Effects of Casting Position and Bar Shape on Bond of Plain Bars

Twenty-five lap splice specimens were reinforced with plain round or square longitudinal bars in the top or bottom position to evaluate the effects of casting position and bar shape on bond. All specimens failed in bond, and the bond of square bars may be evaluated by calculating their equivalent round diameter. Top cast factors of 0.3 and 0.6 for round and square bars, respectively, reasonably capture the reductions in bond resistance. Maximum load predictions based on the CEB-FIP draft Model Code 2010 provisions for bond are overly conservative for all combinations of bar shape and casting position, whereas CEB-FIP Model Code 1990 provisions for bond reasonably and conservatively capture the behavior of specimens with bottom-cast round bars, but do not appear to capture the behavior of specimens with bottom- or top-cast square bars or top-cast round bars.