• Eight high-strength concrete flat slabs were tested under central static loading. • Near-column openings reduced the punching shear capacity, stiffness and energy absorption. • Adding 0.6% waste tyre steel fibers (WTSFs) improved flat slab shear capacity, stiffness and energy absorption. • WTSFs effectively mitigated the weakness effect from openings near the column. This paper reports the findings of an experimental investigation on the punching shear response of eight small-scale high-strength concrete flat slabs, examining both slabs with and without column-adjacent openings. The study evaluates the effects of square opening sizes of 100, 200, and 300 mm near the column and the inclusion of 0.6% waste tyre steel fibers (WTSFs). The slabs, with 1,080 mm × 1,080 mm × 100 mm dimensions, were subjected to a centrally applied static load through a 100 mm square column having 150 mm height. Openings resulted in a significant reduction in punching shear capacity of up to 57.835%, stiffness loss of up to 71.645%, and energy absorption of up to 72.686%, depending on the opening size and slab type. The incorporation of WTSFs effectively improved the punching shear capacity, stiffness, and energy absorption up to 29.5%, 34.145%, and 149.955%, respectively, while also controlling crack propagation and enhancing ductility. Code-based comparisons were conducted using ECP-203, ACI-318, NZS 3101, CSAA 23.3, DIN 1045-1, and EC2. Moreover, ECP-203, ACI-318, NZS 3101, EC2, and DIN 1045-1 showed higher safety margins with mean V u, test / V u, pred values of 1.107, 1.185, 1.173, 1.202, and 1.249, respectively, indicating conservative predictions. CSAA 23.3 yielded a value of 1.029, showing closer agreement with experimental results. Integrating WTSFs into flat slab construction provides an effective strategy to compensate for the structural weakening caused by service openings.
Ndabamenye et al. (Sun,) studied this question.