Research On The Effect Of Ship-Bridge Impact Load Based On The Response Spectrum Analysis

With the rapid development of transportation industry at home and abroad,the number of navigable ships and cross-channel bridges in major river basins is increasing,leading to the increasing probability of ship-bridge collision accidents.Not only will ship-bridge collision accidents do great harm to ship,but also can destroy the bridge,which causes disastrous consequences for life and public property.Therefore,ship impacting load has become an important factor that threats the safety of amphibious transportation.In this paper,some approaches such as experimental study,simplified model analysis method and FE simulation are used to estimate the maximum dynamic response of bridge pier under ship collision and then put forward static load which is equal to impact force time histories.The main research contents are as follows:Firstly,according to the ship bow structure of a 5000 DWT bulk carrier,two types of bulbous bow scaled models and one upper bow scaled model are designed and manufactured.The crushing force and deformation energy absorption are numerically and experimentally obtained on a way of quasi-static compression.The stress state and deformation including both of internal structure and external shape during the crushing process are discussed,respectively.Meanwhile,the collapse stiffness of different bow structures is analyzed.Secondly,in order to investigate the influence of collapse stiffness of ship bow on impacting force and bow deformation response during the ship-bridge collision,ship FE models of 1000 DWT,3000DWT and 5000 DWT with different bow structures are established,respectively.The simulations of the quasi-static compression and dynamic collision under various velocities are carried out in LS-DYNA.The static crushing stiffness of ship bow(sk)and impact force time histories are received.According to the influence factor of stiffness(β)deduced from deformation energy of ship bow(impact force-displacement curves),the dynamic crushing stiffness of ship bow(dk)are calculated.The above factors plus the parameters of pier constitute the simplified model of ship-bridge collision,which could calculate the impact force time histories quickly.In addition,a combination of the AIS data of ships on some navigation areas confirms the application range of the simplified model.Thirdly,based on the theories of response spectrum,the natural vibration characteristic of some pier is calculated by Midas civil and single freedom models such as SDOF dynamic system and corresponding SDOF static system under specific natural vibration frequency of the pier are established.According to the impact force time histories and their peak values from the simplified model,the greatest dynamic and static displacement response of the single freedom models are obtained,respectively.The ratio of the two responses is defined as dynamic magnification factor(iD M F).In combination with the natural vibration frequency of the pier and dynamic magnification factor(iD M F),response spectrum curves of ship-bridge collision are established and discussed.Finally,high-resolution model of the pier is established by ANSYS,and shipbridge collision simulations under various working conditions was carried out.The impact force time histories and displacement response of the pier are investigated,respectively.According to the model combination and the results from SDOF dynamic system,displacement responses of the pier are conservatively calculated.In addition,based on the maximum displacement response of the pier and the response spectrum curves,equivalent static force formulae are proposed for some ships with different types of bow structure.In this paper,a simplified model which could calculate impact force time histories quickly is proposed.Then,the estimation predicting the maximum displacement response of pier during the ship-bridge collision is discussed.Meanwhile,some equivalent static force formulae that can rapidly and accurately estimate dynamic impact force are deduced,which may be meaningful to the design of ship structure and bridge construction.