Mechanical Performance of Puzzle-Shaped Shear Connectors Subjected to Fully Reversed Cyclic Stress

Abstract

Recent innovations in composite dowels have led to the realization that robust hybrid systems can provide excellent strength and stiffness. In this contemporary era, puzzle-shaped and modified clothoid-shaped shear connectors are attracting interest, particularly in Europe. Their popularity stems from their outstanding shear capacities and their ease of manufacturing by virtue of having a single cutting line. Moreover, earlier studies based on pushout tests have proven this fact. Composite beams in buildings experience fully reversed cyclic stress between compression and tension during seismic events. When the concrete slab starts to crack under tensile stress, the shear capacity of the composite dowel can deteriorate considerably. Nevertheless, the influence of this cyclically applied stress on mechanical performance remains unclear. This study specifically examined puzzle-shaped shear connectors, with cyclic loading tests conducted using a component model of the composite beam, which can carry the various stress histories to the concrete slab. In all, findings obtained from 14 specimens with several influential factors clarified the cyclic behaviors and stress transfer mechanisms of puzzle-shaped shear connectors. Based on the experimentally obtained results, the applicability of existing evaluation equations was investigated with respect to the ultimate shear strength and shear force–slip displacement relation. Results indicate that those formulas overestimate the mechanical capacities of composite dowels under fully reversed cyclic stress. For that reason, this study has led to an evaluation formulation of mechanical performance that reflects the stress history effects. Ultimately, this study has proven that the proposed equations can assess the ultimate shear strength and shear force–slip displacement accurately while embracing simplicity.