Behavior of Composite Concrete Beams with Smooth Interface

Abstract

Design and detailing requirements for composite concrete beams are specified in clause 17.5 of building code 318 of the American Concrete Institute. These requirements rely on monolithic action of the entire cross section to develop flexural and shear resistance, and for deflection control. Detailing of the interface between the precast web and cast-in-place flange to resist horizontal shear in a composite concrete beam is crucial in developing a monolithic action for such beams. This paper presents the results of recent research on the behavior of composite concrete beams with a smooth interface. Current provisions of the American Concrete Institute's code on flexural strength, shear strength, and deflection characteristics are found to be satisfactory. However, the code clauses dealing with horizontal shear are found to be very conservative. Based on test results, an equation to represent the shear transfer strength of a smooth interface is developed. Suitable suggestions are made for consideration during the future revisions to design codes.