Study On Static And Fatigue Performance Of The Short Studs In Steel—UHPC Lightweight Composite Bridge Deck

In the steel-UHPC light combination bridge structure,the steel structure and the UHPC layer are connected into a whole through shear studs.The structure can improve the stiffness of steel bridge panels,while the weight has also been well controlled,so it can effectively solve the problem of fatigue damage of steel structure and pavement The thickness of UHPC layer is about 50mm,in order to meet the requirements of the thickness of the protective layer,at the same time to facilitate welding shear nails,the height of the shear pin should be reduced and the diameter of the nail will be constant,so it is difficult to meet the standard requirement of shear pin length diameter ratio greater than 4,in addition,due to the mechanical properties of UHPC and ordinary concrete is significantly different,It is necessary to lead to the failure mode of the composite structure,the bearing capacity and fatigue characteristics of the short and thick shear nails are different from those of the ordinary concrete.In order to study the static and anti-fatigue properties of short and thick shear nails in light combined bridge deck,this thesis studies the following aspects:(1)This thesis summarizes the fatigue diseases and causes of orthotropic rigid bridge panels,as well as the diseases and causes of traditional pavement,introduces the mechanical parameters of UHPC,the concept and research status of steel-UHPC light composite bridge deck as well as the shear force of the research results.(2)With the help of ABAQUS software,the simulation model of the short shear test is introduced,Through the analysis of the deformation and stress distribution of the short and coarse shear nails,it is found that the shear nail is not in the pure shear state,but in the bending,shear,tension of the complex stress state,in addition,by comparing with ordinary shear nails,it is found that the deformation and stress distribution of the short and thick shear nails are basically the same as those of ordinary shear nails,but the shear efficiency of the short and thick shear nail is higher,and the bearing capacity to meet the requirements,indicating that the application of short and thick shear nails in the light combination bridge deck is feasible.(3)Through the analysis of the factors affecting the bearing capacity of the short and thick shear nails,it is found that the diameter of the shear nail and the concrete strength are the key factors affecting the bearing capacity and shear stiffness.The height of the shear nail has no effect on its bearing capacity and shear stiffness.In addition,the interfacial bonding between the steel and the UHPC has a certain influence on the bearing capacity,but has a great influence on the shear stiffness,and the interface bond can increase the shear stiffness by about 16%.(4)By comparing the fatigue test data of the short and coarse shear nails and comparing with the standard and other classical fatigue formulas,it can be found that the existing fatigue formula is no longer suitable for the short and thick shear nails.Based on this,the paper proposes the evaluation of the fatigue performance of the short and thick shear nails based on the principal stress rather than the shear stress,and determines its fatigue resistance as FAT90.(5)The finite element model of beam is established and the fatigue position and detail of the short and thick shear nail structure are determined.The fatigue performance is evaluated by the nominal principal stress method.It is found that the fatigue life of short and thick shear nails meets the design requirements.