Study On The Mechanical Behavior And Influencing Factors Of Fatigue Performance Of Steel Bridge Deck Pavement

Orthotropic steel bridge deck asphalt pavement technology has been developed rapidly in recent years,gussasphalt,epoxy asphalt concrete,UHPC high-strength concrete and other new pavement materials have been widely used.The fatigue durability of steel deck pavement,especially for thinner steel bridge deck,fatigue resistance of bridge deck pavement is still a technical difficulty.The actual mechanical behavior and stress state of steel bridge deck pavement are the key reference for the fatigue resistance design of pavement materials,but it is mainly determined by numerical simulation currently,so it is necessary to carry out bridge detection and evaluation verification.At present,the design and test evaluation of epoxy asphalt mixture generally refer to common asphalt mixture,the fatigue performance and its influencing factors of epoxy asphalt mixture are still lack of in-depth research.In order to understand the actual stress state and mechanical behavior of steel bridge deck asphalt pavement,to evaluate the influencing factors and rules of fatigue performance of epoxy asphalt mixture,in this paper,the stress state evaluation and analysis of steel bridge deck pavement in service are carried out,and the deformation performance requirements of pavement are put forward.Aiming at the reinforcement design objective of steel bridge deck pavement,the microstructure,performance characteristics and optimization design of epoxy asphalt are studied,and the fatigue performance of epoxy asphalt mixture and its influencing factors are studied and evaluated systematically.The analysis of stress state evaluation data of existing bridge deck pavement shows that the modified asphalt concrete bridge deck pavement shows remarkable viscoelasticity under static load,vehicle speed,longitudinal slope of bridge deck and overload have obvious influence on the force of bridge deck pavement,and the deformation process of bridge deck pavement shows obvious viscoelasticity,and the effect of plastic cumulative deformation should be considered.Different from the modified asphalt concrete bridge deck pavement,epoxy asphalt is a kind of thermosetting material.The epoxy asphalt steel bridge deck pavement has the characteristics of instantaneous elastic deformation under continuous load,and will not accumulate plastic deformation.The test data show that under normal temperature and standard load conditions,the dynamic transverse tensile strain of common modified asphalt pavement is lower than 300??,and that of epoxy asphalt pavement is lower than 200??.In fact,steel deck pavement bears complex three-dimensional stress,so it is necessary to comprehensively consider the design of bridge deck pavement structure.The finite element numerical simulation calculation and real test data of bridge deck pavement structure are compared and analyzed,the results show that the distribution law of finite element calculation value and dynamic load test value is basically the same according to elastic assumption,the range of the basic strain of pavement and guide the design and evaluation of pavement materials can be reflected by the finite element model calculation according to the elastic assumption.The microstructure of epoxy asphalt varies with the amount of epoxy resin,with the increase of epoxy resin curing agent content,epoxy resin curing agent phase and asphalt phase will be reversed,the critical content of epoxy resin is 37% when evaluated epoxy asphalt is reversed.When the content of epoxy resin is less than 37%,the asphalt exists as a continuous phase,the cured epoxy resin is dispersed in the asphalt phase in the form of small particles,and the epoxy asphalt behaves as the thermoplastic of the asphalt.When the content of epoxy resin is more than 37%,the epoxy resin solidified to form a cross-linked network structure,at this point,the cured epoxy resin forms a continuous phase and the matrix asphalt is dispersed phase,epoxy asphalt is transformed into thermosetting material which mainly displays the performance of epoxy resin.When the content of cured epoxy resin reaches 50%,the cross-linked structure is uniform and compact,and the strength and deformation properties of epoxy asphalt reach the comprehensive optimal level.The epoxy asphalt mixture with 50% epoxy resin has excellent high temperature stability and deformation performance.The results of trabecular bending test and four-point bending fatigue test for epoxy asphalt mixture indicate that the order of fatigue performance of epoxy asphalt mixture with different gradation types is fine gradation,medium gradation,coarse gradation,the asphalt aggregate ratio has a significant effect on the performance of epoxy asphalt mortar,which is mainly reflected in the thickness of "structural asphalt membrane" on aggregate particles.Properly increasing the asphalt aggregate ratio can improve the fatigue performance of epoxy asphalt mixture,but the skid resistance performance optimum design of pavement should be considered comprehensively.The results of comparative analysis show that particle size,specific surface area,and physical and geometrical properties of fillers have significant effects on the fatigue properties of epoxy asphalt mixture.Experiments show that the epoxy asphalt mortar performance can be significantly enhanced by using fillers with small particle size,large specific surface area and rough particle surface,thereby improving the fatigue resistance performance of epoxy asphalt mixture.Aggregate fracture area ratio of trabecular bending fracture surface statistical results show that coarse gradation and low asphalt aggregate ratio have more internal cracks for epoxy asphalt mixture,and aggregate fracture has a significant impact on the fatigue performance of epoxy asphalt mixture.The results of particle fracture analysis show that epoxy asphalt concrete is different from common asphalt concrete,aggregate fracture strength significantly affects the bending strength of the mixture,increasing the fracture strength of aggregate particles can enhance the bending strength of epoxy asphalt mixture,and then improving the fatigue resistance performance of epoxy asphalt mixture.The application of the research in the project was investigated and analyzed,it shows that reinforced epoxy asphalt pavement can significantly improve the stiffness of steel bridge deck pavement structure system and prolong the fatigue durability of pavement.The analysis of existing bridge detection data can also provide reference for the design of steel deck pavement structure,assessment of stress state of pavement structure,and the design and evaluation of epoxy asphalt mixture.