Behavior of composite concrete beams with smooth interface

Design and detailing requirements for composite concrete beams are specifie d in clause 17.5 of building code 318 of the American Concrete Institute. T hese requirements rely on monolithic action of the entire cross section to develop flexural and shear resistance, and for deflection control. Detailin g of the interface between the precast web and cast-in-place flange to resi st horizontal shear in a composite concrete beam is crucial in developing a monolithic action for such beams. This paper presents the results of recen t research on the behavior of composite concrete beams with a smooth interf ace. Current provisions of the American Concrete Institute's code on flexur al 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 repres ent the shear transfer strength of a smooth interface is developed. Suitabl e suggestions are made for consideration during the future revisions to des ign codes.