Tests of Composite Beams with Web Openings

An experimental investigation to study composite beams with rectangular web openings is presented. Six composite beams and one steel beam were tested. W14 × 34, W18 × 45 and W18 × 46 sections were used. Opening sizes were fixed, with depths equal to 60 percent of the steel beam depth and lengths equal to twice the opening depth. Concrete slab dimensions were held constant. Opening locations were varied to investigate moment-shear ratios ranging from 3 to 33 feet (0.9 to 10 m). Web openings reduce the strength of composite beams. Beams with high moment-shear ratios fail by general yielding in the steel below the neutral axis and crushing in the concrete. Beams with medium to low moment-shear ratios fail by the formation of plastic hinges in the steel below the opening, accompanied by a diagonal tension failure in the concrete slab. The concrete in composite beams contributes significantly not only to the flexural strength, but also to the shear strength of the beams at web openings.