Study On Mechanical Properties Of Bridge Protective Device Under Impact Load

With the rapid development of transportation industry,the number and scale of bridges are also increasing at a high speed.A large number of bridges alleviated the traffic pressure,at the same time,they brought a great influence on water transportation,the probability of ship-bridge collision also increased and the consequences of the collision were also more serious.In this paper,ANSYS/LS-DYNA,a non-linear finite element software,is used to solve the problem of ship-bridge collision and ship-protective device-bridge collision.It discusses the protective effect of the device from the aspects of maximum collision force,energy conversion and damage to the structure.Then it discusses the influence of the steel plate thickness on its protective effect.At last,it propose two improvements for the protective device and then compares their protective effect with the original device.The main contents and conclusions of this paper are as follows:(1)It summarizes the research progress of protective device and the theory of ship-bridge collision.(2)It summarizes the commonly used calculation formula of the ship-bridge collision,and compares the calculation results of different formulas.The results show that: compared with some western's formulas,the calculation results of impact force that in Chinese bridge specification is smaller,so the guidance of the collision design is limited.(3)It establishes a finite element model of ship-bridge collision under a specific conditions by ANSYS/LS-DYNA,then analyses the collision force and the energy transfer with time.The results show that: without a protective device,the bridge and the boat absorbs most of energy,this part of the energy will cause damage to the bridge.In the collision,there is a great deal of stress in the bottom of the pier,bottom and top of pile foundation,which poses a great harm to the safety of the bridge.(4)It establishes a finite element model of ship-protective device-bridge collision under the same conditions with chapter three by ANSYS/LS-DYNA,and analyses the simulation results of the the whole collision process.It studies the protective effect of thedevice and the influence of the steel plate thickness on its protective effect.The comparative studies show that: the protective device absorbs most of the impact kinetic energy through its own elasto-plastic deformation,which can effectively reduce the impact force and the energy absorbed by the bridge to achieve good effect of protecting the bridge.(5)Two improved methods of the traditional steel box device are given in the last chapter,and the two kinds of devices are analyzed by ANSYS/LS-DYNA under the same working conditions.The results show that: foam aluminum and foam aluminum sandwich panels have a good absorption rate for impact energy.Among them,the protective device filled with aluminum foam better resistance to deformation,and the anti-collision device using the foamed aluminum sandwich panel has the advantage of reducing the impact force and improving the energy absorption rate.