Refinement Numerical Analysis And Calculation In Ship-Bridge Collision Based On Frpanti-Collision Floating Pontoon

At present pier anti-collision facilities develop from steel floating pontoon structures of elastic plastic material to flexible anti-collision facilities of viscoelastic materials,the theory of ship-bridge collision also develop from the initial equivalent static analysis to the stress wave propagation and coupling analysis based on the impact dynamics.Finite element numerical analysis and calculation are also widely used in ship-bridge collision.This paper relies on the actual project-Huanghuayuan Jialin River bridge FRP anti-collision floating pontoon.Then choose the explicit dynamic finite element analysis software LS-DYNA to analyze the Pier 3 closely in ship-bridge collision.The main work in the paper include refinement of finite element numerical simulation and a detailed analysis during ship-bridge collision.The refinement of finite element numerical simulation is mainly to control some parameters,which consist of geometric mesh,constraints of the superstructure to the bridge piers,collision contact,hourglass control and mass scaling.At the same time,the effect of fluid inside and outside of the pontoon has been considered through two-way fluid-structure interaction,and combined 2m/s unyawed dynamic water effect in Jialin River.The detailed analysis during ship-bridge collision include energy change(the energy absorbed by pier and the energy dissipation of the floating pontoon),stress change(the stress of the bow,the floating pontoon,the pier and the impact force of the pier),deformation(the collision depth of the bow,the floating pontoon and the displacement of pier top),velocity change and the damage of the ship and floating pontoon.In this paper,the following conclusions are obtained by the calculation and analysis in the past six months:(1)In terms of energy,the energy of the pier absorption of the existing conditions of the floating pontoon significantly reduced.The proportion reduced more than 87% and the maximum reach 94.56%.The energy dissipation of the floating pontoon accounts for 74.0%-85.1% of the initial kinetic energy of the ship 9MJ,and the internal energy of deformation in the floating proportion can be the main,which reflects the excellent energy dissipation characteristics of the FRP bridge piers anti-collision floating pontoon.(2)In terms of stress,the maximum tensile stress of pier section is 21.13 MPa,19.96 MPa,24.07 MPa without anti-collision floating pontoon,and reduced to 8.32 MPa,5.18 MPa,8.16 MPa under the protection of anti-collision floating pontoon.The reduction ratio is 60.62%,74.05%,66.10%.The maximum compressive stress of pier section is 25.12 MPa.In addition,there is an obvious stress concentration phenomenon on the bow and the floating pontoon.(3)In terms of the impact force of the pier,the impact force of the pier is 35.4MN,31.5MN,32.9MN in the condition of anhydrous,static and dynamic water without floating pontoon,and which is 5.94 MN,5.25 MN,5.06 MN under the protection of the floating pontoon.So the impact force is reduced more than 83%,which less than the actual resistance of bridge pier.(4)In terms of the deformation and displacement,the collision depth is more than0.8m without the floating pontoon,and which reduced to 0.165 m to 0.289 m under the protection of the floating pontoon.The reduction ratio is 64.1%-80.2%.Then the reduction ratio of pier top displacement is 64.4%-75.3%.(5)In terms of the damage of ship and floating pontoon,the volume ratio of damage to the bow is 15.09%,16.27%,14.91% in three different conditions without floating pontoon,and which reduced to 8%,2.13%,1.54% under the protection of the floating pontoon.The damage volume ratio of FRP floating pontoon is small,whose maximum is 11.88%,which concentrated in the cylindrical shell 1-1,the top floor of the pontoon shell,the side wall of the pontoon shell,as well as the cylinder lining.(6)In terms of speed,the vibration velocity of the pier is greatly reduced under the protection of the floating pontoon.(7)In terms of the influence of static and dynamic water,the total energy absorbed by the pier and the normal stress in the section of the pier are increased by a small margin.On the other hand,there are beneficial effects for deformation,stress and damage ratio of ships,floating pontoon in collision process.