Adjustment method of bridge seismic importance factor based on bridge network connectivity reliability

When considering the importance of bridge seismic design, the Code for Seismic Design of Urban Bridges and Specifications for Seismic Design of Highway Bridges in China emphasize the grade of lines and the difficulty of structural repair. It does not fully consider the role of bridges in road network. Therefore, the reliability of road network under earthquake action cannot be guaranteed. Combining the bridge seismic design standard with the importance of bridge in road network, this paper proposed the method of seismic importance adjustment factor (SIAF) on the basis of seismic importance factor reflecting the line grade and the difficulty of bridge repair. Firstly, the SIAF concept and the calculation method from SIAF to road network connectivity reliability are introduced. Afterwards, the method for determining the proposed bridge SIAF based on the mad network design target is explained. Finally, road network cases are used to illustrate determination method of proposed bridge SIAF under the road network reliability design target. The results show that: when the path is relatively simple and the number of bridges in series is large, the design standard defined in the existing specifications cannot meet the mad network performance requirements, so it is necessary to improve the bridge seismic design standard; when there are many parallel paths, the reliability of road network is high, therefore, from the perspective of economy, the design standard can be lowered appropriately; SIAF can adjust the seismic design standard to ensure that the connectivity reliability of the mad network meets the design target in earthquake, and the bridge construction achieves a good balance between road network reliability and economy. This method can provide reference for further revision and improvement of existing normative practices.