Caltrans and aashto highway bridge criteria focus on collapse prevention during an extreme seismic event, and allow or require substantial damage to occur as part of the mechanism resisting extreme earthquakes in high seismic zones. Such damage implies possible extended closure of the facility until repaired, and, in the case of toll roads, loss of revenue until traffic is restored. A special study was made to determine the feasibility of bridge design criteria which will obtain a higher degree of seismic reliability for the orange county, california toll roads. The study included a seismic hazard analysis of the area, development of site specific response spectra with several different probabilities of exceedance, a review of caltrans criteria, and evaluation of various strategies for improving the structural performance or controlling damage. The principal strategies considered were: a two level design approach; the use of energy dissipators at abutments only; seismic isolation; and lighter weight superstructures. Evaluations were made by preparing a range of bridgedesigns using a linear elastic analysis for strength design and a nonlinear analysis to assess performance. Cost estimates were prepared using the results of the analytical work. Criteria are proposed for implementation in the design of bridges in the orange county, california toll road corridors. This paper appears in transportation research record no. 1290, Third bridge engineering conference, march 10-13, 1991, denver, colorado, volume 2.
Samenvatting