Research On Studs In Steel-UHPC Lightweight Bridge Deck

The traditional orthotropic steel bridge deck has two diseases: the pavement layer is vulnerable and the steel bridge deck is easy to fatigue damage.The lightweight composite bridge deck formed by combining the steel deck and the UHPC layer through the stud shear connector can be very good to solve such problems.The UHPC layer in the lightweight composite bridge deck is usually thin,it is about45-60 mm,so the height of the studs in it is strictly limited.The height of sud is very short.At the same time,due to the obvious difference between the mechanical properties of UHPC and ordinary concrete,the force of short studs is different from that of traditional studs in ordinary concrete structures,and its basic performance needs to be studied.At present,the research in this area is relatively scarce.For this reason,this thesis focuses on the following contents relying on the National Natural Science Foundation of China(5206080102);(1)The development process of orthotropic bridge deck and the existing diseases and causes of the traditional pavement layer are introduced.The superiority of the mechanical properties of UHPC is used as the reason for the pavement layer.It introduces the concept of lightweight composite bridge deck and the current research status of the stud’s shear connector.(2)Analyzing the working mechanism and two failure models of stud shear connector by elastic foundation beam theory and introducing the calculation formulas about the bearing capacity 、shear stiffness and load-displacement curve of stud connectors given by national standards and scholars.(3)In order to study the static performance of the short stud shear connector,the push-out experiment was carried out on the short studs of different lengths(30mm、35mm and40mm)and diameters(13mm、16mm and 19mm)in the 50 mm UHPC layer,and the load-slip curve,shear capacity and failure mode of the specimen were obtained.The experimental results show that the damage of the specimens is that the root of the stud is sheared and damaged,and the UHPC layer is only damaged in a small area near the root of the stud.The diameter of the stud has a great influence on the shear resistance of the stud,while the length of the stud has almost no effect.The load-displacement curve of the stud in the push-out test is divided into elastic,elastoplastic and failure stages.The limit slip value of the stud in the test is small and the failure is relatively sudden,showing strong brittleness.(4)Using the ABAQUS finite element analysis software,a nonlinear finite element analysis was performed on the studs,and compared with the experimental results,which verified the rationality of the finite element software simulation results.At the same time,analyzing the stress and deformation of the stud connector,it is concluded that the stud is not only subjected to shear force,but is in a complex stress state of shear,bending,and tension.Finally,through the analysis of different parameters,it is concluded that the ultimate bearing capacity of the stud is mainly affected by the diameter of the stud,and its bearing capacity is proportional to the square of the diameter of the stud.The welding seam of the stud has a contribution of about 15% to its bearing capacity,so the welding quality should be strictly noticed during construction.The bearing capacity of studs in UHPC is about 50% higher than that in C50,and the shear stiffness is also much greater than that of ordinary concrete,it indicates that UHPC can significantly improve the shear performance of studs.The load-slip curves of studs of different lengths are almost the same,so the length of studs has almost no effect on their shear performance.(5)For the introduction of the experimental results,the calculation formulas of various specifications and scholars about studs were collected,compared with them,and the applicability of the existing formulas to short stud shear connectors was evaluated.