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 #:118
Building Type: Unreinforced Masonry Building : Brick masonry in mud/lime mortar
Country: Iran
Author(s): Nima T. Bekloo

Last Updated:
Regions Where Found: Buildings of this construction type can be found in throughout the Persian Empire, except places near the sea. Thistype of housing construction is commonly found in both rural and urban areas. This building type is more common in old and traditional cities.
Summary:

This building structure derives its name from the four earrings ...

Length of time practiced: More than 200 years
Still Practiced: Yes
In practice as of:
Building Occupancy: Residential, unknown typeSingle dwellingMulti-unit, unknown typeResidential, 2 unitsResidential, 3-4 unitsResidential, 5-9 units
Typical number of stories: 1-2
Terrain-Flat: Typically
Terrain-Sloped: Off
Comments: The main function of this building typology is single-family house. Sometimes (especially in the old times) thewhole family (inc


 

Features

 

 

Plan Shape Square, solidSquare, with an opening in planRectangular, solidRectangular, with an opening in plan
Additional comments on plan shape Building configuration in plan is often rectangular or octagonal, or sometimes even polygon with more arms.
Typical plan length (meters) 5-20
Typical plan width (meters) 5-20
Typical story height (meters) 4-20
Type of Structural System Masonry: Stone Masonry Walls: Rubble stone (field stone) in mud/lime mortar or without mortar (usually with timber roof)Masonry: Stone Masonry Walls: Massive stone masonry (in lime/cement mortar)Masonry: Earthen/Mud/Adobe/Rammed Earth Walls: Mud wallsMasonry: Earthen/Mud/Adobe/Rammed Earth Walls: Mud walls with horizontal wood elementsMasonry: Earthen/Mud/Adobe/Rammed Earth Walls: Adobe block wallsMasonry: Earthen/Mud/Adobe/Rammed Earth Walls: Rammed earth/pile constructionMasonry: Unreinforced Masonry Walls: Brick masonry in mud/lime mortarMasonry: Unreinforced Masonry Walls: Brick masonry in mud mortar with vertical posts
Additional comments on structural system Lateral load-resisting system: The vertical load-resisting system is earthen walls. Load bearing walls and dome-roof systemGravity load-bearing system: The lateral load-resisting system is earthen walls. Load bearing walls and dome-roof system.
Gravity load-bearing & lateral load-resisting systems 1. Sometimes walls and dome of the buildings constructed with mud mixed with pebbles as well. 2. Nowadays somepeople use cement based mortar as well.
Typical wall densities in direction 1 >20%
Typical wall densities in direction 2 >20%
Additional comments on typical wall densities The typical structural wall density is more than 20 %. (20% to40%.)
Wall Openings Due toits load bearing system, it does not have many openings. The openings are usually less than 30% of wall area.Sometimes openings are also provided in the roof as well. These are usually around 50 cm in diameter.
Is it typical for buildings of this type to have common walls with adjacent buildings? Yes
Modifications of buildings Because the structural system is the load bearing system, it is possible only to modify some small openings.
Type of Foundation Shallow Foundation: Wall or column embedded in soil, without footingShallow Foundation: Rubble stone, fieldstone isolated footingShallow Foundation: Rubble stone, fieldstone strip footing
Additional comments on foundation
Type of Floor System Masonry floor, unknownVaulted masonry floorShallow-arched masonry floorEarthen floor, unknownOther floor system
Additional comments on floor system The construction materials have no ductility. By building it in vault form, the forces are distributed on the surface.
Type of Roof System Roof material unknownMasonry roof, unknownVaulted masonry roofShallow-arched masonry roofEarthen roof, unknownVaulted earthen roofWooden roof, unknownRoof system, other
Additional comments on roof system The construction materials have no ductility. By building it in vault form, the forces are distributed on the surface.
Additional comments section 2 The typical plan dimension depend on the building function (residential, barn, mosque etc). Thedimensions may vary, but over all the structure have a regular plan shape.

 

Building Materials and Construction Process

 

 

Description of Building Materials


Structural Element Building Material (s)Comment (s)
Wall/Frame Wall: Brick & adobeWall: Characteristic Strength-40-120 kg/cm2Mix Proportion/Dimensions- 20x10x10 - 50x50x20 cm Varies from places and ages
Foundations Brick & stoneCharacteristic Strength: 40-150 kg/cm2Mix Proportion/Dimensions: Not much bigger than the walls Varies from places and ages
Floors Brick & adobeCharacteristic Strength: 40-120 kg/cm2Mix Proportion/Dimensions: 20x10x10 - 50x50x20 cm Varies from places and ages
Roof Brick & adobeCharacteristic Strength: 40-120 kg/cm2Mix Proportion/Dimensions: 20x10x10 - 50x50x20 cm Varies from places and ages
Other

Design Process


Who is involved with the design process? ArchitectTechnologistBuilderOther
Roles of those involved in the design process
Expertise of those involved in the design process There were no academically qualified engineers or architects and no Standards for design of this type of buildingstructures were available. These are constructed by empiricism or experimentation. However, it is still a topic ofresearch. There are no academically qualified engineers or architects for this type of buildings.

Construction Process


Who typically builds this construction type? OwnerMasonBuilderOther
Roles of those involved in the building process The builder lives in the house. Traditionally every body has a co-operation in construction their own home.
Expertise of those involved in building process These are constructed by empiricism or experimentation.
Construction process and phasing It is basically owner built construction where experienced persons, master builders and maybe some local contractors, with help of laborers, built the structure with shovel, hack, float and other old construction equipment. Theconstruction of this type of housing takes place in a single phase. Typically, the building is originally designed for itsfinal constructed size.
Construction issues

Building Codes and Standards


Is this construction type address by codes/standards? No
Applicable codes or standards
Process for building code enforcement

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 This type of construction is a non-engineered, and not authorized as per development control rules. This type can only be seen in small villages and old towns nowadays. Building permits are not required to build thishousing type.

Building Maintenance and Condition


Typical problems associated with this type of construction Since These types are ancient, sometimes they clash with urban developement
Who typically maintains buildings of this type? BuilderOwner(s)Other
Additional comments on maintenance and building condition Often, the whole family workstogether for the maintenance of the building.

Construction Economics


Unit construction cost Approximately US$ 80.
Labor requirements For construction of an average size of house, 4-8 people work for about 6 months.
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy Houses of this type are mostly occupied by a single family.
Number of inhabitants in a typical building of this construction type during the day >20
Number of inhabitants in a typical building of this construction type during the evening/night >20
Additional comments on number of inhabitants
Economic level of inhabitants Very low-income class (very poor)Low-income class (poor)Middle-income classHigh-income class (rich)
Additional comments on economic level of inhabitants Nowadays very small number of people live in this type of building. Economic Level: The ratio of price of housingunit to the annual income can be 1:1 for poor class families.
Typical Source of Financing Owner financedPersonal savingsInformal network: friends or relativesGovernment-owned housing
Additional comments on financing
Type of Ownership RentOwn outrightUnits owned individually (condominium)Owned by group or poolLong-term lease
Additional comments on ownership
Is earthquake insurance for this construction type typically available? Yes
What does earthquake insurance typically cover/cost Earthquake insurance is included in fire insurance and is based on the value of thebuilding. It depends on the owner capital demand, usually for every US$ 5000 additional coverage, it costs about US$ 6/year added to the fire insurance.
Are premium discounts or higher coverages available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features? Yes
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

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type As stated above, this type has been constructed thousands of years ago, so there must be many other earthquakesespecially historical ones that affected these buildings. However, no exact information is available.
Additional comments on earthquake damage patterns Overall damage patterns observed in past earthquakes for this type of construction included-(walls):Vertical and diagonal cracks in walls, more often alongmortar joints(roof and floors):No significant damage except that caused by walldamage especially when walls under the dome slipleaving the dome roof without any support (other): Crushable brick material, weak mortar band

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.TRUE
Building Configuration-VerticalThe building is regular with regards to the elevation. (Specify in 5.4.1)TRUE
Building Configuration-HorizontalThe building is regular with regards to the plan. (Specify in 5.4.2)TRUE
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.TRUE
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.TRUE
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. TRUE
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);TRUE
Foundation-Wall ConnectionVertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation.FALSE
Wall-Roof ConnectionsExterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. N/A
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).TRUE
MaintenanceBuildings 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 These are special type of structures which are not covered by the National Building Code
Vertical irregularities typically found in this construction type Other
Horizontal irregularities typically found in this construction type SetbackOther
Seismic deficiency in walls Constructed of low strength brittle materials, thestructural elements are unreinforced, walls are large andheavy
Earthquake-resilient features in walls Well defined load path,high rigidity, continuous bearing (Shear) walls
Seismic deficiency in frames Brittle material, mostly no confinements
Earthquake-resilient features in frame Vaulted roof and massive masonry piers.
Seismic deficiency in roof and floors Constructed of low strength brittle materials, heavy inweight, the roof is unreinforced, opening in the roof,slipping of the roof over walls large span,
Earthquake resilient features in roof and floors well defined load path,perfect distribution offorces and stresses
Seismic deficiency in foundation Lack of Lateral resistance
Earthquake-resilient features in foundation N/A

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 This type of structure has a continuous load path, like concrete shear walls, with concrete shell at top that connects thewalls. However, present buildings are constructed of extremely weak and brittle materials. Once cracked, the materials startcrumbling.

Retrofit Information

 

 

Description of Seismic Strengthening Provisions


Structural Deficiency Seismic Strengthening
Not enough distancebetween adjacent buildings For buildings with different heights: 1.Destroy some common part of the adjacent walls to reach distance of 1% wallheight. 2. Join all the buildings in an area to make them behave as a one single structure.
Damages in load path(exterior walls) 1. Add a shear wall to the system. 2. Embed some materials to maintain the wall. 3. Fill the cracks by plaster,cement
Opening in roof Strengthening all around the opening by wood or steel bars.
Heavy weight Remove the heavy weight materials of the roof and replace them with light new materials.
#NAME? #NAME?

Additional comments on seismic strengthening provisions Iranian codes stated that they are not suitable for monuments.
Has seismic strengthening described in the above table been performed? No.
Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages? Both intervention options have been used; they are used for both matters.
Was the construction inspected in the same manner as new construction? No.
Who performed the construction: a contractor or owner/user? Was an architect or engineer involved? Owner, local masons without any no academic background in engineering.
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? N/A
Additional comments section 6

 

References

History of engineering in IranFarshad,M.Iranian code of practice for seismic resistant design of buildings Std.2800, BHRC 2005, Section 3 unreinforced masonry structures, BalkhPublication 1997


Iran insurance co., http://www.iraninsurance.ir


Iranian retrofitting provision for existing buildings, Section 7 masonry structures and infillsIIEES


Iranian code of practice for seismic resistant design of buildings Std.2800, BHRC 2005, section 3 unreinforcedmasonry structures


Earthquake Engineering Theory and ApplicationsMoghaddam,H.Farahang Publication 2002


Persians masters of empireResearches groupTime Life Book Publication


Authors



Name Title Affiliation Location Email
Nima T. Bekloo Mr. CPEng, MIEAust Melbourne/ Australia poosad@gmail.com

Reviewers


Name Title Affiliation Location Email