Bond Behavior of Embedded Reinforcing Steel Bars for Varying Levels of Transversal Pressure

Abstract

Because of columns loads, reinforced concrete (RC) continuous beams in skeleton structures are subjected to transverse compressive stress at support locations. Such lateral pressure can enhance the bond between the main top reinforcing bars and the surrounding concrete because of the confinement effect. Thus, the development length can be reasonably decreased compared to the case of no lateral pressure. However, different codes of practice, such as the Egyptian code standard ECP 203-2007 and the American Concrete Institute (ACI) code standard ACI 318-11, stipulate increasing the reinforcement location factor for upper reinforcement implemented in the calculation of the development length of such bars. On the other hand, the Comite Euro-International du Béton (CEB-FIP) model code standard CEB-FIP 2010 considers this enhancement in bond stress calculations as being due to transverse compression stress. To assess such effects, pull-out tests were performed on reinforcing bars embedded in short RC columns subjected to different levels of axial pressure. The experimental findings showed the same trend as manifested in the CEB-FIP 2010 results, where increasing the lateral pressure on the reinforcing bar resulted in decreasing the development length for both smooth and deformed steel bars. In contrast, the results of development length calculations based on both ECP 203-2007 and ACI 408R-03 were constant regardless of the level of lateral pressure on the reinforcing bar. This highlights the need for both ECP 203-2007 and ACI 408R-03 to consider the effect of transverse lateral pressure on development length calculations due to varying lateral pressure on the reinforcing bar.