Confined Masonry Building with Concrete blocks, tie-columns and beams, Iran

From World Housing Encyclopedia


1. General Information

Report: 27

Building Type: Confined Masonry Building with Concrete blocks, tie-columns and beams

Country: Iran

Author(s): Behrokh Hosseini Hashemi, Faramarz Alemi, Mohsen Ghafory Ashtiany

Last Updated:

Regions Where Found: Buildings of this construction type can be found in 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.

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.

Length of time practiced: 25-60 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Single dwelling

Typical number of stories: 1

Terrain-Flat: Typically

Terrain-Sloped: Typically

Comments: These buildings are typically found in flat, sloped and hilly terrain. They do not share common walls with adjacent buildings. T


2. Features

Plan Shape: Rectangular, solid

Additional comments on plan shape: 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.

Typical plan length (meters): 5

Typical plan width (meters): 9

Typical story height (meters): 3

Type of Structural System: Masonry: Confined Masonry: Concrete blocks, tie columns and beams

Additional comments on structural system: The vertical load-resisting system is confined masonry wall system. Gravity loads sustain by bearing masonry brick walls. 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.

Gravity load-bearing & lateral load-resisting systems:

Typical wall densities in direction 1: 15-20%

Typical wall densities in direction 2: 15-20%

Additional comments on typical wall densities: The typical structural wall density is up to 20 %. Total wall area/plan area (for each floor) 0.2.

Wall Openings: 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.

Is it typical for buildings of this type to have common walls with adjacent buildings?: No

Modifications of buildings: This type of construction does not have many modifications.

Type of Foundation: Shallow Foundation: Reinforced concrete strip footing

Additional comments on foundation:

Type of Floor System: Other floor system

Additional comments on floor system: The floor/ and roof are considered to be a rigid diaphragm.

Type of Roof System: Roof system, other

Additional comments on roof system: The floor/ and roof are considered to be a rigid diaphragm.

Additional comments section 2: 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. Buildings of this type in some places are located close together and in other places are scattered When separated from adjacent buildings, the typical distance from a neighboring building is 5 meters.


3. Building Process

Description of Building Materials

Structural Element Building Material (s) Comment (s)
Wall/Frame Clay brick masonry. / Steel bars. Clay brick masonry: 150 Kg/sq cm 10 Kg/sq cm characteristic strength, 1:6 / 55 X 110 X 220 (mm) mix proportions/dimensions Steel bars: 3000 Kg/sq cm characteristic strength
Foundations Concrete. 210 Kg/sq cm characteristic strength, 1:2:4 mix proportions
Floors Wood
Roof Wood
Other

Design Process

Who is involved with the design process? EngineerArchitect

Roles of those involved in the design process: 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.

Expertise of those involved in the design process: 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.


Construction Process

Who typically builds this construction type? Other

Roles of those involved in the building process: It is typically built by developers and the builders does not necessary live in this building type.

Expertise of those involved in building process: The main problem is the construction of this type of buildings in rural areas, due to lack of skilled worker.

Construction process 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.

Construction issues:


Building Codes and Standards

Is this construction type address by codes/standards? Yes

Applicable codes or standards: 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. The year the first code/standard addressing this type of construction issued was 1987. Iranian Code of Practice for Seismic Resistant Design of Building, 1st Edition- 1987 and 2nd Edition-1999.

Process for building code enforcement: 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.


Building Permits and Development Control Rules

Are building permits required? Yes

Is this typically informal construction? No

Is this construction typically authorized as per development control rules? No

Additional comments on building permits and development control rules:


Building Maintenance and Condition

Typical problems associated with this type of construction:

Who typically maintains buildings of this type? Owner(s)Renter(s)

Additional comments on maintenance and building condition:


Construction Economics

Unit construction cost: A unit construction may cost 500,000 Rials/sq m ( 250 $US/sq m).

Labor requirements: For a typical one story building needs about 30 to 40 days to complete the load bearing structure.

Additional comments section 3:


4. Socio-Economic Issues

Patterns of occupancy: One family usually occupies each house.

Number of inhabitants in a typical building of this construction type during the day: <5

Number of inhabitants in a typical building of this construction type during the evening/night: <5

Additional comments on number of inhabitants: Roughly an Iranian family has 4~6 members.

Economic level of inhabitants: Very low-income class (very poor)

Additional comments on economic level of inhabitants: For Poor Class the Housing Price Unit is 5000 and the Annual Income is 1000. Ratio of housing unit price to annual income: 5:1 or worse

Typical Source of Financing: Owner financedPersonal savingsCommercial banks/mortgages

Additional comments on financing:

Type of Ownership: Own outrightOwn with debt (mortgage or other)

Additional comments on ownership:

Is earthquake insurance for this construction type typically available?: No

What does earthquake insurance typically cover/cost:

Are premium discounts or higher coverages available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features?: No

Additional comments on premium discounts:

Additional comments section 4:


5. Earthquakes

Past Earthquakes in the country which affected buildings of this type

Year Earthquake Epicenter Richter Magnitude Maximum Intensity
1990 Manjil 7.6 IX

Past Earthquakes

Damage patterns observed in past earthquakes for this construction type:

Additional comments on earthquake damage patterns:


Structural and Architectural Features for Seismic Resistance

The main reference publication used in developing the statements used in this table is FEMA 310 “Handbook for the Seismic Evaluation of Buildings-A Pre-standard”, Federal Emergency Management Agency, Washington, D.C., 1998.

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.

Structural/Architectural Feature Statement Seismic Resistance
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. FALSE
Building Configuration-Vertical The building is regular with regards to the elevation. (Specify in 5.4.1) TRUE
Building Configuration-Horizontal The building is regular with regards to the plan. (Specify in 5.4.2) TRUE
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. N/A
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. FALSE
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. TRUE
Wall and Frame Structures-Redundancy The number of lines of walls or frames in each principal direction is greater than or equal to 2. TRUE
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); TRUE
Foundation-Wall Connection Vertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation. TRUE
Wall-Roof Connections Exterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. FALSE
Wall Openings TRUE
Quality of Building Materials Quality of building materials is considered to be adequate per the requirements of national codes and standards (an estimate). TRUE
Quality of Workmanship Quality of workmanship (based on visual inspection of a few typical buildings) is considered to be good (per local construction standards). FALSE
Maintenance Buildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber). FALSE

Additional comments on structural and architectural features for seismic resistance:

Vertical irregularities typically found in this construction type: Other

Horizontal irregularities typically found in this construction type: Other

Seismic deficiency in walls: Unequal stiffness distribution.

Earthquake-resilient features in walls:

Seismic deficiency in frames: Poor quality of workmanship and materials.

Earthquake-resilient features in frame:

Seismic deficiency in roof and floors: Lack of proper connection between roof and masonry shear walls They are not perfectly rigid diaphragm.

Earthquake resilient features in roof and floors:

Seismic deficiency in foundation:

Earthquake-resilient features in foundation:


Seismic Vulnerability Rating

For information about how seismic vulnerability ratings were selected see the Seismic Vulnerability Guidelines

High vulnerabilty Medium vulnerability Low vulnerability
A B C D E F
Seismic vulnerability class |- o -|

Additional comments section 5:


6. Retrofit Information

Description of Seismic Strengthening Provisions

Structural Deficiency Seismic Strengthening
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 (existing and new construction).
New Construction Roof: Proper connections of the wood beams to the tie beams.

Additional comments on seismic strengthening provisions: No

Has seismic strengthening described in the above table been performed?

Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages?

Was the construction inspected in the same manner as new construction?

Who performed the construction: a contractor or owner/user? Was an architect or engineer involved?

What has been the performance of retrofitted buildings of this type in subsequent earthquakes?

Additional comments section 6:


7. References

  • 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

Authors

Name Title Affiliation Location Email
Behrokh Hosseini Hashemi Assistant professor IIEES No. 27, Arghavan St., Dibaji, Farmanieh, Tehran, Iran behrokh@iiees.ac.ir
Faramarz Alemi Professor IIEES No. 27, Arghavan St., Dibaji, Farmanieh, Tehran, Iran alemi@dena.iiees.ac.ir
Mohsen Ghafory Ashtiany Professor President of IIEES No. 27, Arghavan St., Dibaji, Farmanieh, Tehran, Iran ashtiany@dena.iiees.ac.ir

Reviewers

Name Title Affiliation Location Email
Farzad Naeim Vice President John A. Martin & Associates Los Angeles CA 90015, USA farzad@johnmartin.com
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