Fatigue Life Evaluation on Short Suspenders of Long-Span Suspension Bridge with Central Clamps

Abstract

Suspenders are crucial load-bearing members of suspension bridges, and they are prone to fatigue damage under repetitive vehicle and wind loads. Field observation shows that short suspenders at the midspan or the ends of bridges may be more vulnerable. This study investigated the influence of using rigid central clamps on the fatigue performance of short suspenders, and two finite-element models of a long-span suspension bridge, with and without central clamps, were developed for comparison. Results show that central clamps can significantly mitigate the bending stress of short suspenders by reducing the relative motion between cables and the girder. Although wind-induced stresses of suspenders are smaller in amplitude than those induced by the vehicle load, the wind loads also contribute significantly to fatigue damage of suspenders because of the large number of stress cycles. Based on a vehicle-load model and the wind spectrum developed from field-monitored data, a fatigue life evaluation procedure was developed, and the fatigue lives of suspenders of the bridges with and without central clamps were calculated, respectively. Results suggest that when there are no central clamps, suspenders may have fatigue lives shorter than the design value.