Design And Optimization Research On Modular Erection System Of Vehicle-Launched Bridge

As compared with the conventional bridge constructions,Vehicle-Launched Bridges(VLB)have several unique characteristics such as fast erection and less operating staffs.When roads and bridges are destroyed by the natural disasters such as flood and earthquake,VLBs can quickly set up bridges to ensure that rescuers and aid equipments be delivered to the disaster areas in time.However,traditional VLBs can only build bridges with fixed length,which could cause waste of performance while facing the narrow barriers.Therefore,it is highly required to design a modular VLB that can construct both multiple short bridges and a single long bridge.The development of this novel VLB can not only make up for the shortcomings of the assembled steel bridges in China such as low efficiency,but also effectively solve the barriers with various widths.This is critically important to carry out rescue and relief tasks in emergencies and disasters.In the present research,a new type of modular erection system of VLB was proposed with the in-depth studies on the designing schemes,structural design,kinematics,dynamics,mechanical performance,finite element analysis and structural optimization.The specific research contents are shown as follows:1.In terms of the analysis on the structural designs of traditional two-section push-type VLBs,a new type of modular erection system of VLB was proposed.Integrated with the requirements in both design and function,the specific structures of the modular bridge and erection mechanism were determined.Then,driving devices were selected,Finally,the detailed design of the modular erection system of VLB was completed.2.In terms of the kinematics analysis on the erection mechanism,the expressions and curves of the speed and acceleration of key components were obtained.According to the establishment of the dynamic model of the erection mechanism,the change law of the driving force of hydraulic cylinder was figured out.Additionally,simulation analysis of the erection mechanism by using Adams performed,and the theoretical and simulation results were compared to verify the correctness.The above findings could be utilized as references in the motion control of erection mechanism.3.Finite element models of modular bridge were built by using the HyperMesh Also,two typical vehicles were used for axle load distribution,and the specific load conditions were applied based on the different load locations.After that,static analysis of modular bridge was initiated by using Abaqus.As a consequence,stress and displacement diagrams under various working conditions were obtained for single-bridged or double-bridged modular bridges.At last,it was verified that the modular bridge could meet the requirement in load which could be used as the basis for the structural optimization of the modular bridge.4.According to the variable density method intopology optimization,the structure of modular bridge was optimized by using optimization module in Abaqus.The optimizing scheme on modular bridge structure was solved under the hypothesis of the bridge fulfilling the requirement in strength.Finally,lightweight design of the modular bridge was achieved.