Bridge seismic importance adjustment factor based on seismic risk

Abstract

The current seismic design code is based on a uniform seismic hazard level rather than a uniform risk. As a result, the reliability of bridges and corresponding bridge networks cannot be guaranteed. To control the seismic risk of bridges under design requirements, the concept of bridge seismic importance adjustment factor (SIAF) is proposed to adjust bridge seismic importance factor in seismic design codes. Taking the ductility seismic design of regular bridge as an example, the relationship between seismic importance adjustment factor and seismic risk is studied. The direct loss of bridge damage and the indirect loss of increased path travel time are critical issues in the seismic design of bridges. Therefore, the seismic risk analyzed in this paper includes the risk of bridge repair cost and the risk of increased path travel time. According to the design target of seismic risk, the seismic importance adjustment factor that meets the target requirements is determined. The results show that SIAF can adjust the seismic design level of bridges to meet the requirements of the seismic risk target. In the bridge case, if the decision maker wants the risk of bridge repair cost to be controlled within 3%, SIAF greater than 1.071 can meet the seismic design requirements. If the decision maker wants the risk of path travel time of 10 bridges in series to be controlled within 6%, SIAF greater than 0.924 can meet the seismic design requirements. The proposed method of determining the seismic design level of bridges based on the seismic risk design targets can provide guidance for the formulation of bridge seismic design standards.