Structural response of cable-stayed bridges to cable loss.

Cable-stayed bridges are highly redundant structures that are vulnerable to intentional and accidental extreme events that may lead to cable loss. The potential loss of a major element, which imposes dynamic effects to the structure, can subsequently lead to the collapse of the whole structure. Codes recommend the use of dynamic amplification factors to simulate the response of cable-supported structures to the loss of a cable. Recent research has identified that this method is conservative and there is little or no guidance for carrying out detailed dynamic analysis for cable loss. The loss of one or more cables due to blast and fire using dynamic analysis method is investigated and compared to the code recommended method to account for effect of time and the event leading to cable loss hereby recommending a simplified method of dynamic analysis for cable loss. Three cable-stayed bridge models namely Model A (road traffic bridge with three semi-fan cable arrangements), Model B (road and foot traffic bridge with one single harp cable arrangement) and Model C (footbridge with two symmetrical semi-fan cable arrangement) were modelled and non-linear dynamic analysis carried out for the loss of the backstay and the longest cable using Abaqus 6.13. The effect of the cable loss due to blast and fire on the remaining cables, cable-deck connection, cross beam, longitudinal girder, deck and pylon were examined and compared to the code recommended method. The relationship between cable loss time and the natural period of the bridge was also investigated in this research. A progressive collapse check was then carried out and Dynamic Amplification Factors (DAF) were obtained for the cable loss scenarios considered for the vehicular and pedestrian cable-stayed bridges. It is therefore of importance to study whether these structures can withstand these accidental/intentional loads, fulfil their economic benefit to society and establish a guideline for carrying out the dynamic analysis not only for road traffic cable-stayed bridges but also cable-stayed footbridges