Research On Shear Behavior Of Stud Connectors In Steel-Concrete Composite Structure

Steel-concerte composite structures consist of steel and concrete material parts which are connected by shear connector.The two different material parts are combined as a composite structure system through adhesion,friction and mechanical action.The stud connector is widely used in steel-concrete composite structures because of the advantages of independent direction,good ductility,small occupied space and easily guaranteed construction quality.The mechanical behavior of stud connector is very complex,especially the shear behavior,and it has important effects on the interfacial slip of steel-concrete composite structures.In this paper,the shear bearing capacity and shear stiffness of stud connector are furtherly researched by the methods of push-out test and finite element numerical simulation.The main results are as follows:(1)Based on the test results of shear behavior of stud connectors,the load-slip curves,failure modes,shear bearing capacity and shear stiffness of the stud connectors with different diameters and heights were obtained.The results indicate that the shear bearing capacity and the shear stiffness increase with the increasing of aspect ratio,but the shear stifffness will change slightly when the aspect ratio is more than ten.At the same time,based on the push-out test results of eighty stud connectors at home and abroad,the formula for calculating shear bearing capacity of stud connectors under shear failure with the consideration of stud height was fitted,which supplemented the formula for calculating in the Code for design of steel and concrete composite bridges(GB 50917-2013).(2)Through the method of finite element numerical simulation,the calculation models of stud connectors were established to simulate the process from loading to failure,and get the load-slips,failure modes,and shear bearing capacity.Based on the small difference between test results and numerical simulation results,the reliability of the numerical simulation method was verified.Then,factors affecting shear bearing capacity of stud connectors such as concrete strength,yield strength of stud connector,diameter and length-diameter ratio of stud connector were analyzed.The results show that the shear bearing capacity of stud connector increases with the increasing of concrete strength,stud diameter and stud aspect ratio,but increasing the diameter of stud is the most effective way,and the shear bearing capacity of stud connector keeps almost unchanged with the increasing of yield strength of stud connector.(3)By using the method above,the calculation models of group stud connectors were established to study the effect of group studs effect on the load-slip curve and load transfer between layers of stud connectors.At the same time,the number of layers of stud connectors,the properties of concrete materials and the distance between layers of stud connectors which affect the group studs effect were analyzed.The results show that the shear bearing capacity and shear stiffness of single stud connector are significantly reduced by the group studs effect,and the non-uniformity coefficient of load transfer between layers decreases in the direction from the bottom to the top of the stud connectors is gradually reduced.When the number of layers of stud connectors increases gradually,the shear bearing capacity and shear stiffness of single stud connector will decrease.Increasing the strength grade of concrete has no obvious effect on the shear bearing capacity and shear stiffness of single stud connector.When the distance between the layers of the stud connectors reaches 7.9 times the diameter of stud,the group studs effect will not work.