| Report # | 27 |
| Report Date | 06-05-2002 |
| Country | IRAN |
| Housing Type | Confined Masonry Building |
| Housing Sub-Type | Confined Masonry Building with Concrete blocks, tie-columns and beams |
|
Author(s)
|
Behrokh H. Hashemi, Faramarz Alemi, Mohsen G. Ashtiany |
|
Reviewer(s)
|
Farzad Naeim |
Important
This encyclopedia contains information contributed by various earthquake engineering professionals around the world. All opinions, findings, conclusions & recommendations expressed herein are those of the various participants, and do not necessarily reflect the views of the Earthquake Engineering Research Institute, the International Association for Earthquake Engineering, the Engineering Information Foundation, John A. Martin & Associates, Inc. or the participants' organizations.
Summary
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.
1. General Information
Buildings of this construction type can be found in This type of construction is used all over the rural areas of Iran. The percentage of this housing type in those regions is almost 10%. This type of housing construction is commonly found in rural areas. This construction type has been in practice for less than 100 years.
Currently, this type of construction is being built. .
Figure 1: Typical Building
| 
Figure 2A: Key Load-Bearing Elements
| 
Figure 2B: Key Load-Bearing Elements
|
|
2. Architectural Aspects2.1 Siting
These buildings are typically found in flat terrain. They do no share common walls with adjacent buildings. This value of 5 meters is average distance. Buildings of this type in some places are located close together and in other places scattered When separated from adjacent buildings, the typical distance from a neighboring building is 5 meters.
2.2 Building Configuration
The typical shape of a building plan for this housing type is rectangular. To view outside the building, typically a window opening is built in external walls. These windows almost take 40% of the external walls areas. The other wall has one or two doors. The door sizes are typically 90 X 210 (cm). The overall window and door areas are about 25% of the overall wall surface area.
2.3 Functional Planning
The main function of this building typology is single-family house. In a typical building of this type, there are no elevators and 1-2 fire-protected exit staircases. Building of this type can have as the one main entry so the two doors.
2.4 Modification to Building
This type of construction does not have many modifications.
3. Structural Details3.1 Structural System
| Material | Type of Load-Bearing Structure | # | Subtypes | Most appropriate type |
| Masonry | Stone Masonry
Walls | 1 | Rubble stone (field stone) in mud/lime
mortar or without mortar (usually with
timber roof) | ☐ |
| 2 | Dressed stone masonry (in
lime/cement mortar) | ☐ |
| Adobe/ Earthen Walls | 3 | Mud walls | ☐ |
| 4 | Mud walls with horizontal wood elements | ☐ |
| 5 | Adobe block walls | ☐ |
| 6 | Rammed earth/Pise construction | ☐ |
Unreinforced masonry
walls | 7 | Brick masonry in mud/lime
mortar | ☐ |
| 8 | Brick masonry in mud/lime
mortar with vertical posts | ☐ |
| 9 | Brick masonry in lime/cement
mortar | ☐ |
| 10 | Concrete block masonry in
cement mortar | ☐ |
| Confined masonry | 11 | Clay brick/tile masonry, with
wooden posts and beams | ☐ |
| 12 | Clay brick masonry, with
concrete posts/tie columns
and beams | ☐ |
| 13 | Concrete blocks, tie columns
and beams | ☑ |
| Reinforced masonry | 14 | Stone masonry in cement
mortar | ☐ |
| 15 | Clay brick masonry in cement
mortar | ☐ |
| 16 | Concrete block masonry in
cement mortar | ☐ |
| Structural concrete | Moment resisting
frame | 17 | Flat slab structure | ☐ |
| 18 | Designed for gravity loads
only, with URM infill walls | ☐ |
| 19 | Designed for seismic effects,
with URM infill walls | ☐ |
| 20 | Designed for seismic effects,
with structural infill walls | ☐ |
| 21 | Dual system – Frame with
shear wall | ☐ |
| Structural wall | 22 | Moment frame with in-situ
shear walls | ☐ |
| 23 | Moment frame with precast
shear walls | ☐ |
| Precast concrete | 24 | Moment frame | ☐ |
| 25 | Prestressed moment frame
with shear walls | ☐ |
| 26 | Large panel precast walls | ☐ |
| 27 | Shear wall structure with
walls cast-in-situ | ☐ |
| 28 | Shear wall structure with
precast wall panel structure | ☐ |
| Steel | Moment-resisting
frame | 29 | With brick masonry partitions | ☐ |
| 30 | With cast in-situ concrete
walls | ☐ |
| 31 | With lightweight partitions | ☐ |
| Braced frame | 32 | Concentric connections in all
panels | ☐ |
| 33 | Eccentric connections in a
few panels | ☐ |
| Structural wall | 34 | Bolted plate | ☐ |
| 35 | Welded plate | ☐ |
| Timber | Load-bearing timber
frame | 36 | Thatch | ☐ |
| 37 | Walls with bamboo/reed mesh
and post (Wattle and Daub) | ☐ |
| 38 | Masonry with horizontal
beams/planks at intermediate
levels | ☐ |
| 39 | Post and beam frame (no
special connections) | ☐ |
| 40 | Wood frame (with special
connections) | ☐ |
| 41 | Stud-wall frame with
plywood/gypsum board
sheathing | ☐ |
| 42 | Wooden panel walls | ☐ |
| Other | Seismic protection systems | 43 | Building protected with base-isolation systems | ☐ |
| 44 | Building protected with
seismic dampers | ☐ |
| Hybrid systems | 45 | other (described below) | ☐ |
3.2 Gravity Load-Resisting System
The vertical load-resisting system is confined masonry wall system. Gravity loads sustain by bearing masonry brick walls.
3.3 Lateral Load-Resisting System
The lateral load-resisting system is confined masonry wall system. In both directions of the buildings lateral load-resisting system are provided by masonry brick shear walls which are confined with concrete tie column and beams.
3.4 Building Dimensions
The typical plan dimensions of these buildings are: lengths between 5 and 5 meters, and widths between 9 and 9 meters. The building has 4 to 6 storey(s). The typical span of the roofing/flooring system is 2.5 meters. Typial Span: Span may be 3 too. The typical storey height in such buildings is 3 meters. The typical structural wall density is none. Total wall area/plan area (for each floor) 0.2.
3.5 Floor and Roof System
| Material | Description of floor/roof system | Most appropriate floor | Most appropriate roof |
| Masonry | Vaulted | ☐ | ☐ |
Composite system of concrete joists and
masonry panels | ☐ | ☐ |
| Structural concrete | Solid slabs (cast-in-place) | ☐ | ☐ |
| Waffle slabs (cast-in-place) | ☐ | ☐ |
| Flat slabs (cast-in-place) | ☐ | ☐ |
| Precast joist system | ☐ | ☐ |
| Hollow core slab (precast) | ☐ | ☐ |
| Solid slabs (precast) | ☐ | ☐ |
Beams and planks (precast) with concrete
topping (cast-in-situ) | ☐ | ☐ |
| Slabs (post-tensioned) | ☐ | ☐ |
| Steel | Composite steel deck with concrete slab
(cast-in-situ) | ☐ | ☐ |
| Timber | Rammed earth with ballast and concrete or
plaster finishing | ☐ | ☐ |
| Wood planks or beams with ballast and concrete or plaster finishing | ☐ | ☐ |
| Thatched roof supported on wood purlins | ☐ | ☐ |
| Wood shingle roof | ☐ | ☐ |
| Wood planks or beams that support clay tiles | ☐ | |
Wood planks or beams supporting natural
stones slates | ☐ | ☐ |
Wood planks or beams that support slate,
metal, asbestos-cement or plastic corrugated
sheets or tiles | ☐ | ☐ |
Wood plank, plywood or manufactured wood
panels on joists supported by beams or walls | ☐ | ☐ |
| Other | Described below | ☑ | ☑ |
The floor/ and roof are considered to be a rigid diaphragm.
3.6 Foundation
| Type | Description | Most appropriate type |
| Shallow foundation | Wall or column embedded in
soil, without footing | ☐ |
Rubble stone, fieldstone
isolated footing | ☐ |
Rubble stone, fieldstone strip
footing | ☐ |
Reinforced-concrete isolated
footing | ☐ |
Reinforced-concrete strip
footing | ☑ |
| Mat foundation | ☐ |
| No foundation | ☐ |
| Deep foundation | Reinforced-concrete bearing
piles | ☐ |
Reinforced-concrete skin
friction piles | ☐ |
| Steel bearing piles | ☐ |
| Steel skin friction piles | ☐ |
| Wood piles | ☐ |
| Cast-in-place concrete piers | ☐ |
| Caissons | ☐ |
| Other | Described below | ☐ |
Figure 3: Critical Structural Details: Concrete tie column | 
Figure 4A: An Illustration of Key Seismic Deficiencies: lack of Connection Between Wooden Beam and Concrete Tie Beam and Poor Quality of Materials | 
Figure 4B: Wall cross-section showing a concrete tie beam ad roof-to-wall connection |
Figure 4C: Wall side view showing a concrete tie beam and roof-to-wall connection |
4. Socio-Economic Aspects4.1 Number of Housing Units and Inhabitants
Each building typically has 1 housing unit(s). 1 units in each building. The number of inhabitants in a building during the day or business hours is less than 5. The number of inhabitants during the evening and night is less than 5.
4.2 Patterns of Occupancy
One family usually occupies each house.
4.3 Economic Level of Inhabitants
| Income class | Most appropriate type |
| a) very low-income class (very poor) | ☑ |
| b) low-income class (poor) | ☐ |
| c) middle-income class | ☐ |
| d) high-income class (rich) | ☐ |
Economic Level:
For Poor Class the Housing Price Unit is 5000 and the Annual Income is 1000.
| Ratio of housing unit price to annual income | Most appropriate type |
| 5:1 or worse | ☑ |
| 4:1 | ☐ |
| 3:1 | ☐ |
| 1:1 or better | ☐ |
What is a typical source of
financing for buildings of this
type? | Most appropriate type |
| Owner financed | ☑ |
| Personal savings | ☑ |
Informal network: friends and
relatives | ☐ |
Small lending institutions / micro-
finance institutions | ☐ |
| Commercial banks/mortgages | ☑ |
| Employers | ☐ |
| Investment pools | ☐ |
| Government-owned housing | ☐ |
| Combination (explain below) | ☐ |
| other (explain below) | ☐ |
In each housing unit, there are 1 bathroom(s) without toilet(s), 1 toilet(s) only and no bathroom(s) including toilet(s).
4.4 Ownership
The type of ownership or occupancy is outright ownership and ownership with debt (mortgage or other).
Type of ownership or
occupancy? | Most appropriate type |
| Renting | ☐ |
| outright ownership | ☑ |
Ownership with debt (mortgage
or other) | ☑ |
| Individual ownership | ☐ |
Ownership by a group or pool of
persons | ☐ |
| Long-term lease | ☐ |
| other (explain below) | ☐ |
5. Seismic Vulnerability5.1 Structural and Architectural Features
Structural/
Architectural
Feature | Statement | Most appropriate type |
| True | False | N/A |
| Lateral load path | The structure contains a complete load path for seismic
force effects from any horizontal direction that serves
to transfer inertial forces from the building to the
foundation. | ☐ | ☑ | ☐ |
Building
Configuration | The building is regular with regards to both the plan
and the elevation. | ☑ | ☐ | ☐ |
| Roof construction | The roof diaphragm is considered to be rigid and it is
expected that the roof structure will maintain its
integrity, i.e. shape and form, during an earthquake of
intensity expected in this area. | ☐ | ☑ | ☐ |
| Floor construction | The floor diaphragm(s) are considered to be rigid and it
is expected that the floor structure(s) will maintain its
integrity during an earthquake of intensity expected in
this area. | ☐ | ☐ | ☑ |
Foundation
performance | There is no evidence of excessive foundation movement
(e.g. settlement) that would affect the integrity or
performance of the structure in an earthquake. | ☑ | ☐ | ☐ |
Wall and frame
structures-
redundancy | The number of lines of walls or frames in each principal
direction is greater than or equal to 2. | ☑ | ☐ | ☐ |
| Wall proportions | Height-to-thickness ratio of the shear walls at each floor level is:
Less than 25 (concrete walls);
Less than 30 (reinforced masonry walls);
Less than 13 (unreinforced masonry walls); | ☑ | ☐ | ☐ |
Foundation-wall
connection | Vertical load-bearing elements (columns, walls)
are attached to the foundations; concrete
columns and walls are doweled into the
foundation. | ☑ | ☐ | ☐ |
Wall-roof
connections | Exterior walls are anchored for out-of-plane seismic
effects at each diaphragm level with metal anchors or
straps | ☐ | ☑ | ☐ |
| Wall openings | The total width of door and window openings in a wall
is:
For brick masonry construction in cement mortar : less
than ½ of the distance between the adjacent cross
walls;
For adobe masonry, stone masonry and brick masonry
in mud mortar: less than 1/3 of the distance between
the adjacent cross
walls;
For precast concrete wall structures: less than 3/4 of
the length of a perimeter wall. | ☑ | ☐ | ☐ |
| Quality of building materials | Quality of building materials is considered to be
adequate per the requirements of national codes and
standards (an estimate). | ☑ | ☐ | ☐ |
| Quality of workmanship | Quality of workmanship (based on visual inspection of
few typical buildings) is considered to be good (per
local construction standards). | ☐ | ☑ | ☐ |
| Maintenance | Buildings of this type are generally well maintained and there
are no visible signs of deterioration of building
elements (concrete, steel, timber) | ☐ | ☑ | ☐ |
| Other | | ☐ | ☑ | ☐ |
5.2 Seismic Features
| Structural Element | Seismic Deficiency | Earthquake Resilient Features | Earthquake Damage Patterns |
| Wall | Unequal stiffness distribution. | | |
| Frame (columns, beams) | Poor quality of workmanship and materials. | | |
| Roof and floors | Lack of proper connection between roof and masonry shear walls They are not perfectly rigid diaphragm. | | |
| | | |
5.3 Overall Seismic Vulnerability Rating
The overall rating of the seismic vulnerability of the housing type is C: MEDIUM VULNERABILITY (i.e., moderate seismic performance), the lower bound (i.e., the worst possible) is B: MEDIUM-HIGH VULNERABILITY (i.e., poor seismic performance), and the upper bound (i.e., the best possible) is D: MEDIUM-LOW VULNERABILITY (i.e., good seismic performance).
| Vulnerability | high | medium-high | medium | medium-low | low | very low |
| | very poor | poor | moderate | good | very good | excellent |
Vulnerability
Class | A | B | C | D | E | F |
| ☐ | ☑ | ☐ | ☑ | ☐ | ☐ |
5.4 History of Past Earthquakes
| Date | Epicenter, region | Magnitude | Max. Intensity |
| 1990 | Manjil | 7.6 | IX |
Figure 5: Damage caused by the absence of concrete posts (1990 Manjil earthquake) | 
Figure 6A: Illustration of Seismic Strengthening Techniques | 
Figure 6B: Damage due to large opening, absence of masonry shear wall and short column behavior in concrete post (1990 Manjil earthquake) |
Figure 6C: Damage in the wall panel (1990 Manjil earthquake) | 
Figure 6D: Collapse due to heavy roof (1990 Manjil earthquake) |
6. Construction6.1 Building Materials
| Structural element | Building material | Characteristic strength | Mix proportions/dimensions | Comments |
| Walls | Clay brick masonry. | 150 Kg/cm² 10 Kg/cm². | 1:6 / 55 X 110 X 220 (mm). | |
| Foundation | Concrete. | 210 kg/cm². | 1:2:4 | |
| Frames (beams & columns) | Steel bars. | 3000 kg/cm². | | |
| Roof and floor(s) | Wood. | | | |
6.2 Builder
It is typically built by developers and the builders does not necessary live in this building type.
6.3 Construction Process, Problems and Phasing
Typically developers build these types of constructions. Process starts with the foundations and then bearing walls. Process continues by adding the concrete tie columns and then tie beams then placing of wood beams and finally putting the finishing on the hole building. The construction of this type of housing takes place incrementally over time. Typically, the building is originally designed for its final constructed size.
6.4 Design and Construction Expertise
As far as the design concern, engineers do their job properly. But the main problem is the construction of this type of buildings in rural areas, due to lack of skilled worker. For design of building, engineers and architectures are both involved. However, during the construction process they do not spend any time to visit the site.
6.5 Building Codes and Standards
This construction type is addressed by the codes/standards of the country. The first official issue about this type of building was in 1987. The Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard 2800) addressed this type of construction. Iranian Code of Practice for Seismic Resistant Design of Building, 1st Edition- 1987 and 2nd Edition-1999 Iranian National Building Code, Part: 8, Reinforced and unreinforced masonry buildings
Year the first code/standard addressing this type of construction issued: 1987
National building code, material codes and seismic codes/standards: Iranian Code of Practice for Seismic Resistant Design of Building, 1st Edition- 1987 and 2nd Edition-1999
When was the most recent code/standard addressing this construction type issued? 1999.
The building department of municipalities approves the design and holds the designer responsible for the projects. For those constructions, which are supported by government's fund, there is a proper control during construction. But for the others, there is not any control.
6.6 Building Permits and Development Control Rules
This type of construction is a non-engineered, and not authorized as per development control rules. Building permits are required to build this housing type.
6.7 Building Maintenance
Typically, the building of this housing type is maintained by Owner(s) and Tenant(s).
6.8 Construction Economics
A unit construction may cost 500,000 Rials/m² ( 250 $US/m²). For a typical one story building needs about 30 to 40 days to complete the load bearing structure.
7. Insurance
Earthquake insurance for this construction type is typically unavailable. For seismically strengthened existing buildings or new buildings incorporating seismically resilient features, an insurance premium discount or more complete coverage is unavailable.
8. Strengthening
8.1 Description of Seismic Strengthening Provisions
Strengthening of Existing Construction :
| Seismic Deficiency | Description of Seismic Strengthening provisions used |
| Shear wall | Add new shear wall |
| Tie beams | Increasing the size of the existing tie beams and adding new tie beams for added new walls |
| Roof | Proper connections of the wood beams to the tie beams |
Strengthening of New Construction :
| Seismic Deficiency | Description of Seismic Strengthening provisions used |
| Shear wall | |
| Tie beams | |
| Roof | Proper connections of the wood beams to the tie beams. |
Seismic strengthening techniques are illustrated in Figures 7A, 7B, and 7C.
8.2 Seismic Strengthening Adopted
Has seismic strengthening described in the above table been performed in design and construction practice, and if so, to what extent?
No.
8.3 Construction and Performance of Seismic Strengthening
Figure 7A: Seismic Strengthening: Tying the wooden beam to the concrete tie beam using an anchor bar | 
Figure 7B: Seismic Strengthening: Addition of a new concrete post |
Reference(s)- A Simple Pictorial Guideline for Constructing Earthquake Resistant Adobe Building In Different Rural Areas
Hosseini Hashemi,B. and Alemi,F.
to be published in Farsi
- Manjil-Rudbar Earthquake of June 20,90 Reconnaissance Report
IIEES Publication No. 70-91-1, Tehran, Iran 1991
- Iranian Code of Practice for Seismic Resistant Design of Building, 1st Edition- 1987 and 2nd Edition-1999
Building and Housing Research Center, BHRC-PN S 253, Tehran, Iran
- Iranian National Building Code - Part 8: Reinforced and unreinforced masonry buildings
Ministry of Housing and Urban Development, Tehran, Iran
Author(s)- Behrokh H. Hashemi
Assistant Professor, IIEES
No. 27 Arghavan St. Dibaji Farmanieh, Tehran 19531, IRAN
Email:behrokh@iiees.ac.ir FAX: (98-21) 229-9479
- Faramarz Alemi, IIEES
No. 27 Arghavan Street Dibaji Farmanieh, Tehran 19531, IRAN
Email:f-alemi@dena.iiees.ac.ir FAX: (98-21) 229-9479
- Mohsen G. Ashtiany
Professor/President, IIEES
No. 27 Arghavan Street Dibaji Farmanieh, Tehran 19531, IRAN
Email:ashtiany@dena.iiees.ac.ir FAX: (98-21) 229-9479
Reviewer(s)- Farzad Naeim
Vice President
, John A. Martin & Associates
Los Angeles CA 90015, USA
Email:farzad@johnmartin.com FAX: (213) 483-3084
