The International Conference on Earthquake Engineering and Seismology. Naveed Anwar. ICEES April 2011 NUST, Islamabad Pakistan

Transcription

1 The International Conference on Earthquake Engineering and Seismology Naveed Anwar ICEES April 2011 NUST, Islamabad Pakistan

2 The why, the how and the what of Performance Based Design and Review of Tall Buildings Application of recent research and development to real world problems within the associated cost and time constraints Demonstrated outcome for the client/owners/public CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 2

3 Naveed Anwar Faculty, SEC, AIT CEO, AIT Consulting Thaung Htut Aung Projects Coordinator, AIT Consulting Rojit Shahi Project Specialist, AIT Consulting Amelia Kusuma Project Specialist, AIT Consulting Deepak Rayamajhi External Consultant, AIT Consulting Pennung Warnitchai Associate Prof., SEC, AIT Keerati Tunthasuwattana Manager, ACECOMS, AIT CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 3

4 Why do we need to carryout Performance Based Design/ Evaluation when we have the building and design codes

5 Client/Owner Architect Structural Designer Geotech Consultants Peer Reviewer Builder/Contractor General Building Codes Structural Design Codes Law Makers Building Officials Legal and Justice System Public/ Users/ Occupants 5

6 Traditional codes govern design of general, normal buildings Over 95% buildings are covered, which are less than about 50 m Not specifically developed for tall buildings > 50 m tall Prescriptive in nature, no explicit check on outcome Permit a limited number of structural systems Do not include framing systems appropriate for high rise Based on elastic methods of analysis Enforce uniform detailing rules on all members Enforce unreasonable demand distribution rules Do not take advantage of recent computing tools CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 6

7 Applied Technology Council (ATC-72) Pacific Earthquake Engineering Research Center (PEER) Building Seismic Safety Council Research Center (BSSCR) Federal Emergency Management Agency (FEMA 356) Basic ASCE Documents (ASCE 7, ASCE 3, ASCE 4) Structural Engineering Association of California (Blue Book and SEAOC PBD Framework) Guidelines from National Earthquake Hazard Reduction Program (NEHRP) Los Angeles Tall Buildings Structural Design Council (LATBSDC) Council on Tall Buildings and Urban Habitat (CTBUH) CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 7

8 What is needed and needs to be done to carry out an effective Performance Based Design and Evaluation

9 To enhance the structural performance Improved serviceability, safety and reliability Explicit check on various performance indicators To improve cost effectiveness Achieve efficient use of materials, resources and time Direct reduction cost through reduction of structural material quantities Objectives to be achieved through Better structural system selection and its proportions Use of advanced design methodologies and tools CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 9

10 Enhancement of Performance Dynamic response parameters Lateral load response Vertical load response Demand and capacity ratios Response irregularity, discontinuity Explicit Performance Evaluation at Service, DBE and MCE Cost Effectiveness Capacity utilization ratio Reinforcement ratios Reinforcement volume ratios Concrete strength and quantity Rebar quantity Constructability, time and accommodation of other constraints CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 10

11 Level of Earthquake Seismic Performance Objective Frequent/Service: 50% probability of exceedance in 30 years (43-year return period) Serviceability: Structure to remain essentially elastic with minor damage to structural and non-structural elements Design Basis Earthquake (DBE): 10% probability of exceedance in 50 years (475- year return period) Code Level: Moderate structural damage; extensive repairs may be required Maximum Considered Earthquake (MCE): 2% probability of exceedance in 50 years (2475-year return period) Collapse Prevention: Extensive structural damage; repairs are required and may not be economically feasible 11

12 Seven site specific ground motions records are used. Determined by qualified geotechnical and geological consultant, for the site located near by building. For the evaluations, Average of 7 pairs of ground motions approach is used to determine the overall response and vulnerability of the building. CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 12

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15 Service Level MCE Level 15

16 RC column RC shear wall Element Action Type Classification Expected Behavior RC coupling beams (Deep beam, l n /d<4.0) RC coupling beams (slender beam, l n /d 4.0) Axial-flexure Shear Flexure Shear Ductile Brittle Ductile Brittle Linear Linear Nonlinear Linear Shear Ductile Nonlinear Flexure Shear Ductile Brittle Nonlinear Linear CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 16

17 Item Limit Story Drift Coupling Beams Core Wall Flexure Core Wall Shear Columns BRB 0.5 percent Shear strength to remain essentially elastic Remain essentially elastic Remain essentially elastic Remain essentially elastic Remain elastic (no yielding permitted) Essentially elastic behavior is defined as no more than 20% of the elements with ductile actions having a D/C between 1.0 and 1.5. No elements will be allowed to have a D/C >1.5 Brittle actions are limited to D/C of 1.0 CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 17

18 Element Action Type Classification Expected Behaviour Acceptance Limit Plastic hinge Beams rotation Ductile Nonlinear Hinge rotation ASCE limit Shear Brittle Linear D/C for strength capacity Axial-Flexural Columns interaction Ductile Nonlinear Hinge rotation ASCE limit Shear Brittle Linear D/C for strength capacity Shear Walls Axial-Flexural interaction Ductile Nonlinear Tensile strain in rebar rotation Compressive strain in concrete Shear Brittle Linear D/C for strength capacity CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 18

19 Item Limit Story Drift Coupling Beam Rotation (Diagonal Reinforcement) Coupling Beam Rotation (Conventional reinforcement) Core Wall Reinforcement Axial Strain Core Wall Concrete Axial Strain BRB 3 percent 0.06 radian rotation limit radian rotation limit Rebar strain = 0.05 in tension and 0.02 in compression Concrete Compression Strain = ρ(fy / f c) 9 times yield strain Brittle actions are checked against 1.3 times the average MCE demand using expected material strength and code specified strength reduction factors. CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 19

20 How to carry out an effective Performance Based Design and Evaluation so that it can provide useful outcome

21 Client/ Owner Engineer in Record (Sy^2) Carryout Code Based Design Specialist Geotech Consultant (Fugro) or ASCE 7 Develop Site Specific Ground Motions and Demand Spectrums PBD/ PBE Reviewers (AIT Consulting) Carry out explicit Performance Evaluation for Service Level for frequent earthquakes Design Basis Level for once-in-lifetime event MCE Basis for extreme earthquake PBD/ PBE Peer Reviewers (MKA) Review the PBE carried out by 21

22 Design/ Evaluation Stage Analysis Type Software Used Code based design and preliminary evaluation Response spectrum analysis ETABS V9.5 SAP 2000 V 14.2 Serviceability check Response spectrum analysis ETABS V9.5 SAP 2000 V 14.2 Collapse prevention check Nonlinear time history analysis Perform3D V4.0.4 SAP 2000 V 14.2 CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 22

23 Concrete Confinement effect is considered Mander s confinement model is used Tensile strength is neglected Use tri-linear backbone curve Takeda hysteresis model Reinforcing Steel Use tri-linear backbone curve 1% of strain hardening Kinematic Hysteresis model CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 23

24 Fiber modeling Two parallel fiber sections are used Shear behavior is modeled as elastic Nonlinear Shell Element 7 layer NL shell with explicit cover, mid portion, vertical and horizontal bars CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 24

25 Use rigid diaphragm Equivalent slab outrigger beams connected the core and columns Moment curvature hinges are used CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 25

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27 Located in Philippines 50-story building with 3½ - story below grade parking Total height of m above ground level 34.5 x 26 meters plan dimension Designer : Sy^2 + Associates Inc Performance reviewer : AIT Consulting Peer reviewer for Performance Based Design: Magnusson Klemencic Associates CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 27

28 BRBs (43 rd 47 th floor) Principal Major Direction BRBs (19 th 23 rd floor) Principal Minor Direction Tower 1 28

29 Principal Major Direction Principal Minor Direction BRB in Plan CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 29

30 Designer : Sy^2 + Associates Inc Performance reviewer : AIT Consulting Type of Building : Residential Building Number of stories :19-story building (plus 3 basements) Comprised of three towers (19-, 14-, and 7-story) Total area : 49,000 m2 Structural System : Reinforced Concrete Moment Resisting System with Shear Walls CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 30

31 Part 1 Part 2 Part 3 Layout Plan of Each Part of the Building Part 1 is the tallest part and has irregularity in plan, with 19 floors. Part 2 is the second tallest part of the building with few irregularities in plan and 14 floors. Part 3 is the lowest part and generally regular in geometry and stiffness with 7 floors. CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 31

32 Part 1 Part 2 Part 3 32

33 Reinforced concrete residential building 70-Story building plus 5 basements Total height of 242m height Approximate floor area of 100,000 m 2 Structural system: Moment resisting frames with shear walls Mega-truss wall (MTW) panels to control the lateral deformation Designer : R.S Caparros Associates Sy^2 + Associates Inc. Performance Reviewer : AIT Consulting CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 33

34 ` Typical tower framing plan Sectional elevation of MTW panel 34

35 Modeled using ETABS for DBE Response Spectrum Member stiffness properties are adjusted in accordance with effective stiffness values given in Table 6-5 of FEMA 356 provisions Typical Floor Plan Full 3D Finite Element Model CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 35

36 3D nonlinear model using PERFORM-3D Seven pairs of site ground motions used Shear wall modeling Inelastic wall element is used. Fiber modelling technique is used to model the flexural behaviour. Out-of-plane bending and shear is kept elastic. Out of plane stiffness of the wall is reduced to 1/4 value to account the effect of concrete cracking. Full 3D Finite Element Model CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 36

37 Floor area: 56,000 m 2 Type of building: Residential Building Structural system: Reinforced concrete moment resisting building with shear walls CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 37

38 Floor area: 85,000 m 2 Type of building: Residential Building Structural system: Reinforced concrete moment resisting building with shear walls CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 38

39 Floor area: 100,000 m 2 Type of building: Residential Building Structural system: Reinforced concrete moment resisting building with shear walls CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 39

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41 Mode Natural Period (s) Mode Shape Translation in minor dir Translation in major dir Torsion Major Minor Mode 1 Mode 2 Mode 3 41

42 Torsional Translation in Major direction Translation in Minor direction T 1 =5.32 sec 60% in Minor direction T 6 =1.28 sec 18% in Minor direction T 9 =5.32 sec 6.5% in Minor direction T 2 =4.96 sec 66% in Major direction T 4 =1.56 sec 15% in Major direction T 7 =0.81 sec 5.2% in Major direction T 3 =4.12 sec T 5 =1.30 sec T 8 =0.65sec 42

43 Load Cases Base Shear (KN) % of Seismic Weight DBE level (In major dir.) 21, DBE level (In minor dir.) 22, MCE level (In major dir.) 47, MCE level (In minor dir.) 46, Design base shear is larger than minimum limit of 3% set by LATBSDC-2008 Nonlinear dynamic base shear is approximately 2 times higher than design base shear 43

44 Weak Direction (Y) Strong Direction (X) CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 44

45 Weak Direction (Y) Strong Direction (X) CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 45

46 Story Drift in Principal Major Direction Story Drift in Principal Minor Direction 46

47 Story Shear in Principal Major Direction Story Shear in Principal Minor Direction 47

48 Story Moment about Principal Minor Axis Story Moment about Principal Major Axis 48

49 Story Story Wall Compressive Axial Strain at Location 1-2 Compressive Strain=2 times MCE strain Wall Tensile Axial Strain at Location 1-2 Compressive Strain=2 times MCE strain TAB MIN ARC MIN CHY MIN TAB MAX ARC MAX CHY MAX 20 DAY MIN 20 DAY MAX 10 ERZ MIN LCN MIN 10 ERZ MAX LCN MAX 0 ROS MIN 0 ROS MAX -10 Average MIN -10 Average MAX Axial Strain Axial Strain Wall Compressive Axial Strain Wall Tensile Axial Strain 49

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51 Summary of Beams Flexural Deformation Girder Shear Design Check Summary 100% 100% 90% 90% 80% 80% 70% 70% 60% 50% 40% Beyond CP Between LS and CP Between IO and LS Before IO 60% 50% 40% Under demand Just enough Good 30% 30% 20% 20% 10% 10% 0% PART 1 PART 2 PART 3 0% PART 1 PART 2 PART 3 51

52 Summary of Column Flexural Deformation Column Shear Design Check Summary % 100% 90.00% 90% 80.00% 80% 70.00% 70% 60.00% 50.00% 40.00% Beyond CP Between LS and CP Between IO and LS Before IO 60% 50% 40% Under demand Just enough Good 30.00% 30% 20.00% 20% 10.00% 10% 0.00% PART 1 PART 2 PART 3 0% PART 1 PART 2 PART 3 52

53 100% 90% % 70% 60% 70 50% 40% Frame Shear Wall 30% 20% 10% 0% % (X-dir) % (Y-dir) % (X-dir) % (Y-dir) % (X-dir) % (Y-dir) 30 Part 1 Part 2 Part 3 Percentage of Total Base Shear Distributed to Shear Walls and Moment Resisting Frame from Equivalent Static Analysis CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 53

54 Part Level Maximum Displacement Check Seismic gap size : 250 mm 89.3 mm 82.6 mm 62.1 mm 59.8 mm ( ) mm = mm < 250 mm ( ) mm = mm < 250 mm CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 54

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56 Shear Walls Items -Good Flexural Response Performance Overview Flexure deformation-100% within acceptable limit -Fair Response in Shear Shear Capacity-Some shear walls may be overstressed in Part 1 and Part 2 Girders Columns -Good Flexural Response Flexure deformation-only 1% beyond acceptable limit in Part 2 -Fair Response in Shear Shear capacity Approximately 6%, 8% and 3% seems to be overstressed in Part 1, 2, and 3 respectively -Good Flexural Response Flexure deformation nearly 100% within acceptable limit - Fair Response in Shear Shear capacity Approximately 8% in Part 1 and 3% in Part 2 seem to be overstressed. 56

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61 This is an attempt to explicitly check that the Building Is serviceable under Frequent Earthquakes Has limited damage during Design Basis Earthquake Does not collapse in Maximum Credible earthquake This is done by Avoiding the uncertainties that are inherent in traditional code based. Avoiding the uncertainties in the use of global force reduction/over strength factor R Considering the higher mode effects Considering the nonlinearities and dynamics in appropriate manner Use the state of the art knowledge and techniques for tall building design CE Design of Tall Buildings - January 2011, Dr. Naveed Anwar 61