| The headed stud is the most commonly used shear connector in steel-concrete composite structure.At present,the diameter of the commonly used shear stud is 16~22mm.However,if the small diameter shear stud is used in the area with large shear force in the composite structure,it will cause the arrangement of stud too close,which is not unfavorable to the casting of concrete.In addition,with the increase of the span of the bridge,more and more high-strength concrete is used,which includes HSSFC and UHPC.Compared with ordinary concrete,HSSFC and UHPC not only have high strength,but also have greatly improved in durability.Therefore,the mechanical properties of large diameter shear stud connector in HSSFC and UHPC are studied in this paper.The main contents are as follows:(1)The push-out experimental of eight groups of shear stud connectors that changed parameters include the strength of the concrete and the diameters of the stud were conducted to investigate the shear performance,the results show that the failure model of all the specimens includes two kinds,stud shear failure and welding damage respectively.The different diameter of studs in the same strength of the concrete,with the increase of stud diameter,the shear bearing capacity and shear stiffness increase,while the peak slip decreases.The same diameter of studs in different strength of the concrete,with the increase of strength of the concrete,the shear stiffness increases greatly,the increase of the ultimate shear capacity is not obvious,and the peak slip reduces.(2)Three-dimensional nonlinear finite element models were performed to understand stress state of shear stud and concrete slab by ABAQUS,it turns out to be that effective height of stud is smaller in high-strength concrete,which leads to the strain in the middle of the stud is very small.And the variation trend of strain is different from ordinary concrete.In addition,on the base of the finite element calculation,the diameter of the shear stud and the strength of the concrete are further changed to investigate the influence on the mechanical properties of stud connector,the calculation results show that when the high-strength or the ultrahigh performance concrete is used,it is better to be combined with large diameter stud.(3)On the basis of the results of the test and the finite element calculation,the formula for shear bearing capacity which given in the code for design of steel structure is modified.And the formula of shear stiffness and peak slip are also given.Finally,according to the above formula,and considering the correlation between the peak slip and ultimate slip,a calculation method of load-slip curve is proposed which uses three fold line model. |
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