Research On Finite Element Model Updating Of Chongqing CaiYuanba Yangtze River Bridge

Either in the bridge's static and dynamic responses analysis or in long-term monitoring and health state evaluation, a baseline element model which reflecting the real behaviors of the bridge accurately and effectively is indispensable. But due to every kind of reduction, assumption, material and construction deviations, the differences between the responses which are estimated by the initial finite element model established according to construction drawing and the bridge's real responses are inevitable. Therefore, finite element updating works to adjust the material characteristics, boundary conditions and some others of the initial finite element model by using the bridge field test response data, in order to establish a finite element model which is capable to reflect the actual responses. Model updating has become one of the research focuses of civil engineers. It is essentially part of the optimization issue. Parameters selecting, objective function constructing and optimization algorithm are the core of model updating.Grounded on CaiYuanba Yangtze River Bridge, this paper brings forward an updating parameter selection method based on shape function, and working together with NSGA-â…¡multi-objective optimization algorithm, it successfully realizes the updating of the complicated long-span bridge.The main works are as follows:â‘ An updating parameter selection method based on shape function is presented, it can reduce the number of updating parameters effectively, so that the optimization problem of solving ill-conditioned equation causing by too many updating parameters of long-span bridge be overcome. The numerical simulation analysis based on a three-span continuous beam and CaiYuanba Yangtze River Bridge shows that, the updating parameter selection method based on shape function is feasible and effective; the effect of linearity shape function is a little better than that of constant value shape function.â‘¡Translating different responses of long span bridge into multi-objects to optimize at the same time by using NSGA-â…¡optimization algorithm. It avoids the subjective influence of choosing weight coefficient by human. The numerical simulation analysis based on a three-span continuous beam and CaiYuanba Yangtze River Bridge shows that, multi-objective optimization method based on NSGA-â…¡algorithm can obtain a relatively ideal model updating results. â‘¢Based on the static and dynamic loading test datas of CaiYuanba Yangtze River Bridge, the initial finite element model of the bridge is updated using shape function method presented in this paper and NSGA-â…¡optimization algorithm. After the updating, frequency errors decreased 26.52% and deflection differences decreased 68mm at the most, so as to realize the model updating of the bridge effectively, the model after the updating can used as the baseline model of health monitor.