Study On Energy Dissipation Mechanism And Force Transmission Mechanism Of A New Type Of GFRP Flexible Tube Against Ship Collision

With the rapid development of the modern transportation industry,more and more bridge will be built across rivers,lakes and sea.The size of ship will becomes bigger and bigger,a lot of ship cross the bridges every day and the speed of ship is becoming progressively faster at the same time.The ship itself is not easy to control leads to a contradiction between the ship and the bridge has become increasingly prominent,the probability of the collision between ship and bridge is also more and more high,so a serious of factors threat the safety of the bridge.Therefore,research and application of pier anti-collision facilities is imminent.A good performance of collision avoidance facilities can not only protect the safety of the bridge,but also ensure that the ship will not cause damage to build a wreck accident.This paper combined with the practical engineering case such as a bridge's pier collision pontoon in Chongqing and another bridge's bridge collision floating box in Guangzhou,through theoretical derivation,numerical simulation analysis of a new type of flexible GFRP collision floating box internal energy dissipation mechanism and force transmission mechanism.The main contents are as follows:(1)Firstly,according to the stress-strain knowledge in elastic-plastic mechanics,combining the energy theory and the thin shell strain energy theory,deriving the formula of the deformation energy of the tube.Then take the circular energy dissipation as an example,we calculate the strain energy of a circular energy dissipation cylinder by using the law of conservation of power and the total kinetic energy of the ship combined with the material parameters of GFRP.The energy stored in other polygonal energy dissipation can be reduced(expanded)according to the energy stored in the circular energy,and the reduction(expansion)factor can be analyzed by numerical calculation results.(2)Using the famous non-linear dynamic analysis software LS-DYNA,the different shape simulation analysis of the internal energy dissipation tube in the GFRP anti ship collision box is carried out.According to the results of LS-DYNA calculation,how much energy is stored and the size of the impact force transferred to the pier are analyzed by the deformation energy dissipation tube.Verity the agreement between the theoretical calculation results of the last step and the numerical results of thesoftware,then make some modest adjustments.Finally,according the results of the calculation and the actual engineering results,we can know that which shape is the best in energy dissipation and impact force transmitted to the pier.(3)Similarly,based on the most appropriate shape of the tube which is confirmed in previous,the LS-DYNA software is used to analyze the amount of energy stored at different thickness of the same shape,and the impact force transmitted to the pier.Analyzing the results and obtaining the optimum thickness.(4)Using the LS-DYNA to simulate the GFRP anti ship collision floating box which has been optimized.First,the optimized floating box is designed that a weak connection is added to the shell surface of the floating box and the pier.The weak connection is a wave plate which is connected by the dovetail to the swallowtail through on the box shell.Because the dovetail tenon on the corrugated plate is not continuous,it can move up and down in the dovetail slot.When the floating box is impacted by a ship,the semi-circular plate in the corrugated plate can produce larger deformation and absorb more energy,and the force transmitted to the pier will be smaller.Therefore,the floating box with weak connection can bear the impact of large tonnage ships and produce better energy dissipation effect.For the semicircle plate in the weak connection,the simulation analysis or the different wall thickness of the plate is carried out by LS-DYNA,we can get the energy stored in the floating box with different semicircle thickness and the impact force transferred to the pier.The results are analyzed to determine the optimum thickness of the semicircle plate in the weak connection.Based on the above research,the theoretical formula for storing the deformation energy of the energy dissipation tube is put forward,and the correctness of the formula is verified by the software calculation.At the same time,the reasonable shape and thickness of the internal energy dissipation tube in the floating box are calculated and analyzed by the software,which provides the theoretical basis for the future engineering practice.