Effects of Differential Displacements Between the Ground Anchors in Suspension Bridges

A simple model to evaluate the effects of relative displacements between the ground anchors of a suspension bridge is proposed. An equation system is defined, which allows for the evaluation of the structural response under a general displacement set of the ground anchor points. Then, the most interesting and likely cases are analyzed in detail with reference to a suspension bridge having geometrical and mechanical characteristics typical of a long-span bridge. A simple procedure for the assessment of variation in cable stress is also given, which can be used to choose the optimum values for stress in cables under dead loads, as a percentage of their strength. The results obtained showed that expected movements do not significantly impact the structure in its lifetime and that the effects become negligible for very long-span bridges. Finally, the results obtained can be easily used for the condition monitoring of suspension bridges.