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CE 496 B Structural Design III

CE 496 B Structural Design III. Spring 2011 Howard Lum. Seismic Design Criteria. California Building Code (CBC) 2010 ASCE 7-05 Minimum Load Requirements for Buildings and Other Structures AISC 341-05 Seismic Design for Steel Buildings

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CE 496 B Structural Design III

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  1. CE 496 BStructural Design III Spring 2011 Howard Lum

  2. Seismic Design Criteria California Building Code (CBC) 2010 ASCE 7-05 Minimum Load Requirements for Buildings and Other Structures AISC 341-05 Seismic Design for Steel Buildings American Concrete Institute (ACI 318-08) Building Code Requirements for Structural Concrete (Chapter 21) Site Specific Geotechnical Report

  3. Seismic Design • Seismic Accelerations - SDS and SD1 • Occupancy Category (OC) per CBC Table 1604.5 (our project - OC II) • Importance Factor I (our project, I=1.0) • OC and SDS and SD1 - determine Seismic Design Category (SDC) per CBC Sect. 1613.5.6 • SDC is used in: • Lateral load system selection • Seismic load factors in load combination • Allowable seismic drifts • Seismic structural detailing

  4. Seismic Design Category (SDC) Reference: CBC Tables 1613.5.6

  5. Dynamics of Structure • Single Degree of Freedom System: • Lumped mass - m • Single damping - c (5% typical) • Linear Stiffness - k • Period - T = 2π √m/k

  6. Site Specific Response Spectrum SDS Short) Earthquake Response Spectrum (ASCE 11.4-1) SD1 T0 TS TL

  7. Seismicity Ss in g S1 in g

  8. 0.52 g

  9. LB Response Spectrum (2005)Use USGS data for current project PGA

  10. Tohoku Earthquake March 2011 PGA=2.70 g

  11. Steel Properties Fu Fy

  12. Seismic Design Methods • ASCE Table 12.6-1 provides 3 methods • Equivalent Lateral Force (ASCE 12.8) • Base shear static analysis • Lumped Mass at each level • Orthogonal directions of analysis(transverse & longitudinal) • Modal Response Spectrum Analysis (ASCE 12.9) • Linear elastic dynamic analysis • Seismic Response History Analysis (ASCE Ch.16) • Non-linear dynamic analysis using time histories

  13. Vertical distribution of Forces • Reference: ASCE 12.8.3 • Fx = Cvx * V • where Cvx = wxhxk/∑wihik w1 F1 (upper deck) F2 (pipe support deck) w2 V=F1+F2 hi

  14. Horizontal Truss as Diaphragm

  15. Seismic Load Design • Strength Design (12.4.2.3) to ensure adequate capacity • (1.2 + 0.2 SDS)D + *QE + 0.5L • (0.9 – 0.2 SDS)D + *QE • Drift Control (12.8.6) to limit content damage and maintain building separation

  16. Steel Structural Systems Moment Frame Concentric Braced Frame Eccentric Braced Frame

  17. Design of beam-column in a moment frame Combined Axial & Bending: • Moment resisting frames • Axial Force: • Vertical gravity load + seismic overturning forces • Moment and Shear: • Lateral loads

  18. AISC Equations H1-1a & H1-1b Large Axial Compression (>= 20%): REQUIRED CAPACITY PrPc =Pn MrxMcx = Mnx Mry Mcy = Mny Small Axial Compression (< 20%):

  19. Dynamic Analysis Modal analysis – linear elastic response spectrum

  20. Dynamic Analysis Time History – Non-linear system

  21. Seismic Retrofit ExampleBase Isolators

  22. Example – Landslide Protection Before After

  23. Example – Pumping Plant Seismic Upgrade Eagle Mountain Pumping Plant Hinds Pumping Plant

  24. Example – Discharge Pipelines Seismic Upgrade

  25. Earthquake Structural Failure

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