Research On The Bridge Response And Calculation Method For The Ship Impact Force Under Ship-bridge Collision

Large quantities of bridges across the waterway have been built with the rapid development of the transportation industry and the people’s demand of convenient transportation in china.And at the same time,the tonnage,quantity and speed of ships have also been greatly improved.The rapid development of this two fields has resulted in the increasing frequency of ship-bridge collision accidents,and the consequences of the collision have become more and more serious.Therefore,ship impact load has become a non-negligible factor that threatens bridge safety during bridge design,construction,and use.In this paper,the finite element numerical simulation method and empirical formula method are employed to study the bridge response under ship impact load and the equivalent static calculation method of ship impact loads.The main contents are as follows:（1）Five commonly used specification formulae for ship impact force calculation during ship-bridge collision are used to calculate the collision force when the bridge is hit by 3000DWT,5000DWT and 10000DWT bulk carriers.It is found that compared with foreign specifications,the formula in specifications for highway in China is more sensitive to changes in ship weight,and this specification is more suitable for the calculation of the impact force when the bridge is collided by small tonnage ships.The impact force calculated by the code of railway bridge in china is always smaller than the results calculated by other codes（2）The finite element models of 3000DWT,5000DWT and 10000DWT bulk carriers colliding with the rigid bridge pier were established with the background of the1^st pier of Wuhan Baishazhou bridge.The characteristics of the energy and collision force of ships with different stiffness are analyzed,and the global and local average value of impact force verse time curves are compared with the standard result.It is found that taking the global average value of the impact force verse time curves as the equivalent static force will lead to a dangerous result.While the local average value will approach the peak value of the impact force verse time curves,which means this equivalent method is conservative.（3）The flexible pier model of the 1^st pier of Wuhan Baishazhou bridge is established,and the influence of the modeling method of bridge structure on the simulation results is discussed in this paper.The results show that,compared with using the mass block to simulate the superstructure of the bridge,using a beam to simulate the superstructure only causing an increase in peak impact force within 2%.Therefore,it is reasonable to only consider the influence of its mass on the impact force when simulating the superstructure of a bridge.For the consideration of the displacement response of the bridge pier,the simulation of pile-soil interaction can be simplified by consolidation at 13 times the pile diameter.（4）The finite element models of 1000DWT raked bow ship,1000DWT flat bow barge and 3000DWT bulbous bow bulk carrier impacting flexible bridge pier were established.The impact force verse time curve,energy verse time curve,ship deformation mode and displacement verse time curve of pier top when three types of ship impacting the pier are also obtained.It is found that there are significant differences in the characteristics of impact force verse time curves when ships with different bow forms collide with bridge piers.And the time that the maximum displacement appears is later than the time of the peak impact force appears.（5）The displacement response of bridge pier under horizontal static load and ship impact load is analyzed by Midas FEA.And a new static equivalent method of ship-bridge collision force is proposed.Based on this method,formulas for calculating the equivalent static force of three kinds of ships colliding with bridge piers are obtained,and the fitted formulas are compared with the formulas in existing specifications.The results show that with the increase of the initial kinetic energy,the growth trend of the collision force gradually slows down.The formula in the railway specification of China is more applicable for estimating the impact force when ships with small bow stiffness collide with bridge piers.In this thesis,the response of bridge piers and ship structure under ship-bridge collision is discussed,and a new static equivalent method of ship-bridge collision force is proposed.The formulas for rapid estimation of equivalent static force when three bow types of ships collide the pier are obtained by fitting.The results of this paper is referential for the calculation of ship-bridge impact force in relevant codes.