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Session IVa – "A Seismic Rehabilitation Agenda for Older Hazardous Concrete Buildings". Richard McCarthy Executive Director California Seismic Safety Commission. Mitigation of Seismic Risk in Older Concrete Buildings. EERI Concrete Building Coalition and NEESR Grand Challenge
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Session IVa – "A Seismic Rehabilitation Agenda for Older Hazardous Concrete Buildings" Richard McCarthy Executive Director California Seismic Safety Commission
Mitigation of Seismic Risk in Older Concrete Buildings EERI Concrete Building Coalition and NEESR Grand Challenge Craig Comartin and Jack Moehle
California, 1994 Turkey, 2003 “50% of the casualties are coming from 5% of the buildings.” Kircher et al., “Estimated Losses due to a Repeat of the 1906 San Francisco Earthquake, Earthquake Spectra, 2006. Project background
“Current guidelines identify most older concrete buildings as collapse risks.” Craig Comartin, EERI President, 2006 Earthquake Conference Project background 100 80 Percentage Otani (1999) 60 40 Kobe, 1995 20 Erzincan, 1992 Luzon, 1990 0 Mexico City, 1985 Operational Heavy Collapse Older Concrete Building Damage Rating Otani, 1999
Project thesis • Available guidelines are too conservative • most buildings are found inadequate • retrofit costs are high • This “always bad” message • is not credible • is impeding action • Improved procedures • can reduce the problem • can make retrofit programs feasible • What we learn can be translated to other building types and localities.
Project aims • Develop a consensus on the “killer” buildings • Demonstrate cost-effective retrofit • Identify mitigation policy alternatives • Promote active mitigation programs
Stewart Moehle Comerio May Matamoros Mosalam Lopez Hutchinson Steele Project Team Disciplines: Seismic hazard Inventory Simulation Laboratory Field Building Regional Public policy EOT Anagnos Ramirez Leadership team
Research program overview • Inventory • by structural type • by occupancy • by ownership • Participants • building and safety • housing agencies • structural engineers • real estate professionals
Research program overview • Testing to collapse • Multi-directional loadings • Realistic axial loads • Simple retrofit methods
Flexible/Weak Foundation Research program overview • Systems studies • SFSI • Membrane effects
450 FEMA 356 400 Shear 350 300 Monotonic 250 Cyclic Envelope 200 150 100 50 0 0 2 4 6 8 Displacement Research program overview • Improved simulation • model development • simulation capability • Regional simulation
Research program overview • Crafting and evaluating appropriate policies • Identify different classes of the problem • Structural configuration • Occupancy • Economic conditions • Identify feasible mechanisms • Model risk reduction impacts • Evaluate economic impacts • Costs borne by building owners, governments, and other stakeholders • Regulatory considerations
Collaborations with existing organizations • ASCE Standards Committees • American Concrete Institute • Applied Technology Council • EERI Concrete Coalition