Description

The World Housing Encyclopedia (WHE) Report Database contains 130 reports on housing construction types in 43 seismically active countries. Each housing report is a detailed description of a housing type in a particular country. The description is prepared from a number of standard closed-ended questions and some narrative that have been provided by report authors. Each report has five major categories including architectural and structural features; Building Materials and Construction Process; Socio-economic Issues; Past Performance In Earthquakes, Seismic Features and Vulnerability; and Retrofit. All of the housing reports in this database have been contributed by volunteers. If you are interested in writing a housing report please contact the WHE Editorial Board.

About

The World Housing Encyclopedia (WHE) is a collection of resources related to housing construction practices in the seismically active areas of the world. The mission is to share experiences with different construction types and encourage the use of earthquake-resistant technologies worldwide. The technical activities of the WHE are steered by an international team of 22 professionals specializing in different aspects of seismic safety of buildings and structures. They bring relevant experience from 16 seismically active countries across the world. For more information about the World Housing Encyclopedia, visit http://www.world-housing.net/.

General Information

 

Report #:91
Building Type: EMSB1- single storied brick masonry house generally with GI roof
Country: Bangladesh
Author(s): Mehedi Ansary
Last Updated:
Regions Where Found: Buildings of this construction type can be found in all parts of Bangladesh. This type of housing construction is commonly found in both rural and urban areas.
Summary:

This is a one-story brick masonry house of fired bricks ...

Length of time practiced: 76-100 years
Still Practiced: Yes
In practice as of:
Building Occupancy: Single dwelling
Typical number of stories: 1
Terrain-Flat: Typically
Terrain-Sloped: 3
Comments:


 

Features

 

 

Plan Shape Rectangular, solidL-shape
Additional comments on plan shape Mostly L-shaped, sometimes rectangular.
Typical plan length (meters) 3-5
Typical plan width (meters) 2-4
Typical story height (meters) 2.8
Type of Structural System Masonry: Unreinforced Masonry Walls: Brick masonry in lime/cement mortar
Additional comments on structural system The vertical load-resisting system is earthen walls. Traditionally, 10 inch wall is used as load bearing walls. But sometimes poor people use 5 inch wall. Poorer construction do not have any kind of plaster. The lateral load-resisting system is earthen walls. Sometimes there is a continuous lintel, sometimes none. In earthquake prone areas like Chittagong, Sylhet etc. approximately 50% private housing units have continuous lintel. But on the government buildings, the percentage is much lower.
Gravity load-bearing & lateral load-resisting systems Tie columns are not used.
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 %. 15 - 20%.
Wall Openings At least three for a single room (two windows and one door). The buildings generally comprise of two to three rooms. The inner and outer rooms have at least two doors. Opening per wall is around 20%. Doors and windows are located in the middle of the wall.
Is it typical for buildings of this type to have common walls with adjacent buildings? No
Modifications of buildings
Type of Foundation Shallow Foundation: Wall or column embedded in soil, without footing
Additional comments on foundation Stepped brick foundations with cement mortars are used. Generally foundation bottom lies 2 to 3 ft below GL.
Type of Floor System Other floor system
Additional comments on floor system
Type of Roof System Roof system, other
Additional comments on roof system GI roofs with purlins.
Additional comments section 2 In the villages this type of housing may be located several 100 meters apart. When separated from adjacent buildings, the typical distance from a neighboring building is 2 meters.

 

Building Materials and Construction Process

 

 

Description of Building Materials


Structural Element Building Material (s)Comment (s)
Wall/Frame Brick, cement mortar1:4 (cement: sand)
Foundations Brick, cement mortar1:4 (cement: sand)
Floors
Roof
Other

Design Process


Who is involved with the design process? Owner
Roles of those involved in the design process Owners are the architect and masons are the engineer for this type of housing.
Expertise of those involved in the design process They do not have a large role, but masons can be trained by the engineers according to the code guideline for construction.

Construction Process


Who typically builds this construction type? Mason
Roles of those involved in the building process The house owners hire masons to build these houses. Sometimes masons live in similar houses.
Expertise of those involved in building process No formal training. Masons are trained by their seniors.
Construction process and phasing - trench line is planned - excavate 2 to 3 ft deep trench - 6 inch thick sand layer - lay brick and use cement mortar to join them The construction of this type of housing takes place in a single phase. Typically, the building is originally not desig
Construction issues

Building Codes and Standards


Is this construction type address by codes/standards? Yes
Applicable codes or standards This construction type is addressed by the codes/standards of the country. Bangladesh National Building Code. The year the first code/standard addressing this type of construction issued was 1993. BNBC 1993.
Process for building code enforcement There is no enforcement of building codes for this type of construction.

Building Permits and Development Control Rules


Are building permits required? No
Is this typically informal construction? Yes
Is this construction typically authorized as per development control rules? No
Additional comments on building permits and development control rules There are no guidelines for this type of housing. No prior approval is required.

Building Maintenance and Condition


Typical problems associated with this type of construction
Who typically maintains buildings of this type? Owner(s)
Additional comments on maintenance and building condition

Construction Economics


Unit construction cost Total project: US Dollar 50/sq m.
Labor requirements The labor requirements for a typical house of about 30 to 50 sq.m are about 100 to 120 man-days.
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy As the joint family tradition is strong in the rural areas, an extended family occupy the housing unit. Typically, the families comprise of a father and two-three sons. As the family further expands, the sons families occupy independent units.
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 5-10
Additional comments on number of inhabitants
Economic level of inhabitants Middle-income classHigh-income class (rich)
Additional comments on economic level of inhabitants The middle class housing unit roughly costs USD 1,000, on the other hand the rich housing unit costs USD 1,500 to 2,000. Ratio of housing unit price to annual income: 1:1 or better
Typical Source of Financing Owner financedPersonal savingsSmall lending institutions/microfinance institutions
Additional comments on financing
Type of Ownership RentOwn outright
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

 

Earthquakes

 

 

Past Earthquakes in the country which affected buildings of this type


YearEarthquake Epicenter Richter Magnitude Maximum Intensity
1885Bogra-Sirajganj
1897Assam
1918Srimangal
1997Bangladesh-India Border
78
810
7.68
5.67

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type During the 1897 Assam earthquake, almost 90% of this type of structure suffered some kind of damage.
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 pathThe 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-VerticalThe building is regular with regards to the elevation. (Specify in 5.4.1)FALSE
Building Configuration-HorizontalThe building is regular with regards to the plan. (Specify in 5.4.2)FALSE
Roof ConstructionThe 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.FALSE
Floor ConstructionThe 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.N/A
Foundation PerformanceThere is no evidence of excessive foundation movement (e.g. settlement) that would affect the integrity or performance of the structure in an earthquake. N/A
Wall and Frame Structures-RedundancyThe number of lines of walls or frames in each principal direction is greater than or equal to 2.TRUE
Wall ProportionsHeight-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);FALSE
Foundation-Wall ConnectionVertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation.TRUE
Wall-Roof ConnectionsExterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. FALSE
Wall OpeningsTRUE
Quality of Building MaterialsQuality of building materials is considered to be adequate per the requirements of national codes and standards (an estimate). FALSE
Quality of WorkmanshipQuality of workmanship (based on visual inspection of a few typical buildings) is considered to be good (per local construction standards).FALSE
MaintenanceBuildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber).TRUE

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 Weak from earthquake point of view; sometimes there are no plaster; lack of lintel bands; no measures to strengthen the corners.
Earthquake-resilient features in walls
Seismic deficiency in frames
Earthquake-resilient features in frame
Seismic deficiency in roof and floors
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 vulnerabilityLow vulnerability
ABCDEF
Seismic vulnerability class |- o -|

Additional comments section 5 General lack of awareness about the earthquake resistant construction practices.

Retrofit Information

 

 

Description of Seismic Strengthening Provisions


Structural Deficiency Seismic Strengthening
Inadequate wall resistance due to the absence of seismic provisions Covering the wall with 1 ft wide seismic belt (steel wire mesh with cement mortar) at lintel level on both sides of the wall.
Foundations Strengthening of New Construction : Provision of strip foundation
Walls Strengthening of New Construction : Provision of RC ring beams at plinth, lintel etc. levels. Provision of vertical steel reinforcement bars at the wall corners and intersections.

Additional comments on seismic strengthening provisions
Has seismic strengthening described in the above table been performed? Proposed for the damaged buildings of 2003 Rangamati earthquake.
Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? N/A
Was the construction inspected in the same manner as new construction? N/A
Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? N/A
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? N/A
Additional comments section 6

 

References

Report on "Seismic Risk of Five Selected Cities of Bangladesh" for CARE-Bangladesh, BUET. February, 2003. Project Leader Dr. Mehedi A. Ansary


Bangladesh National Building Code, 1993


Guidelines for Earthquake Resistant Non-engineered Construction IAEE


Authors


Name Title Affiliation Location Email
Mehedi Ansary PhD Department of Civil Engineering, Bangladesh University of Engineering & Technology Dept. of Civil Engg., BUET, Dhaka-1000 ansaryma@yahoo.com

Reviewers

Name Title Affiliation Location Email