Seismic Evaluation and Retrofit of Existing Steel Structures. Canadian Seismic Research Network

Transcription

1 Seismic Evaluation and Retrofit of Existing Steel Structures Canadian Seismic Research Network Robert Tremblay École Polytechnique, Montréal, Canada August 2013

2 Plan Development of Guidelines based on ASCE Braces & Connections in CBFs Connections in MRFs Use of Ductile Brace Fuses for CBFs Use of Supplemental Dampers

3 Guidelines Based on ASCE Section Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 Ch 6 Ch 7 Ch 8 Ch 9 Ch 10 Ch 11 Ch 12 Ch 13 Ch 14 Ch 15 App 1 Title General Requirements Seismic Performance Objectives and Ground Motions Evaluation and Rehabilitation Requirements Tier 1 Evaluation Tier 2 Deficiency-based Evaluation and Rehabilitation Tier 3 Systematic Evaluation and Rehabilitation Analysis Procedures and Acceptance Criteria Foundations and Geologic Site Hazards Steel Concrete Masonry Wood And Light Metal Framing Architectural, Mechanical, And Electrical Components Seismic Isolation And Energy Dissipation System Specific Performance Procedures Tier 1 Checklists R. Tremblay, Ecole Polytechnique of Montreal 3

4 Assessment of 10-Storey CBF in 1980 X-Bracing Chevron Bracing N 9144 = = = Gravity loads: Roof: Dead = 3.0 kpa Snow = var. Floor: Dead = 3.0 kpa Partitions = 1.0 kpa Live = 2.4 kpa Exterior walls = 1.0 kpa X-Bracing N-S Chevron Bracing E-W 4572 Y. Balazadeh-Minouei, S. Koboevic & R. Tremblay Ecole Polytechnique R. Tremblay, Ecole Polytechnique of Montreal 4

5 Assessment based on NBCC 2010 & CSA S16-09 (R d = 1.5) Braces X-Bracing N-S R. Tremblay, Ecole Polytechnique of Montreal 5

6 Assessment based on NBCC 2010 & CSA S16-09 (R d = 1.5) Brace Connections X-Bracing N-S R. Tremblay, Ecole Polytechnique of Montreal 6

7 Assessment based on NBCC 2010 & CSA S16-09 (R d = 1.5) Columns X-Bracing N-S R. Tremblay, Ecole Polytechnique of Montreal 7

8 Assessment based on ASCE (LDP) Braces = Deformation-Controlled m = Ductility factor Q CE = Expected Strength Q UD = Seismic Demand R. Tremblay, Ecole Polytechnique of Montreal 8

9 Assessment based on ASCE (LDP) X-Bracing N-S NBCC 2010 R. Tremblay, Ecole Polytechnique of Montreal 9

10 Assessment based on ASCE (NDP) R. Tremblay, Ecole Polytechnique of Montreal 10

11 Assessment based on ASCE (NDP) X-Bracing N-S NBCC 2010 ASCE 41 LDP R. Tremblay, Ecole Polytechnique of Montreal 11

12 Assessment based on ASCE (LDP) Columns = Force-Controlled Q CL = Lower-Bound Strength Q UF = Seismic Demand Columns subjected to P & M: R. Tremblay, Ecole Polytechnique of Montreal 12

13 Assessment based on ASCE (LDP) X-Bracing N-S NBCC 2010 R. Tremblay, Ecole Polytechnique of Montreal 13

14 Assessment based on ASCE (NDP) X-Bracing N-S R. Tremblay, Ecole Polytechnique of Montreal 14

15 Assessment based on ASCE (NDP) X-Bracing N-S NBCC 2010 ASCE 41 LDP R. Tremblay, Ecole Polytechnique of Montreal 15

16 Assessment based on ASCE (NDP) Braces + Columns R. Tremblay, Ecole Polytechnique of Montreal 16

17 Assessment based on ASCE (NDP) ASCE 41 NDP with linear columns X-Bracing N-S R. Tremblay, Ecole Polytechnique of Montreal 17

18 6 m = 24 m W200x52 W200x52 4 m = 16 m W200x36 W200x36 Assessment & Retrofit 4-Storey CBF (Braces & Connections) W250x80 W200x A 6 m = 24 m Structure Plan View E N 306 kn 2L76x51x kn 2L102x89x kn 2L102x89x kn 2L127x76x kn Frame Elevation Gravity loads: Roof: Dead = 3.0 kpa Snow = 1.52 kpa Floor: Dead = 3.0 kpa Partitions = 1.0 kpa Live = 2.4 kpa Exterior walls = 1.0 kpa A325 3/4 Bolts = [mm] Brace Connection at Level 1 Y. Jiang, R. Tremblay & L. Tirca Ecole Polytechnique, Concordia University R. Tremblay, Ecole Polytechnique of Montreal 18

19 Test Program on 2L Braces and Connections In Braced Frame In 12 MN Load Frame R. Tremblay, Ecole Polytechnique of Montreal 19

20 R. Tremblay, Ecole Polytechnique of Montreal 20

21 Detailed 2L Brace O/S Model Brace with End Gusset Plate Connections Fiber Cross-Section End Connection End Connection Model Stitch Connector R. Tremblay, Ecole Polytechnique of Montreal 21

22 R. Tremblay, Ecole Polytechnique of Montreal 22

23 R. Tremblay, Ecole Polytechnique of Montreal 23

24 Retrofit Strategy Retrofitted connection with slotted holes 15% less capacity Similar ductility Original Connection Retrofitted Connection R. Tremblay, Ecole Polytechnique of Montreal 24

25 Hybrid Simulations (Collapse Predictions) R. Tremblay, Ecole Polytechnique of Montreal 25 R. Tremblay, Ecole Polytechnique of Montreal 25

26 Collapse Prediction (FEMA P695) R. Tremblay, Ecole Polytechnique of Montreal 26

27 Brace Connections Samples made from new material Samples taken from existing structures P. Castonguay & R. Tremblay Ecole Polytechnique J. Hartley, A. Caruso & C. Rogers McGill University R. Tremblay, Ecole Polytechnique of Montreal 27

28 Existing: a) P (kn) D01X - Yielding on Brace Gross Section D02X - Failure of Parallel Welds D03X - Bearing and Tearing D04X - Failure on Net Section D05X - Bolt Shear Failure D06X - Block-Shear Failure b) inel (mm) Strengthened: 800 P (kn) inel (mm) R. Tremblay, Ecole Polytechnique of Montreal 28

29 Assessment / Buildings per 1965 Codes R. Tremblay, Ecole Polytechnique of Montreal 29

30 Connections in MRFs N. Kyriakopoulos & C. Christopoulos University of Toronto R. Tremblay, Ecole Polytechnique of Montreal 30

31 CJP Weld Failure Weld Zipping Backing Bar R. Tremblay, Ecole Polytechnique of Montreal 31

32 P=V b /2 NOTE: Height of column = H M c =M b *(H/ 2-a)/ H V c a C bearing C bearing No force transfer in top plate V b C st C st V b N.A. V b M b a T T = C st + C bearing V c M c P Frame Fm Pushover Base Shear Force (kn) nd Floor 3rd Floor 4th Floor Penthouse Penthouse No P D Total Drift (mm) R. Tremblay, Ecole Polytechnique of Montreal 32

33 Use of Ductile Fuses Control Forces in CBFs Achieve Higher Displacement Capacities Develop Enhanced Hysteretic Response to Control Drifts T u P / P y C u HSS 102x76x6.4 - KL/r = / y R. Tremblay, Ecole Polytechnique of Montreal 33

34 E. Desjardins, A. Desrochers & F. Légeron Université de Sherbrooke R. Tremblay, Ecole Polytechnique of Montreal 34

35 E. St-Onge & R. Tremblay Ecole Polytechnique R. Tremblay, Ecole Polytechnique of Montreal 35

36 O. Egloff & R. Tremblay Ecole Polytechnique R. Vincent & S. Moreau Goupe Canam 1.2 T u 0.8 P / AFy Design Design C u -1.2 Test 1 - L F /L H = / h s R. Tremblay, Ecole Polytechnique of Montreal 36

37 Axial Load (kn) T. Morrison & C. Rogers McGill University 140 Original vs. Retrofited Tests System Deformation (mm) Original Sample Retrofitted Sample TestData1 TestData2 R6D09b1 R6D09b R. Tremblay, Ecole Polytechnique of Montreal 37

38 C. Caprarelli, N. Danila & L. Tirca Concordia University F orce [k N] Displace m ent [m m ] Ex pe riment al res ult Pinchin g Sk elet on curve R. Tremblay, Ecole Polytechnique of Montreal 38

39 M. Gray, C. Christopoulos & J. Packer University of Toronto R. Tremblay, Ecole Polytechnique of Montreal 39

40 Use of Supplemental Dampers Existing Guideline (ASCE-7 ch18, ASCE-41 ch14) Trial-and-error approach based on experience Hard to evaluate design alternatives from performance target Hard to assess response under multiple hazards Does not provide insight on selection of damping system Proposed CSRN Performance Spectra-based Guideline Ties performance targets directly to design properties Direct design, minimize iteration Assess alternative options at the beginning of design stage Assess multiple hazards at the beginning of design stage J. Guo & C. Christopoulos University of Toronto R. Tremblay, Ecole Polytechnique of Montreal 40

41 P-Spectra Procedure Overview Using basic building properties, evaluate damping variables that gives desired performance from performance spectra Transform performance spectra solution to MDOF Verify design using NLTHA (expected to be close to target) R. Tremblay, Ecole Polytechnique of Montreal 41

42 Performance Spectra R. Tremblay, Ecole Polytechnique of Montreal 42

43 Features of P-Spectra Shows system sensitivity to damping properties Shows system sensitivity to ground motions East vs. West Viscous vs. hysteretic damping Shows system performance at other hazard levels V f scales with hazard R. Tremblay, Ecole Polytechnique of Montreal 43

44 Normalized Base Shear, R v Generic Hysteretic Damping Performance Spectrum Specific T f Specific V f Increasing values of ratio of unbraced to braced stiffness, a Values of normalized residual drift ratios for different values of a Increasing values of damper ductility, m d Normalized Displacement, R d Normalized Residual Drift, R s R. Tremblay, Ecole Polytechnique of Montreal 44

45 Conclusions Several Challenges in the Development of Guidelines Braces, Brace Connections & Columns may be Critical in CBFs Connections Critical in PR MRFs Ductiles Fuses Proposed to Enhance the Performance of CBFs Effective Design Method Proposed for Supplemental Damping R. Tremblay, Ecole Polytechnique of Montreal 45