Impact Test And Multi-Objective Analysis Of Corrugated Steel Tube-UHPC Composite Anti-Collision Structure

The accidents of bridge structure damaged by vehicle impact are increasing day by day,resulting in huge economic losses and adverse social effects.Current research on anti-collision devices is mainly based on the traditional ideas of ship collision research,such as rubber protection,artificial island and composite material protection devices.However,the above measures have certain problems in engineering applications.For example,the rubber protection ability is weak.The traditional concrete artificial island is very serious in damage to itself and the vehicle during the high-energy intense collision.Simple composite anti-collision device suffers from severe local fracture when subjected to impact,and the overall energy absorption efficiency of the structure is low.Under this background,Associate Professor Fan Wei of Hunan University proposed a new type of corrugated steel pipe-UHPC combined anti-collision device,which can effectively reduce the impact response during the collision process and protect the bridge structure.At the same time,it can realize the reuse of components to a certain extent,and have long-term economic benefits and great application potential.For this new structure,the main work and conclusions are as follows:(1)a multi-objective optimization mathematical model were established,where the maximum impact force and the ratio of energy absorption to t price were regarded as the objective function,and cross-section aspect ratio of UHPC beam,UHPC strength,longitudinal reinforcement ratio and volumetric ratio of stirrup were set as design variables.Based on the design of experiments(DOE),the sample points were selected and the high-order response surface model was established.The statistical analysis techniques such as analysis of variance were used to verify the overall fitting effect and the prediction accuracy,and the sensitivity of the parameter changes was studied.Finally,the response surface model and multi-objective genetic algorithm were combined to form a multi-objective optimization analysis method for the impact-resistant performance of UHPC beams.The developed method can be applied in the similar optimization designs such as infrastructures subjected to falling rock impacts,vehicle and vessel collisions.Also,the findings in this study would facilitate designing UHPC-based protective structures in the future.(2)Based on the proposed corrugated steel tube-UHPC composite anti-collision structure,the specimen design,material property test and drop hammer impact test are carried out.The impact resistance performance of drop hammer height,thickness of corrugated pipe,arrangement density of corrugated pipe,stiffening rib and hammer head form are mainly studied.The time history response of force and displacement under impact load is recorded,and the deformation process of anti-collision structure is photographed by high-speed camera.The test results show that the anti-collision structure has good cushioning effect and energy absorption stability.The failure mode and structural response under impact are mainly related to the relative stiffness between UHPC panel and bellows..(3)Based on the compression test results of bellows,the material parameters of stainless steel are modified,and the finite element model of impact analysis of bellows-UHPC composite anti-collision structure is established by LS-DYNA.Comparing the numerical simulation with the drop hammer impact test results,it can be seen that the finite element model can accurately simulate the structural responses such as deformation damage,impact force time history,displacement time history and so on.It has certain validity and applicability..On this basis,the influence of main design parameters on impact resistance is analyzed by combining finite element analysis with response surface proxy model.(4)Taking the common three-column bent pier in engineering application as an example,the protective scale at two velocities is proposed..Using the verified finite element model of truck and collision avoidance device,the design scheme and simulation work are carried out.The results show that the anti-collision structure can effectively absorb the impact energy of trucks,reduce the impact response of piers,and significantly reduce the damage of bridges and vehicles.The results show that the anti-collision structure can effectively absorb the impact ene rgy of trucks,reduce the impact response of piers and reduce the damage of bridges and vehicles.Finally,the multi-objective optimization design of the anti-collision device is carried out,and the maximum impact force and the displacement of the impact point of the pier are further reduced after optimization.In view of the excellent material properties of UHPC,the new combined anti-collision device of corrugated steel tube-UHPC has a good application prospect in bridge protection.