World Housing Encyclopedia Report

Transcription

1 World Housing Encyclopedia Report Country: China Housing Type: Multi-story base isolated brick masonry building with reinforced concrete floors and roof Contributors: Fu Lin Zhou Zhong Gen u Wen Guang Liu Primary Reviewer: Ravi Sinha Created on: 6/5/2002 Last Modified: 6/17/2003 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... 6 Evaluation of Seismic Performance and Seismic Vulnerability Earthquake Damage Patterns Building Materials and Construction Process Construction Economics...16 Insurance...17 Seismic Strengthening Technologies References Contributors Figures...21

3 1 General Information 1.1 Country China 1.3 Housing Type Multi-story base isolated brick masonry building with reinforced concrete floors and roof 1.4 Summary This is typically a 5--8 story building with commercial on the ground floor, residential above. Brick masonry buildings have been used in China thousands of years ago. This construction practice possesses the advantages of easy manufacture and low cost, however the brittleness of brick masonry material with the weak seismic resistance induces severe damage or collapse of buildings and causes deaths of thousands of people who live in these houses during earthquake attacks. Since 1990, the base isolated brick masonry buildings with reinforced concrete floors/roof have been used more and more widely in China. The base isolated building consists of isolation system (laminated rubber isolation devices), superstructure and substructure. The base isolation system is located atop the walls or columns at the basement or at the ground floor level in a building without basement. The superstructure consists of conventional multi-story brick masonry walls and reinforced concrete floors/roof. The substructure is a part of the building beneath the isolation system and it consists of the basement and the foundation structure. The base isolated masonry structure preserves original advantages of easy manufacture and low cost with 4-12 times of increase in seismic safety as compared to that of non-isolation masonry structure. The high seismic resistance of base isolation structure house has been proved by shaking table tests and many real earthquake experiences in China and other countries. The wide usage of base isolation technology indicates that the era of strong earthquake proof buildings is coming in China. 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 Page 1

4 < 200 years > 200 years Is this construction still being practiced? Yes No Additional Comments: NA 1.6 Region(s) Where Used Urban areas in western, eastern, northern, southern and central China. 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 For a typical floor, one window with 1800 mm width and 1500 mm height in each 3100 mm length of outside wall. One or two doors each with 900 mm width and 2100 mm height in each 3300 mm length of inside wall. The overall windows and doors areas are about 26% of the overall wall surface area. 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 6 meters 2.3 Building Configuration Rectangular 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) Additional Comments: NA 2.5 Means of Escape NA 2.6 Modification of Buildings NA Page 3

6 3 Socio-Economic Issues 3.1 Patterns of Occupancy families typically occupy one house. (2-4 families typically occupy each floor. There are 5-8 floors typically in a house). 3.2 Number of Housing Units in a Building 32 units in each building. Additional Comments: Usually there are units in building. One family typically occupies one housing unit. 3.3 Average Number of Inhabitants in a Building How many inhabitants reside in a typical building of this construction type? <5 5 to > 20 Other During the day / business hours During the evening / night Additional Comments: On an average a Chinese family consists of 4 persons. 3.4 Number of Bathrooms or Latrines per Housing Unit Number of Bathrooms: 1 Number of Latrines: 1 Additional Comments: NA 3.5 Economic Level of Inhabitants Economic Status Very poor Poor Middle Class Rich House Price/Annual Income (Ratio) / / /30000 / Additional Comments: NA 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 Additional Comments: NA 3.7 Ownership Page 4

7 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: NA Page 5

8 4 Structural Features 4.1 Lateral Load-Resisting System System of structure: The base isolation house structure system consists of isolation layer (laminated rubber bearing isolators), superstructure and substructure. The isolation layer is located on the top of walls or columns in basement or in the first story of house without basement. The superstructure consists of common multi-stories brick masonry wall with reinforced concrete floors/roof, which is same as the general house structure supported on the rubber bearing isolators. The substructure consists of a common basement and base, which is same as the general building structure. The laminated rubber bearing isolators are the key lateral load resisting elements of seismic resistance. Their features are: Size: diameter 350 mm mm, height 160 mm -200 mm. Component: thickness 3-8mm rubber layers bond with thickness 1-3 mm steel sheets interval each other. Characteristics of isolation pads: High vertical stiffness and high vertical compression capacity for supporting superstructure. Low horizontal stiffness, large horizontal deformation capacity for isolating ground motion. Suitable value of damping ratio for dissipating ground motion energy. Adequate initial horizontal stiffness for resisting wind loads. Seismic performance: During earthquake, the isolation structure will work as follows: 1. All horizontal deformations of superstructure elements will concentrate on the isolation layer, the structure will be kept within the elastic limit, so that no damages will occur in the structure. 2. The natural period of isolation structure will become very long due to the low horizontal stiffness of isolation layer, so that the isolation structural seismic response will be reduced to 1/4-1/8 of the non-isolation structural seismic response, protecting the structure from any damage and becoming very safe in strong earthquake. 3. The horizontal deformation of rubber bearing isolators will be limited by enough damping ratio. 4.2 Gravity Load-Bearing Structure Gravity load is carried by the masonry load-bearing walls, which transfer them to the foundation through the isolation pads. Page 6

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

10 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 Additional Comments: NA 4.5 Type of Floor/Roof System Material Masonry Structural Concrete Steel Timber Description of floor/roof system Vaulted Composite masonry and concrete joist 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 Composite steel deck with concrete slab 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 Floor Roof Other Additional Comments: The floor/roof is considered to be a rigid diaphragm. 4.6 Typical Plan Dimensions Length: meters Width: meters 4.7 Typical Number of Stories Typical Story Height 3 meters Additional Comments: According to China code, the limited number N of stories for unreinforced brick masonry house in seismic areas is: Seismic Intensity (Ground motion) VI (55 gal) VII (110 gal) VIII (220 gal) I (400gal) N general buildings N isolation building Page 8

11 4.9 Typical Span 3 meters Additional Comments: The span, center-to-center distance between the walls for wall structures, is Typical Wall Density NA 4.11 General Applicability of Answers to Questions in Section 4 General building type described in Section 1.4 Page 9

12 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 Statement True 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). False N/A Other Additional Comments: The superstructure and foundation is individually connected to the rubber bearing isolators with bolts which possess adequate seismic resistant to transfer the seismic forces (vertical loads, shear loads and moments) between the foundation and superstructure. 5.2 Seismic Features Page 10

13 Structural Element Seismic Deficiency Wall Frame (columns, beams) Earthquake-Resilient Features Earthquake Damage Patterns During earthquake, the isolation structure will work as follows: 1. All horizontal deformations of superstructure elements will concentrate on the isolation layer, the structure will be kept within the elastic limit, so that no damages will occur in the structure. 2. The natural period of isolation structure will become very long due to the low horizontal stiffness of isolation layer, so that the isolation structural seismic response will be reduced to 1/4-1/8 of the non-isolation structural seismic response, protecting the structure from any damage and becoming very safe in strong earthquake. 3. The horizontal deformation of rubber bearing isolators will be limited by enough damping ratio. Roof and floors Other Additional Comments: 1. The natural period of isolation structure is very long due to the low horizontal stiffness of isolation layer. This causes the isolation structural seismic response to reduce to 1/4-1/8 of the response of similar non-isolation structure. This protects the structure from any damage and makes it very safe in strong earthquake 2. No damage has been observed for base-isolation buildings in many strong earthquakes in China so far. Page 11

14 5.3 Seismic Vulnerability Rating High (Very Poor Seismic Performance) A Seismic Vulnerability Class Vulnerability Medium B C D < E 0 Low (Excellent Seismic Performace) F > 0 - probable value < - lower bound > - upper bound Page 12

15 6 Earthquake Damage Patterns 6.1 Past Earthquakes Reported To Affect This Construction Year Earthquake Epicenter Richter magnitude(m) injian Autonomous Yunan Province Yunan Province Taiwan Straits, China Maximum Intensity (Indicate Scale e.g. MMI, MSK) VII (110 GAL) VIII (220 GAL) VIII ( 220 GAL) VIII ( 220 GAL) Additional Comments: No damage has been observed in base-isolation buildings during these earthquakes. Page 13

16 7 Building Materials and Construction Process 7.1 Description of Building Materials Structural Element Building Material Walls Brick masonry Foundations RC Roof and floors RC Laminated rubber bearing isolators Rubber and Steel Characteristic Strength Compression fc = 4.2 MPa shear fv = 0.2 MPa Compression fc = 10 MPa Steel yield fy= 235 MPa Compression fc = 17 MPa Steel yield fy = 335 MPa Compression fu = 90 MPa Tension ft = 2.0 MPa Mix Proportions/ Dimensions Comments mortar 1:6 cement/sand brick NA size mm Low strength concrete and mild-steel is used for foundation diameter mm height mm 7.2 Does the builder typically live in this construction type, or is it more typically built by developers or for speculation? It is typically built by developers for sale. 7.3 Construction Process The entire process of building construction is as follows: 1. Developer buys the land and then entrusts the designer for designing the building with base isolation. 2. Developer selects the construction company for constructing the designed building. 3. Developer buys the rubber bearing isolators from special factory. 4. Developer entrusts the testing center to test and check the characteristics of rubber bearing isolators that will be used in the construction. 5. Contractor constructs the foundation and basement. 6. Contractor fixes the rubber bearing isolators on top of the basement. This process may be manually done. 7. Contractor constructs the superstructure on rubber bearing isolators. 8. Contractor constructs the non-structural elements and finishing of the building. 9. The quality of construction is checked to ensure that it is acceptable. The superstructure is checked to ensure that it has free space to move in horizontal and vertical directions during earthquake. The horizontal space should be greater than 200 mm, and the vertical space should be greater than 20 mm. 10. Developer sells the house. 7.4 Design/Construction Expertise The design of superstructure and substructure of buildings can be done by the general structural engineers. The structural engineers who have enough knowledge and experience in designing the base-isolation buildings can do the design of base-isolation system. 7.5 Building Codes and Standards Is this construction type addressed by codes/standards? Yes No Title of the code or standard: 1. Building design code for seismic resistance (GB ). 2. Technical rule for seismic isolation with laminated rubber bearing isolators (CECS ). 3. Standard of rubber bearing isolators (JG ). Year the first code/standard addressing this type of construction issued: 2000 National building code, material codes and seismic codes/standards: Same as above. When was the most recent code/standard addressing this construction type issued? Role of Engineers and Architects Engineers design the base-isolator, superstructure and substructure. Page 14

17 Architects design the building plan, and details of architectural treatment for isolation layer. 7.7 Building Permits and Development Control Rules Yes Building permits are required Informal construction Construction authorized per development control rules No 7.8 Phasing of Construction Yes Construction takes place over time (incrementally) Building originally designed for its final constructed size 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 Building code is enforced through quality control procedures during construction. Separate quality certification is not required Typical Problems Associated with this Type of Construction The construction cost of isolation building may increase 3-5 % compared to that of non-isolation building. Page 15

18 8 Construction Economics 8.1 Unit Construction Cost (estimate) RMB 1200 / m² (US$ 145 / m²) 8.2 Labor Requirements (estimate) 20 days are required for the construction of foundation and basement, during which labor with only general technical level is required 3 days are required for fixing the rubber bearing isolators, during which labor with only general technical level is required 60 days are required for constructing the superstructure (around 10 days each storey), during which labor with only general technical level is required. Page 16

19 9 Insurance 9.1 Insurance Issues Yes 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 No Additional Comments: NA 9.2 If earthquake insurance is available, what does this insurance typically cover/cost? Page 17

20 10 Seismic Strengthening Technologies 10.1 Description of Seismic Strengthening Provisions Type of intervention Structural Deficiency Retrofit NA (Strengthening) Description of seismic strengthening provision used NA Additional Comments: No damages have been experienced for this type of buildings during past earthquakes in China. So far, there has been no necessity to strengthen the isolation buildings Has seismic strengthening described in the above table been performed in design practice, and if so, to what extent? NA 10.3 Was the work done as a mitigation effort on an undamaged building, or as repair following earthquake damage? NA 10.4 Was the construction inspected in the same manner as new construction? NA 10.5 Who performed the construction: a contractor, or owner/user? Was an architect or engineer involved? NA 10.6 What has been the performance of retrofitted buildings of this type in subsequent earthquakes? NA Page 18

21 11 References Zhou F. L., Seismic Control of Structures. China Seismic Publishing House, Zhou F. L., Stiemer S. F. and Cherry S., Design Method of Isolating And Energy Dissipating System for Earthquake Resistant Structures. Proc. of 9th World Conference on Earthquake Engineering. Tokyo-Kyoto. Aug Vol. VIII. Zhou F. L., Stiemer S.F. and Cherry S., A New Isolation and Energy Dissipating System for Earthquake Resistant Structures. Proc. of 9th European Conference on Earthquake Engineering. Moscow, Sept Zhou F. L., The Technical Report on Mission As Consultant of UNIDO. Summary of the International Post-SMiRT conference Seminar on Seismic Isolation, Passive Energy Dissipation and Active Control of Vibrations and Structures, Santiago, Chile. August Zhou F. L., Progress of Application and Development in Base Isolation and Passive Energy dissipation for civil and Industrial Structures. Proc of International Post-SMiRT Conference Seminar. Cheju, Korea, August Zhou F. L., Progress of Application, New Projects, R and D and Development of Design Rules for Seismic Isolation and Passive Energy Dissipation of Civil Buildings, Bridges and Nuclear and Non- Nuclear Plants in P R China. Proc.of International Post-SMiRT Conference Seminar on Seismic Isolation, Passive Energy Dissipation and Active Control of Seismic Vibration of Structures. Taormina, Italy, August Zhou F. L., New System of Earthquake Resistant Structures in Seismic Zone. Computational Mechanics in Structural Engineering. ELSEVIER APPLIED SCIENCE PUBLISHERS LTD, London and New York Zhou F. L., Kelly J M, Fuller K N G, Pan T C, et al. Recent Research Development and Application on Seismic Isolation of Buildings in P R China. Proc. of International Workshop IWADBI, Shantou, China. May Zhou F. L., Design control of structural response for seismic isolation system. EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION, No.1, Zhou F. L. and Zhou. Y., Technical rule for seismic isolation with laminated rubber bearing isolators (CECS 126:2001). Chinese Engineering Construction Standard. Beijing China Page 19

22 12 Contributors Name Title Affiliation Address City Zipcode Country Phone Fax Webpage Fu Lin Zhou Zhong Gen u Professor Associate Professor Guangzhou University Guangzhou University No. 248Guang Yuan Zhong No. 248Guang Yuan Zhong Road Road Guangzhou Guangzhou China China zhoufl@public.guangzhou.gd.cn xuzhonggen@263.net Wen Guang Liu Associate Professor Guangzhou University No. 248Guang Yuan Zhong Road Guangzhou China liweng@sina.com Page 20

23 13 Figures FIGURE 1: Typical Building Page 21

24 FIGURE 2: Building Elevation Showing the Location of Base Isolation Devices Page 22

25 FIGURE 3: Typical Floor Plan FIGURE 4: Floor Plan Showing the Layout of Isolation Devices Page 23

26 FIGURE 5A: Perspective Drawing Showing Connection between Isolators and Adjacent Structural Elements FIGURE 5B: Comparison of Seismic Performance for a Base Isolated and a Conventional Building Page 24

27 FIGURE 5C: Testing Facility for Base Isolation Devices Page 25

28 FIGURE 5D: Components of Rubber Isolation Devices FIGURE 5E: Building Elevation Showing the Location of Base Isolation Devices (Cont. of Figure 2.) Page 26

29 FIGURE 5F: Base Isolation Device and the Connection with Adjacent Structural Elements FIGURE 5G: Installation of Base Isolation Devices Page 27

30 FIGURE 5H: Lead-Core Rubber Isolation Devices Page 28

31 FIGURE 5I: Load-Deformation Curve for Isolation Devices Page 29

32 FIGURE 6A: Typical Earthquake Damage of Brick Masonry Buildings without base isolation (1976 Tanshan Earthquake) FIGURE 6B: Base Isolated Brick Masonry Building Remained Undamaged in the 1996 Yunan Earthquake (magnitude 7.0) Page 30