Analysis Of Fatigue Damage Mechanism Of Highway Bridge Expansion Joint And Research On Rapid Repair Technology

As an integral part of the bridge superstructure,the bridge expansion joint is an important component to ensure that the bridge structure can expand and contract freely under the action of internal and external environment.However,the bridge expansion joint is exposed to the natural environment for a long time and is directly subjected to repeated crushing and impact of vehicle loads,which makes them susceptible to structural damage,especially for highway bridge expansion joint.Therefore,for the structural characteristics of highway bridge expansion joint,it is important to study their stress characteristics and fatigue life under the action of moving vehicle loads,as well as their rapid repair technology after the damage with important engineering theoretical guidance and application significance.Based on ABAQUS finite element analysis software,this paper firstly investigated the force characteristics and fatigue life change law of the highway bridge expansion joint under different working conditions of moving vehicle loads with the highway bridge expansion joint（GQF-E80）as the main research object;then,for the characteristics of large dynamic response and low fatigue life of concrete in the anchorage area,a nano-SiO₂-based reinforced CRM concrete material was developed.Then,the CRM concrete material based on nano-SiO₂ reinforcement was developed as a rapid repair material for bridge expansion joint anchorage zone concrete;finally,a set of rapid repair construction technology for the highway bridge expansion joint was proposed by using the new bridge expansion joint rapid repair material and combining with the application cases of bridge expansion joint rapid repair construction.The main research content and conclusions are as follows:（1）Based on the field research on the common structure and damage forms of bridge expansion joint in Zhengzhou section of Lianhuo Expressway and combined with literature,a systematic study and summary of the common structural forms,damage forms and causes of the highway bridge expansion joint is conducted to provide basic materials for the analysis of the force characteristics and fatigue life of bridge expansion joint.（2）Based on ABAQUS finite element analysis software,the finite element model of bridge expansion joint was established and combined with structural dynamics theoretical analysis method to study the stress characteristics of bridge expansion joint under different working conditions in terms of different vehicle speeds,different overload ratios,and different anchorage zone concrete strengths.The increase in vehicle overload ratio makes the maximum stress,the maximum vertical displacement,and the maximum main tensile stress of concrete in the anchorage zone of the bridge expansion joint increase linearly;the increase of concrete strength in the anchorage zone can reduce the dynamic response of the bridge expansion joint under the action of moving vehicle load to a certain extent,and the reduction of the dynamic response of concrete in the anchorage zone is more obvious.（3）Based on the force characteristics of bridge expansion joint under different working conditions,combined with the theory of fatigue life estimation,the calculation method of bridge expansion joint fatigue life estimation was proposed,and the influence law of speed,overload ratio,and anchorage zone concrete strength change on the bridge expansion joint fatigue life was revealed,the results showed that:with the increase of vehicle driving speed,the bridge expansion joint fatigue life decreases;vehicle overload will seriously reduce the bridge expansion joint fatigue life.When the vehicle overload ratio reaches 40%,the E-shaped side beam and anchorage concrete can not meet the design requirements and will suffer premature fatigue damage;the increase of anchorage concrete strength can prolong the fatigue life of the bridge expansion joint,and the increased of anchorage concrete fatigue life is more significant.（4）The optimum doping amount of nano-SiO₂ in the new bridge expansion joint quick repair material and the strengthening effect of nano-SiO₂ in the new bridge expansion joint quick repair material were studied through the basic mechanical properties test and impact test,and the strengthening mechanism was analyzed through scanning electron microscope test.The results showed that the nano-SiO₂ material can improve the compressive strength,flexural strength,and impact resistance of the rapid bridge expansion joint repair material within a certain doping level,especially the early strength;meanwhile,it is found that the nano-SiO₂doping ratio in the new bridge expansion joint rapid repair material reaches 1.5%with the best effect,and the properties of the new bridge expansion joint rapid repair material under this doping level meet the requirements of bridge expansion joint rapid repair construction.（5）Based on the new bridge expansion joint fast repair material,combined with the actual construction application engineering cases of bridge expansion joint fast repair in the test section,the bridge expansion joint fast repair construction technology was proposed to realize the bridge expansion joint fast repair within 12h open traffic,the research results will have certain promotion and application value.