Physics-Based Stochastic Model to Determine the Failure Load of Suspension Bridge Main Cables

A new methodology to determine the safety of suspension bridge main cables is proposed in this paper and illustrated by simulating the failure of a corrosion-deteriorated cable composed of 9,061 wires. The approach is the first to use a finite-element (FE) model to predict the failure load, account for load recovery due to friction in broken wires, and simulate the reduced strength of the cable as a three-dimensional random field. To obtain cable failure load, the load is increased gradually, causing individual wires break according to their residual strength variability. Because of the load transfer to surrounding wires, the breakage of an individual wire affects the stress state of its surrounding wires. Consequently, as the load is increased, this local damage spreads to its immediate vicinity, and eventually the entire cable fails. Because of the complexity of the problem, the critical failure load is determined through a Monte Carlo simulation approach that accounts for the uncertainty in the spatial variability of the residual strength of the individual wires. The probability distribution of the load that will drive a suspension bridge cable to failure is reported and investigated in the paper.