Performance-Based Design Approach in Seismic Analysis of Bridges

The seismic design requirements used in the United States are based on the recommendations of the American Association of State Highway and Transportation Officials. These requirements are primarily based on the importance of the structure, the level of deformation imposed on the structure, soil conditions, and the ductility of structural members, especially piers and supports. In the performance-based design approach, the design is primarily focused on meeting a performance objective, which is in line with a desired level of service. Currently, the effort toward implementing the performance-based design approach in buildings is under way in the United States. The seismic performance criteria for buildings have been established and reported by various organizations. It seems that at least three levels of performance, ranging from “fully operational” to “near collapse” can be used to meet the postearthquake conditions, safety, usage, and occupancy for the varous levels of service expected from all types of structures. In this paper a critical evaluation of these performance criteria and their relevance to highway bridge design, in conjunction with the current design practice, is discussed. Various types of designs such as those based on strength, deformation, nonlinear behavior, and energy, which can be used to meet the specified performance levels in seismic design of highway bridges, are also discussed in the paper. Examples of real applications of the method in highway bridges are reviewed. Furthermore, the procedure by which the performance-based method has been implemented in these example cases is described and discussed in the paper.