Bearing Angle Model for Bond of Reinforcing Bars in Concrete

Abstract

The ribs of deformed reinforcing bars can cause bond failure by splitting the concrete cover or by shearing the concrete in front of the ribs. As deformed bars are pulled out, the rib face angle is flattened by the concrete key, which decreases the rib face angle to a smaller bearing angle. Analytical expressions are derived to predict bond forces with respect to splitting and shearing in this paper, and the bearing angle is a key variable. As the bearing angle decreases, the splitting bond strength also decreases, while the shearing bond strength increases. The splitting failure and the shearing failure occur instantaneously and interactively, reaching the ultimate bond strength in the case of bars confined by low transverse reinforcement. The shearing of the concrete key with increasing slip further reduces the splitting bond force, thus lowering the bond stress. The bearing angle model (BAM) is proposed to predict bond strength and to simulate bond failure mechanisms. The behaviors simulated using the proposed support existing knowledge on bonds and earlier experimental observations.