Perfobond strip (called PBL, hereafter) proposed by Leonhardt in Germany is widely used as the validated shear connector in steel-concrete composite structures. Fujii et al. proposed a fracture mechanism of PBL as follows: Slip force (shear force) acting on a PBL causes the expanding force which splits the concrete around the PBL. If restraint force, which is caused by cover concrete, rebar etc., resisting the expanding force exist, the slip strength is enhanced. Consequently, the fracture of PBL will happen when the expanding force exceeds the restraint force. Also, based on the above concept, they have given the evaluation formula of PBL slip strength and verified it by comparing previous experimental results. However, bonding force and frictional force are not taken into account in the formula. Through the loading tests of the composite girder, we found that the bonding and the frictional force, which appear along the boundary surface between concrete deck and steel flange, work as resistance force to not only the slip strength but also the expanding force. In this paper, the effects of the bonding force and the frictional force on the ultimate slip behavior of PBL are investigated experimentally, and an evaluation formula of PBL slip strength is improved by taking their effects into account.
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