Nonlinear Simulation Research Of Long-span Load-distribution Girder Based On FEM

As the assistant equipment of weight vehicle for the army cross the bridge or landing,the long-span load-distribution girder (Referred to as load-distribution girder)made of aluminum alloy is not only light and handy but also assembled convenient.Temporarily laying on the bridge or the road surface for the weight vehicle of the army passing,the load-distribution girder will develop the bearing potential of the bridge or the road surface.Because the traditional strength and stiffness test can not grasp the whole structure mechanics performance.The load-distribution girder will have a linear elastic deformation under load,it maybe contact with the load-distribution device layout under the load-distribution girder.Therefore,it is necessary of nonlinear simulation analysis for load-distribution girder. This paper proceed the nonlinear simulation study of long-span load-distribution girder based on the FEM.Firstly combining with the structure characteristic of load-distribution girder,the load-distribution girder’s FE Model was builded.And rigid zone method was used to build the FE Model of hinge pin and ball hinge support.To reduce the computational scale,the FE Model has been simplified reasonably. The linear static analysis results of Load-distribution girder indicate that the initial deflection of load-distribution girder is larger.Secondly in order to improve the efficiency of contact nonlinear analysis of long-span load-distribution girder,combining with the contact characteristic of load-distribution girder, a finite-element iterative method based on the nodal displacement vector was put forward. The nodal displacement vector in the contact region of load-distribution girder was iterated by applying nodal displacement in the presented method, Iterative solution on ANSYS structure linear static analysis was adopted to search for the contact balance state of load-distribution girder, so the selection of parameters and the tediously long reiterative process in traditional contact analysis were avoided.The simulation results of the load-distribution girder tension stress and deflection were obtained through the contact nonlinear analysis of load-distribution girder.The calculation efficiency was raised. Comparison between simulation results and test shows that the simulation results of load-distribution girder coincides with the test values basically.And the simulation results of load-distribution girder indicate that the intensity and stiffness of load-distribution girder under the regulated static load is qualified.Thirdly the deformation was introduce into the FE Model through model updating method.Then the constrained modal of load-distribution girder was analyzed.The results show that the deflection has less effect on the structural modal,and the load-distribution device provide the structural rigidity of load-distribution girder and stop the low order modal.The stress state was introduce into the stiffness matrix through ANSYS initial stress modal analysis technology.Then the work modal of load-distribution girder was analyzed.The results show that stress state has more effect on the structural modal. The large-scale compressive stress give rise to stress stiffness including a large number of negative element,so the structural rigidity was reduced,and the inherent frequency of work modal is under the constrained modal of load-distribution girder.Fourthly nonlinear transient dynamics analysis of load-distribution girder was proceeded based FE iterative method under the moving load of lOkm/h and20km/h.The results show that after twice and third FE iterative calculation.the time-history of stress and deflection of load-distribution girder and the bearing reaction of contact node and ball hinge support was obtained.The intensity and stiffness of load-distribution girder under the moving load of20km/h is qualified,the weaknesses of load-distribution girder is the arc plate of ramp.The speed of moving load has less effect on the maximum stress and deflection, but more effect on the bearing reaction of contact node.Load-distribution girder has strong applicability to weight vehicle of high speed,and the speed depends on the carrying capacity of load-distribution device and bridge.The mechanical properties of load-distribution girder was grasped through nonlinear simulation study,which provide theoretical direction to the use and optimization design of load-distribution girder.The FE iterative method based on the nodal displacement vector improve the solution efficiency of load-distribution girder and nonlinear transient dynamics greatly.FE iterative method based on the nodal displacement vector,rigid zone method and model updating method provide new method and idea to the efficient solution of contact nonlinear analysis,nonlinear modal analysis and nonlinear transient dynamics of large-scale structure.