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 #:117
Building Type: Unreinforced Masonry Building : Brick masonry in mud/lime mortar, with vertical posts
Country: Iran
Author(s): Nima T. Bekloo, NA

Last Updated:
Regions Where Found: Buildings of this construction type can be found in all parts of the Persian Empire, especially next to the desert(Kavir). This type of housing construction is commonly found in both rural and sub-urban areas.
Summary:

The 'Four arches' or Char Taaqi (in Persian) derives its ...

Length of time practiced: More than 200 years
Still Practiced: No
In practice as of: Unknown
Building Occupancy: Institutional housingOther
Typical number of stories: 1
Terrain-Flat: Typically
Terrain-Sloped: Occasionally
Comments: This construction system was common in the past formonumental building structures.


 

Features

 

 

Plan Shape Square, solidRectangular, solid
Additional comments on plan shape This building is square in the plan. This type of building has also been constructed with other plan shapes as wellhowever, then the name would be different.
Typical plan length (meters) 7-30
Typical plan width (meters) 7-30
Typical story height (meters) 7-20
Type of Structural System Masonry: Earthen/Mud/Adobe/Rammed Earth Walls: Mud wallsMasonry: 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 lateral load-resisting system is huge masonry piers connected by the arches at the topand the dome-roof system.Gravity load-bearing system: The vertical load-resisting system is earthen walls: huge masonry piers connected by the arches at the top and the dome-roof system.
Gravity load-bearing & lateral load-resisting systems Plaster of paris was one of the materials that was used for the mortar.
Typical wall densities in direction 1 >20%
Typical wall densities in direction 2 >20%
Additional comments on typical wall densities The typicalstructural wall density is more than 20 %. 15% to 30%.
Wall Openings Large openings are provided in all four sides in between huge pierslocated at the corners. Sometimes an opening is also provided in the roof for natural light. These are usually around 50cm in diameter.
Is it typical for buildings of this type to have common walls with adjacent buildings? No
Modifications of buildings Some modifications could have been made in the roof opening and the shapes of the arches over time. The roofopenings could have been made smaller or larger, and the arches modified as shown in figures.
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 Wooden beams or trusses and joists supporting heavy flooring
Additional comments on floor system Vaulted Masonry; The construction materials have no ductility. With building it in vault form, the forces distribute on surface.
Type of Roof System Masonry roof, unknownVaulted masonry roofShallow-arched masonry roofEarthen roof, unknownVaulted earthen roofRoof system, other
Additional comments on roof system Vaulted Masonry; The construction materials have no ductility. With building it in vault form, the forces distribute on surface.
Additional comments section 2 These buildings do not share common walls with adjacent buildings; theyare mostly free standing buildings. However, sometimes when these are built in the middle of other buildings (as intersection), there is no gap between adjacent buildings. This building type was used as public places like temples, mosques, street or bazaar, intersections, public baths, ormaybe sometimes as house of an important person because with this technique the house could be constructedbigger and higher. In a typical building of this type, there are no elevators and no fire-protected exitstaircases. Depending on the building function, there could be up to four exits on all four sides.

 

Building Materials and Construction Process

 

 

Description of Building Materials


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

Design Process


Who is involved with the design process? ArchitectTechnologistBuilderOther
Roles of those involved in the design process There were no academically qualified engineers or architects and no standard codes for design of this type of buildingstructures were available. These might have been constructed by empiricism or experimentation. However, it is still atopic of research.
Expertise of those involved in the design process There are no academically qualified engineers or architects for this type of buildings.

Construction Process


Who typically builds this construction type? MasonBuilderOther
Roles of those involved in the building process Experienced persons, master builders and maybe some contractors with help of laborers built the structure.
Expertise of those involved in building process
Construction process and phasing Tools/equipment typically used: shovel, hack, float and other old construction equipment.The construction of this type of housing takes place in asingle phase. Typically, the building is not originally designed for its final 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 is a historic building typology and is not being constructed anymore, except for creating the pastarchitecture of Persia. Building permits are not required to build this housing 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 Sometimes the governormaintains the building.

Construction Economics


Unit construction cost Approximately US$70-80 /m2.
Labor requirements 5-15 people for about 6-12 month depending on the size of the building
Additional comments section 3

 

Socio-Economic Issues

 

 

Patterns of occupancy Public places, for small to large population. Each dome-roofprovides cover to one large platform at ground level.
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 10-20
Additional comments on number of inhabitants
Economic level of inhabitants Middle-income classHigh-income class (rich)
Additional comments on economic level of inhabitants Economic Level: The ratio of price of housing unit to the annual income can be 1:1 for middle class families.
Typical Source of Financing Personal savingsInformal network: friends or relativesGovernment-owned housingOther
Additional comments on financing Government from taxes or people of an area gathered and built -for example- a public bath or mosque.
Type of Ownership Own outrightOwned by group or poolOther
Additional comments on ownership It is a public building owned by the government or people of the area.
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 it is based on the value of thebuilding.Depends on the owner capital demand, usually for every US$5000 additional cover, it costs about US$6/year added to fire insurance. That is what the insurance company quotes, however, these structures are now parts ofthe governors' properties.
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
2003Bam
6.5VIII

Past Earthquakes


Damage patterns observed in past earthquakes for this construction type As stated above this type has been constructed thousands years ago, hence there must have been many otherearthquakes especially the historical ones that affected these buildings. However, information in not available.
Additional comments on earthquake damage patterns Overall damage patterns observed in past earthquakes for this type of construction included crushing of brick material and:(frame): diagonal cracks more often in mortar, shearand tensile failure at the column bottom (roof and floors): No significant damage except that causedby column failure(other): Crushing of brick material

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 OpeningsFALSE
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
Vertical irregularities typically found in this construction type Other
Horizontal irregularities typically found in this construction type SetbackChange in vertical structureOther
Seismic deficiency in walls Brittle material, mostly no confinements
Earthquake-resilient features in walls Vaulted roof and massive masonry piers.
Seismic deficiency in frames Constructed of low strength brittle materials, the structuralelements are unreinforced.
Earthquake-resilient features in frame Well defined load path, highrigidity
Seismic deficiency in roof and floors Constructed of low strength brittle materials, heavy inweight, the roof is unreinforced, opening in the roof, largespan
Earthquake resilient features in roof and floors Well defined load path, perfectdistribution of forces andstresses
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 continuous load path like concrete columns with concrete shell connecting the columns atthe top, except that bricks and mortars do not have that material properties.

Retrofit Information

 

 

Description of Seismic Strengthening Provisions


Structural Deficiency Seismic Strengthening
No shear wall Add a shear wall to the system by filling between the arches.
Damages in load path (columns) 1. add a shear wall to the system by filling between the arches. 2. embed some materials to maintain the column.
opening in roof; Unreinforced arch Strengthening all around the opening; Reinforcing of the arch by prestressed with cable or steel bar at spring level
heavy weight Remove the heavy weight materials of the roof and replace them with light new materials.
large span Constructing some horizontal tie beams (timber, cable or steel bar).

Additional comments on seismic strengthening provisions Unreinforced arch - Reinforcing of the arch by prestressed with cable or steel bar at spring level
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? They are used for both issues.
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? Government.
What has been the performance of retrofitted buildings of this type in subsequent earthquakes? N/A
Additional comments section 6 The construction materials used in these buildings do not comply with the Iranian codes.

 

References

History of engineering in IranFarshad,M.Balkh Publications 1997


Iranian retrofitting provision for existing buildings : Section 7 - Masonry structures and infillsIIEES


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


Earthquake Engineering Theory and ApplicationsMoghaddam,H.Farahang Publication 2002


Siamak Ahi webblog, http://chaartaagh.blogspot.com/


Authors



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

Reviewers


Name Title Affiliation Location Email