Study On The Protection Performance Of Cap Cutwater And Steel Box Against Ship Collision

It is an important factor for bridge safety that ship-bridge collision,the performance of anti-collision device is an important on reducing the damage of the bridge.At present,the collision mechanisms has been studied,but the anti-collision performance of cap cutwater,steel box and its combination are studied seldom.In this paper,the finite element models of the ship,the pile cap,the anti-collision device,the pile and the soil were established.The anti-collision performance of cutwater,steel box,steel box and cutwater,steel box and spring were studied by the finite element method.Finally,the anti-collision performance of steel box in Hongkong Zhuhai Macao Bridge was analyzed.The study conclusions are as following:1)The anti-collision device of cap cutwater: it can poke the bow in the collision,and the ship takes away most of the initial kinetic energy after collision.It can reduce the energy exchange,collision time,the maximum force and displacement.The maximum force,the maximum displacement,collision time,energy exchange and the cap resistance of along and cross the bridge were considered comprehensively,when ? is 75 degrees,the anti-collision performance of cap cutwater is best.At the same time,after the change law of the maximum force of ship collision with ?,tonnage W and other factors were analysised,the calculation formula of the maximum force is put forward.2)The anti-collision device of steel box: it has great relationship for the anti-collision performance with the relative stiffness.The maximum force and displacement will decrease first then increased with the increase of the relative stiffness.When the relative stiffness is greater than 60,the maximum force and displacement are basically unchanged.When the relative stiffness is between 20~40,the anti-collision steel box has good performance.The relationship between the impulse of the whole collision process and the relative stiffness is approximately exponential.The impulse increases with the increase of the relative stiffness.When the relative stiffness is greater than 60,the impulse is almost unchanged.On this basis,the calculation formula of impulse is put forward.3)The performance comparison among four anti-collision devices of combination,cutwater and steel box: in the same conditions,the anti-collision performance of the steel box and spring combined model is the best for reducing the maximum force;the anti-collision performance of cutwater is the best for reducing the impulse of whole collision process;the anti-collision performance of the steel box and cutwater combined model is the best for controlling the maximum displacement,the final deformation energy of ship and steel box.4)In view of anti-collision design of the Hongkong Zhuhai Macao Bridge,the performance of steel box was been studied.It can reduce about 37.7% of the maximum force and about 53.5% of the maximum displacement under the condition of frontal collision;it can reduce about 43.9% of the maximum force and about 18.6% of the maximum displacement under the condition of side collision.They are able to meet the security requirements of bridge.The calculation results of fitting formulas in this paper are close to the results of numerical simulation of the steel box of Hongkong Zhuhai Macao Bridge.