Mechanical assessment and investigation of the shear strength of steel-concrete composite beams with web openings

Composite beams can achieve high material and spatial efficiency in high-rise structures by integrating equipment, such as ventilation or supply lines, through cut-out apertures in the steel web. These apertures result in a redistribution of internal forces, generating further localized requirements for the design of steel, concrete, and shear connections. Composite beams with a single flange and composite dowels provide considerable advantages in ceiling construction. To evaluate the vertical shear performance of steel-concrete composite beams with web openings under static load, five composite beams were tested, and one controlled composite beam was subjected to a concentrated load. The empirical data included vertical load, deflection, slide, and cross-sectional strain, and monotonic static loading was applied. The findings indicate a significant decrease in the composite beam's stiffness and load-bearing capability upon opening holes in the web. Furthermore, the longitudinal strain in the entire region of the hole no longer follows the assumption of a flat, planar geometry. Increasing the thickness may increase the bearing capacity, while raising the reinforcing ratio could improve the deformation capability. When the reinforcing ratio of the concrete wing above the opening is between 51.26% and 55.54% of the cross-section, it holds most of the shear force. Moreover, when web openings are present, the concrete wing significantly enhances the composite beam's vertical shear-bearing capacity. This study presents experimental evidence supporting the use of composite beams that include web openings.