Reliability based design optimization of long-span bridges considering flutter

Three reliability based design optimization methods, namely reliability index approach, performance measure approach and sequential optimization and reliability assessment are applied to a long-span suspension bridge under probabilistic flutter constraint. Uncertainties in extreme wind velocity as well as flutter derivatives obtained in wind tunnel are considered. The RBDO problem presented in this research seeks to minimize the bridge girder weight by varying the thicknesses of the girder plate while satisfying the structural reliability level under flutter. In order to solve this problem, the three RBDO methods mentioned above were programmed in Matlab code, which calls Abaqus finite element models to obtain structural responses and FLAS code, developed by our research group, to calculate flutter velocity. The proposed Messina Bridge was used as an application example of these methods. Prior to solve the RBDO problem, reliability analyses were performed in order to obtain the safety level of the original design. The results obtained by different RBDO methods are then compared for their accuracy and computational efficiency.