Efficient Long-Term Extreme Response Analysis of Floating Bridges Using Multiple Timescale Spectral Analysis

Abstract

Floating pontoon bridges offer viable alternatives to cable-supported bridges when crossing long straits. Design of such large floating structures requires estimation of long-term load effects (e.g. 100years) under stochastic wave loading. The long-term extreme response of such floating structures can be estimated using the so-called full-long term method, where the structural response is calculated for all possible environmental conditions over a long-term period. Such a procedure is naturally computationally demanding and depends highly on the computational efficiency of the short-term response calculation. Although the procedure is rather efficient in frequency domain compared to time domain, the computational demand can still be considerable when the number of environmental variables is large. Here, we shall explore the possibility of carrying out the short-term response calculations using multiple timescale spectral analysis, which allows analytical approximations of the short-term response statistics. Through comparisons with the more time-consuming numerical solution, we report reasonably accurate estimations with a significant gain in the computational effort.