Flat slabs. Reinforced concrete. Openings. Excentric load.

The construction system based on flat slabs directly supported on columns holds several advantages that make it suitable for use in buildings: construction simplicity, optimal use of floor-to-ceiling height, architectural layout freedom, among others. The need for various utilities installations to pass through floors leads to openings being located near the slab- column connection, reducing the concrete area responsible for transferring forces in the connection, a situation that can be exacerbated when there is transfer of bending moment. Despite the increasing number of studies on the impacts caused by eccentric loading, the presence of openings, and the use of shear reinforcement, almost no research has been done on the combination of all these factors. The aim of this research is to study the punching shear resistance in internal slab-column connections with symmetric openings adjacent to square columns and shear reinforcement in the form of stirrups with transfer of bending moment. The experimental study consists of the failure testing of five internal slab-column connections with dimensions of 2500x2500x180 mm, loaded with an eccentricity of 525 mm in one direction. The influence of using stirrups as shear reinforcement in the presence of rectangular openings was analyzed. The results obtained show that the chosen shear reinforcement partially recovered the lost resistance due to the openings. The results were compared with the calculation prescriptions of ACI 318-19, Eurocode 2, NBR 6118:2023, and fib Modelcode 2010, which underestimated the punching shear resistance of slabs with openings, transfer of bending moment, and shear reinforcement.