FRICTION AND BONDING BEHAVIOR BETWEEN STEEL AND CONCRETE UNDER RESTRICTION STRESS

Steel and concrete are commonly used as construction materials for building structures. The force transfer mechanism in the connections between steel and concrete includes friction, bearing, bonding and mechanical shear connecting. This force transfer mechanism was summarized in the AIJ Design Standard for Composite Structures in 2014. The force transfer mechanism of connections of composite structures comprises the mechanism of shear force causing relative slip along the contact surfaces between steel such as steel plate and concrete and is due to the effect of friction and bonding, which is the fundamental properties of the force transfer mechanism between steel and concrete. It is important to quantitatively evaluate the force transfer mechanism s performance due to friction stress and bond stress and to accurately incorporate it into a method for evaluating the strength of connections in actual building structures. On the other hand, reproducing the experimental results of the shear connector using perfobond strip requires to consider frictional and bonding resistance between steel and concrete, as well as the direct shear resistance of concrete across the opening in perforated steel plate. Similarly, in experiments on connections with headed studs, the contact surface between the steel plate joined to the stud and the concrete also needs to be evaluated. In this paper, ultimate and residual stresses under restriction stresses applied perpendicularly to the contact surface for friction and the bonding behavior of the contact surface between steel and concrete is investigated by conducting push-out tests mainly on specimens using high strength concrete and high restriction stress. It is clear from a database including these and previous test results that the ultimate and the residual stresses are linearly proportional to the restriction stress irrespective of the contact surface condition. Furthermore, this paper proposes new formulations for ultimate and residual stresses under restriction stress to the contact surface on friction and bonding behavior of contact surfaces between steel and concrete. Predictions from the proposed formulation agree closely with test results under various contact surface conditions.