Research On Dynamic Response Of Pier Under Ship Impact And Anti-collision Measures

In recent years,with the development of the transportation,the number and scale of the ships and bridges are increasing,and the accidents of the ship-bridge collision frequently occur,which has caused wide attention of people.Using LS-DYNA software,we conduct a numerical simulation for the working conditions of a 2000t-ship impacting a river-crossing continuous rigid frame bridge.we design a new type of bridge pier anti-collision device,carry out finite element analysis of bridge pier with anti-collision device under ship impact,and get some conclusions.The main research work and findings of this paper are in the following.(1)we build a continuous rigid frame bridge model and a 2000t-grade bulk ship model.we carry out a finite element simulation and calculation of whole process of the ship-pier collision,analyze the impact force on the bridge pier,displacement of bottom of pier,bending moment of top of pile and other dynamic response during the collision.The main reason about the bridge damages is that the displacement of the pier and the bending moment of the pile top are too large.(2)Under different working conditions,we conduct a comparative and parametric(ship speed,water level,collision angle and whether the bridge is the prestress structure)analysis of dynamic response of bridge pier,and obtain the following conclusions: the ship speed has a significant effect on the dynamic response of the bridge pier,the greater the speed is,the greater the dynamic response of the bridge pier becomes;the water level had little effect on the dynamic response of bridge pier,the lower the water level is,the greater the dynamic response of the bridge pier is;frontal impact is the most adverse circumstance in the collision;prestress structure cannot reduce the impact force between ship and bridge,while it can protect the pile by increasing the ability of anti-cracking of the pile,and reduce the damage of the ship collision accident to the bridge effectively.(3)We analyze and compare the dynamic response of the bridge pier with and without the bridge pier anti-collision device under the ship collision,we obtain the following conclusions: anti-collision device can poke the bow,reduce the direct damage to the pier from the ship effectively;it can extend the impact time,cuts down the impact force and the displacement of the bottom of pier greatly;it can reduce the damage to the pile foundation;it allows ship to retain most of the kinetic energy,reduces energy conversion indirectly.The loss of kinetic energy is converted mainly into the deformation energy of the anti-collision device,thus decrease the bow deformation energy.It can also greatly reduce the damage to the ship when protecting pier,which prove the rationality and validity of the anti-collision device.(4)We discuss the influence of factors such as ship speed,water level,steel cofferdam strength,steel cofferdam thickness on the dynamic response of bridge pier and the property of anti-collision device,and get the following conclusions: the ship speed had little effect on the dynamic response of bridge pier,the greater the speed is,the greater the dynamic response of the bridge pier becomes,the more obvious the effect of anti-collision device on pier;when the collision angle is 15 degrees,the performance of anti-collision device is the best,however the performance of anti-collision device may be low if the collision angle is too large or too small;the dynamic response of bridge pier is greater when the steel cofferdam strength,thickness are big.A small steel strength,a medium steel cofferdam thickness will be most beneficial for anti-collision.