Seismic collapse assessment of single-column bridge piers using the applied element method

Several single-column-bent bridges collapsed in the past under earthquakes. Different factors associated with poor structural design and/or construction including inadequate and/or prematurely-terminated Longitudinal Reinforcement (LR), insufficient concrete confinement, or insufficient Transverse Reinforcement (TR) were identified and reported. Different alternate designs or retrofitting solutions were also proposed and examined. One of the well-known samples of this bridge type was the elevated Hanshin Expressway Bridge (HEB) collapsed in the 1995 Kobe earthquake. In that incident, eighteen circular Single-Column Piers (SCPs), monolithically connected to the deck, failed and collapsed. Here, the seismic progressive collapse behavior of SCPs of the HEB was investigated using nonlinear dynamic analyses of 3D numerical models created via the Applied Element Method (AEM). The obtained results agreed well with field observations after the earthquake. Two alternate design solutions for improving the seismic response of the original model were also considered and the efficiency of the solutions was assessed. The results showed that the AEM is capable to model the progressive collapse procedure for concrete bridges with sufficient accuracy. The results proved higher effects of the anchorage length of the LR as well as the space between the TR in the collapse behavior of the pier.