Research On Time-dependent Reliability Of Bridge Structure Under Vessel Collision

With the massive construction of bridges across the river and bay in China in recent years and the increasing tonnage and flow of ships,the issue of ship collision safety is gradually taken seriously.During the design period of the bridge,the resistance of the bridge structure in the coastal area will be decayed and unrecoverable with time due to the impact of chloride erosion,which will affect the performance of the bridge structure and lead to the change of the reliability of the bridge structure under ship collision.Under this background,Starting from the study of the durability of bridge structures in coastal areas,with the research of bridge engineering reliability as the core and the purpose of improving the vessel collision safety of bridge structures,a systematic and in-depth study is carried out on the time-dependent reliability of the bridge structure in the coastal salt erosion environment.By analyzing the typical failure mode of a typical bridge type under vessel collision and determining the damage criterion,a time-dependent reliability analysis model of vessel collision is established on this basis,and the time-varying reliability analysis of vessel collision is established.This paper aims at the frontier of bridge vessel collision safety research,which has very important scientific and practical significance to ensure the safety of navigation bridges vessel collisions.Firstly,This paper describes the current status and trends of domestic and foreign research on bridge vessel collision reliability and reinforced concrete structure durability.Based on the summary of the existing bridge vessel collision reliability and concrete structure durability theory,the influence of steel bar corrosion and material strength changes on the resistance attenuation of the bridge structure is considered.The deterioration law of reinforced concrete materials and the time-dependent resistance law of structures under the erosion of chloride in coastal areas were explored.Combined with the durability attenuation model of concrete structure,the method and procedure for calculating the time-dependent reliability of vessel-bridge structure collision are proposed,and the technical route for calculating the vessel collision time-dependent reliability is given.Secondly,on the basis of summarizing and analyzing the vessel collision incidents at domestic and abroad,aiming at the extensiveness of the vessel collision with bridge substructure,according to the structural damage criterion,The function of the bridge vessel collision limit state is determined,At the same time,the factors affecting the vessel-bridge collision time-dependent reliability were explored,and the probability model of the factors affecting the vessel-bridge collision time-dependent reliability was given,combined with the concrete structure durability attenuation model,a method and process for calculating the vessel-bridge collision time-dependent reliability are proposed.For bridge structures whose function cannot be clearly expressed,a time-dependent reliability analysis of vessel collisions based on response surface method is proposed,the corresponding program is compiled to solve the reliable index calculation problem of implicit and nonlinear bridge structure function.Combined with bridge engineering examples,based on the established durability attenuation model of reinforced concrete structure under chloride ion erosion environment,the time-dependent resistance analysis with bridge structure is carried out considering the reduction of the yield strength of the longitudinal reinforcement and stirrup of the pile section and the attenuation of the protective layer concrete compressive strength.Establish dynamic finite element model of bridge structure for time history analysis,the response surface method was used to iteratively calculate and analyze the time-dependent reliability index and failure probability of the bridge structure under vessel collision.It provides a reference for the application of bridge ship collision time-dependent reliability analysis in practical engineering.Finally,the research on the time-dependent reliability of the bridge structure ship collision is prospected,and the content that needs further study is analyzed and summarized.