Effect of Construction Joint on the Shear Friction Strength of Concrete

콘크리트의 전단마찰내력에 대한 시공줄눈의 영향

To evaluate the shear friction performance of concrete interfaces with construction joint, a total of 18 push-off specimens were tested under direct shear and constant axial compressive forces. The main parameters investigated were concrete unit weight, arrangement type of transverse reinforcement (V-type for perpendicular configuration to the shear plane and X-type for $45^{\circ}$-degree inclined configuration), and the magnitude of axial compressive stresses. The initial shear cracking stress and the slope at the ascending branch of the shear load-relative slip relationship were independent of the type of transverse reinforcement and concrete unit weight, whereas they tended to increase as the axial compressive stresses increases. The shear friction strength increased in proportion to the summation of the applied axial stresses and shear transfer capacity (${\rho}_{vf}f_y$) of transverse reinforcement. The X-type transverse reinforcement had higher shear transfer capacity than the V-type reinforcement. From the mechanical model derived using the upper bound theorem of concrete plasticity, the concrete cohesion and coefficient of friction at the interfaces with construction joint could be estimated to be 1.56 MPa and $36.3^{\circ}$, respectively.