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FEMA Task Order to BSSC The Simplified Seismic Design Project

FEMA Task Order to BSSC The Simplified Seismic Design Project. William T. Holmes Structural Engineer Rutherford & Chekene San Francisco, CA. Team. FEMA Project Officer: Mike Tong Project Management Committee Bill Holmes, Chair Jim Harris John Hooper Dominic Kelly Barry Welliver

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FEMA Task Order to BSSC The Simplified Seismic Design Project

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

  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. 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. 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 shown—or judged—to be equivalent.

  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. 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. 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 type—if 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. Summary Work Plan—Phase 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. Summary Work Plan—Phase 2 • FEMA/BSSC/PMC selects and hires Project Working Groups (PWGs) to develop procedures and run concurrent P695 type analysis—two 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. Schedule • Year 1 • 35% of development by PWG’s by Sept 29, 2010. • Year 2 • Balance of development subcontracts • Review Panel • Summary Report and Recommendation • Report to PUC

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