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Report # 64 : Reinforced concrete frame building with masonry infills

September 15, 2011 By

by Polat Gulkan, Mark Aschheim, Robin Spence

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.

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Filed Under: Asia & Mideast, RC Moment Frame, Reinforced Concrete, Turkey

Report # 101 : Tunnel form building

September 15, 2011 By

by Ahmet Yakut, Polat Gulkan

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.

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Filed Under: Asia & Mideast, RC Structural Wall, Reinforced Concrete, Turkey

Report # 104 : Adobe House

September 15, 2011 By

by Mehrdad Mehrain, Farzad Naeim

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.

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Filed Under: Adobe / Earthen, Asia & Mideast, Iran

Report # 114 : Stonework building with wooden timber roof

September 15, 2011 By

by Masoud N. Ahari, Alireza Azarbakht

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.

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Filed Under: Asia & Mideast, Iran, Masonry, Stone Masonry

Report # 118 : Earring system (Shekanj) in dome-roof structures with unreinforced brick and adobe materials

September 15, 2011 By

by Nima T. Bekloo

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.

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Filed Under: Asia & Mideast, Iran, Masonry, Unreinforced Masonry

Report # 117 : Four arches (Char taaqi) with dome-roof structures, and unreinforced brick and adobe materials.

September 15, 2011 By

by Nima T. Bekloo

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.

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Filed Under: Asia & Mideast, Iran, Masonry, Unreinforced Masonry

Report # 42 : Houses with mud walls and thatch roofs

September 15, 2011 By

by Svetlana Uranova, Ulugbek T. Begaliev

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.

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Filed Under: Adobe / Earthen, Asia & Mideast, Kyrgyzstan

Report # 159 : Reinforced concrete buildings in Pakistan

August 22, 2011 By

by Yasir Irfan Badrashi, Qaisar Ali, Mohammad Ashraf

This report addresses reinforced-concrete buildings in Pakistan. Due to the rapid urbanization in Pakistan in the recent past and consequently the scarcity and inflated cost of land in the major cities, builders have been forced to resort to the construction of reinforced-concrete buildings both for commercial and residential purposes. It is estimated that reinforced-concrete buildings constitute 10 to 15% of the total building stock in the major cities of Pakistan and this percentage is on the rise. However, construction of reinforced concrete buildings in Pakistan is still in nascent stage with construction procedures lacking compliance with the established construction procedures. This report is based on survey of the building stock of 5 major cities in Pakistan and hence provides a realistic picture of construction of reinforced-concrete buildings in Pakistan. The statistics provided in this report are based on personal observation of the authors as well as opinion of professionals working in the construction industry who were interviewed in the course of this survey.

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Filed Under: Asia & Mideast, Pakistan, RC Moment Frame, Reinforced Concrete

Report # 147 : Traditional Naga Type House

August 22, 2011 By

by Amir Ali Khan

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.

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Filed Under: Asia & Mideast, India, Timber

Report # 145 : Pillar walaghar (URM infilled RC frame buildings)

August 22, 2011 By

by Yukta Bilas Marhatta, Jitendra K Bothara, Meen Bahadur Magar, Gopal Chapagain

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.

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Filed Under: Asia & Mideast, Nepal, RC Moment Frame, Reinforced Concrete
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