Two-story unreinforced brick masonry building with wooden floors, Kyrgyzstan

From World Housing Encyclopedia


1. General Information

Report: 41

Building Type: Two-story unreinforced brick masonry building with wooden floors

Country: Kyrgyzstan

Author(s): Svetlana Uranova, Ulugbek T. Begaliev

Last Updated:

Regions Where Found: Buildings of this construction type can be found in the cities throughout Kyrgyzstan. It is estimated that around 5% of residential buildings in Bischkek and 5-7% of buildings in other cities are of this type. This type of housing construction is commonly found in urban areas.

Summary: This is a non-engineered construction practiced in Kyrgyzstan in the period from 1920 to 1957. The load-bearing structure in buildings of this type consists of unreinforced brick masonry walls and wooden floor beams. Brick masonry walls are usually constructed in mud mortar. Walls are usually perforated with rather large door and window openings. The wall length between the adjacent cross walls is on the order of 9-10 m. Wooden floor elements (beams) are not tied together and they do not behave as diaphragms. Based on performance in past earthquakes, this building type is considered highly vulnerable to seismic effects.

Length of time practiced: 76-100 years

Still Practiced: No

In practice as of:

Building Occupancy: Single dwellingResidential, 10-19 unitsMixed residential/commercial

Typical number of stories: 2

Terrain-Flat: Typically

Terrain-Sloped: 3

Comments:


2. Features

Plan Shape: Rectangular, solid

Additional comments on plan shape: Typical shape of a building plan for this housing type is rectangular.

Typical plan length (meters): 30

Typical plan width (meters): 12

Typical story height (meters): 3.5

Type of Structural System: Masonry: Unreinforced Masonry Walls: Brick masonry in mud/lime mortar

Additional comments on structural system: Gravity load-bearing system: Elements of gravity load-resisting system are the same as lateral load-resisting system. Wooden floor beams also carry gravity loads. The beams are supported by the wall; however, without any special anchorage. Typical beam cross-sectional dimensions are: 70-150 mm width and 150-250 mm depth. Wooden floors typically do not have concrete topping. Details of floor structures and wall-floor connections are illustrated in Figure 4. Lateral load-resisting system: The lateral load-resisting system in buildings of this type consists of unreinforced brick masonry walls. Brick masonry walls are usually constructed in mud mortar. Typical wall thickness ranges from 380 mm to 510 mm. Walls are usually perforated with rather large door and window openings. Window and door lintel beams are made of timber board or steel bars embedded in mortar. Typical lintel details are shown in Figure 5. Wooden floors do not act as diaphragms.

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 is 15%. The range between the ratios of the area of all the walls in each principal direction divided by the total area of the plan is 7-8%.

Wall Openings: Typical size of window openings is 1.2m-1.5m(height) x 1.5-2m (width), and the door openings are: 2m (height)x1m (width). There are 16-20 windows at each floor level in the building. The overall window and door areas constitute around 15% 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: Modifications in buildings of this type are common e.g. installation of new doors and windows, new walls and partitions, deletion of doors and windows, demolition of existing load-bearing walls and partitions, construction of new balconies, etc.

Type of Foundation: Shallow Foundation: Rubble stone, fieldstone strip footing

Additional comments on foundation:

Type of Floor System: Other floor system

Additional comments on floor system: Timber: wood planks of breams with ballast and concrete or plaster finishing

Type of Roof System: Roof system, other

Additional comments on roof system: Timber: wood shingle roof

Additional comments section 2: Typical separation distance between buildings: minimum 10 meters


3. Building Process

Description of Building Materials

Structural Element Building Material (s) Comment (s)
Wall/Frame Wall: Brick masonry Wall: Characteristic Strength-Rt<30kPa; brick compressive strength is over 750 MPa, and mortar compressive strength of over 50 MPa. Rt= adhesion between mortar and bricks
Foundations Stone
Floors Wood Typically pine or aspen wood
Roof Wood Typically pine or aspen wood
Other

Design Process

Who is involved with the design process? Other

Roles of those involved in the design process:

Expertise of those involved in the design process:


Construction Process

Who typically builds this construction type? Other

Roles of those involved in the building process: In general, this is a non-engineered construction (constructed without qualified technical expertise). Usually an engineer managed the construction of this type.

Expertise of those involved in building process:

Construction process and phasing: Construction of this type was practised many years ago. Usually an engineer managed the construction; however, construction workers did not have any construction-related experience. In some cases, buildings of this type had been constructed without a proper design documentation. This building is not typically constructed incrementally and is not 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:


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: Cost of load-bearing structure is on the order of 100 US$/sq m.

Labor requirements: 10 people need to work for 12-24 months in order to build a building of this type.

Additional comments section 3:


4. Socio-Economic Issues

Patterns of occupancy: There are 2-4 housing units per building unit at each floor level. Usually there are 8 - 16 units in each building. One family occupies one housing unit. In general, between 8 to 16 families occupy one building of this type.

Number of inhabitants in a typical building of this construction type during the day: 44105

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: Low-income class (poor)Middle-income class

Additional comments on economic level of inhabitants: 70% poor and 30% middle class inhabitants occupy buildings of this type. Ratio of housing unit price to annual income: 5:1 or worse

Typical Source of Financing: Personal savings

Additional comments on financing:

Type of Ownership: Own 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:


5. Earthquakes

Past Earthquakes in the country which affected buildings of this type

Year Earthquake Epicenter Richter Magnitude Maximum Intensity
1992 Suusamir, Kyrgyzstan 7.4 VII
1986 Kairakuum, Tadjikistan 6.8 VII
1988 Spitak, Armenia

—-

Past Earthquakes

Damage patterns observed in past earthquakes for this construction type: The epicenter of the Suusamir earthquake was in the hilly area (mountains). Maximum earthquake intensity (based on the 12-point intensity scale) was 9. Buildings of this type affected by the earthquake were away from the epicenter, located in the region with intensity 6-7 on the same 12-point intensity scale. In the Kairakum earthquake, intensity reported in the cities (where this type of construction is found) was 6-7. Most buildings of this type suffered various extent of damage to masonry walls. Buildings of this type were also damaged in the 1988 Spitak, Armenia earthquake (see Figure 6).

Additional comments on earthquake damage patterns: Overall damage patterns observed in past earthquakes for this type of construction included damage to the walls or complete collapse of buildings; the extent of damage depends on the direction of seismic waves, earthquake intensity, and pier dimensions. Wall failure was due to in-plane or out-of-plane shear, more often as a result of out-of-plane shear.


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. FALSE
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. FALSE
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. FALSE
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). FALSE
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: - Brick masonry walls have poor shear, tension and compression resistance, and steel reinforcement is generally not provided; - Window and door lintels are made of timber boards or steel bars; - Walls are usually perforated with rather large door and wind

Earthquake-resilient features in walls:

Seismic deficiency in frames:

Earthquake-resilient features in frame:

Seismic deficiency in roof and floors: Wood beams are not joined in the 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

Additional comments on seismic strengthening provisions: Seismic strengthening is not considered feasible for buildings of this type. If strengthening were to be implemented, there would be a need to install new floors, provide jacketing of the walls (on both faces) etc. This is considered to be expensive and therefore the buildings of this type, if severely damaged in an earthquake, are replaced with new buildings. In case of minor damage (e.g. cracks developed in the walls), these cracks are repaired without strengthening.

Has seismic strengthening described in the above table been performed? N/A

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:


7. References

  • Seismic Hazard and Building Vulnerability in Post-Soviet Central Asia Republics. Nato Series.Netherland.
  • Buildings and Construction Design in Seismic Regions. Handbook.Bishkek.1996.

Authors

Name Title Affiliation Location Email
Svetlana Uranova Dr., Head of the Laboratory KRSU Kievskai 44, Bishkek 720000 Kyrgyz Republic uransv@yahoo.com
Ulugbek T. Begaliev Head of Department KNIIPC Vost Prom Zone Cholponatisky 2, Bishkek 720571 Kyrgyz Republic utbegaliev@yahoo.com

Reviewers

Name Title Affiliation Location Email
Svetlana N. Brzev Instructor Civil and Structural Engineering Technology, British Columbia Institute of Technology Burnaby BC V5G 3H2, Canada sbrzev@bcit.ca
Print/export
QR Code
QR Code reports:report_41 (generated for current page)