Web openings in inverted steel and concrete composite beams – Experimental insights and numerical simulation

Abstract

Composite beams can achieve high material and spatial efficiency in high-rise buildings by integrating equipment, such as ventilation or supply lines, through cut-out openings in the steel web. These openings lead to a redistribution of internal forces, creating additional local demands on the design of steel, concrete, and shear connectors. Composite beams with single flange and composite dowels provide significant potential in the construction of ceilings. The so-called integral ceiling, which possesses an inverted cross-section and a concrete slab under tension, offers additional advantages such as enhanced accessibility from the top for maintenance work and the possibility of thermal activation. The existing literature on inverted composite beams, particularly in the context of web openings, is limited. Therefore, this paper presents experimental investigations on inverted composite beams with web openings to gain insights into the local structural mechanisms within these regions, mainly focusing on the shear bearing capacity. A total of 24 tests were conducted, investigating various configurations of openings with different geometries and modified parameters such as reinforcement, prestressing, slab height, and slab orientation. The experimental results are enriched by numerical simulations to investigate the distribution of global and local internal forces. Results indicate similar bearing behaviour and failure mechanisms to those of composite beams under positive bending moments, suggesting that existing design provisions may be applicable.