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Motivation and Development of PBEE for Existing and New Buildings

Motivation and Development of PBEE for Existing and New Buildings William T. Holmes Structural Engineer Rutherford & Chekene Three areas of interest Retrofit of existing buildings Performance based codes (primarily new buildings) Broad view

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Motivation and Development of PBEE for Existing and New Buildings

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  1. Motivation and Development of PBEE for Existing and New Buildings William T. Holmes Structural Engineer Rutherford & Chekene IRCC Workshop October 18, 2006

  2. Three areas of interest • Retrofit of existing buildings • Performance based codes (primarily new buildings) • Broad view IRCC Workshop October 18, 2006

  3. Performance Based Seismic Design: Why the emphasis in the last decade? • The high cost of seismic retrofit, if done to comply with the prescriptive code requirements developed for design of new buildings, • may be too high for economic feasibility • may not provide the performance intended • Economic losses were higher than expected by owners due to both damage repair costs and business interruption in the Loma Prieta, and Northridge earthquakes (in this country). IRCC Workshop October 18, 2006

  4. Phase 1 Project (1991-92)Identified major issues and recommended solutions On Performance Goals (Issue 11.2): Incrementalize and prioritize strengthening activities to the greatest extent possible. Identify the performance expectation of each increment. Specify requirements for Life Safety, which would form the core of the Guidelines Issues Identification and Resolution FEMA 237: Issues ResolutionPredecessor to FEMA 273 IRCC Workshop October 18, 2006

  5. higher performance Operational Level Damage Control Range Immediate OccupancyLevel Life Safety Level Collapse Prevention Level Limited Safety Range lower performance Building Performance Levels from FEMA 273 1-A 1-B Code for new buildings 3-C 5-E IRCC Workshop October 18, 2006

  6. Performance Level Serve as an effective “Alternate Means” For Equivalent Performance Prescriptive Criteria Method (Improve current code) Introduction of Innovative Systems For Superior Performance Alternate to Prescriptions Hazard Characterization Traditional Performance Based Code Process Applied to Seismic Design Performance Objective Performance Requirements Means of Verification IRCC Workshop October 18, 2006

  7. Conclusions/Opinions Regarding Performance Based Codes • Near term use of performance based design concepts in codes will be: • tuning the prescriptive provisions • enabling development of “standards” for acceptance of new systems • Providing method to determine equivalence for “alternate means” • facilitating designs “over code” (voluntary) • Performance based design (at least using the detailed probabilistic methods, will not be the primary code method for a long time--if ever. IRCC Workshop October 18, 2006

  8. A Broader View ofEarthquake Engineering • Design of New Buildings • Prescriptive “complete” method • Simplified methods • Individual Existing Buildings • Evaluation • Retrofit • Determination of expected losses • Groups of Buildings • Risk analysis • Economic portfolio analysis • Regional loss studies • Research and Reconnaissance IRCC Workshop October 18, 2006

  9. Integration of all Uses • Groups Of Buildings: • Portfolio Analysis • Regional Loss Studies • Mitigation Studies • Building Rating Systems: • Probable Maximum Loss • Other • Individual Buildings: • Evaluation • Retrofit Casualties Repair Costs Downtime Percentage or Dollars Performance Objective IRCC Workshop October 18, 2006

  10. Integration of all Uses • Groups Of Buildings: • Portfolio Analysis • Regional Loss Studies • Mitigation Studies • Building Rating Systems: • Probable Maximum Loss • Other • Individual Buildings: • Evaluation • Retrofit Casualties Repair Costs Downtime Percentage or Dollars Performance Objective IRCC Workshop October 18, 2006

  11. Unified Performance System • Groups Of Buildings: • Portfolio Analysis • Regional Loss Studies • Mitigation Studies • Building Rating Systems: • Probable Maximum Loss • Other Evaluation Retrofit Building Rating Portfolio Analysis Loss Studies Mitigation Studies Casualties Repair Costs Downtime Means of Verification IRCC Workshop October 18, 2006

  12. Interest and Demand from StakeholdersConsidering Broad Perspective IRCC Workshop October 18, 2006

  13. Elastic Limit Collapse Base Shear Force Displacement IO LS CP $, % replacement 25% 50% 100% 0 Casualty rate 0.0001 0.001 0.01 .25 0.0 Downtime, days 1 7 30 180 0 Needed Extension of FEMA 356 Concepts for Broader View Performance Level IRCC Workshop October 18, 2006

  14. Uncertainty is Big Issue IRCC Workshop October 18, 2006

  15. Core of “Performance Engine” Extend over all ground motions Consider uncertainty P M Desirable Characteristics of the Verification Method Ground Motion Structural Response Component and global damage level Losses: Casualties Cost of Repair Loss of use Average Annual Loss Cost Benefit Analysis Death, Dollars, and Downtime IRCC Workshop October 18, 2006

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