Probabilistic seismic demand model for regular bridges based on the modified Park-Ang damage index

In this paper, a modified damage model is established to solve the non-convergence problem existing in the Park-Ang damage index. The scatter of the modified damage index is significantly reduced compared to the original Park-Ang damage index. Then the finite element analysis models of 8 representative regular bridges samples were established with the main parameters variable such as the column height. The total 19120 increment dynamic analysis (IDA) curves were obtained by using the IDA method. These IDA curves are expressed in terms of one intensity measure (IM), i.e., the spectral acceleration at the fundamental period with 5% damping, and one engineering demand parameter (EDP), i.e., the modified Park-Ang damage index. At last, the probabilistic seismic demand model of regular bridges was established by using probability analysis based on the result of IDA curves. It is found that the seismic damage demand is reasonably standard beta distributed at given IM levels. The quadratic equation is suitable to establish the correlation between the mean value of the seismic damage demad and the IM. It is concluded that the established probabilistic seismic demand model is suitable for 3different site conditions and can largely simplify the computational effort of seismic demand in the performance- based seismic design and assessment of regular bridges.