Council on Tall Buildings. and Urban Habitat

Transcription

1 Performance-Based Seismic Design: International Practices Professor Guo-Qiang Li, Tongji University, Shanghai, China Ron Klemencic, President Magnusson Klemencic Associates, USA

2 CTBUH Seismic Workshop Eight Countries Participated Australia/New Zealand Chile China Indonesia Japan Korea Philippines USA

3 Code-Based Seismic Design All countries have codes that cover basic seismic design requirements Minimum acceptable lateral strength and stiffness Minimum acceptable detailing practices

4 Performance-Based Seismic Design Required for Tall/Irregular Buildings Alternate Design Approach China and Japan Indonesia, Philippines, USA

5 Consistent Goals of PBSD A decision maker states a desire that a building be able to perform in a certain way: Protect life safety Minimize potential repair cost Minimize disruption of use The engineer uses his or her skill to provide a design that will be capable of achieving these objectives

6 Performance- Based Code Seismic Demand Definition Frequent Design Commonly around 50 year return period, Extremely Rare Commonly 1,000 to 2,500 year return period Intermediate (Design Level) Commonly around 500 year return period

7 Performance Objectives + Ground Motion x% - 50 years Performance Level Design Ground Shaking Acceptable Performance Level (maximum acceptable damage, given that shaking occurs)

8 Operational Performance Levels Immediate Occupancy Frequent EQ Life Safety Collapse Prevention Intermediate EQ Extremely Rare EQ

9 Computer Models Frequent and Intermediate (Design Level) EQ 3D linear elastic model Used to initially proportion elements

10 Extremely Rare EQ 3D non-linear model Dynamic Time History Analysis used Static (Push-over) also used in Chile, China and Japan Computer Models

11 Japan Requirements Allowable stress and horizontal load-carrying capacity calculation Current Japanese Code Procedure Building Height 60m Yes Response and limit capacity calculation Other methods equal or superior to (1) or (2) (1), (2) and (3) are the seismic design methods based on static and/or elasto-plastic pushover analysis. No Alternative Methods (1) (2) (3) (4) Time-history dynamic response analysis Design review and evaluation by the panel members, and special permission are required. Masayoshi Nakai

12 Definition of Seismic Demand Level (Japan) Acceleration (cm/sec 2 ) Design input motions for horizontal direction ( Example of Notification motions) (1.5 ERE) (ground surface) Extremely Rare Earthquakes (ERE) (5 times) (ground surface) (exposed bedrock) Rare Earthquakes (RE) Amplification factor (:Gs) of acceleration for the standard surface ground (:soil type 2) is considered. (: the abbreviated calculation) Return Period: RE: 50 years ERE: 500 years 250 (ground surface) (exposed bedrock) Period (sec.) Acceleration response spectra for the Notification motions ( h=5% ) Masayoshi Nakai

13 Performance Objectives (Japan) Summary of performance objectives / minimum requirements Performance objectives or minimum requirements Rare Earthquakes (RE) Demand levels Extremely Rare Earthquakes (ERE) General Damage Limit Collapse Limit Drift story angle 1/200 or less 1/100 or less Story ductility factor Stresses in each structural elements Ductility factor of each structural elements Short-term allowable stress or less 2.0 or less 4.0 or less Masayoshi Nakai

14 Korean Seismic Performance Objectives 2) Seismic Design Code CHANG MINWOO

15 Design Earthquake Level (Korea) 2) Seismic Design Code CHANG MINWOO

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17 The Chilean Practice in Seismic Design Chile has several loading and design codes, differentiated by their function or structural system. The loading codes are: NCh433 for Residential and Office Buildings NCh2745 for Base Isolated Buildings NCh2369 for Industrial Facilities Performance Based Design: Not in the Codes On a limited number of special projects, Non-linear analysis models (push-over, time history) To identify failure mode and performance level CTBUH th World Congress renelagos engineers

18 The Chilean Practice in Seismic Design Elastic demands of Chilean Codes: (PE: 10% in 50 years) NCh 2745 Of 2003 for Base Isolated Buildings NCh 433 Of 2009 for Residential and Office Buildings NCh 2369 Of 2003 for Industrial Facilities NCh 2745 NCh 2745 NCh 433 NCh 433 NCh 2369 CTBUH th World Congress Acceleration Spectra renelagos engineers

19 The Chilean Practice in Seismic Design NCh 433 Of 2009 Chilean Seismic Code for Buildings: Type of analysis: Modal spectrum analysis - Linear elastic Design loads: Elastic response reduced by R* Base Shear: Minimum Base shear Drift control: At the Center of Mass and at perimeter Elastic Spectrum: Sa (seismic zone 3) Design Earthquake: are reduced forces by R* CTBUH th World Congress renelagos engineers

20 The Chilean Practice in Seismic Design NCh 433 Of 2009 Chilean Seismic Code for Buildings: Base shear limitations: IA o P/6g Base shear 0.35 SIA o P/g If Base Shear is out of range, forces and displacements must be scaled to the exceeded limit. Minimum base shear for normal buildings: - V bs in seismic Zone 2 is 5.0%P - V bs in seismic Zone 3 is 6.7%P CTBUH th World Congress renelagos engineers

21 Seismic Design Procedure Specified By AS (2007) Life safety and collapse prevention are the primary performance objectives Force-based design approach depending on: building importance level level of seismic hazard site condition building height Concrete and steel codes specify detailing requirements depending on the level of ductility demand Kourosh Kayvani

22 Performance-based Measures in AS (2007) Largely a prescriptive code, with some performance-based measures in the context of life safety and collapse prevention. Recognition of four levels of importance with seismic hazards corresponding to return periods typically between 500 to 2500 years. Nonlinear static (push-over) analysis allowed for obtaining Structural Performance factor (S p ) and ductility factor (µ) Kourosh Kayvani

23 Performance-based Measures in AS (2007) Serviceability limit state (SLS) performance objective is considered only for buildings of the highest importance level (of 4) to remain serviceable immediately after lower return period (500 years) earthquake shaking. Limits storey drift, typically to 1.5% of story height, primarily for maintaining structural integrity rather than limiting damage. Kourosh Kayvani

24 The Goal: PEER TBI Guidelines in US to provide guidance for the seismic design and review of tall buildings to streamline the design and review process to lead to consensus on best practices that s widely supported It s a rule book to a game with no rules

25 PEER TBI Guidelines Service Level Service Earthquake: 43-year return period 2.5% damped spectra Performance Goal: Does not compromise structure s safety Repair not required for occupancy Essentially elastic response

26 PEER TBI Guidelines MCE Level Maximum Considered Earthquake 975 year-return period Performance Goal Minor risk of collapse (~10%) Modest residual drift (< 1%) 3-D nonlinear response history analysis (Perform) Different acceptance criteria for Deformation-controlled elements Force-controlled elements

27 Performance-Based Seismic Design in China Three levels of earthquakes the minor earthquake: 50 years return period the moderate earthquake: 475 years return period the severe earthquake: 1600~2400 years return period I f I I r

28 Performance-Based Seismic Design in China Target performances of Buildings No damage under minor earthquakes Repairable under moderate earthquakes No collapse under severe earthquakes

29 Performance-Based Seismic Design in China Performance objective level Minor earthquake No damage No damage No damage No damage Moderate earthquake Severe earthquake Building performance objectives under various earthquakes No damage for normal use Slight damage Usable after normal maintenance Slight damage Usable after normal maintenance Minor to moderate damage Usable after repair Minor damage Usable after slightly repair Moderate damage Usable after strengthening Minor to moderate damage Deformation <3[ U e ] Serious damage Usable after heavy repair

30 Inter-story drift requirements of various performance objectives Performance objective level Minor earthquake Moderate earthquake Severe earthquake 1 far less than [θe] less than [θe] slightly larger than [θe] 2 far less than [θe] slightly larger than [θe] less than 2 times of [θe] 3 much less than [θe] less than 2 times of [θe] less than 4 times of [θe] 4 less than [θe] less than 3 times of [θe] less than 0.9 times of [θp]

31 Provisions of PBSD in code 2010 Limit of relative inter-story drifts Structural material Type of structure [θ e ] [θ p ] Reinforced concrete Frame 1/550 1/50 Frame-Shear wall, Frame-Core tube 1/800 1/100 Shear wall, Frame tube-core tube 1/1000 1/120 Steel Multi-story and tall structures 1/250 1/50

32 Convention Centro for Shanghai Expo 2010

33 Architecture of Convention Centro

34 Structure of Convention Centro Mega-frame (span: 54m)

35 Under construction

36 Application of buckling restrained braces (BRB) in Shanghai Expo Center

37 Target seismic performance Minor earthquake Moderate earthquake Severe earthquake Global behavior No damage Repairable Collapse prevention Limit of inter-story drift 1/300 1/100 1/50 Columns Elastic Elastic Limited plastic deformation Beams Elastic Elastic Limited plastic deformation Ordinary braces Elastic Elastic Limited plastic deformation BRB Elastic Plastic Plastic

38 Structural system Steel consumption Braces Beams Columns Trusses Total BRBF 431t 2341t 3063t 1959t 7794t CBF 1120t 2458t 3271t 1959t 8808t

39 Summary Performance-based Seismic Design allows for cost-savings and better understanding of the building s performance. Global Financial Tower 492m Jinmao Tower 420m Shanghai Center Tower 632m

40 Thank you for your attention!