World Housing Encyclopedia Report

Transcription

1 World Housing Encyclopedia Report Country: Uzbekistan Housing Type: Precast reinforced concrete frame panel system of seria IIS-04 Contributors: Shamil Khakimov Bakhtiar Nurtaev Primary Reviewer: Svetlana Brzev Created on: 6/5/2002 Last Modified: 7/2/2003 This encyclopedia contains information contributed by various earthquake engineering professionals around the world. All opinions, findings, conclusions, and recommendations expressed herein are those of the various participants, and do not necessarily reflect the views of the Earthquake Engineering Research Institute, the International Association for Earthquake Engineering, the Engineering Information Foundation, John A. Martin & Associates, Inc. or the participants' organizations.

2 Table of Contents General Information...1 Architectural Features... 3 Socio-Economic Issues... 4 Structural Features... 5 Evaluation of Seismic Performance and Seismic Vulnerability... 9 Earthquake Damage Patterns Building Materials and Construction Process Construction Economics...15 Insurance...16 Seismic Strengthening Technologies References Contributors Figures...20

3 1 General Information 1.1 Country Uzbekistan 1.3 Housing Type Precast reinforced concrete frame panel system of seria IIS Summary This housing type is used for the construction of residential and public buildings in many cities throughout Uzbekistan -- including the capital city Tashkent -- which are located in zones with intensities between 7-9. Residential buildings of this type are generally 9 to 12 stories high, whereas public buildings of the same construction are 1 to 4 stories high. All seismic load-resisting (and also nonstructural) components, e.g., foundations, columns, girders, slabs, staircases, wall panels, etc., are manufactured in specialized plants. Subsequently, the materials are transported to the building site. The positive features of this construction type are 1) the ability to manufacture all building materials in an industrialized setting, and 2) the gain in efficiency because the same building components may be used both for residential and public buildings. The key drawback is that the welded joints cause seismic vulnerability, when the building is located in zones of extremely high seismic loads. These joints have shown extremely brittle behavior in earthquakes. Earthquake damage is mainly concentrated in the column joints, or in the column-to-girder joints. In some cases non-bearing walls and exterior wall panels have collapsed. FIGURE 1: Typical Building 1.5 Typical Period of Practice for Buildings of This Construction Type How long has this construction been practiced < 25 years < 50 years < 75 years < 100 years < 200 years > 200 years Is this construction still being practiced? Yes No Additional Comments: This traditional construction practice has been followed for over 35 years. The frame panel seria IIS-04 was first used in Page 1

4 1.6 Region(s) Where Used Tashkent and other cities of Uzbekistan and Central Asia. In Tashkent, this housing type accounts for over 18% of the residential building stock and for over 25% of the public building stock. 1.7 Urban vs. Rural Construction Where is this construction commonly found? In urban areas In rural areas In suburban areas Both in rural and urban areas Page 2

5 2 Architectural Features 2.1 Openings In this housing type, the main load-bearing elements are the columns, beams and joints (a frame structure). Therefore, seismic vulnerability does not depend on the number and size of the openings. The size of the windows and doors ranges from 2.25 m to 4.5 m. 2.2 Siting Is this type of construction typically found on flat terrain? Is this type of construction typically found on sloped terrain? (hilly areas) Is it typical for buildings of this type to have common walls with adjacent buildings? Yes No The typical separation distance between buildings is 30 meters 2.3 Building Configuration Usually a rectangular plan. 2.4 Building Function What is the main function for buildings of this type? Single family house Multiple housing units Mixed use (commercial ground floor, residential above) Other (explain below) 2.5 Means of Escape The means of escape depends upon the number of apartments on the floor. If a building has "point block" planning (2-4 apartments without a corridor at each floor level), there is typically one staircase and one exit. 2.6 Modification of Buildings Minor modifications of interior partition walls may be done by the owners. Page 3

6 3 Socio-Economic Issues 3.1 Patterns of Occupancy It depends on the size of the multi-story building. Typically, over 60 families live in a 12-story building. 3.2 Number of Housing Units in a Building 60 units in each building. Additional Comments: Usually more than 60 units in a building. 3.3 Average Number of Inhabitants in a Building How many inhabitants reside in a typical building of this construction type? During the day / business hours < 5 5 to > 20 Other During the evening / night 3.4 Number of Bathrooms or Latrines per Housing Unit Number of Bathrooms: 1 Number of Latrines: Economic Level of Inhabitants Economic Status House Price/Annual Income (Ratio) Very poor / Poor / Middle Class 5000/720 Rich / 3.6 Typical Sources of Financing What is the typical source of financing for buildings of this type? Owner Financed Personal Savings Informal Network: friends and relatives Small lending institutions/microfinance institutions Commercial banks / mortages Investment pools Combination (explain) Government-owned housing Other 3.7 Ownership Type of Ownership/Occupancy Rent Own outright Own with Debt (mortgage or other) Units owned individually (condominium) Owned by group or pool Long-term lease Other Additional Comments: Almost 90% of the buildings are privately owned and 10% are rented from the local government. Page 4

7 4 Structural Features 4.1 Lateral Load-Resisting System The lateral load-resisting system is reinforced concrete frame, which consists of precast columns and beams and cast in-situ or precast concrete shear walls. Precast frame elements are joined together in the space frame structure. Shear walls may be made of precast panels or cast in-situ elevator cores in the taller buildings of this type (e.g., 12-story buildings). In medium-rise buildings of this type (e.g., 4-5 stories), the entire lateral load-resisting system consists of a RC frame only (i.e., shear walls are not present). Precast floor panels are joined in a rigid diaphragm for the distribution of lateral forces. 4.2 Gravity Load-Bearing Structure The gravity load-bearing structure consists of reinforced concrete frame, including precast columns and beams and precast floor panels. Page 5

8 4.3 Type of Structural System Material Masonry Concrete Steel Timber Various Type of Load-Bearing Structure Stone masonry walls # Subtypes 1 Rubble stone (field stone) in mud/lime mortar or without mortar (usually with timber roof) 2 Massive stone masonry (in lime or cement mortar) Earthen walls 3 Mud walls 4 Mud walls with horizontal wood elements 5 Adobe block or brick walls 6 Rammed earth/pise construction Unreinforced brick masonry walls 7 Unreinforced brick masonry in mud or lime mortar 8 Unreinforced brick masonry in mud or lime mortar with vertical posts 9 Unreinforced brick masonry in cement or lime mortar (various floor/roof systems) Confined masonry 10 Confined brick/block masonry with concrete posts/tie columns and beams Concrete block masonry walls 11 Unreinforced in lime or cement mortar (various floor/roof systems) 12 Reinforced in cement mortar (various floor/roof systems) 13 Large concrete block walls with concrete floors and roofs Moment resisting 14 Designed for gravity loads only (predating seismic codes i.e. frame no seismic features) 15 Designed with seismic features (various ages) 16 Frame with unreinforced masonry infill walls 17 Flat slab structure 18 Precast frame structure 19 Frame with concrete shear walls-dual system 20 Precast prestressed frame with shear walls Shear wall structure 21 Walls cast in-situ 22 Precast wall panel structure Moment resisting frame 23 With brick masonry partitions 24 With cast in-situ concrete walls 25 With lightweight partitions Braced frame 26 Concentric 27 Eccentric Load-bearing 28 Thatch timber frame 29 Post and beam frame 30 Walls with bamboo/reed mesh and post (wattle and daub) 31 Wooden frame (with or without infill) 32 Stud wall frame with plywood/gypsum board sheathing 33 Wooden panel or log construction Seismic protection 34 Building protected with base isolation devices or seismic systems dampers Other 35 Page 6

9 4.4 Type of Foundation Type Description Shallow Foundation Wall or column embedded in soil, without footing Rubble stone (fieldstone) isolated footing Rubble stone (fieldstone) strip footing Reinforced concrete isolated footing Reinforced concrete strip footing Mat foundation No foundation Deep Foundation Reinforced concrete bearing piles Reinforced concrete skin friction piles Steel bearing piles Wood piles Steel skin friction piles Cast in place concrete piers Caissons Other 4.5 Type of Floor/Roof System Material Description of floor/roof system Floor Roof Masonry Vaulted Composite masonry and concrete joist Structural Concrete Solid slabs (cast in place or precast) Cast in place waffle slabs Cast in place flat slabs Precast joist system Precast hollow core slabs Precast beams with concrete topping Post-tensioned slabs Steel Composite steel deck with concrete slab Timber Rammed earth with ballast and concrete or plaster finishing Wood planks or beams with ballast and concrete or plaster finishing Thatched roof supported on wood purlins Wood single roof Wood planks or beams that support clay tiles Wood planks or beams that support slate, metal asbestos-cement or plastic corrugated sheets or tiles Wood plank, plywood or manufactured wood panels on joists supported by beams or walls Structural concrete Precast hollow-core slabs 4.6 Typical Plan Dimensions Length: meters Width: meters Additional Comments: Typical plan dimensions: 18x18m, 12x36m, 15x24m 4.7 Typical Number of Stories Typical Story Height 3 meters 4.9 Typical Span 6 meters Additional Comments: The typical span may be either 6 or 3 meters. Page 7

10 4.10 Typical Wall Density 5% 4.11 General Applicability of Answers to Questions in Section 4 This contribution describes a generic building type and is not based on a case study of a particular building. Page 8

11 5 Evaluation of Seismic Performance and Seismic Vulnerability 5.1 Structural and Architectural Features: Seismic Resistance Structural/ Architectural Feature Lateral load path Building configuration Roof construction Floor construction Foundation performance Wall and frame structuresredundancy Wall proportions Foundation- wall connection Wall-roof connections Wall openings Quality of building materials Quality of workmanship Maintenance Other Statement True False N/A The structure contains a complete load path for seismic force effects from any horizontal direction that serves to transfer inertial forces form the building to the foundation. The building is regular with regards to both the plan and the elevation. 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. 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. There is no evidence of excessive foundation movement (e.g. settlement) that would affect the integrity or performance of the structure in an earthquake. The number of lines of walls or frames in each principal direction is greater than or equal to 2. Height-to-thickness ratio of the shear walls at each floor level is: 1) Less than 25 (concrete walls); 2)Less than 30 (reinforced masonry walls); 3) Less than 13 (unreinforced masonry walls). Vertical load-bearing elements (columns, walls) are attached to the foundations; concrete columns and walls are doweled into the foundation. Exterior walls are anchored for out-of-plane seismic effects at each diaphragm level with metal anchors or straps. The total width of door and window openings in a wall is: 1) for brick masonry construction in cement mortar: less than 1/2 of the distance between the adjacent cross walls; 2) for adobe masonry, stone masonry and brick masonry in mud mortar: less than 1/3 of the distance between the adjacent cross walls; 3) for precast concrete wall structures: less than 3/4 of the length of a perimeter wall. Quality of building materials is considered to be adequate per requirements of national codes and standards (an estimate). Quality of workmanship (based on visual inspection of few typical buildings) is considered to be good (per local construction standards). Buildings of this type are generally well maintained and there are no visible signs of deterioration of building elements (concrete, steel, timber). Additional Comments: Precast floor panels are constructed with special grooves and steel dowels projected on all four sides for achieving the cast in-situ joint. This type of floor structure subjected to lateral loads was tested in the lab. The roof diaphragm is considered to be rigid provided that the quality of construction is adequate. 5.2 Seismic Features Page 9

12 Structural Element Seismic Deficiency Earthquake-Resilient Features Earthquake Damage Patterns Partition walls (cladding) Frame (columns, beams) Roof and floors Wall panels, (vertical diaphragms) Exterior and interior partition walls are non-load-bearing (i.e., they carry their own weight only). The most vulnerable parts of a frame are beam-column joints; these welded joints are located in the area of extremely high loads. As a result of the welding, steel reinforcement bars may have loose ductility. Also, the concrete poured in these joints is often poorly vibrated. The joints between the precast slabs (grouted in-situ) are sometimes not properly filled with grout and may lose their strength in an earthquake. The assembled reinforced concrete diaphragms are inadequately welded to the columns. Vertical bars discontinued during the site installation; Due to poor quality of construction, the diaphragm strength may be reduced by 50%. Due to poor quality of wall-column and wall-beam joints, the walls may experience serious damage in an earthquake. Damage to beam-column joints Damage of horizontal panel joints and the subsequent loss of rigid diaphragm behavior Failure of precast diaphragm-to-frame connections. Page 10

13 5.3 Seismic Vulnerability Rating Seismic Vulnerability Class 0 - probable value < - lower bound > - upper bound High (Very Poor Seismic Performance) Vulnerability Medium Low (Excellent Seismic Performace) A B C D E F < 0 > Page 11

14 6 Earthquake Damage Patterns 6.1 Past Earthquakes Reported To Affect This Construction Year Earthquake Epicenter Richter magnitude(m) Maximum Intensity (Indicate Scale e.g. MMI, MSK) 1988 Spitak (Armenia) 7.5 I- (MSK) 1984 Gazli 7.2 I (MSK) Additional Comments: Buildings of this type were damaged during the 1988 Spitak earthquake, as illustrated in Figures 6A and 6B. Page 12

15 7 Building Materials and Construction Process 7.1 Description of Building Materials Structural Element Building Material Characteristic Strength Mix Proportions/ Dimensions Comments Partition Walls Reinforced concrete These walls are not lateral load-resisting elements Mix - 1: 1.5: 2.4: 0.45 Dimensions (mm) Foundations Wall panels (vertical diaphragms) Roof and floors Column Girder Reinforced concrete Reinforced concrete Reinforced concrete Reinforced concrete Reinforced concrete MPa (cube compressive strength) 30 MPa (cube compressive strength) 30 MPa (cube compressive strength) 40 MPa (cube compressive strength) 40 MPa (cube compressive strength) Mix- 1: 1,4: 2: 0,49 Dimensions: (mm) Mix- 1: 1.75: 3.21: 0.51 Dimensions (mm) Mix- 1: 1.75: 3.24: 0.44 Dimensions : (mm) 1: 2: 3: 0.5 Cross sectional dimensions: (mm) height ( mm) Mix- 1: 1.4: 2.8: 0.49 Cross-sectional dimensions: (mm) 7.2 Does the builder typically live in this construction type, or is it more typically built by developers or for speculation? A builder may live in this construction type, and his children may attend the schools housed in buildings of this type. Typically, frame panel buildings are constructed by order of the municipality. 7.3 Construction Process Based on the order of the government, a design agency develops a seria of industrialized construction elements. Based on the information provided by the design agency, a concrete plant prepares a set of metal forms for the columns, girders, diaphragms, slabs, wall panels, staircases, etc., corresponding to the requirements of a seria. Based on the order of a municipality or other clients, design firms develop designs of individual buildings or typical (standardized) building designs. A concrete plant manufactures and delivers all required building elements to the construction site. A construction company erects the building at the construction site. The main pieces of equipment used for the construction are a tower crane, welding equipment, and concrete mixers. 7.4 Design/Construction Expertise All designs are reviewed by the State Expert Bureau of the State Committee on Architecture and Construction (SCAC); the revisions are incorporated in the final design (if required). Once the review is completed, the designs are forwarded to the concrete plants and the construction company. The concrete strength is evaluated in the laboratory in the concrete plant, and the reinforcement schedule is checked and compared with the design documents. Periodically (once in six months), the laboratory data are examined by a representative of the State Architecture Construction Control Department (SACC) of SCAC. SCAC also monitors the construction quality at the site. In addition to this, a representative of the design agency or firm also performs a site inspection. The builders should take into account the designer's comments made during the site inspection. Once the construction is complete, a special state expert committee needs to approve the building and to issue the building permit. 7.5 Building Codes and Standards Is this construction type addressed by codes/standards? Yes No Title of the code or standard: The construction is carried out based upon the catalogs of frame panel seria IIS-04 (developed in 1973), and upon the National Building Code of Uzbekistan: "Construction in Page 13

16 Earthquake-prone Areas" (KMK ). National building code, material codes and seismic codes/standards: National Building Code, Material Codes and Seismic Codes/Standards; National Building Code of Uzbekistan: Construction in Earthquake-prone Areas (KMK ). When was the most recent code/standard addressing this construction type issued? Role of Engineers and Architects Use and selection of the typical, standard production of seria IIS-04 depend upon load conditions. Engineers and architects cannot change any construction details (joints, connections) in the existing seria, which is approved by the government. Only the agency that has developed the seria is able to change the details. 7.7 Building Permits and Development Control Rules Building permits are required Informal construction Construction authorized per development control rules Yes No 7.8 Phasing of Construction Construction takes place over time (incrementally) Building originally designed for its final constructed size Yes No 7.9 Building Maintenance Who typically maintains buildings of this type? Builder Owner(s) Renter(s) No one Other 7.10 Process for Building Code Enforcement Design of buildings using the seria IIS-04 is carried out in accordance with the National Building Code of Uzbekistan: Construction in Earthquake-prone Areas Typical Problems Associated with this Type of Construction Builders often have difficulty following the requirements for welding the joints between columns, girders and diaphragms. Page 14

17 8 Construction Economics 8.1 Unit Construction Cost (estimate) sum/m² (110 US$/m²) 8.2 Labor Requirements (estimate) A 12-story residential building with 48 housing units and with plan dimensions 18x18m may be erected by 10 workers in 10 months. Page 15

18 9 Insurance 9.1 Insurance Issues Earthquake insurance for this construction type is typically available Insurance premium discounts or higher coverages are available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features Yes No 9.2 If earthquake insurance is available, what does this insurance typically cover/cost? Approximately 30% of the construction cost. Page 16

19 10 Seismic Strengthening Technologies 10.1 Description of Seismic Strengthening Provisions Type of intervention Structural Deficiency Retrofit Beam-column joints (Strengthening) Frame (column) Description of seismic strengthening provision used Reinforcing of joints with steel plates Installation of additional (external) steel ties (straps) Additional Comments: Seismic strengthening of a building in Tashkent is illustrated in Figures 7A and 7B Has seismic strengthening described in the above table been performed in design practice, and if so, to what extent? Yes. Seismic strengthening was performed on some buildings in Tashkent Was the work done as a mitigation effort on an undamaged building, or as repair following earthquake damage? 10.4 Was the construction inspected in the same manner as new construction? 10.5 Who performed the construction: a contractor, or owner/user? Was an architect or engineer involved? 10.6 What has been the performance of retrofitted buildings of this type in subsequent earthquakes? Page 17

20 11 References National Building Code of Uzbekistan, "Construction in Earthquake-prone Areas," (KMK ). Concrete and Reinforced Concrete - Design Codes and Standards Construction Catalog: seria IIS Klyachko M. A., Earthquakes and Us. Intergraf, Saint Peterburg, Russia, 1999 (in Russian). Page 18

21 12 Contributors Name Shamil Khakimov Bakhtiar Nurtaev Title Head of the Department Deputy Director Affiliation Institute of Typical and Experimental Institute of Geology and Geophysics Design AO UzLITTI Address Nyazova 17 Khodjibaeva 49 City Tashkent Tashkent Zipcode Country Uzbekistan Uzbekistan Phone Fax Nurtaev@ingeo.uz Webpage Page 19

22 13 Figures FIGURE 1: Typical Building Page 20

23 FIGURE 2: Key Load-Bearing Elements Page 21

24 FIGURE 3: Plan of a Typical Building FIGURE 4: Critical Structural Details Page 22

25 FIGURE 5: An Illustration of Key Seismic Features and/or Deficiencies Page 23

26 FIGURE 6A: Building damage in Leninakan (1988 Spitak, Armenia earthquake) FIGURE 6B: Building damage in Leninakan (1988 Spitak, Armenia earthquake) Page 24

27 FIGURE 6C: Building damage (1988 Spitak, Armenia earthquake) Page 25

28 Page 26

29 FIGURE 6D: Building damage (1988 Spitak, Armenia earthquake) Source: Klyachko 1999 FIGURE 6E: Building damage (1994 Shikotansk, Russia earthquake) Source: Klyachko 1999 Page 27

30 FIGURE 6F: Building damage (1994 Shikotansk, Russia earthquake) Source: Klyachko 1999 FIGURE 7A: Illustration of Seismic Strengthening Techniques Page 28

31 Page 29

32 FIGURE 7B: Illustration of Seismic Strengthening Techniques Page 30