Report #: 76

Report Date:

Country: KYRGYZSTAN

Housing Type:

Housing Sub-Type:

Author(s): Jacob Eisenberg, Svetlana Uranova, Marat Abdibaliev , Ulugbek T. Begaliev

Last Updated:

Regions Where Found: There are about 30 base isolated buildings in Bishkek (Kyrgyzstan). In 1982, two 3-story brick masonry wall buildings were built in the area with high seismicity (9-10 per MSK scale). A residential block (microdistrict) of 9-story concrete large panel buildings protected with seismic isolation belt was built in the period 1983-1990. Several 9-story large panel concrete buildings were built in the center of Bishkek. One of the buildings is also equipped with a dynamic damper. Some buildings with seismic isolation belt were built in Kazahkstan and Russia (Kamchatka).

Summary: Sliding belt is a base isolation system developed for seismic protection of buildings by reducing and limiting the level of seismic forces. The sliding belt system is installed at the base of the building, between the foundation and the superstructure. The foundation is usually made of cast-in-situ concrete and the superstructure is typically a loadbearing wall structure, either 9-story large concrete panel system or 3-story brick masonry construction. Once the earthquake base shear force exceeds the level of friction force developed in the sliding belt, the building (superstructure)starts to slide relative to the foundation. It is expected that the lateral load transferred to the superstructure is approximately equal to the frictional force that triggers the sliding of the structure. The sliding belt consists of the following elements: a) sliding supports, including the 2 mm thick stainless steel plates attached to the foundation and 4 mm Teflon (PTFE) plates attached to the superstructure, b) reinforced rubber restraints for horizontal displacements (horizontal stop) and c) restraints for vertical displacements (uplift). A typical large panel building with plan dimensions 39.6m x10.8 m has 63 sliding supports and 70 horizontal and vertical restraints. The sliding belt scheme was developed in CNIISK Kucherenko (Moscow) around 1975. The first design application in Kyrgyzstan was made in 1982. To date the system has been applied on over 30 buildings in Bishkek, Kyrgyzstan. All these buildings are residential buildings and are presently occupied. Base isolated buildings of this type have not been exposed to the effects of damaging earthquakes as yet.

Length of time practiced: Less than 25 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Residential, 50+ units

Typical number of stories: 9

Terrain-Flat: Typically

Terrain-Sloped: 3

Comments:

Plan Shape: Rectangular, solid

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

Typical plan length (meters): 50.4

Typical plan width (meters): 10.8

Typical story height (meters): 3

Type of Structural System: Structural Concrete: Precast Concrete: Large panel precast wallsOther: Seismic Protection Systems: Building protected with base-isolationOther: Seismic Protection Systems: Building protected with seismic dampersOther

Additional comments on structural system: Lateral load-resisting system: Lateral load-resisting system includes the superstructure (e.g. large reinforced concrete panel construction or brick masonry construction) and the foundation. The sliding belt is installed at the base of the building, between the foundation and the superstructure. The sliding belt consists of the following elements: a) sliding supports, including the stainless steel plates attached to the foundation and the Teflon (PTFE) plates attached to the superstructure, b) reinforced rubber restraints for horizontal displacements (horizontal stop), and c) restraints for vertical displacements (uplift). The steel plates are 2 mm thick; the plate width is approximately equal to the foundation width, and the length depends on the size of the Teflon plate located at the center (usually projects by 150 mm on each side). The dimensions of Teflon plates are usually 400 mm x 400 mm for 9-story buildings and 200 mm x 200 mm for 5-story buildings; typical plate thickness is 4 to 6 mm. Horizontal stops consist of rigid reinforced structure with steel plates and a rubber damper. Vertical stops consist of steel anchor bolts. A typical large panel building (plan dimensions 39.6m x10.8 m) is equipped with 63 sliding supports and 70 horizontal and vertical restraints. A gap between rubber damper and sliding support for a 9-story building is usually 50 mm; this means that the horizontal stops will be activated once the building has moved by 50 mm in the horizontal direction. The recommended “seismic gap” ranges from 100 to 120 mm. In buildings constructed in Bishkek 300 mm gap was provided. No special provisions were made for flexible water supply and electrical facilities in the buildings protected with this system.

Once the earthquake base shear force exceeds the level of frictional force developed in the sliding belt (approximately equal to 10% of the building weight), the building (superstructure) starts to slide relative to the foundation. The design recommendations state that the frictional coefficient value for Teflon-steel sliding is 0.1 (unless a different value is obtained by the tests). However, it should be noted that once the sliding is initiated, building continues to vibrate and restraints get activated as well. The analysis is based on rather complex formulas based of research studies that have been modified for the design practice. Simplified design calculations are not commonly used in the design of this construction type; comprehensive analysis is deemed required. Seismic design of the superstructure is performed based on the results of the dynamic analysis. The level of seismic forces (seismic demand) is reduced as compared to the conventional buildings by up to 50%.

The sliding belt scheme was developed by CNIISK Kucherenko in Moscow around 1975; other institutes in the former Soviet Union also contributed to the development. Late L. S. Kilimnik was the leader in the development of the seismic belt system. The first design applications of seismic belt scheme were made in Bishkek in 1982. Two types of tests, static tests under horizontal loads and dynamic tests of full-scale buildings using the vibration equipment, were conducted in 1980. The design recommendations for base isolated buildings of this type were developed based on the results of these tests.

Gravity load-bearing system: Gravity load-bearing structure is a conventional building construction, either large panel construction or brick masonry construction. Majority of base isolated buildings of this type are large panel concrete buildings with monolithic joints (seria 105). This construction type was described in detail in another contribution from Kyrgyzstan (by S. Uranova and U. Begaliev). Brick masonry buildings are 3-story high and are equipped with the reinforced concrete members and steel mesh, typical for brick masonry construction in the former Soviet Union. It should be noted, however, that the construction of conventional 3-story high brick masonry construction was otherwise not permitted in high seismic zones (intensity 9 to 10 on the MSK scale).

Gravity load-bearing & lateral load-resisting systems:

Typical wall densities in direction 1: 10-15%

Typical wall densities in direction 2: 10-15%

Additional comments on typical wall densities: Total wall area/plan area is about 0.14. Wall density in two principal directions is not equal; in one of the directions wall density is less by 20 to 30% as compared to the other direction.

Wall Openings: Wall openings are same as in typical large panel buildings. Usually, for a 3.6m long panel, a window size is 1.82m(width)x1.53m(height); for 2.7m long panel - window size is 1.24m(width)x1.53m(height). The size of a door is 0.9m(width)x2m(height). The size of a balcony door (together with window) is either 2.25m or 1.66 m(width) or and 1.9m (height). Overall window and door areas make up to 20% of the overall wall area. There are 16 windows for a building with 10.8m x 25.2m plan dimensions.

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

Modifications of buildings: Typical patterns of modification include the perforation of walls with door openings and the creation of door opening instead of the window.

Type of Foundation: Shallow Foundation: Reinforced concrete strip footing

Additional comments on foundation: Foundation include seismo-isolation sliding belt

Type of Floor System: Other floor system

Additional comments on floor system: Structural Concrete: Precast solid slab panels

Type of Roof System: Roof system, other

Additional comments on roof system: Structural Concrete: Precast solid slab panels

Additional comments section 2: When separated from adjacent buildings, the typical distance from a neighboring building is 10 meters.

Who is involved with the design process?: EngineerArchitectOther

Roles of those involved in the design process: Design of buildings of this construction type was done completely by engineers and architects. Researchers also participated in the development of design documentation. Engineers played a leading role in each stage of construction.

Expertise of those involved in the design process: The expertise required for the design and construction of this type is available. Building designs were prepared by design institutes. The academic background of the designers is the same as for conventional construction. It is not required to have designers with high academic degrees eg. M.Sc. and Ph.D. on the team.

Who typically builds this construction type?: Builder

Roles of those involved in the building process:

Expertise of those involved in building process: Construction of base isolated buildings and the approval of the designs was controlled by research institutes (State Experts) like any other new construction performed in accordance with the Building Code requirements.

Construction process and phasing: Specialized construction companies make precast concrete elements and perform casting of concrete in-situ. Precast elements are fabricated at the plants. In case of precast foundation and superstructure construction, steel and Teflon plates are installed at the plant. Horizontal restraints (rubber dampers) and vertical restraints are installed at the site. The main construction equipment is the same as in the case of conventional concrete construction and it includes crane, welding equipment and concrete mixers.

This building is not typically constructed incrementally and is designed for its final constructed size.

Construction issues

Is this construction type address by codes/standards?: Yes

Applicable codes or standards: SNiP II-7-81. Building in Seismic Regions.Design code The first (still most recent) code/standard addressing this type of construction was issued 1981.

SNiP II-7-81. Building in Seismic Regions. Design code. CNIISK. Recommendations for Design of Buildings with Seismic Isolation Belt and Dynamic Vibration Dampers, Moscow, 1984.

Process for building code enforcement: Building permit will be given if the design documents have been approved by the State Experts. State Experts check the compliance of design documents with pertinent Building Codes. According to the building bylaws, a building cannot be used without the formal approval of a special committee. The committee gives the approval if design documents are complete and the construction has been carried out in compliance with the Building Codes.

Are building permits required?: Yes

Is this typically informal construction?: No

Is this construction typically authorized as per development control rules?: Yes

Additional comments on building permits and development control rules:

Typical problems associated with this type of construction: Installation/construction of sliding belt is a rather complex technological problem as compared to the conventional construction.

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

Additional comments on maintenance and building condition:

Unit construction cost: For load-bearing structure only (including the seismic belt) the cost is about 230$/m.sq. For a similar prefabricated concrete panel building (seria 105) without a seismic belt the construction cost would be US$ 150-200/m.sq. Therefore, the increase in unit cost due to the installation of seismic belt is in the range from 15 to 50 %.

Labor requirements: It would take from 8 to10 months for a team of 15 workers to construct a load-bearing structure.

Additional comments section 3:

Damage patterns observed in past earthquakes for this construction type: This building type was tested by special vibration equipment that applied loads equal to design seismic loads.

Additional comments on earthquake damage patterns: Damage of bearing structures of upper floors less than in similar buildings without seismic protection systems.

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.

Vertical irregularities typically found in this construction type: Other

Horizontal irregularities typically found in this construction type: Other

Seismic deficiency in walls: Application to large panel construction - Panel joints; quality of construction,especially welding of reinforcing bars from the adjacent panels and filling the gaps between the panels with concrete is not satisfactory in some cases: poor quality of panel joints and brick masonry

Earthquake-resilient features in walls: Due to a large number and uniform distribution of panel joints existing in one building, deficient construction of some joints does not have a major impact on the overall seismic resistance of the building as a whole.

Seismic deficiency in roof and floors: Within the panel joints- quality of construction, especially welding of reinforcing bars from the adjacent panels and filling the gaps between the panels with concrete is not satisfactory in some cases.

Earthquake resilient features in roof and floors: Includ(ing) a large number and uniform distribution of panel joints in one building, deficient construction of some joints does not have a major impact on the overall seismic resistance in the building as a whole

Other earthquake-resilient features: Seismic Belt: The sliding belt is efficient in reducing the level of seismic forces in the building.

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

Has seismic strengthening described in the above table been performed?: No. Buildings of this type are already strengthened by means of seismic belt.

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.

CNIISK. Recommendations for Design of Buildings with Seismic Isolation Belt and Dynamic Vibration Dampers, Moscow, 1984. (in Russian)

King, Stephanie, Vitaly Khalturin and Brian E. Tucker. Seismic Hazard and Buildings Vulnerability in Post-Soviet Central Asia Republics. Proceedings of the NATO Advanced Research Workshop on Earthquake Risk Management Strategies for Post-Soviet Central Asian Republics, Almaty, Kazakhstan, Kluwer Academic Publishers, Dordrecht, Netherlands, 1999.

Uranova, S.K., and Imanbekov, S.T. Building and Construction Design in Seismic Regions-Handbook. Kyrgyz NIIP Stroitelstva, Building Ministry Kyrgyz Republic, Bishkek, Kyrgyz Republic, 1996 (in Russian).

Eisenberg, J. et al. Seismoisolation in Russia and former USSR Countries: Recent Developments. Proceedings of the International Post-SMiRt Conference Seminar, Cheju, Korea, Korea Earthquake Engineering Research Center, Seoul, Korea, 1999,Vol.1, p. 99-115.

Eisenberg, J. et al. Applications of Seismic Isolation in the USSR. Proceedings of the Tenth World Conference on Earthquake Engineering, Balkema, Roterdam, Vol.4, 1992, p. 2039-2044.

Eisenberg, J. and Bealiev, V.S. Operating Experience in Designing and Construction of the System of Special Seismic Isolation of Buildings and Constructions in the former Russia. Proceedings of the Eleventh World Conference on Earthquake Engineering, Pergamon, Elsevier Science Ltd., Oxford, England, 1996, Disc 1, Paper No. 263.

Experimental Buildings with Seismic Protection in Petropavlovsk-Kamchatskiy (in Russian)