Research Opportunities -- Improving Earthquake- Resilient Construction Stephen Mahin Byron and Elvira Nishkian Professor of Structural Engineering Director, Pacific Earthquake Engineering Research Center University of California, Berkeley Quake Summit 2010 San Francisco, CA September 9, 2010

Seismic Performance Goals? Preserve Life Safety and Prevent Collapse

If collapse can be prevented, what level of damage is acceptable? Fractured Spiral Fractured Spiral Fractured Bar Buckled Bars Yielded and buckled members Local Failure Permanent Offset Fracture

Research traditionally focuses on achieving ductile behavior Brittle 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 response Brittle 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

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 locations Make it easy to inspect Make it economical to repair  Systems that: Minimize lateral displacements Minimize accelerations Minimize 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 Performance Framework Environmental Hazard Structure Simulation Evaluation $=  xyz Robust Procedures Accurate Models Effective Inelastic Mechanisms PBEE

NEES capabilities  People  Ideas  Tools

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 Remarks PBEE 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 Remarks PBEE 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.

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