A Study On Buffeting Dynamic Reliability Of A Long-span Suspension Bridge

As bridges grow towards long-span and flexibility, the buffeting of bridges induced by turbulence and dynamic reliability problems become the research object for more and more researchers. Based on the current buffeting theory and dynamic reliability theory, with a long-span bridge taken as an example, this paper focuses on its buffeting responses and dynamic reliability. This research is focused mainly on the following aspects: At first, the buffeting analysis method in the time domain is introduced, including the simulation of the turbulent wind velocity and the Quasi-steady Aerodynamic Forces theory of buffeting calculation. The formulas for calculating buffeting forces time-history according to the wind velocity time-history are deduced in details. The compiled APDL programs are used to fulfill the wind force, in this way the wind-induced buffeting responses are calculated. Secondly, based on the first passage mechanism,and on the basis of stationary,normal and ergodic stochastic processes,corresponding formulas for calculating dynamic reliability of single component or node are deduced, and the formulas are given by adopting simplified series connection invalidation mode to calculate the structure system buffeting dynamic reliability probability limit. Upon this, five kinds of reliability formulas which take into account of the influence of different wind velocity,different attack angle,different time duration are applied to calculate the reliability probability on seven nodes on the girder; the variation along with wind velocity,attack angle and time duration of reliability probability of every node on the girder is compared; the differences of each formula are also compared. Finally, the reliability probability limit of the girder system is calculated. It is shown that the first passage dynamic reliability of the suspension bridge girder satisfies the requirement of stiffness. Finally, given that the structure fatigue longevity obey the Weibull distribution, the fatigue reliability formula can be deduced. Based on the stress time-history of the main cable, the rain-flow method is applied to compile the corresponding program, which sums up the frequencies of the stress impulse. Upon this, the fatigue reliability of three different elements on the cable are calculated. It is shown that the fatigue reliability of the cable meets the corresponding demand.