Research On Identification Of Impact Loads Of Ship Towards Bridge Pier

Failure of bridges by ship collision happens in offshore regions and inland rivers frequently.In recent years,with the increase of sea crossing bridges and,at the same time ever increasing marine traffic volume,bridge and ship collision risk rises.Although bridges are designed against the ship impact loads in some way,the collisions occurred still cause significant property loss and death toll.To better coping with ship collisions,appropriate designs of bridges against ship impact load and deployment of effective anti-collision devices are necessary,for which a real ship-bridge impact load model is required.In this paper,according to the sparse characteristics of impact load in time-domain,the sparse recovery theory is employed to identify the impact loads,and its results are compared with those of existing methods.The main contents of this paper are as follows.The selection of regularization parameters for the inverse problem of impact load identification is studied.For the classical L2 norm regularization method-the Tikhonov regularization method,the L-curve criterion is used to determine the optimal regularization parameters according to the characteristics of relationship between the solution norm and the residual norm on log-log scale.An alternative L1 norm regularization method is proposed to improve the solution of the inverse problem.The linear relations of ??Hf-y?₂?² and ?f?₁ with ? are exploited to analyze the sparsity and accuracy of the solution,and range of the L1 norm regularization parameter is determined.Applied to the impact loads identification for a three-degree-of-freedom system by simulations and tests of a 3-story laboratory model,the L1 norm regularization and the Tikhonov regularization method are used to recover the impact loads and compared.Results show that the L1 norm regularization method has a better performance in terms of identification accuracy,stability and robustness over the Tikhonov regularization method.Aiming at the ship-pier collision analysis and impact force identification,the ANSYS/LS-DYNA software is employed to build a finite element model for ship-pier collision simulations.The impact loads and displacements of the pier top are analyzed for scenarios of different impact angle,velocity and ship mass.The L1 norm regularization method and the Tikhonov regularization method are used to identify the simulated impact loads.Results show that the Tikhonov method fails to identify the impact loads,while the L1 norm method can produce relatively better estimates.