Performance of Stud Clusters in Precast Bridge Decks

Abstract

A new design approach to clustered stud shear connection in composite bridges with precast decks is required to accommodate highly concentrated shear force in small area. Shear connection of the prefabricated slab consists of stud connectors, mortar in a shear pocket and reinforcement around the pocket. More general design approach for the shear connection is provided by relative strength between shear strength of shear connectors, bearing strength of mortar in shear pockets, and the shear strength of precast deck. Considering the relatively high strength mortar in the bearing zone of the shear connection this paper deals with structural performance of stud clusters to simplify the connection details. In a shear pocket, closer stud spacing than the current pitch requirement was considered. Push-out tests were conducted to evaluate the ultimate strength according to expected failure modes. The main parameters of the test were stud spacing and confining details. In order to use group arrangement of stud connectors, it is necessary to prevent premature failure of bearing zone by strengthening the shear connection using confining reinforcements. An empirical equation of ultimate shear strength of the shear connection was proposed to consider the effect of stud spacing when the spacing is less than five times stud diameter. Fatigue tests showed that the fatigue endurance of clustered stud connectors with spacing of more than three times stud diameter can be evaluated using current design codes.