Research Opportunities -- Improving Earthquake-Resilient Construction
Stephen MahinByron and Elvira Nishkian Professor of
Structural EngineeringDirector, Pacific Earthquake Engineering
Research CenterUniversity of California, [email protected]
Quake Summit 2010 San Francisco, CA September 9, 2010
Seismic Performance Goals?Preserve Life Safety and Prevent Collapse
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If collapse can be prevented, what level of damage is acceptable?
Fractured Spiral Fractured Spiral Fractured Bar
Buckled Bars
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Yielded and buckled members
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Local Failure
Permanent Offset
Fracture
Research traditionally focuses on achieving ductile behaviorBrittle fractures were detected in welded steel moment connections following Northridge, Kobe & other earthquakes.
Fracture
OLD: Brittle fractures, possible collapse hazard
Fracture
Research traditionally focuses on achieving ductile responseBrittle fractures were detected in welded steel moment connections following Northridge, Kobe & other earthquakes. Integrated analytical, theoretical and experimental research
lead to connections dependable ductile behavior
Is this what we really want?
Fracture
NEW: Ductile, large inelastic displacement capacity Local buckling, fracture & permanent offset
Difficult & costly repair
Ricles et al
Even moderate damage may mean buildings lose their functionality
Natural disasters cause wide-spread moderate damage
Such damage can have substantial long-lasting social, economic and cultural impacts on a city.
Sustainable development
UN Brundtland Commission“ meet needs of present generations without compromising the ability of future generations to meet their needs”
Selection of materials; Use of recycled materials; Consideration of material re-use and disassembly
for reuse; Energy efficiency Durability and longevity Reparability More efficient and lower impact construction; More efficient design methods, and more efficient
structural systems and layouts; Integration of structural forms to help achieve the
needs of other disciplines; Reducing the impacts of abnormal events such
earthquakes by minimizing the need for repair and disruption of service.
“Resiliency”
Beyond Safety: Issues for Sustainable and Earthquake-Resilient Structures
In Earthquake Engineering, our future challenge is to develop new or improved structures that:
protect public safety, and are economical, but that can be constructed quickly with minimal
disruption to the public and to the environment, and
can withstand strong earthquake ground shaking (and other hazards) safely, with little disruption or cost associated with post-earthquake inspections and repairs.
Recycle
Such approaches are consistent with, and supportive of, emerging trends related to sustainable development and “green” design.
Resilient structures, networks and communities
Sheltering in Place vs.
Damage Free
Sheltering in Place vs.
Damage Free
Beyond Safety: Issues for Sustainable and Earthquake-Resilient Structures
Safety Reduce post-earthquake disruption
and speed recovery of normal operations
Recycle
Systems that:Place damage known locationsMake it easy to inspectMake it economical to repair
Systems that:Minimize lateral displacements Minimize accelerationsMinimize residual displacements
Beyond Minimum Safety: Disaster-Resilient Structures
Recycle
Numerous structural concepts possible High performance materials Self-centering structural
concepts Rocking Foundations Next-generation braced and
damped systems Inertial damping systems Seismic Isolation
Assessing trade-offs in improving performance by increasing strength,
stiffness and toughness?
Performance-Based Earthquake Engineering (PBEE) Evaluation
PerformanceFramework
EnvironmentalHazard
Structure Simulation Evaluation
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Robust ProceduresAccurate Models
Effective InelasticMechanisms
PBEE
NEES capabilities People Ideas Tools
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Collaboratory By bringing researchers, educators and students
together with the members of the broad earthquake engineering and information technology communities, providing them ready access to powerful experimental, computational, information management and communications tools, and facilitating interaction as if they were “right across the hall,” the NEES collaboratory will be a powerful catalyst for transforming the face of earthquake engineering.
After William Wulf, NRC (1989)
Collaboratory
The missing link….. A principal aspect of collaboratories were
campaigns. Broad, scientifically challenging problems of national
importance Worked on by:
Grand Challenges Small group projects Individual investigator projects Government and academic organizations Private companies
Centers such as PEER focus on broad problem focused research themes
NEES can be harnessed to enable campaigns suggested by NEHRP strategic plan and other important social and scientific problems.
Concluding RemarksPBEE concepts can be used to proactively
achieve designs that are not only safer and more economical, but also more resilient.
PBEE investigations show significant impacts associated with nonstructural damage in small earthquakes and with structural damage and permanent offsets in larger events.
New technologies, devices and materials enable structures to minimize nonstructural and structural damage and to self-center.
Concluding RemarksPBEE provides the critical framework to
assess tradeoffs in performance and cost. Many opportunities as well as scientific and
technical challenges related achieving resilient communities, including buildings, transportation and lifelines.
Problems are multidisciplinary in nature and require collaboration among various disciplines, design professionals and industry.
ありがとうございました
THANK YOU
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