Study On The Mechanical Behavior In Positive Bending Moment Of Fully Prefabricated Steel-Concrete Composite Beams With Epoxy Resin Joint Bridge Decks

In the face of the national demand of bridge industry upgrading,in order to promote the industrial construction of bridges,funded by the National Natural Science Foundation of China "Design Theory and Intelligent Construction Method of prefabricated composite structure Bridges in Mountainous areas"(U20A20312).The research group proposed a new fully prefabricated steel-concrete composite structure bridges using epoxy resin joint bridge decks and detachable high-strength bolt shear connectors.In order to investigate the positive moment mechanical behavior of the fully prefabricated steel-concrete composite structure bridges,the positive moment loading test of the fully prefabricated composite beams with four epoxy resin joint bridge decks were carried out,and the failure modes and mechanical characteristics of the fully prefabricated composite beams were clarified.The numerical models of the fully prefabricated composite beams under the positive moment loading were established and the whole process behavior analysis of the typical components were carried out.The influence of structural parameters such as shear connectors with high strength bolts and epoxy joints on the strength and stiffness of composite beams are discussed.The calculation methods for flexural bearing capacity and deformation correction of composite beams with epoxy resin joint bridge decks are proposed.The main research contents and conclusions of this paper are as follows:(1)The positive moment static bending test of a group of 4 fully prefabricated composite beams were carried out.The concrete decks were 1 cast slab and 3 epoxy resin joint decks,and the joint shapes were linear,stepped and ladder-shaped respectively.The results show that the site casting composite beams in bending,epoxy resin joint decks composite beams mainly for bending shear failure;The bearing capacity and early stiffness of the composite beams with cast-in-place deck are about 5% higher and 13%higher than those with epoxy resin joint decks.The type of epoxy resin joints have little effect on the bearing capacity of composite beams with epoxy resin joint decks.The slip of the two types of composite beams along the long direction of the beam shows the trend of "the slips at the end of the beams are greater and the slips at the middle of the beams are smaller".In addition,the slip near the epoxy resin joints are also large.The strain of concrete slab and steel beam along the height direction satisfies the assumption of flat section,and the curvature is roughly the same.(2)The failure of epoxy resin joints of bridge decks are the cohesive failure of concrete near epoxy resin joints.Considering the stress difference between the highstrength bolt shear connector and the traditional bolt shear connector,the stress of the high-strength bolt shear connector in the composite beam can be divided into three stages:friction stage,slip stage and pressure stage,due to the gap between the high-strength bolt shear connector and the reserved hole wall and the need to apply the pre-tightening force.(3)Combined with the experimental verification,the refined analysis models of the fully prefabricated composite beams were established,the refined analysis of the whole process of the fully prefabricated composite beams were carried out,the force transmission mechanism of the fully prefabricated composite beams were defined,and the influence of the joint forms,groove depth,bolt preload,bolt strength,shear connection degree,reserved aperture,steel beam strength and concrete strength parameters on the stress of the fully prefabricated composite beams were discussed.The results show that joints,steel beam strength and shear connection have significant effects on the flexural capacity of the composite beams,bolt preload has significant effects on the early stiffness of the composite beams,and groove depth,concrete strength,bolt strength and reserved aperture have little effects on the ultimate flexural capacity of the composite beams.(4)According to the test results and finite elements analysis,combined with the theoretical research of current norms and relevant literature,the calculation formulas of flexural capacity and deformation correction of fully prefabricated composite beams considering the influence of epoxy joints and shear connectors of high-strength bolts are proposed,which are proved to be in good agreement.