Research on application of uplift-restricted slip-permitted (URSP) connectors in steel-concrete composite frames

Abstract

Tensile stresses and cracks in concrete slabs induced by a hogging moment have always been a disadvantage of steel-concrete composite structures and key issue of concern in the design of such structures. To reduce the tensile stress and control the crack width of the reinforced concrete (RC) slab, a new type of connector, called the uplift-restricted and slip-permitted (URSP) connector has been proposed and successfully applied in the area subjected to a negative bending moment in steel-concrete composite bridges. The feasibility of the URSP connector in steel-concrete composite frame buildings is investigated in this study based on a comprehensive parametric analysis. The effects of URSP connectors on the cracking behavior, as well as the stiffness and strength of composite frames, are systematically analyzed using an elaborate finite element model, which resembles a typical composite beam-column joint subjected to both lateral loads and vertical loads. In addition, an optimized arrangement length of URSP connectors is proposed for practical design. The research findings indicate that the application of URSP connectors greatly improves the crack resistance of RC slabs without an obvious reduction of the ultimate capacity and lateral stiffness of the composite frame. It is recommended that the distribution length of URSP connectors at each beam end should be 20-25% of the frame beam length.