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FEMA Task Order to BSSC The Simplified Seismic Design Project

William T. HolmesRutherford

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FEMA Task Order to BSSC The Simplified Seismic Design Project

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    1. William T. Holmes Rutherford & Chekene 1 FEMA Task Order to BSSC The Simplified Seismic Design Project William T. Holmes Structural Engineer Rutherford & Chekene San Francisco, CA

    2. William T. Holmes Rutherford & Chekene 2 Team FEMA Project Officer: Mike Tong Project Management Committee Bill Holmes, Chair Jim Harris John Hooper Dominic Kelly Barry Welliver Project Review Committee-to be named Development Working Groups-to be named

    3. William T. Holmes Rutherford & Chekene 3 Background Ongoing concern that the ratcheting development process of building code seismic regulations has resulted in complexities that may be counter-productive for providing performance objectives Of some buildings Designed by some engineers Convention Construction rules and Simplified design base shear are examples of efforts from development of the UBC

    4. William T. Holmes Rutherford & Chekene 4 BSSC Efforts 1998-2000: Simplified Procedures Task Group SPTG under TS 2 in 2000 Update Developed three options 1. Clarify/simplify by editing, possibly for sub-groups of the entire building universe 2. Procedure with limited use simpler (but more conservative) than general code, but that can be shown to produce equal or safer structures that the full code 3. Procedure completely different than general code (perhaps capacity design), but that could be shownor judgedto be equivalent.

    5. William T. Holmes Rutherford & Chekene 5 Results from SDPG SPTG favored approach 3 (new procedures) but PUC discouraged its development due to concerns of equivalency. SDPG developed provisions for rigid wall, flexible diaphragm buildings combining approach 1 and 2. Resulting Provisions achieved very little simplification and saw little, if any, of the light of day. SDPG developed draft provisions for low-rise bearing wall and building frame systems that had simplified calculations (fewer) due to conservative base shear.

    6. William T. Holmes Rutherford & Chekene 6 2003 Provisions Update Simplified Design development effort from a stand-alone committee: Simplified Design Task Group Simplify design for low rise by encouraging good buildings Many limitations starting with 3 stories or less and Bearing Wall or Braced Frame Systems. Limited irregularities Limited layout of lateral force resisting system Primarily simplified calculations, but not simplified concepts or reduced detailing requirements. Appeared as appendix to Chapter 4, in 2003 Provisions Was carried into ASCE 7-05

    7. William T. Holmes Rutherford & Chekene 7 Genesis of Current Project ASCE 7 Simplified Method not extensively used FEMA continued to get complaints Mike Tong solicited comments from a large number of stakeholders around the country and became convinced that additional effort was justified, especially considering Advantages may result even if limited to moderate and low seismicity. Advantages may result even if limited to a narrowly defined building typeif extensively built FEMA P695 (ATC 63) is now available to demonstrate buildings designed by a procedure entirely different than the normal code are equivalent

    8. William T. Holmes Rutherford & Chekene 8 Summary Work PlanPhase 1 PMC performs initial investigation Tasks and Report Organization Summary of past efforts Examples from other countries Regional needs and potential building types Development of Approach Simplified/prescriptive/capacity design for specific building types Confirmation lf acceptance with P695 Methods valid Methods to incorporate into ASCE 7 or other reference location Challenges/Restrictions of approach Recommendations for one or more building types Detailed Work Plan for Phase II Meeting with Review panel of 12 or more members Revise report considering input from review panel

    9. William T. Holmes Rutherford & Chekene 9 Summary Work PlanPhase 2 FEMA/BSSC/PMC selects and hires Project Working Groups (PWGs) to develop procedures and run concurrent P695 type analysistwo such groups currently anticipated PWG = practitioner/code writer + academic and student for analysis PMC closely oversees development work Results are reviewed by Review Panel and refined. Results presented to PUC for review and possible action.

    10. William T. Holmes Rutherford & Chekene 10 Schedule Year 1 35% of development by PWGs by Sept 29, 2010. Year 2 Balance of development subcontracts Review Panel Summary Report and Recommendation Report to PUC

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