Strength of Composite Beams with Web Openings

An ultimate strength analysis of composite beams with unreinforced, rectangular web openings is presented. The analysis is developed for general beam geometry and material properties, and for a single web opening of any practical depth, width and location. The beneficial effects of strain hardening and the shear contribution of the slab are neglected, and a four hinge failure mechanism at the opening is assumed. Analytical results indicate that a composite section with a web opening has a significantly higher bending strength than the corresponding noncomposite section, and that variations in opening length, height and eccentricity can have a significant effect on the ultimate strength. Comparison of the analytical results with the limited experimental data available indicates that the theory provides a very conservative estimate of the ultimate strength. The discrepancy between theory and test results is attributed primarily to strain hardening and the shear contribution of the slab.