Report #: 53

Report Date:

Country: RUSSIA

Housing Type:

Housing Sub-Type:

Author(s): Mark Klyachko, Yuriy Gordeev, Freda Kolosova

Last Updated:

Regions Where Found: Buildings of this construction type can be found in seismically prone areas of Russia (Far East, Siberia, Baikal Lake Region, North Caucasus) and CIS states (Central Asia, Armenia, Georgia, etc.) where it accounts for 10 to 15% of the housing stock.

Summary: This is a typical residential construction found both in urban and rural areas. It represents a construction practice followed in the former Soviet Union. Buildings of this type constitute 15 to 30% of the housing stock in seismically prone areas of Russia (Far East, Siberia, BaikalLake Region, North Caucasus) and in CIS states (Central Asia, Armenia, Georgia, etc.). The main load-bearing system for lateral and gravity loads consists of concrete block masonry walls and concrete floor slabs. Seismic resistance is relatively good, provided that the welded block wall connections are present and well constructed.

Length of time practiced: 25-60 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Residential, 20-49 units

Typical number of stories: 2-4

Terrain-Flat: Typically

Terrain-Sloped: Occasionally

Comments:

This is the Soviet Union construction practice followed during the last 50-60 years (after the Second World War).

Building Occu

Plan Shape: Rectangular, solid

Additional comments on plan shape: In general all building plans are of rectangular shape.

Typical plan length (meters): 43

Typical plan width (meters): 12

Typical story height (meters): 2.7

Type of Structural System: Masonry: Unreinforced Masonry Walls: Concrete block masonry in cement mortar

Additional comments on structural system: Lateral Load-Resisting System: Lateral load-resisting system consists of concrete block masonry walls and precast reinforced floor structure. In most cases floor structure consists of the precast reinforced concrete hollow core panels, which are combined in horizontal diaphragm by means of cast-in-situ reinforced concrete bond beams (belt) constructed at the building perimeter.

Gravity Load-Bearing Structure: Same as lateral load-resisting system.

Gravity load-bearing & lateral load-resisting systems:

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 %. 20-25%.

Wall Openings: Windows: 10-15%; Doors: 5-8%.

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

Modifications of buildings: Typical modification patterns include the demolition of interior walls and perforation of walls with door openings.

Type of Foundation: Shallow Foundation: Reinforced concrete strip footing

Additional comments on foundation:

Type of Floor System: Other floor system

Additional comments on floor system: Precast hollow core concrete slabs

Type of Roof System: Roof system, other

Additional comments on roof system: Precast hollow core concrete slabs

Additional comments section 2: In hilly areas from 1.5% to ~15%; on the flat terrain approximately 85% When separated from adjacent buildings, the typical distance from a neighboring building is 5 meters.

Who is involved with the design process?: EngineerArchitect

Roles of those involved in the design process: Design performed by Professional Engineers and Architects.

Expertise of those involved in the design process: Expertise for design of buildings of this type was available, including the construction quality procedure developed by the author of this contribution.

Who typically builds this construction type?: Other

Roles of those involved in the building process: Buildings of this type were built by government-owned construction companies.

Expertise of those involved in building process:

Construction process and phasing: All precast structure members and concrete blocks are manufactured in special construction plants. Masonry mortar is usually produced in the factory, too. Lifting crane is used for the erection of the building. The construction of this type of housing takes place in a single phase. Typically, the building is originally designed for its final constructed size.

Construction issues

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

Applicable codes or standards: Code/Standard: Building Catalog of Typical Project for housing seria of 1-306c, 1-307c, 1957y, issued1951 The year the first code/standard addressing this type of construction issued was 1951. Construction in the Seismic Regions. SNiP II-7-81*. The most recent code/standard addressing this construction type issued was 1981. Afterward, numerous amendments were introduced.

Process for building code enforcement: The process consists of issuing permits for the design & construction, including the architectural permits and urban planning/municipal permits. Designers need to have licence to practice and are responsible to follow the building codes. Building inspection is performed and the permit is issued.

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: Use of rigid mortars in the construction and a low cohesion in the masonry.

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

Additional comments on maintenance and building condition: The maintenance is performed either by the owner (city) or (periodically) by a contractor # a maintenance firm.

Unit construction cost: 250-350 $US/sq m (per the official rate).

Labor requirements: It takes about 30 man-months to build a 4-story building with plan dimensions 12m x 42m.

Additional comments section 3:

Damage patterns observed in past earthquakes for this construction type: Some buildings of this type were damaged in the 1959 and 1971 Kamchatka earthquakes and 1988 Spitak earthquake.

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: -Absence of lime and plastifier; -Low cohesion of masonry (<120 kPa); (cohesion is equal to tension strength of masonry when shear stress=0). -Low-strength masonry and cement mortar.

Seismic deficiency in roof and floors: #NAME?

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

Additional comments on seismic strengthening provisions: The recommended methods for seismic strengthening of buildings of this construction type are:

METHOD OF EXTERIOR FRAME (MEF) Goal: To increase lateral seismic stability of buildings with load-bearing masonry or large-block concrete walls. Concept: The system of precast or “cast-in-situ” concrete buttresses (counterforts) (1) tied to the longitudinal exterior wall. Application: This method has been used successfully for seismic strengthening of buildings with longitudinal bearing walls and deficient lateral earthquake resistance both as self-contained strengthening system and as a combination with PTS (for stringer walls) or with SIS (for extended masonry buildings with widely spaced lateral inner walls). Description: The MEF is performed by constructing special concrete buttresses (counterforts) tied to the longitudinal load-bearing walls at the building ends and other locations as required. In order to ensure a uniform seismic performance of the existing structure strengthened with the buttresses, the buttresses are tied to the existing walls by means of the dowels and anchors. This solution does not require the pairs of buttresses (counterforts) to be tied at each floor level; it is considered to be adequate to install a prestressed tie to connect the buttresses (counterforts) at the roof level.

STRENGTHENING OF BUILDINGS USING THE POST # TENSIONING SYSTEM (PTS) Goal: To increase seismic resistance of existing buildings. Concept: The reduction in principal tensile stresses induced by seismic loads to allowable levels. Description and sequence of operations: -Drilling of the vertical holes is carried out by means of special equipment; the amount of opening (10) is not less than one for each partition. -The wire cables (2) are pulled through each opening (10). -Cables are anchored at the basement level and then post-tensioned up to 1600 KN. -A special cement-based grout (1) is injected into the holes and the cables are subsequently anchored at the roof level. The post-tensioning of walls prevents the formation of cracks in an earthquake and results in the increased seismic resistance of the indivdual walls and the building as a whole. Equipment: For drilling: “GEARMEC” (Sweden); for post-tensioning: IMS system (Yugoslavia).

THE METHOD OF ADDED STIFFNESS (SIS) Goal: Seismic strengthening of masonry buildings to achieve increased seismic reliability and safety. Concept: The stiffness increase is achieved by means of a new reinforced concrete wall (overlay) attached to the existing wall. In this way, the coupled perforated shear walls are formed, and lateral seismic loads are redistributed: the seismic loads remove on the spine walls from principal one. Description: The SIS method consists of constructing new cast-in-situ concrete walls (1) of 10-15 cm thickness reinforced with steel wire mesh. The new walls are attached to the existing ones using dowels (3) and anchors (4). The new walls may be constructed with additional pilasters (2) if required. Equipment: Sheathing “MEVA” (Germany), instruments: “Bosch” and “Hilti” (Germany).

THE METHOD OF UPPER DAMPING STOREY (UDS) Goal: To develop a big mass damper for the self-damping of buildings under seismic impact. Concept: To achieve a flexible structure with stiffness and mass capable of reducing the seismic demand in an existing building to a permissible level. Application: Masonry or block buildings with deficient seismic resistance D=2.0 (MSK scale). A very effective application for 4- to 5-story residential masonry and large-block houses with D=1.0-1.5. The superstructure can be constructed as a “cold” garret or as additional floor (duplex apartment).

Has seismic strengthening described in the above table been performed?: Yes. A number of buildings of this type have been strengthened using the above described methodology.

Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages?: In most cases repair was executed after earthquake damage.

Was the construction inspected in the same manner as new construction?: Yes

Who performed the construction: a contractor or owner/user? Was an architect or engineer involved?: Strengthening of buildings is accomplished by contractor. All processes are controlled by engineers.

What has been the performance of retrofitted buildings of this type in subsequent earthquakes?: N/A

Manual on Certification of Buildings and Structures in the Seismic-Prone Areas, Second Edition, CENDR, Petropavlovsk, Kamchatka, Russia, 1990.

—- Recommendations for Preventive Seismic Strengthening of Buildings, CENDR, Russia, 1993