Failure analysis of suspension bridge tower using Direct Analysis Method (DAM)

Abstract

The 120 m pedestrian suspension bridge recently inaugurated in Pacitan, East Java, suddenly collapsed when it was empty. It is one of the hundreds of similar bridges constructed through a current government project. Although there were no casualties, finding the cause of the failure is essential to ensure the safety of other bridges that have been or are currently being built. Moreover, field investigations showed that the change in the cable orientation between the bridge tower and cable endpoint of the suspension bridge and the insufficient capacity of the bracing connection in the bridge tower triggered the failure. The analysis is usually conducted through a numerical simulation using a relatively complex non-linear finite element analysis. However, this research adopted second-order elastic analysis using the Direct Analysis Method (DAM) of the AISC Code, a common method for designing steel structures. This method was relatively more straightforward but applicable in proving that the carrying capacity of the bridge tower decreased drastically due to the bracing failure, which is possibly the explanation for the collapsed bridge at the minimum load condition.