Transcript Slide 1

Development of Performance-based Seismic
Design Standards & Criteria
Ronald O. Hamburger, SE, SECB
Senior Principal
Simpson Gumpertz & Heger
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Code Procedures
• Require buildings have complete
structural systems
• Require systems have sufficient
strength to resist specified forces
2003
• Limit permissible drifts under
specified forces
• Require members and connections
be “detailed” prescriptively
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Building Codes Imply Performance
 Ability to resist frequent, minor
earthquakes without damage
2003
100 yrs
 Ability to resist infrequent,
moderate earthquakes with
limited structural and
nonstructural damage
500 yrs
 Ability to resist worst
earthquakes ever likely to occur
without collapse or major life
safety endangerment
2,500 yrs
Performance is not guaranteed
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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
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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.”
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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)
Seismic
Evaluation of
Buildings
 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
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ASCE-31
Seismic
Rehabilitation of
Buildings
ASCE-41
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Selecting Performance
Present Generation
Joe’s
Joe’s
Beer!
Food!
Operational
Beer!
Food!
Immediate
Occupancy
Beer!
Food!
Life
Safety
Collapse
Prevention
Operational – negligible impact on building
Immediate Occupancy – building is safe to occupy but
possibly not useful until cleanup and repair has occurred
Life Safe – building is safe during event but possibly not
afterward
Collapse Prevention – building is on verge of
collapse, probable total loss
Code-equivalent Performance
Joe’s
Beer!
Food!
Frequent event (varying between 50- and 100year return periods)
Immediate
Occupancy
DBE
MCE
Beer!
Food!
Life
Safety
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Collapse
Prevention
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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
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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
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Performance-based design
A new approach
Owner
Designer
Building Official
Select
Performance
Objectives
Develop
Preliminary
Design
Assess
Performance
Capability
Revise
Design
No
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Does
Performance
Meet
Objectives?
Building
Official
&
Peer
Reviewers
Yes
Done
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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
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