 years, many buildings have not been designed for an earthquake of a magnitude that could occur within the building's lifetime.

Report # 65 : Wood frame single family house by Christopher Arnold Housing Type: Timber Building     Country: USA Wood frame construction is typical for single family houses throughout the USA. Historically, in the East, Midwestern and South, brick masonry and stone were used for house construction, but this began to be superseded by wood frame around the turn of the 19th century. In the earthquake-prone western part of the US, wood frame has been dominant over stone and brick. The development of present-day wood frame construction began with the appearance of standardized sawn lumber and cheap machine-made nails. By 1840, the typical wood frame house was built of milled lumber in standard sizes. The standardized wood frame structure is now augmented by a wide range of compatible standardized components such as doors, windows, electrical and plumbing fixtures, and the like, that are designed to be easily installed in the wood structure. Because wood frame walls are hollow, alternative levels of insulation can be installed, enabling accommodation of any climatic conditions and easy installation of plumbing and electrical services within walls, in the open spaces above the ceilings, within the floor structure, and in the space between the first (ground) floor and the ground below. Because of their light weight (compared to brick or stone), their relatively large number of walls, and the use of a multiplicity of nails for connections, wood frame houses have traditionally performed well in earthquakes. Deaths and serious injuries are very rare in these structures. Today's wood frame construction is highly codified and regulated, with a good standard of inspection by suburban local building departments in earthquake-prone regions. In smaller towns and rural areas quality control may be lacking.

Report # 66 : Precast reinforced concrete frame panel system of seria IIS-04 by Shamil Khakimov, Bakhtiar Nurtaev Housing Type: Precast Concrete Building     Country: UZBEKISTAN This housing type is used in the construction of residential and public buildings in many cities throughout Uzbekistan (including the capital city Tashkent) that are located in zones with intensities between 7-9. Residential buildings of this type are generally 9 to 12 stories high, whereas public buildings of the same construction are 1 to 4 stories high. All seismic load-resisting (and also nonstructural) components, e.g., foundations, columns, girders, slabs, staircases, wall panels, etc., are manufactured in specialized plants. The materials are subsequently transported to the building site. The positive features of this construction type are (1) the ability to manufacture all building materials in an industrialized setting, and (2) the gain in efficiency inasmuch as the same building components may be used both for residential and public buildings. The key drawback is that the welded joints cause seismic vulnerability when the building is located in zones of extremely high seismic loads. These joints have shown extremely brittle behavior during earthquakes. Earthquake damage is mainly concentrated in the column joints, or in the column-to-girder joints. In some cases non-bearing walls and exterior wall panels have collapsed.

Report # 67 : Popular, non-engineered urban housing on flat terrain by Argimiro C. Gandica, Francisco L. Almansa Housing Type: RC Moment Frame Building     Country: VENEZUELA This is an urban housing construction type found in the Andean states of Venezuela. In some cities, e.g., Mérida, this construction accounts for 40% of the total building stock. Typical buildings of this type are two to three stories high. Typically, there are two or three bays in the longitudinal direction (spaced at 3 to 4 m) and four or five bays in the transverse direction (4 to 5 m apart). The main load-bearing system consists of reinforced concrete frame (columns and beams) with hollow clay tile, and masonry-infill walls. The roof structure consists of lightweight roofing (zinc and/or acclimatized galvanized sheets) supported by I-shaped steel beams. The building's roof level is used as a terrace with a one-meter-high masonry parapet, which serves as a guardrail on the slab perimeter. This is a non-engineered construction, i.e., these buildings are constructed by the owners. Because of the lack of adequate detailing in the longitudinal and transverse steel reinforcement bars, beam-column connections are inadequate and do not provide the continuity required for adequate seismic performance.

Report # 68 : Precast, prestressed concrete frame structure with concrete shear walls by Radovan Dimitrijevic Housing Type: Precast Concrete Building     Country: SERBIA This housing type is a prefabricated frame structure, consisting of precast concrete columns and other structural elements, e.g., waffle floor slabs, edge girders, stairs, and wall panels. The frame structure carries the gravity load, while shear walls are the main lateral load-resisting elements. The main feature of this technology is that the key structural elements are joined together by prestressing in two orthogonal horizontal directions. The technology has been used in Yugoslavia during the last 40 years under the proprietary name, IMS Building System, and it can be found in all major Yugoslav cities, including Belgrade, Novi Sad, Nis, etc., and also in other countries, such as Cuba, the Philippines, and Egypt. To date, around 400,000 housing units (approximately 2.5 million m² of the built area) have been constructed using this technology. Design applications include both residential housing and public buildings (e.g., hospitals). Seismic performance of the main IMS structural elements has undergone extensive experimental laboratory tests, and has also been tested in a few major earthquakes. Several buildings of this type sustained the effects of the 1968 Banja Luka earthquake without any damage.

Report # 69 : Confined masonry building with concrete floor slabs by Nikola Muravljov, Radovan Dimitrijevic Housing Type: Confined Masonry Building     Country: SERBIA This type of construction has been used for single-family and medium-rise residential buildings throughout urban and rural Yugoslavia during the past 30 years. The structure consists of load-bearing masonry (brick, stone, concrete block) walls confined with reinforced-concrete posts and tie-beams. The walls are typically made of hollow clay tiles. Floor slabs are composed of prefabricated joists infilled with brick elements and topped with a reinforced-concrete slab in-situ.

Report # 70 : Solid brick masonry house with composite hollow clay tile and concrete joist roof slabs by Virginia I. Rodriguez, Maria I. Yacante, Sergio Reiloba Housing Type: Confined Masonry Building     Country: ARGENTINA This housing type is found in the urban areas of San Juan province. It is a one-story, detached or semi-detached building, mainly used as a single-family house. The strength of this construction type is due to its solid brick walls confined with concrete tie-beams and tie-columns. The roof slabs are of composite concrete and masonry hollow clay tile construction, which form a diaphragm tied to the walls. The deficiency of this type of construction is found in the slabs which suffer serious deterioration due to the effects of humidity. This housing type is expected to have good seismic behavior.

Report # 71 : Reinforced concrete frame structure with diagonal bracing and brick infill walls by Maria D. Bostenaru, Ilie Sandu Housing Type: RC Moment Frame Building     Country: ROMANIA This is a post-World War II variant of the well-known Romanian 'inter-bellum' building. This urban housing construction was practiced in Romania over a rather short period of time after World War II until nationalization in 1947. Buildings of this type are still in use, mainly as apartment buildings. They are typically 7 to 11 stories high and the main load-bearing structure consists of a reinforced concrete space frame with reinforced concrete diagonal bracings. The floor structure consists of RC solid slabs and beams cast-in-place. The frames are infilled with brick masonry walls (typical wall thickness 140 mm or 280 mm). These buildings were designed according to the temporary guidelines issued in 1941 by the Ministry of Public Works (MLP) and based on German recommendations. This region is well known as a seismically prone area, with the epicenter of damaging earthquakes close to Vrancea. Earthquakes of Richter magnitude over 7.0 occur once in 30 years. Bucharest, the capital, is located around 150 km south of the epicenter and lies in the main direction of the propagation of seismic waves. The Bucharest area is located on the banks of the Dâmbovita and Colentina rivers, on non-homogeneous alluvial soil deposits. During the earthquake of 4 March 1977 (Richter magnitude 7.2), over 30 buildings collapsed in Bucharest, killing 1,424 people. It should be noted that although buildings of this construction type experienced severe damage (mainly cracking in the columns and the brick masonry infill walls) collapse was not reported. After the 1977 Vrancea earthquake, the damaged buildings were repaired and strengthened. One of the buildings described in this contribution was retrofitted by strengthening the existing columns with new reinforced concrete jackets and by replacing the existing brick masonry infill walls with new lightweight concrete block walls. The diagonal bracings were removed as a part of the retrofit. Another example shows a triangular-shaped building with the original bracing preserved during the retrofit.

Report # 72 : Traditional rural house in Kutch region of India (bhonga) by Madhusudan Choudhary, Kishor S. Jaiswal, Ravi Sinha Housing Type: Adobe / Earthen House     Country: INDIA The Bhonga is a traditional construction type in the Kutch district of the Gujarat state in India, which has a very high earthquake risk. A Bhonga consists of a single cylindrically shaped room. The Bhonga has a conical roof supported by cylindrical walls. Bhonga construction has existed for several hundred years. This type of house is quite durable and appropriate for prevalent desert conditions. Due to its robustness against natural hazards as well as its pleasant aesthetics, this housing is also known as "Architecture without Architects." It performed very well in the recent M7.6 Bhuj earthquake in 2001. Very few Bhongas experienced significant damage in the epicentral region, and the damage that did occur can be mainly attributed to poor quality of the construction materials or improper maintenance of the structure. It has also been observed that the failure of Bhongas in the last earthquake caused very few injuries to the occupants due to the type of collapse.

Report # 73 : Unreinforced Brick Masonry Apartment Building by Marjana Lutman, Miha Tomazevic Housing Type: Unreinforced Masonry Building     Country: SLOVENIA This construction was commonly used for residential buildings in all Slovenian towns, and it constitutes up to 30% of the entire housing stock in Slovenia. The majority of these buildings were built between 1920 and 1965. They are generally medium-rise, usually 4 to 6 stories high. The walls are unreinforced brick masonry construction laid in lime/cement mortar. In some cases, the wall density in the longitudinal direction is significantly smaller than in the transverse direction. In pre-1950 construction, there are mainly wooden floor structures without RC tie-beams. In post-1950s construction, there are concrete floors with RC bond-beams provided in the structural walls. Roof structures are either made of wood (pitched roofs) or reinforced concrete (flat roofs). Since this construction was widely practiced prior to the development of the seismic code (the first such code was issued in 1964), many buildings of this type exceed the allowable number of stories permitted by the current seismic code (maximum 2 or 3 stories for unreinforced masonry construction). Buildings of this type have been exposed to earthquake effects in Slovenia. However, this construction type experienced the most significant damage in the 1963 Skopje, Macedonia, earthquake, which severely damaged or caused the collapse of many buildings.

Report # 74 : Uncoursed rubble stone masonry walls with timber floor and roof by Yogeshwar K. Parajuli, Bijay K. Upadhyay Housing Type: Stone Masonry House     Country: NEPAL This is a typical rural housing construction in the hills and mountains throughout Nepal. It is a traditional construction practice followed for over 200 years. These buildings are basically loose-fitting, load-bearing structures constructed of uncoursed rubble stone walls in mud mortar, with timber floors and roofs. They are expected to be extremely vulnerable to the effects of earthquakes due to their lack of structural integrity.

Report # 75 : Stone masonry apartment building by Mohammed Farsi, Farah Lazzali, Yamina Ait-M Housing Type: Stone Masonry House     Country: ALGERIA This is a typical residential construction type found in most Algerian urban centers, constituting 40 to 50% of the total urban housing stock. This construction, built mostly before the 1950s by French contractors, is no longer practiced. Buildings of this type are typically 4 to 6 stories high. The slabs are wooden structures or shallow arches supported by steel beams (jack arch system). Stone masonry walls, usually 400 to 600 mm thick, have adequate gravity load-bearing capacity; however, their lateral load resistance is very low. As a result, these buildings are considered to be highly vulnerable to seismic effects.

Report # 76 : Load-bearing wall buildings protected with the "sliding belt" base isolation system by Jacob Eisenberg, Svetlana Uranova, Marat Abdibaliev, Ulugbek T. Begaliev Housing Type: Seismic Protection Systems     Country: KYRGYZSTAN Sliding belt is a base isolation system developed to protect buildings from seismic effects by reducing and limiting the level of seismic forces. The sliding belt system is installed at the base of the building between the foundation and the superstructure. The foundation is usually made of cast-in-situ concrete and the superstructure is typically a load-bearing wall structure, either a 9-story, large concrete panel system, or a 3-story brick masonry construction. Once the earthquake base shear force exceeds the level of friction force developed in the sliding belt, the building superstructure starts to slide relative to the foundation. The lateral load transferred to the superstructure is expected to be approximately equal to the frictional force that triggers the sliding of the structure. The sliding belt consists of the following elements: (a) sliding supports, including 2-mm-thick stainless steel plates attached to the foundation and 4-mm Teflon (PTFE) plates attached to the superstructure, (b) reinforced rubber restraints for horizontal displacements (horizontal stop), and (c) restraints for vertical displacements (uplift). A typical large panel building with plan dimensions 39.6 m x 10.8 m has 63 sliding supports and 70 horizontal and vertical restraints. The sliding belt scheme was developed in CNIISK Kucherenko (Moscow) around 1975. The first design application in Kyrgyzstan was made in 1982. To date, the system has been applied on over 30 buildings in Bishkek, Kyrgyzstan. All these buildings are residential buildings and are presently occupied. Base-isolated buildings of this type have not yet been exposed to the effects of damaging earthquakes.

Report # 77 : Buildings protected with "disengaging reserve elements" (vyklyuchayu-shchiesya svyazi) by Jacob Eisenberg, Svetlana Uranova, Ulugbek T. Begaliev Housing Type: Seismic Protection Systems     Country: RUSSIAN FEDERATION This building type is characterized with a special system of seismic protection called "Disengaging Reserve Elements" (DRE). DRE are installed at the ground floor level of a building, which is typically a RC frame structure. The upper part of the building, usually 9 stories high, is a load-bearing wall structure, either of large-panel RC construction or brick masonry construction. DRE consist of a "rigid structure" (usually RC wall panel) connected to the adjacent RC frame members by means of disengaging restraints. Disengaging restraints are sacrificial reserve elements (fuses) that serve as restraints for the "rigid structures." Typical restraints are steel plates joined together by means of rivets or steel bolts, steel bars, concrete prisms or cubes, etc. Initially, at the lower ground motion level, DRE and RC frame work together; at that stage, disengaging elements transfer lateral loads to rigid structures. DRE is an adaptive seismic protection system whose unique feature, the variable (self-adjusting) rigidity and periods of vibration during an earthquake, prevent resonance. This system is widely used in seismic-prone areas of Russia and Kyrgyzstan. Buildings of this type have not yet been exposed to the effects of damaging earthquakes.

Report # 78 : Reinforced concrete cast-in situ shear wall buildings ("OD"-type, with "fagure" plan) by Maria D. Bostenaru, Ilie Sandu Housing Type: RC Structural Wall Building     Country: ROMANIA This is typical urban multi-family housing practiced throughout Romania in the period from 1965 to 1989. There are many existing buildings of this type at the present time, with about 8,000 apartments in Bucharest alone. Concrete shear wall construction is commonly used for the residential construction and it accounts for over 60% of new housing. Buildings of this type are typically 10 or 11 stories high. The main load-bearing structure is a cast in-situ concrete shear wall structure supported by RC solid slabs. Each building block consists of several (5-6) identical building units ("tronsons" in Romanian) separated by means of seismic joints. The walls are continuous throughout the building height and orientated in two directions, with only one centrally located wall in the longitudinal direction and eight walls in the transverse direction. In addition, there are some lightweight concrete partition walls. This building plan is known as the honeycomb ("fagure") plan. The buildings are often supported by mat foundations due to soft (alluvial) soil conditions. Many buildings of this type were designed according to the 1963 Romanian Building Code (P13-1963) which was updated in 1970 (P13-1970). The 1963 Code considered a magnitude 7 design earthquake for the Bucharest area. This region is well known as a seismically prone area, with the epicentre of damaging earthquakes close to Vrancea. Earthquakes with the Richter magnitude of over 7.0 occur once in 30 years. Bucharest, the capital, is located around 150 km south of the epicentre and lies in the main direction of the propagation of seismic waves. The Bucharest area is located on the banks of the Dâmbovita and Colentina river, on non-homogeneous alluvial soil deposits. During the earthquake of 4 March 1977 (Richter magnitude 7.2), over 30 buildings collapsed in Bucharest, killing 1,424 people. The buildings of "OD" type suffered damages of various extent in the 1977 earthquake, and one building unit ("tronson") totally collapsed (that was the only shear wall building that collapsed in the FIGURE 1A: Typical Building Page 1 earthquake). Buildings with their longitudinal direction aligned parallel with the direction of seismic waves were most affected. The earthquake action in 1977 was mainly in NNE-SSV direction. Out of 167 building units ("tronson"s) of the "OD" type existing in Bucharest at the time of the 1977 earthquake, only 7 were lightly damaged; the remaining building units suffered a partial collapse (7 units) or damages (19 were significantly damaged, 72 were moderately damaged, and 61 were lightly damaged). According to the reports, damages to this construction type were due to inadequate wall density in the longitudinal direction, inadequate amount and detailing of wall reinforcement, lack of lateral confinement in the walls and in the boundary elements ("bulbs") causing brittle concrete failure and buckling of reinforcement. In addition, the quality of concrete construction was found to be rather poor.

Report # 79 : Concrete shear wall highrise buildings by John Pao, Svetlana N. Brzev Housing Type: RC Structural Wall Building     Country: CANADA This concrete shear wall high-rise represents a contemporary residential and commercial construction commonly found in downtown areas of Canadian cities. This multi-family building contains 100 to 200 units and provides housing for 300 to 500 inhabitants. The height of these buildings is variable and usually ranges from 12 to 35 stories. The lateral load-resisting system consists of reinforced concrete shear walls and concrete floor slabs. The gravity load is carried mainly by concrete columns. Seismic detailing of shear walls in medium-to-high seismic regions is mandatory per the Canadian Concrete Code. Exterior walls are clad in stucco backed by cold-form steel framing or masonry veneer, steel/glazing panels, or precast panels. There is no report on the damage sustained by this building type in past earthquakes in Canada. However, because these buildings are designed according to state-of-the-art seismic codes, their seismic performance is expected to be satisfactory in an earthquake of design intensity (per the seismic design requirements of the National Building Code of Canada).

Report # 80 : Low-strength dressed stone masonry buildings by Ravi Sinha, Vijaya R. Ambati Housing Type: Stone Masonry House     Country: INDIA Construction of stone masonry buildings using easily available local materials is a common practice in both urban and rural parts of India. Stone masonry houses are used by the middle class and lower middle class people in urban areas, and by all classes in rural areas. In rural areas, these buildings are generally smaller in size and are used as single-story, single-family housing. In urban areas, these buildings are up to 4 stories high and are used for multifamily housing. This is a typical load-bearing construction, in which both gravity and lateral loads are resisted by the walls supported by strip footing. If the locally available stone is soft, dressed (shaped) stones are commonly used and can be chiselled at low- or moderate cost. Mud or lime mortar has been used in traditional constructions; however, more recently, cement mortar is being increasingly used. Because soft sandstone is readily available in the Kutch region of Gujarat in the western part of India, stone block masonry constructions are widely used for both single- and multi-story constructions. These houses are usually built by local artisans without formal training and the resulting constructions are structurally weak and incapable of resisting large seismic forces. In the Kutch region, which was affected by the 2001 Bhuj earthquake, this construction type is commonly used with a gable end timber roof truss or RCC roof slabs. Thousands of these houses collapsed in the 2001 Bhuj earthquake resulting in the deaths of large numbers of people. This construction type is inherently unsuitable for areas of moderate-to-high seismic hazard, such as the Kutch region of Gujarat.

Report # 82 : Single-family wood frame house by Carlos E. Ventura, Mehdi H. K. Kharrazi Housing Type: Timber Building     Country: CANADA Single-family wood frame construction represents the most common housing construction practice found throughout Canada and constitutes over 50% of the housing stock in British Columbia. A typical Canadian-style modern wood frame house consists of a concrete foundation, upon which a platform is constructed of joists covered with plywood or oriented-strand board (OSB) to form the ground-floor level of the house. This platform is connected directly to the foundation with anchor bolts, or alternatively, supported by a short wall, a so-called "cripple wall," "pony wall," or "stub wall," which should be connected to the foundation with anchor bolts. On this base, the exterior and interior walls are erected, which consist of a horizontal sill plate with vertical timber studs with board or panel sheathing nailed to the studs on the outside of the building. The roof structure typically consists of prefabricated trusses, which are covered with sheathing and roof tiles (Rainer and Karacabeyli 2000). Because this is generally considered to be a non-engineered construction, the Canadian National Building Code does not usually require direct professional architectural or engineering involvement. Specific seismic construction requirements and calculation/design requirements for seismic resistance are currently not included in Part 9 of the Code, which addresses low-rise residential wood frame construction. There is no evidence of substantial damage to this type of construction in past earthquakes in Canada, which have occurred away from densely populated urban centers. However, recent experimental research studies (Earthquake 99 Project at the University of British Columbia), focused on seismic performance of wood frame construction, have revealed vulnerability in this type of construction to seismic effects, depending on the age and wood construction technology.

Report # 83 : Precast concrete panel apartment buildings by Maria D. Bostenaru, Ilie Sandu Housing Type: Precast Concrete Building     Country: ROMANIA This multi-family urban housing construction type was built in Romania from the 1960s through the 1990s. The load-bearing system is a precast-reinforced-concrete large-panel construction. Buildings of this type are typically high-rises (10 or 11 stories), although there are also low-to medium-rise buildings (4 to 8 stories) with different structural details. In general, these buildings consist of a rectangular plan, with a honeycomb ("fagure") layout, typically housing four apartments per floor. Wall panels are laid in both the longitudinal and the transverse direction. The panels are mechanically coupled at the base with continuous vertical reinforcement bars. This region is well-known as an earthquake-prone area, with the epicenter of damaging earthquakes close to Vrancea. Earthquakes with a Richter magnitude of over 7.0 occur, on average, every 30 years. Bucharest, the capital, is located around 150 km south of the epicenter and lies in the main direction of the propagation of seismic waves. The Bucharest area is located on the banks of the Dâmbovita and Colentina rivers, on non-homogenous alluvial soil deposits. During the earthquake of 4 March 1977 (Richter magnitude 7.2), over 30 buildings collapsed in Bucharest, killing 1,424 people. There was no significant damage reported to the buildings of this construction type in the 1977 earthquake. Consequently, this construction technique has continued to be practiced since the earthquake. The building described in this report was built after the 1977 earthquake and so far has not been exposed to damaging earthquakes.

Report # 84 : A single-family, two-storey house with brick walls and timber floors by Maria D. Bostenaru, Ilie Sandu Housing Type: Unreinforced Masonry Building     Country: ROMANIA This type of urban housing was constructed in Romania in the 1930s as single-family housing for the middle class. Typical buildings described in this report are one- or two-story buildings with load-bearing masonry walls. These buildings called "vila" in Romania are characterized by a rectangular plan and are usually semidetached; they share a common wall with the adjacent building. A great variety of buildings exist of this structural type. The building type described in this report has load-bearing brick masonry walls constructed of mud mortar. The floor structure consists of timber planks and joists. These buildings are located in an area well-known to be earthquake-prone. The epicenter is located close to Vrancea and earthquakes exceeding magnitude 7.0 on the Richter scale recur every 30 to 35 years. The latest earthquake of this severity was the March 1977 Vrancea earthquake (M 7.2). However, the building type described in this report is located in the Bucharest area and although affected by the November 1940 Naruja (Vrancea) earthquake (M 7.4), it usually performed well during the 1940 and 1977 earthquakes. The most common type of damage was in the form of cracks and falling chimneys. Some of the older buildings of this type have been affected by other past earthquakes. Because this construction is common for many Romanian buildings of the "Brâncovenesc" architectural style, new retrofit techniques have been developed in recent years (in addition to the techniques used after the 1977 earthquake).

Report # 85 : One family one storey house, also called "wagon house" by Maria D. Bostenaru, Ilie Sandu Housing Type: Unreinforced Masonry Building     Country: ROMANIA This is one of the oldest housing types in Romania with a statistically significant number of buildings in existence. The overwhelming majority of residential buildings in Romania have been built after 1850. Today. only churches remain from the previous "post-Byzantine" period. Issues relating to the age of historical buildings of cultural value are also discussed within the report. This urban housing type is particularly common in Romanian towns, especially in the southern part of the country, such as in the former Wallachia. It is a middle-class family house constructed from the end of the 19th century until the Second World War. The houses were designed to be semidetached, but have been constructed individually. Thus, in most of cases, the adjacent building, separated structurally, is a totally different construction type, The design of this housing is astonishingly homogeneous, especially considering the relatively lengthy time span the construction has been practiced. The single-unit housing is generally characterized by a rectangular, elongated-shape plan, with an entrance on the long side. The load-bearing system consists of two longitudinal unconfined brick masonry walls and several transversal unconfined brick walls, usually 28 cm thick, which form a wagon-like arrangement -- hence the name of this building type. The horizontal structural system is made out of wood plates and joists separated by a distance of 0.70 m. Buildings of this type have been affected by damaging earthquakes in November 1940 and in March 1977, and by two earthquakes of lower magnitudes in 1986 and 1990. They performed well except for the occurrence of some minor cracking in the plaster.

Report # 86 : Single-family wooden house by Norio Maki, Satoshi Tanaka Housing Type: Timber Building     Country: JAPAN Japan has a long tradition related to wood construction. The main building of the Horyuji-temple, which was constructed in the late 7th century, is the oldest existing wooden structure in the world. Most Japanese housing is of wood construction. In 1993, 68.1% of the 45.8 million units of housing stock consisted of wooden structures. However, in newly constructed housing, the percentage of wooden structures is decreasing. In 1995, the percentage of wooden structures in newly constructed housing was 45.5%. The Hanshin Awaji earthquake disaster in 1995 damaged many wooden structures, especially housing that was constructed according to the pre-1980 building code. Despite the severe damage at the time of the Hanshin earthquake and governmental encouragement of seismic upgrading, retrofitting of these houses is not common.

Report # 87 : Block of flats with 11 floors out of cast-in-situ concrete, gliding frameworks by Maria D. Bostenaru Housing Type: RC Structural Wall Building     Country: ROMANIA This is an urban high-rise, built in Romanian cities, especially in Bucharest, during the Communist era. Romania is known as a seismically prone area. The epicenter of damaging earthquakes is near Vrancea and can affect half of the country at one time. Earthquakes higher than magnitude 7.0 on the Richter scale occur once in 30 years. Bucharest, the capital, is located on the banks of the Dâmbovita and Colentina rivers, on non-homogeneous alluvial soil deposits, around 150 km south of the epicenter in the main direction of the seismic wave propagation. This construction type is another example of a building with reinforced concrete shear walls. Unlike the OD type, described in report #78, this construction has more than just a single load-bearing wall in the longitudinal direction, and thus the behavior of the building under seismic loads is significantly improved. These exclusively residential buildings are found in large green-belt areas, in peripheral neighborhoods, either as an isolated building or in groups. Having uniform height and rectangular form, they generally contain four units on a floor. Characteristically, there is a ground floor with either 4 or 10 upper floors. This example is the Y-type, with 10 upper floors. The structural type is the "Fagure" (honeycomb) one, commonly used in Romanian construction practice. Although the perimeter walls are load-bearing, there are wide openings in them. During the earthquake of 4 March 1977 (Richter magnitude 7.2), over 30 buildings collapsed in Bucharest and killed 1,424 people. This type of building behaved rather well, with only superficial damage observed. Seismic strengthening was thus limited to repairs, where necessary.

Report # 88 : Confined brick masonry house by Marjana Lutman, Miha Tomazevic Housing Type: Confined Masonry Building     Country: SLOVENIA This is a very common single-family residential construction practice found throughout Slovenia, both in urban and rural areas. It is estimated that this construction accounts for approximately 40% of the entire housing stock in the country. Confined masonry has been practiced since the wide use of perforated clay blocks has started in the 1970s. The walls are constructed using perforated clay blocks in lime/cement or cement mortar. The main confining elements include horizontal reinforced concrete bond beams constructed atop the structural walls at each floor level, and vertical reinforced concrete tie-columns at the wall intersections. Floors are either of composite construction, consisting of concrete joists and hollow masonry tiles, or cast in-situ reinforced concrete slabs. Timber roofs are typically used in this type of construction. Since the first national seismic code was issued in 1964, the use of vertical reinforced concrete tie-columns is typically prescribed by the structural design. However, many existing houses were constructed without these critical structural elements. An additional deficiency characteristic for this construction practice is the absence of the top bond-beams along the gable walls (crown beams). This construction is expected to show good seismic performance. Buildings of this type were generally not affected by the past earthquakes in Slovenia.

Report # 89 : Traditional adobe house without seismic features by Virginia I. Rodriguez, Maria I. Yacante, Sergio Reiloba Housing Type: Adobe / Earthen House     Country: ARGENTINA This construction type is used as a single-family house. It is a single-story, detached building, found in the rural and suburban areas of the province of San Juan. This traditional type of construction is built with adobe walls and no cornice. The traditional adobe house has a range of deficiencies: weak connections, heavy roofs, adobe blocks that deteriorate (especially at the base of the walls) due to prolonged exposure to humidity. This housing type is expected to perform poorly in earthquakes.

Report # 91 : Single-storey brick masonry house (EMSB1) by Mehedi Ansary Housing Type: Unreinforced Masonry Building     Country: BANGLADESH This is a one-story brick masonry house of fired bricks with cement or lime mortar; roof is either GI sheet or another material. These houses can be seen throughout Bangladesh. During the 1918 Srimangal, 1930 Dhubri, and other recent earthquakes, this type of housing suffered heavy damage. Houses with a continuous lintel suffered less.

Report # 92 : Historic, braced frame timber buildings with masonry infill ('Pombalino' buildings) by Rafaela Cardoso, Mario Lopes, Rita Bento, Dina D'Ayala Housing Type: Others     Country: PORTUGAL Pombalino buildings (see Figures 1, 2, 3 and 4) are historic masonry buildings that can be identified by the presence of a three-dimensional timber structure (named "gaiola pombalina"), which is enclosed in internal masonry walls above the first floor. The roofs are built with timber trusses clad with ceramic tiles and the floors are made of timber boards laid on timber joists. Ground floor walls are roughly dressed stone masonry supporting a system of vaults made of clay tiles, with stone arches. Foundations are made of short and small-diameter timber piles connected by a timber grid. These buildings were built after the 1755 earthquake when fear of new earthquakes led to the enforcement of anti-seismic provisions, such as establishing a maximum number of stories and introducing an interior timber structure called "gaiola." The buildings originally were mixed-use with commercial enterprises on the ground floor and residences on the upper floors. During the 20th century, most Pombalino buildings underwent substantial refurbishment when they were converted and occupied entirely by banks and companies. For the buildings that have maintained their original uses, the main problems result from poor maintenance.The expected collapse mechanisms due to earthquake actions are the overturning of facades (out-of-plane) or shear failure at the plane of the walls at ground floor level (global shear mechanism), leading to a global collapse mechanism. Typical seismic strengthening of these buildings includes the introduction of a concrete/steel ring beam at the level of the roof eaves. The introduction of steel elements/pre-stressed cables or of anchors connecting parallel masonry walls is also common. Steel elements are also used to connect detached timber elements from the floors and gaiola to the masonry. New techniques applying new materials like Fibre Reinforced Polymers (FRP) are also used to increase the strength of the connections of timber elements that compose the gaiola.

Report # 95 : Prefabricated metal construction of the Modern Movement by Maria D. Bostenaru Housing Type: Steel Moment Frame Building     Country: GERMANY This urban housing construction was practiced for about 20 years during the early 1900s in Germany. Single-family houses and blocks of flats, both built according to the same construction system, are included in this report. This construction was built in what were once the outlying areas of German cities. Typically, these low-cost housing units are rented by the residents. The buildings consist of a row of several individual, 20-meter-long units, each of which usually contains two apartments on each floor. The load-bearing system is iron skeleton with brick infill. Usually, the skeleton is made out of columns and beams, but dense column grids were sometimes used to minimize the spans of metal joists as a cost-saving measure. Experiments with various materials for the bricks were tried as part of the continuous search for improved insulation. The floors are also made out of bricks on iron joists. Stiffening is usually provided by diagonal ties at the staircases, which are placed in the middle of each building unit. Because of the seismic activity, both along the Rhine and in the Swabian Jura affecting Baden-Wuerttemberg, seismic codes (DIN) were issued in 1981 and have been updated. Standards have existed since 1957 and are expected to be included in the new European code, Eurocode 8.

Report # 96 : Early RC frame condominium building with masonry infill walls designed for gravity loads only by Maria D. Bostenaru Housing Type: RC Moment Frame Building     Country: ROMANIA This urban housing construction was practiced in Romania from 1907-1945, but predominantly in the 1930s, in the capital city of Bucharest. These buildings are mid- or high-rise (5-10 upper floors), often with two basements. Although there are several functional variations according to the usage and combination of flats, offices, and shops, this report discusses exclusive housing use. The number of housing units is variable. While smaller mid-rise buildings may contain one large luxury unit on each floor, taller buildings may include as many as eight small one-room flats, sometimes without a kitchen. The shape of the plan, containing L, U, H, or forms that cannot be described geometrically, and the elevation of the building are highly irregular. Upper floors may have recesses in the facade and may have corner towers. The load-bearing structure is RC skeleton designed for gravitational loads only. Columns are unevenly distributed so that beams at least one end are supported as secondary beams. Some beams are supported by columns with inadequate reinforcement or reduced sections of the RC members impede the formation of moment-resisting frames. The facade walls have solid clay brick masonry infill and improve the seismic behavior. The beneficial effect of masonry infill is influenced by the wall thickness, the size/position of openings in walls and the position of the partition wall to the frame. Staircases and elevators weaken the structure by introducing concentrated holes in flexible, thin RC slabs. Bucharest is located on alluvial soil deposits on river banks. Sandy ground or high levels of underground water have often presented problems for the foundation of buildings. Damaging earthquakes (M>7.0), centered in Vrancea, recur three times every century. These buildings were affected by the 1940 and 1977 earthquakes, but performed well relative to their high vulnerability. Out of the 61 buildings heavily damaged in the 1977 earthquake, 28 were of this type but were high-rise (7-9 floors).

Report # 97 : Medium/high rise moment resisting reinforced concrete frame building by Maria D. Bostenaru Housing Type: RC Moment Frame Building     Country: ROMANIA Such buildings generally range from 10 to 17 storeys in height with the ground floor being used for commercial purposes, whilst the upper floors house residential units. The vertical load bearing structure consists of moment-resisting reinforced-concrete frames which also generally serve as the lateral load-resisting system. However, when larger spans are encountered, reinforced-concrete structural walls are included to provide a dual structural system. Masonry infills built from lightweight concrete masonry units provide architectural space delineation. The seismic performance of such buildings constructed prior to 1977 varies from no damage to complete collapse. To date damage has usually been attributable to conceptual and construction mistakes.

Report # 99 : Traditional Nawari house in Kathmandu Valley by Dina D'Ayala, Samanta S. R. Bajracharya Housing Type: Unreinforced Masonry Building     Country: NEPAL The traditional newari house is usually of rectangular plan shape and developed over three storeys. The depth of the plan is usually about six metres with façades of various widths but most commonly between 4 to 8 metres (see also Korn 1976, and NSET-Nepal 2000). The organisation of the house is usually vertical, over 3 storeys, with a spine wall running through the height, creating front and back rooms. At the upper storey the spine wall is sometimes replaced by a timber frame system so as to create a larger continuous space. The staircase is usually a single flight to one side of the plan. The typical interstorey height is quite modest, between 2.20 and 2.50 m., including the floor structure. The bathroom, where present, is found at ground floor, while the kitchen is on the top floor, usually directly under the roof. The first floor is traditionally used as bedrooms, while the second floor is used as living room and for visitors' reception. There are essentially two types of clusters of houses, either in long arrays, or around a court or chauk . In some cases the two types of clusters are adjacent with some units in common. In the arrays each house has front and back façade free. The construction of each unit is usually independent so that the facades are not continuum over party walls but each unit forms a separate cell. In such cases connection between façades and sidewalls are usually very good. The most interesting characteristic of these buildings both from an architectural and seismic point of view is the presence of the timber frame. Usually at ground floor, on the facade, to provide an open space for workshops or shops. It is also found internally at the upper storeys. In some cases the masonry only forms the outer shell while the internal structure is all made of timber elements. In the better built example of this typology there are a number of construction details, usually made of timber, which, coupled with the brick masonry walls, substantially improve the seismic performance of the overall structure. These features are best preserved in older examples. Currently these buildings are substantially being altered by use of western materials and technology, typically adding concrete frames as upper storeys. This type of intervention highly increases the vulnerability of the existing buildings.

Report # 101 : Tunnel form building by Ahmet Yakut, Polat Gulkan Housing Type: RC Structural Wall Building     Country: TURKEY This type of rapidly constructed, multi-unit residential form has been used in Turkey since the late 1970s and early 1980s. It has demonstrated superior earthquake resistance and has also been increasingly utilized as permanent housing in post-earthquake reconstruction programs. Initially, the tunnel form building was targeted for multi-unit residential construction for public or privately sponsored housing projects. Typically, a single building may contain 15 or more stories and up to 40 or 50 residential units. This contribution has been motivated by our intention to not only familiarize readers with the architectural or structural features of the building type, but to also underscore its noteworthy seismic performance that stands in stark contrast to Turkey's recent experience.

Report # 103 : Single-family reinforced concrete frame houses by Mohammed Farsi, Farah Lazzali Housing Type: RC Moment Frame Building     Country: ALGERIA This privately owned housing constitutes about 60 to 70% of the housing stock and is widespread throughout northern Algeria, the region of the country's highest seismic risk. Generally, these buildings are from 1 to 3 stories high. The ground floor is used for parking or for commercial purposes. The structural system consists of reinforced concrete frames with masonry infill walls made out of hollow brick tiles. The infill walls are usually provided in the residential part of the building (upper floors). Due to the limited amount of infill walls at the ground floor level, these buildings are characterized by soft-story behavior during earthquakes. These buildings have most often been built after the development of the 1981 Algerian seismic code. However, the seismic code is not enforced in private construction and most of the buildings have been built without seismic strengthening provisions and historically have been severely affected in Algerian earthquakes, including the May 21, 2003 Boumerdes earthquake. This report does not describe reinforced concrete frame buildings financed by public or private property developers and built according to the seismic code.

Report # 104 : Adobe House by Mehrdad Mehrain, Farzad Naeim Housing Type: Adobe / Earthen House     Country: IRAN This building type is typically one or two stories and used for single-family housing. It is more predominant in the desert, in cold-weather, or other inhospitable climates. It has a large mass and basically no strength, particularly against out-of-plane wall forces. These buildings are the most seismically vulnerable. In the 2003 Bam earthquake, collapse of these buildings was widespread and contributed to many of the 43,000+ deaths. The typical mode of collapse is out-of-plane failure of the walls, resulting in loss of support for the roof. Adobe construction is widespread throughout Iran, and is used both by wealthy families in luxury residences, as well as by poor families in more modest dwellings.

Report # 107 : Reinforced Adobe by Daniel Quiun Housing Type: Adobe / Earthen House     Country: PERU This is a reinforcement system for existing adobe houses, as well as an adaptation for new adobe houses, with the objective to prevent their collapse under severe earthquakes. An extensive experimental research project was developed between 1994 and 1999, with the financial support of GTZ of Germany, the administration of CERESIS, and the execution of the Catholic University of Peru (PUCP). Several reinforcement techniques were studied, and it was concluded that the most appropriate was to reinforce the walls with horizontal and vertical strips of wire mesh electrically welded, covered with mortar. The technique was applied in 1998 as pilot projects in 20 houses in 6 cities in Peru. Later in 1999-2000 it was extended to Chile, Bolivia, Ecuador and Venezuela. We had to wait for an earthquake to assess the effectiveness of the reinforcement. In the earthquake of June 23, 2001 (Mw=8.4), that affected the south of Peru, six reinforced adobe houses had no damage. Neighboring dwellings of unreinforced adobe suffered heavy damage or collapsed. This success motivated several reconstruction programs of new reinforced adobe houses in the Andean zone, in which the technique was improved and applied in more than 500 houses, which are described herein. Shaking table tests on the system used in the new houses at the Structures Laboratory of PUCP demonstrated that the reinforcement provided is effective for resisting severe earthquakes without collapse. The August 15, 2007 Pisco earthquake (Mw8.0), 200 km south of Lima, also provoked the collapse of many traditional adobe houses. In Ica province, 5 houses were reinforced in 1998 using the wire mesh strips, and all withstand the earthquake undamaged.

Report # 108 : Half-timbered house in the "border triangle" (Fachwerkhaus im Dreiländereck) by Maria D. Bostenaru Housing Type: Timber Building     Country: SWITZERLAND This type of construction can be found in both the urban and rural areas of Germany, Switzerland, northern France, and England. The main load-bearing structure is timber frame. Brick masonry, adobe, or wooden planks are used as infill materials depending on the region. This report deals with the two latter types, because they are located in areas where strong earthquakes occur every century. However, this construction has proven particularly safe, and some of the buildings have existed for 700 years. These buildings have characteristic windows and a rectangular floor plan, with rooms opening to a central hall, which were later replaced by a courtyard. Typically, each housing unit is occupied by a single family. While in the past this was the housing of the poor, today affluent families live in these historic buildings. The load-bearing structure consists of a timbered joists and posts forming a single system with adobe or wooden infill. The walls consist of a colonnade of pillars supported by a threshold on the lower side and stiffened by crossbars and struts in the middle. On the upper part they are connected by a "Rahmholz." The roof is steep with the gable overlooking the street. The floors consist of timber joists parallel to the gable plane with inserted ripples. The only notable seismic deficiency is the design for gravity loads only, while numerous earthquake-resilient features - the presence of diagonal braces, the achievement of equilibrium, the excellent connections between the bearing elements, the similar elasticity of the materials used (wood and eventually adobe) and the satisfactory three-dimensional conformation - have completely prevented patterns of earthquake damage. Since 1970, buildings in Switzerland are regulated by earthquake codes (latest update 1989). The 2002 edition will incorporate EC8 recommendations.

Report # 109 : Concrete Shear Wall Buildings by Luis G. Mej, Juan C. Ortiz R., Laura I. Osorio G. Housing Type: RC Structural Wall Building     Country: COLOMBIA These buildings are characterized mainly by cast-in-place, load-bearing, reinforced-concrete shear walls in both principal directions. The buildings are usually multiple housing units found in the major urban areas of Colombia, especially in the Andean and Caribbean regions. They represent about 2 to 3% of the housing stock in the cities with a population between one to seven million. These buildings typically have 7 to 20 stories, generally with a cast-in-place reinforced-concrete floor slab system. In general, these buildings have good seismic performance because of their regular mass distribution in height and symmetrical plan configuration and the great stiffness and strength of the walls that can restrict story drift to less than or equal to 0.005h. In some cases, if the buildings were constructed after the first Colombian Seismic Code in 1984, poor seismic detailing is found.

Report # 111 : Reinforced Concrete Moment Frame Building without Seismic Details by Heidi Faison, Craig D. Comartin, Kenneth Elwood Housing Type: RC Moment Frame Building     Country: USA This report examines reinforced concrete buildings that use moment-resisting frames without ductile detailing to resist seismic loads. While this building type is predominantly used for office buildings and hotels, it is also used in urban areas for multi-family dwellings (condominiums) and university dormitories. It can be found in most urban areas across the country, though it is of particular concern in areas of high seismic hazard like California, Alaska, Washington, and Oregon. Building codes did not include requirements for special seismic detailing of reinforced concrete structures until the 1970's when several earthquakes demonstrated the need for more ductile design. These buildings are vulnerable to numerous failure modes including: failure of column lap splices; strong beam/weak column failures; captive column failure; punching shear failures in flat plate slabs; and shear and axial load failure of columns with wide transverse reinforcement spacing. A discontinuity in stiffness and strength at the bottom story, due to a soft story, often results in a concentration of earthquake damage at the building base. Several examples of past earthquake behavior are given in this report as well as discussion of various retrofit options.

Report # 112 : Unreinforced brick masonry residential building by Qaisar Ali Housing Type: Unreinforced Masonry Building     Country: PAKISTAN In Peshawar and adjoining areas (in northern Pakistan), the most popular residential construction is a single- or double-story unreinforced masonry building with 9-inch-thick, solid burnt-brick walls and a 5- to 6-inch reinforced-concrete roof slab. Sometimes, however, 4.5-inch solid brick walls are also used as load-bearing walls. The layout of these dwellings is usually regular, mostly rectangular, having horizontal dimensions in the range of 30 ft x 60 ft or 60 ft x 90 ft, etc. Building height rarely exceeds 35 ft. Wall connections at the corners are achieved through proper toothing. Lintels, approximately 6- to 9-inches deep, with a width equal to the wall thickness, are provided above openings. In a relatively engineered construction, however, the lintel beam runs throughout the perimeter. Similar residential buildings are also found in other cities of Pakistan, for example, in Islamabad and Lahore. In Karachi, Pakistan's largest city, concrete frame structures with concrete-block infill walls are most often used.

Report # 113 : "Casa Torre" construction: multistory tower masonry with stone pillars and wood or arched beams by Mauro Sassu, Chiara Cei Housing Type: Stone Masonry House     Country: ITALY This construction originated during the Middle Ages in response to the threat of military invasions. The building plan is a square lattice, 5-7 meters, formed by three or four floors, with one room on each floor, and a total height of 15-20 m. It is a common technique found in Pisa but also found frequently in many municipalities of Tuscany and adjacent districts. The structure of the building is supported by four stone columns connected by arches (circle or oval) or by beams at each floor; the floor is supported by a series of wood beams (especially pine) with wood tables and/or clay blocks. The upper floors of the earlier historic buildings often contained a wood balcony supported by cantilevered wood beams. Some balconies were fully enclosed structures with clay-tile roofing. The entrance on the first floor could be accessed by means of a detachable wood staircase.

Report # 114 : Stonework building with wooden timber roof by Masoud N. Ahari, Alireza Azarbakht Housing Type: Stone Masonry House     Country: IRAN Stonework buildings are a common type of rural construction in many parts of Iran (Figure 32). It is widely used in the mountainous areas because of the ease of attaining the building material. More than 71,000 stonework buildings were built in 1968-1972 in comparison to 54,000 brick masonry buildings in these years [1]. Unfortunately these buildings are often found in highly seismic parts of Iran (see maps on WHE webpage for Iran). Buildings of this type are up to two stories high, with height/width aspect ratio on the order of 0.3-0.5. The building materials consists of stone, wood, mud mortar and straw. The major elements of these systems are stonewalls which carry both gravity and lateral loads. These walls consist of stone or stone ballast with mud mortar and straw. For reasons of thermal insulation the thickness of these walls is not less than 50 centimeters (usually 70 centimeters). Details of wall are shown in Figures 11 to 20. The roof includes wooden joists and a set of secondary joists which are plastered with a thick layer of mud (Figures 21 and 22). Different views of this kind of building are shown in Figures 1 to 3. Also a typical building view, plan and layout are shown in Figures 4 to 10. Weak points of this construction type are: the presence of a heavy roof; inadequate behavior of the walls under out-of-plain forces (Figures 23 and 24); poor shear capacity of the mortar; inadequate connection between roof and walls; inadequate connection between intersecting walls; and lack of diaphragm action in floors and roof where the roof elements (wooden beams) do not work together in earthquakes and may collapse (Figures 25 and 27). In general, this kind of structure is frequently used as a house and stable in mountainous villages, but its earthquake performance is not acceptable. Any proper rehabilitation techniques may save many people's lives.

Report # 115 : Reinforced concrete multistory buildings by Mario Rodriguez, Francisco G. Jarque Housing Type: RC Moment Frame Building     Country: MEXICO This report describes Reinforced Concrete (RC) multistory residential buildings in Mexico. This type of construction is found mostly in large cities where space limitations lead to this type of solution. Typically buildings of this type have eight or more stories. Members of the middle and upper classes are the target market for this type of construction. In areas of low seismic risk, waffle slab floor systems without structural RC walls are preferred by developers primarily due to their speed of construction. In areas of medium to high seismic risk, it is typical for this type of building to have a dual system, which combines RC moment frames and RC structural walls as the main lateral load resisting elements. The RC floor systems are constructed of waffle slabs or solid slabs. RC buildings account for about 80% of the entire housing stock in Mexico. Buildings constructed after 1985 are expected to perform well under seismic forces, especially in Mexico City, where the building construction code has been substantially updated to incorporate lessons learned during the 1985 earthquake.

Report # 116 : Timber Frame Brick House with Attic by Amit Kumar, Jeewan Pundit Housing Type: Unreinforced Masonry Building     Country: INDIA This type of house is used for residential purposes. The building type under study has been picked the from central part of India (Madhya Pradesh), but it is found throughout India with small or large variations. Timber is primarily used for the frame structural elements but due to an acute shortage of timber, this construction type is not practiced anymore. Various components of the building change from place to place depending on climate, socio-economic conditions, availability of material, etc. Timber frames, placed in longitudinal and traverse directions, are filled with brick masonry walls. The floor structure is made of timber planks. Most of the buildings are found to be rectangular in shape with few openings. The roofing material is usually light when it is made from galvanized iron sheets. Seismic performance of a perfectly framed building is very satisfactory. Existing old structures, however, require maintenance and strengthening (Figure-1a,1b). It has been observed that nominal cost will be incurred for introducing earthquake resistant features.

Report # 117 : Four arches (Char taaqi) with dome-roof structures, and unreinforced brick and adobe materials. by Nima T. Bekloo Housing Type: Unreinforced Masonry Building     Country: IRAN The 'Four arches' or Char Taaqi (in Persian) derives its name from the four arches that connects tops of four timber or masonry piers enclosing the space. It is an equilateral architectural unit consisting of four arches or short Barrel vaults between four corner piers, with a dome over the central square; this square and the lateral bays under the arches or barrel vaults together constitute a room of cruciform ground plan. This structural system developed about 2500 years ago, after earring system in the Old Persian Empire (Sasanian age). Main goal of this building system was to create wide openings at four side of the structure. This building system was used for special places that carry high population like fire temple (place where Persians worshiped the Fire God), mosque, bazaar and other public places. This is not that difficult to built a dome over four arches. Further, dome structures are ideal for large span structures against gravity loads as it transforms them into horizontal and shear loads. In addition, for lateral loads, domes behave like a truss and distribute the load to other parts of the structure developing a perfect load path. This construction system has been considered, the most prominent structural system in traditional Iranian architecture. These are basically monumental buildings developed close to desert where there was not enough construction materials that could take tensile stresses.

Report # 118 : Earring system (Shekanj) in dome-roof structures with unreinforced brick and adobe materials by Nima T. Bekloo Housing Type: Unreinforced Masonry Building     Country: IRAN This building structure derives its name from the four earrings that are constructed at the four corners of a rectangular building at the spring level of dome roof. This structural system was developed due to the lack of of wood and stone. It was widely constructed more than 3 thousand years ago, after the invention of the dome-roof structures in the Old Persian Empire (Ashkanian & Sasanian). The main problem with the dome-roof building was to transform the rectangular or polygonal plan of the group of walls into the circular plan at the spring level of dome roof. They used to construct the first row of dome and then construct another row on top of previous one with a little offset closer to the center of the dome circle and so on. That was too difficult to construct. This system was invented to resolve this problem. In this system, once the walls were constructed, four earrings (shekanj) built upon four corners of walls intersections, and then it was much easier to build a dome over these. It is an ideal system to resist vertical and gravity loads and transform them into horizontal and shear loads. For lateral loads, domes behave like trusses and distribute the load to the other parts of the structure creating a perfect load path.

Report # 119 : Urban residential buildings of the 19th century in the city of Basel by Kerstin Lang, Hugo Bachmann Housing Type: Stone Masonry House     Country: SWITZERLAND This building type was mainly constructed as residential buildings in the second half of the 19th century until the beginning of the 20th century in the vastly expanding city of Basel, but also in other Swiss cities. The buildings are made of unreinforced masonry with timber floors, are four to five stories high and are attached to each other. The unreinforced masonry walls are usually made of simple stone (more or less regularly cut) or brick masonry, the thickness of the stone masonry walls being larger. The mortar used is usually lime mortar. In some cases, a mixed masonry was used, especially at the ground floors, with larger, well cut stones for the outer layer of the façade walls and simple stones or bricks arranged behind. The buildings are rather regular in plan and elevation. However, the timber floors are often not anchored to the masonry walls and the front and back façades usually have rather large openings for the windows whereas the side walls are solid walls used as fire division wall. The seismic performance of these buildings is expected to be rather poor.

Report # 120 : Unreinforced stone wall rural housing (upper income) by Riccardo Vetturini, Anacleto Cleri, Fabrizio Mollailoli, Paolo Bazzurro Housing Type: Stone Masonry House     Country: ITALY This is a typical house occupied by affluent families in rural areas of central Italy. The building discussed in this report is called "Palazzo Spinola" and is located in the town of Foligno in the Umbria region (see Figures 1 and 2). The building has four stories above ground and a completely below-grade basement. Floor plans and cross sections are shown in Figures 3 to 9. Significant geometrical complexity has resulted from additional construction since it was originally built in the seventeenth century. The original construction includes only a portion of the interior building as well as the entire exterior façade. The building has an interior courtyard within the perimeter of the building. It contains a well and a cloister (a covered path with ornate columns) that separates it from the grounds. These are also part of the original construction and have significant artistic value. The upper portion of the cloister is accessible and serves as a connection between the two exterior wings of the residence. The thick walls are constructed using a typical technique called "a sacco." This construction technique consists of two outer wythes that are poorly connected by transversal bond-stones ("diatoni") and filled with essentially unconsolidated inner cores of rubble masonry, poorly cemented with lime mortar. The floor slabs may be of mixed construction, depending on the era. The ground floor has "a padiglione" vaulted ceilings, which are constructed of solid bricks assembled in fairly regular fashion. The second-floor ceilings are vaulted and partly frescoed. Some of the ceilings in the residence have great artistic value, with painted wooden panels ("cassettoni"). The floor slabs on the upper stories are considerably simpler in construction and are made of timber trusses with hollow-clay tiles in between. The structure supporting the roof is made of timber trusses with both vertical and diagonal struts and bottom chords. Some trusses are more complex, similar to Palladian trusses. Buildings of this type are expected to demonstrate fairly poor seismic performance, mostly due to the ineffective connection between interior and exterior wall wythes and existing structural deficiencies (e.g., flues, niches, etc.); lack of effective wall-to-wall, wall-to-slab, and wall-to-roof connections; and the unbalanced outward thrust of the vaults. The structural strengths are represented by very thick walls present throughout the building, especially at the foundation level, and by the occasional iron tie-rods.

Report # 121 : Unreinforced stone wall rural housing (lower and middle income) by Riccardo Vetturini, Fabrizio Mollailoli, Paolo Bazzurro Housing Type: Stone Masonry House     Country: ITALY Typical house occupied by low-income and middle-class families in rural areas of central Italy. The building studied in this report is located in the municipality of Nocera Umbra, province of Perugia, Umbria region, Italy. This type of building, with minor differences in construction practice and material, is frequently found throughout central Italy. The four-story building was constructed more than 200 years ago and is located on a steep hillside, with the elevation facing the valley completely above grade; the uphill elevation is two stories above grade, with the two stories below ground-level surrounded on two sides by earth-retaining stone masonry walls. This building was severely damaged by the 1997 Umbria-Marche earthquake and was further weakened by the elements before repair and reconstruction efforts began in 2003. Figures 1 through 5 show the damaged building before reconstruction. Figure 6 helps to locate this building in the cluster of buildings around the old citadel. The exterior elevation facing the downhill slope is displayed in Figure 7. The overall floor plan of this building is L-shaped; it accommodates two residential units and has a basement with four separate spaces and entrances for housing farm animals and storing tools. Building plans showing the extent of wall and floor reconstruction can be seen in Figures 8 to 10. Figures 12 to 14 display details of the seismic retrofit. Most buildings of this type, however, are smaller in size, rectangular in shape, and often have one unit. It is very common for these buildings to share perimeter walls with adjacent buildings. In these rural regions it is typical for many generations of a single family to live in the same residence and the building has undergone numerous additions and modifications over its life span to accommodate changing living requirements. The construction modifications are typical of Italian rural regions. The architecture is fairly plain with few architectural details of significant historic value; these were repaired and restored during the seismic reconstruction project. Gravity loads in the building are carried by thick unreinforced stone walls constructed using a technique referred to as "a sacco". The walls consist of two outer stone wythes that are poorly connected by a limited number (if they are present at all) of bond-stones. The space between the two outer wythes is filled with an inner core of smaller rubble masonry, poorly consolidated and poorly graded by a mixture of lime or mud mortar. This construction technique results in walls with limited vertical and lateral capacity because of the presence of voids between the stone masonry and the lack of effective continuity between the inner and outer wythes. The pre-earthquake construction technique and the quality of the mortar in the stone masonry walls were poor. The lack of continuity between the original stone masonry walls and the walls constructed during the various structural additions worsened their condition (see Figure 4). The majority of the floor slabs are constructed of timber beams with intermediate timber joists. Other areas of more recent vintage consist of vaulted floor construction assembled from steel beams and clay-infill bricks arching between them with a lightweight concrete topping layer. Poor seismic performance is expected, mostly because of the ineffective connection between interior and exterior wythes of the walls and existing structural deficiencies (e.g., flues, niches, etc.); lack of effective wall-to-wall, wall-to-slab, and wall-to-roof connections; and lack of continuous foundation-to-roof walls due to the vertically unaligned openings on the façade. Very thick walls present throughout the building, especially at the foundation level, and occasional iron tie-rods add to the structural strength.

Report # 134 : Adobe with timber and clay tile roof by Matthew A. French Housing Type: Adobe / Earthen House     Country: HONDURAS Adobe is commonly used in Honduras predominantly in rural areas in the western regions. The performance of adobe buildings in seismic events has been very poor, but for many rural poor in Honduras, there is no other option but to use this construction method. The building has a simple plan with three rooms of equal size. The roof is sawn timber with clay tiles.

Report # 136 : Adobe with sawn timber roof framing and corrugated iron sheeting by Matthew A. French Housing Type: Adobe / Earthen House     Country: GUATEMALA This very small building doubles as a home and workplace. The homeowner weaves products such as hats, clothes and mats for a living. The building functions as a showroom for her products by the day and as her house for rest at night. Three months before the site visit, the house was washed away by Hurricane Stan that hit the Central American region. Massive rainfall led to landslides in the Lago Antilian area, where the site is located. Her house was destroyed and this is the new one constructed. This case study is characteristic of new adobe construction in the Guatemala today. Timber dowels at the top brick course help to secure the ring beam or timber roof framing to the walls. For economic reasons, the roof is corrugated iron, but the long-term plan is to place clay tiles directly over top for their thermal and aesthetic properties. This case study is testament to the trying and tenuous living conditions which the occupants face. It demonstrates that even though un-reinforced adobe fails, many have no option but to replace it with structurally fragile adobe once more.

Report # 137 : Adobe walls supporting rough timber framed roof with corrugated iron sheeting. by Matthew A. French Housing Type: Adobe / Earthen House     Country: NICARAGUA The plan of this adobe building is a simple rectangle with three rooms. Adobe as a material is very weak under seismic loads, which is the main issue which concerns this building type. Also, the roof does not have sufficent eaves to protect the adobe walls, which has resulted in the dislodging of the exterior plaster. This has erroded the walls, further reducing their structural strength. Adobe is commonly used in Nicaragua, as it is both affordable and accessible, but it is being replaced by more 'modern' materials, such as concrete block and red fired brick.

Report # 138 : Stone masonry residential buildings by Qaisar Ali, Taj Muhammad Housing Type: Stone Masonry House     Country: PAKISTAN In the Northern part of Pakistan, which mostly consists of mountainous terrain and where building stones are more abundantly available than any of the alternate building material, people commonly construct single story stone masonry buildings for residential purpose. A variety of building typologies are in use. An approximate distribution of common types of such buildings is:- Stone masonry houses without mortar with earthen roof (Fig 1a). 10% Stone masonry houses in mud mortar with earthen roofs (Fig 1c). 40% Stone masonry houses in cement mortar with earthen roof (Fig 1d). 10% Stone masonry houses in cement mortar with G.I.Sheet roof (Fig 1f). 30% Stone masonry houses with R.C roofing (Fig 1g) 10%. Construction of houses in rubble stone masonry, in dry or in mud mortar, was most common and was generally practiced in the past in these areas. It is still in practice in most construction. Presently, among all, about 50% of the buildings are of this type. In new construction mud mortar is steadily being replaced with cement mortar. Wall thickness in all cases usually varies from 1 to 1 ½ ft. Roofs are usually earthen and generally consist of thatch covered with mud/earth and supported on wooden beams (or logs) and rafters. Some time wooden columns are also provided beneath the beams along the walls or in between the walls to support the roofing. Wooden rafters, planks and G.I. sheets are also used in modern construction for roofing. Any particular or regular layout is not used for construction of these residential buildings. It varies depending on the available space. Size of the building also varies from a single room to more than one room as per requirement of the family (Figs 3a--3c). These structures are considered, from experience, to be strong enough to withstand the applied gravity loads, but their seismic performance has not properly been investigated and is believed to be vulnerable to earthquake of even moderate shaking, particularly when confining elements such as wooden columns are not used. In a typical type of construction, historically known to be well resistant to seismic effects, horizontal and vertical wooden members are provided in the walls. These horizontal and vertical members are inter-connected at corners and other locations through wooden nails. The remaining space of the wall is then built in stone masonry of any type. This type of construction was commonly practiced in remote North parts of this region in the past and is still in practice for improved seismic performance in some of the buildings (figs 5a--5e).

Report # 141 : Vivienda de Bahareque by Dominik Lang, Roberto Merlos, Lisa Holliday, Manuel A. Lopez M. Housing Type: Timber Building     Country: EL SALVADOR The bahareque construction type refers to a mixed timber, bamboo and mud wall construction technique which was the most frequently used method for simple houses in El Salvador before the 1965 earthquake (Levin, 1940; Yoshimura and Kuroki, 2001). According to statistics of the Vice-ministry of Housing and Urban Development in the year 1971 bahareque buildings had a share of 33.1 % of all buildings in El Salvador, while in 1994 the percentage of bahareque declined to about 11 % (JSCE, 2001b) and in 2004 to about 5 % (9 % in rural areas; according to Dowling, 2004). The term 'bahareque' (also 'bajareque') has no precise equivalent in English, however in some Latin American countries this construction type is known as 'quincha' (engl.: wattle and daub). In order to prevent confusion it should be noted, that in El Salvador the term 'bahareque' is used for all types of this mixed construction type regardless the material of the horizontal elements (struts). Bahareque buildings are characterized by high flexibility and elasticity when carefully constructed and well-maintained, and thus originally display good performance against dynamic earthquake loads. However, bahareque buildings in most cases show high vulnerability during earthquakes. This is caused by poor workmanship (carelessness and cost-cutting measures during construction), lack of maintenance (resulting in a rapid deterioration of building materials), and structural deficiencies such as a heavy roofing made out of tiles. Bahareque structures are primarily of residential use and only one story. The structural walls are mostly composed of vertical timber elements and horizontal struts which are either made of timber slats, cane/reed (carrizo), bamboo (vara de castilla, caña brava or caña de bambú) or tree limb (ramas). These members are generally 2- to 3-inches thick and are fastened at regularly spaced intervals from the base to ceiling height at the vertical elements (with nails, wires or vegetal fibers). This creates basketwork type skeleton which is then packed with mud and clay filler combined with chopped straws (or sometimes with whole canes), and covered with a plaster finish in some cases. In rural areas, the walls are often left plane, without any lime plaster and whitewash, or paint, which gives them a wavy surface with an unfinished character. It should be noted that bahareque houses in rural areas are quite different from those in urban areas both in terms of their esthetical appearance as well as their structural capacity (cf. Figures 1 and 2).

Report # 143 : Mud House of Bangladesh by Amrita Das, Mohammad Shariful Islam, Dr. Md. Jahangir Alam, Nusrat Hoque Housing Type: Adobe / Earthen House     Country: BANGLADESH In Bangladesh, a mud house is one of the traditional housing types that are used by poor families mainly in rural areas as well as in the outskirts of small cities. This building type is typically one or two stories and preferably used for single-family housing. It is more predominant in less flood-prone areas, i.e. in the highlands or in mountainous regions. The masses of these buildings are generally high and their walls are characterized by insignificant strength, particularly against forces that act out-of-plane. This type of building is highly vulnerable to both seismic forces and high pressures due to flood flow. The main load bearing system consists of mud walls of 1.5 to 3.0 ft thickness, which carry the roof load. Clay tiles, thatch or CI sheets are used as roofing materials. The application of these materials depends on their local availability and the ability of the house owners. There is no monolithic joint between the wall and the roof. For this reason, these buildings behave poorly under any type of lateral load (e.g. earthquake, wind).

Report # 144 : Vivienda de Adobe (adobe brick houses) by Dominik Lang, Lisa Holliday, Omar G. Flores Beleton Housing Type: Adobe / Earthen House     Country: GUATEMALA Buildings made of adobe brick masonry can still be found in all parts of Guatemala both in rural and urban areas. Generally adobe houses are characterized by only one story, no basement, and sometimes an irregular plan shape. The main use is residential or small commercial (retail trade) purposes. In the 1970's adobe buildings represented the prevalent construction type in the Republic of Guatemala with a share of more than 39 %. More than half of these buildings (54.3 %) were located in rural settlements, while the rest (45.7 %) was located in urban areas, e.g. Guatemala City (Marroquin and Gándara, 1976). Surprisingly, the percentage of adobe buildings at that time was higher in urban areas than in rural regions. Today, circumstances have changed and adobe structures prevail in rural areas while only remainders of this traditional construction technique can be found in the cities. Based on a more recent statistical survey in the municipality of Guatemala City conducted by ASIES (2003), around 4 % of the building stock is either adobe or bahareque buildings. The latter not being covered in the present report. Throughout the report, a distinction is made between adobe buildings in rural (Figure 1) and urban (Figure 2) areas. This distinction affects some of the building parameters and features herein.

Report # 145 : Pillar walaghar (URM infilled RC frame buildings) by Yukta Bilas Marhatta, Jitendra K Bothara, Meen Bahadur Magar, Gopal Chapagain Housing Type: RC Moment Frame Building     Country: NEPAL This building type is widely constructed in the urban and semi-urban area of Nepal. It has all the characteristics of a vernacular building only with the exception that few of the construction materials are not local. It is one of the most emerging building typologies in Nepal. This is mostly non-engineered building typology. However, in urban areas sometimes competent structural engineers are also involved in the design. This technology was picked up after its relatively better performance during 1988 Udaypur earthquake which recorded M6.4 on Richter scale, that severely hit eastern Nepal. In this type of building a lightly reinforced frame is constructed first and then infill walls are erected later between columns. Though not usual, sometimes walls are constructed first and columns and beams later. These buildings serve multifunctional purposes such as residential, commercial, official, religious, educational, etc. These buildings are highly vulnerable to earthquake because of deficient detailing, inferior construction materials and the inadequate technology employed. Despite the use of modern materials of construction there is an ever growing risk to life and property due to potential earthquake attack. This building type, if designed and constructed properly, is suitable for low rise buildings up to 3 to 4 stories high. It is necessary to disseminate simple techniques of earthquake resistant measures for these buildings to the grass-root level.

Report # 147 : Traditional Naga Type House by Amir Ali Khan Housing Type: Timber Building     Country: INDIA The housing type is most common throughout the Northeast India which lies in the most severe seismic zone of the country (Zone V - corresponding to MSK IX). Majority of this type of houses are used for residential purposes. Typically these houses are built with light weight locally available material like bamboo, wooden planks, thatch etc. These housing types have traditional system of bamboo/wooden posts. Bamboo posts are inserted into the ground to act as compression members and are tied with horizontal bamboo/wooden girders with the help of bamboo ropes (cane) to give a proper shape and framing action. However, there is no protection of bamboo/wooden posts against decaying/termites or any other natural cause. The performance of these houses during the past earthquakes is unknown. However, during the discussions with local people about the performance of these houses in the past major earthquakes, it was noted that the majority of houses survived.

Report # 148 : Vivienda de Minifalda (Wooden houses with heavy bases) by Dominik Lang, Alvaro Amador, Lisa Holliday, Claudio Romero L, Armando Ugarte Housing Type: Timber Building     Country: NICARAGUA The term 'minifalda', translated 'miniskirt' refers to the building's walls which consist of masonry or concrete in the lower part, while the upper part is made of a light wood construction (also 'madera y concreto'). According to a recent population census carried out in 2005 (INEC, 2006), the total percentage of minifalda houses in Nicaragua was around 7% (8% in urban and 5.6% in rural areas). In the year 1998, minifalda represented 9.8% of the total houses in Nicaragua (12.8% in urban and 6.1% in rural areas; according to OPAS, 2001). Comparing the two numbers, it shows that the rate of this construction type on the total building stock in Nicaragua has reduced considerably. The combination of a more stable and consolidated base made of concrete or masonry and a light and flexible upper part of the walls made of wood frame construction, provides these houses with some advantages. However, the heavy roofs, which consist mostly of tiles, increase the vulnerability of the buildings especially during earthquake action.

Report # 150 : Timber-reinforced Stone Masonry (Koti Banal Architecture) of Uttarakhand and Himachal Pradesh, Northern India by Piyoosh Rautela, Girish Chandra Joshi, Yogendra Singh, Dominik Lang Housing Type: Others     Country: INDIA Despite being located in a high seismic risk area, a region in the Himalayan states of Uttarakhand and Himachal Pradesh (Northern India) exhibits an elaborate tradition of constructing multistoried houses. In the Rajgarhi area of Uttarkashi district (Uttarakhand) a large number of intact buildings of the distinct construction type known as Koti Banal can be found. Koti Banal is the name of a village in the Yamuna Valley which represents the traditional knowledge and understanding of earthquake effects on buildings and their earthquake resistant design. Investigations suggest that the region had evolved this elaborate and magnificent earthquake-safe construction style as early as 1,000 years before present. This architectural style further demonstrates the existence of elaborate construction procedures based on principles somewhat akin to that of blockhouse construction. Many features of these buildings are considered as the basics of modern earthquake-resistant design. Generally, ornate multistoried houses with abundant use of wooden beams are characteristic of Rajgarhi area. For buildings of the Koti Banal architecture, locally available building materials such as long thick wooden logs, stones and slates were judiciously used. The height of these structures varies between 7 and 12 m above the base platform which consists of dry stones. These structures are observed to have four (Chaukhat) to five (Panchapura) stories. It is reported that especially buildings of the Koti Banal architecture withstood and performed well during many past damaging earthquakes in the region. In a report on the effects of the 1905 Kangra earthquake (M 7.8), Middlemiss (1910) already describes the well performance of these ?(..) top-heavy constructions? located along steep slopes of the Kangra-Kulu epicentral area, which differed ?entirely from the sun-dried brick-built structures of the Kangra Valley. The performance of these structures has also been corroborated by eye-witness accounts during the 1991 Uttarkashi earthquake which had a magnitude of mb 6.6 in an epicentral distance of 30 km during which many new buildings collapsed while these structures did not suffer any damage. The reasons that these buildings outlived so many centuries mainly lie in their structural configuration which clearly demonstrate that their builders already had the idea of dynamic earthquake actions, particularly out-of-plane failure of masonry walls. The buildings are further characterized by a number of advantageous design features such as regular plan shapes, the sensible use of locally available building materials, the integration of wooden beams over the total height of the building as well as small openings and the arrangement of shear walls.

Report # 152 : Base Isolation of Confined Masonry by Noemi Graciela Maldonado, Dr. Miguel Eduardo Tornello Housing Type: Seismic Protection Systems     Country: ARGENTINA Most of Argentine Republic territory may be considered seismic.Great Mendoza is an important social-economic area in the mid- western region and it has the greatest seismic risk in the country. In the last 200 years or so, there have been important earthquakes affecting building structures. Consequently, new techniques aimed at controlling vulnerability must be developed. Methodology: An investigation of the actual application of Basal Seismic Isolation (BSI) on a building 'Students' House' belonging to the Technological National University (UTN) is implemented. Research of the isolation system for near source motions has been done. The construction of three modules of student houses has been done in 2004, with confined masonry and reinforced concrete for three levels and prestressed slabs. Both buildings have accelerometers to register earthquake effects. The complex is completed with a building of two levels for administration with confined masonry. The aim is to control BSI displacement. The strategy proposed was to add damping to the isolation system within certain limits and the results are compared to similar fixed base building. To control near source displacements, additional damping is an applicable and economic strategy. Although with this strategy there is increased acceleration , it is far less than in the case of fixed base building.

Report # 156 : Typical Single-Story Residential Construction Practices in Trinidad and Tobago by Richard P. Clarke, Rakesh Ramnath Housing Type: Unreinforced Masonry Building     Country: TRINIDAD AND TOBAGO Typical single-story residential construction in Trinidad and Tobago comprises 100 mm thick unreinforced clay tile or concrete block masonry (URM) load-bearing walls supporting the roof. The roofing is a 20 to 30 degree gable or hipped shape and is of approximately 0.2 to 0.5 kN/m2 in weight. It comprises galvanized steel sheets supported by timber laths or cold-formed steel Z-purlins, in turn supported by timber or structural steel rafters. The rafters are nailed or bolted to the top of the walls, without blocking between the rafters. The flexible roof cannot act as a diaphragm. The soil class ranges from IBC classes B to E. Given the significant seismic hazard for Trinidad and Tobago, (i.e. rock PGA in the range of 0.2g to 0.6g for 10% exceedance probability in 50 years), this form of residential construction is quite vulnerable.