1. www.sgh.com © Simpson Gumpertz & Heger Inc. 1 Development of Performance-based Seismic Design Standards & Criteria Ronald O. Hamburger, SE, SECB Senior Principal Simpson Gumpertz & Heger

2. www.sgh.com © Simpson Gumpertz & Heger Inc. 2 Limit permissible drifts under specified forces Require buildings have complete structural systems Code Procedures Require systems have sufficient strength to resist specified forces Require members and connections be “detailed” prescriptively 2003

3. www.sgh.com © Simpson Gumpertz & Heger Inc. 3 Building Codes Imply Performance  Ability to resist frequent, minor earthquakes without damage  Ability to resist infrequent, moderate earthquakes with limited structural and nonstructural damage  Ability to resist worst earthquakes ever likely to occur without collapse or major life safety endangerment 100 yrs 500 yrs 2,500 yrs Performance is not guaranteed 2003

4. www.sgh.com © Simpson Gumpertz & Heger Inc. 4 Building Codes & Peformance Warranties  If a building is affected by an extreme event and performs poorly:  There is an expectation of how the building should have performed but no implied warranty  The only warranty is that the engineer complied with the standard of care  For most buildings, demonstration that a design was performed in accordance with the building code will provide adequate proof of conformance to the standard of care

5. www.sgh.com © Simpson Gumpertz & Heger Inc. 5 Code Basis for Performance-based Design  Section 104- “The provisions of this code are not intended to prevent... or to prohibit any design or method of construction... provided that any such alternative has been approved. An alternative... design shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code.”

6. www.sgh.com © Simpson Gumpertz & Heger Inc. 6 First Generation Standards are Available  ASCE/SEI has standardized FEMA guideline documents on::  Seismic Evaluation  Predict types of damage a building would experience in future events (based on FEMA178)  Rehabilitation  Procedures to design building upgrades to achieve desired performance (based on FEMA 356)  Though not directly recognized by the building codes, these standards are being used as the basis for Performance-based design of new buildings and seismic retrofit Seismic Evaluation of Buildings ASCE-31 Seismic Rehabilitation of Buildings ASCE-41

7. Selecting Performance Present Generation Joe’s Beer! Food! Operational Operational – negligible impact on building Beer! Food! Joe’s Beer! Food! Beer! Food! Joe’s Immediate Occupancy Immediate Occupancy – building is safe to occupy but possibly not useful until cleanup and repair has occurred Beer! Food! Joe’s Beer! Food! Beer! Food! Joe’s Life Safety Life Safe – building is safe during event but possibly not afterward Collapse Prevention Collapse Prevention – building is on verge of collapse, probable total loss

8. www.sgh.com © Simpson Gumpertz & Heger Inc. 8 Code-equivalent Performance Frequent event (varying between 50- and 100- year return periods) DBE Collapse Prevention MCE

9. www.sgh.com © Simpson Gumpertz & Heger Inc. 9 Next Generation Standards are Presently Under Development  ATC-58 Project  10 year program funded by FEMA  Develop next-generation criteria applicable to design of new buildings and upgrade of existing buildings  New performance definitions  Performance expressed in terms of the probability of incurring:  Direct economic loss (repair/replacement cost)  Casualties (deaths & serious injuries)  Downtime (loss of use)  Direct consideration of uncertainty in ground shaking, structural response, damage and the consequences of damage

10. www.sgh.com © Simpson Gumpertz & Heger Inc. 10 2 Phase Project Execution  Phase 1  Development of a performance assessment methodology that can be used to predict the probability of incurring the various losses, as a function of specific design decisions  Presently 35% complete  Phase 2  Development of procedures for designing buildings for desired performance  Establishment of performance provided by current prescriptive procedures  Assessment of adequacy of performance  Development of improved prescriptive methods that will provide desired performance

11. www.sgh.com © Simpson Gumpertz & Heger Inc. 11 Performance-based design A new approach Select Performance Objectives Select Performance Objectives Develop Preliminary Design Develop Preliminary Design Assess Performance Capability Assess Performance Capability Does Performance Meet Objectives? Does Performance Meet Objectives? Done Revise Design No Revise Design No Owner Designer Building Official Yes Building Official & Peer Reviewers

12. www.sgh.com © Simpson Gumpertz & Heger Inc. 12 2 Phase Project Execution  Phase 2  Development of procedures for designing buildings for desired performance  Establishment of performance provided by current prescriptive procedures  Assessment of adequacy of performance  Development of guidance on selection of structural systems, strength, stiffness, etc. that is likely to be able to meet performance goals  Development of improved prescriptive methods that will provide desired performance