tailieunhanh - Seismic Retrofit Practice

Seismic Retrofit Practice James Roberts California Department of Transportation 40 Introduction Identification and Prioritization Hazard • Structural Vulnerability • Risk Analysis Performance Criteria Retrofit Design Conceptual Design • Retrofit Strategies • Analysis • Aesthetics Brian Maroney California Department of Transportation Construction Costs Summary Introduction Until the 1989 Loma Prieta earthquake, most of the United States had not been concerned with seismic design for bridges, although some 37 states have some level of seismic hazard and there are hundreds of bridges in these other states that have been designed to seismic criteria that are not adequate for the seismic forces and displacements that we know today | Roberts J. Maroney B. Seismic Retrofit Practice. Bridge Engineering Handbook. Ed. Wai-Fah Chen and Lian Duan Boca Raton CRC Press 2000 40 Seismic Retrofit Practice Introduction Identification and Prioritization James Roberts Hazard Structural Vulnerability Risk Analysis Performance Criteria California Department of Transportation Retrofit Design Brian Maroney California Department of Transportation Conceptual Design Retrofit Strategies Analysis Aesthetics Construction Costs Summary Introduction Until the 1989 Loma Prieta earthquake most of the United States had not been concerned with seismic design for bridges although some 37 states have some level of seismic hazard and there are hundreds of bridges in these other states that have been designed to seismic criteria that are not adequate for the seismic forces and displacements that we know today. Recent earthquakes such as the 1971 San Fernando California the 1976 Tangshan China 3 the 1989 Loma Prieta California the 1994 Northridge California and the 1995 Hyogo-ken Nanbu Kobe Japan have repeatedly demonstrated the seismic vulnerability of existing bridges and the urgent need for seismic retrofit. The California Department of Transportation Caltrans owns and maintains more than12 000 bridges spans over 6 m and some 6000 other highway structures such as culverts spans under 6 m pumping plants tunnels tubes highway patrol inspection facilities maintenance stations toll plazas and other transportation-related structures. There are about an equal number on the City and County systems. Immediately after the February 9 1971 San Fernando earthquake Caltrans began a comprehensive upgrading of their Bridge Seismic Design Specifications construction details and a statewide bridge seismic retrofit program to reinforce the older non-ductile bridges systematically. The success of the bridge seismic design and retrofit program and the success of future seismic design for California bridges