Experimental and theoretical study of steel–concrete composite beams with openings in concrete flange

Nine specimens of steel–concrete composite beams with openings in the concrete flange were tested in the present study. The main parameters considered were the size and position of the openings. Two modes of failure were observed in the tests, depending on the loading arrangement and the position of the openings. Based on the test results, the bending resistance of composite beams with openings was analytically studied, and a reduced rigidity method was used in calculating the first yield moment of the composite beams. The rigidity of the composite beams was investigated for different parameters of the openings and the loading cases. The equivalent rigidity of the composite beams considering the effect of the openings in the concrete flange and the slip effect in the steel–concrete interface was also derived. The predicted deflections agree well with the test results, and the developed procedure can thus be used in design practice. The reduction coefficient that considers the effect of the openings in the concrete flange on the ultimate bending resistance was also obtained.