Journal of Structural and Construction Engineering (Jul 2021)
Analytical Fragility Curves for Bridges Subjected to Near-Fault and Far-Field Ground Motion(Case Study: Bill Emerson Bridge)
Abstract
Bridges are one of the major infrastructures of a country, which, in the event of severe seismic activity and the occurrence of collapse, can cause severe damage in different regions and create a severe crisis. Bridges with very long spans have always been a great challenge for engineers throughout history. Cable-stayed types of bridges are becoming more and more popular in the construction of long span bridges due to their advantages. A great number of cable stayed bridges in the world are located in the seismic zone and also near active faults so the effect of near field excitations on the seismic vulnerability of cable stayed bridges should be investigated probabilistically in accordance with far field excitations. Generation of vulnerability functions in the form of fragility curves is a common approach for assessing bridges seismic vulnerability. In this article, a set of analytical fragility curves for a case study cable stayed bridge (the Bill Emerson Bridge) are developed based on Incremental nonlinear dynamic analysis (IDA). The findings represent the effect of near fault excitations on the vulnerability of this long span bridge model. For example, the probability of a complete and extensive damage state for the considered cable stayed bridge in 1.5g for far field is 10 and 32 percent respectively, while in the near field, this value increases to about 19 and 44 percent, that indicates increase vulnerability of bridge in near field. The median values of seismic fragility for the considered bridge model decreased significantly in near field excitation in the Extensive and Complete damage states. The results can guide future regional risk assessments regarding the importance of including or neglecting near field excitations impacts on cable stayed bridge’s vulnerability.
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