Study on grouped large diameter short stud connectors in precast steel-thin UHPC composite bridge slab

Abstract

Grouped stud shear connectors have been employed in shear pockets of precast concrete slab to accelerate the construction of bridges. To satisfy the requirements of both the great longitudinal shear strength and small thickness of ultra-high performance concrete (UHPC) slab, grouped large diameter short stud was proposed in this study and fourteen push-out specimens were conducted with the variations in stud diameter, stud spacing, casting method and the strength of grouting material in shear pocket. The indexes including failure mode, load-slip curves, shear strength and shear stiffness were emphatically studied during the test. Additionally, finite element analysis was performed and the simulated calculation results were compared with the test results. For further research, more stud spacing values and different shear pocket shapes were evaluated by the numerical analysis method. The results showed that the cracks development of the cast-in-place specimen was different from that of precast specimens, and the failure of the precast specimens were controlled by the fracture of the stud shank and the local crushing of the concrete. The shear strength and stiffness of the stud increased with the increasing of the stud diameter and stud spacing (varying from 2d to 4d), but premature failure of the shear pocket with normal strength concrete led to the decreasing of the shear strength. The grouped stud effect was not pronounced at the longitudinal stud spacing exceeding 5d. The circular shaped shear pocket was suggested to applied in the prefabricated thin UHPC slab to maximize the shear performance. Furthermore, the shear strength and load-slip curves for grouped large diameter short stud in precast steel-thin UHPC bridge slab were put forward, and the accuracies of proposed models were verified.