NUMERICAL MODELING AND DYNAMIC RESPONSE ANALYSIS OF AN END-ANCHORED FLOATING BRIDGE WITH A DAMAGED PONTOON UNDER REPAIR OPERATION

Floating bridges face potential hazards due to ship collisions throughout their operational lifetime. In the situation where a pontoon is significantly damaged from an accident, a floating drydock may be used to compensate for the lost buoyancy and provide a dry atmosphere for operations. As the repair might take months, a primary concern is whether the repair can be in-site conducted without shutting down the road traffic. This study aims to investigate the feasibility of using a drydock for the repair. The numerical model of the in-operation damaged bridge is established for a comparative dynamic analysis with the intact end-anchored bridge. Eigenvalue analysis is conducted and pendulum modes of oscillation are found with an eigen-period of around 15s. The dynamic responses are analyzed through a series of fully coupled time-domain simulations under various environmental conditions. The results indicate that the standard deviation of the moment about the girder weak-axis increases significantly at the damaged pontoon axis due to the excitation of low-frequency resonant response. Swell wave loads might induce dynamic amplification to the damaged bridge, even with a relatively small wave height. In addition, the internal stress of the bridge girder is investigated and found to be larger, especially, at the lower locations of the cross-section. It is suggested that the responses can be managed by limiting the excitation of pendulum modes or providing special damping devices in practical engineering.