Punching shear performance of reinforced concrete slab-to-steel column connections incorporating ECC and UHPECC

Unlike the conventional reinforced concrete (RC) slab-column connection, the punching shear generated at the RC slab-to-steel column connection may lead to brittle punching shear failure due to the small area around the steel column. Moreover, the unexpected moments arising from eccentric loading can also lead to the failure of the slab in punching shear mode. This paper proposes employing high-performance concrete (HPC) to fill the critical punching shear zone to improve the punching shear resistance of RC slabs to steel column joints. Experiments on eight RC slabs to steel column connections are reported. The test parameters under investigation are the type of HPC used to fill the critical punching shear zone, the distance (S) of the HPC zone measured from the flanges of the steel column and loading condition (concentric and eccentric). The types of HPC include engineered cementitious composite (ECC) and ultra-high performance ECC (UHPECC). The experimental results show that the proposed techniques can significantly improve the cracking load, elastic stiffness, energy absorption capacity, ductility, failure modes, and ultimate load of the slab-to-column connections. The ultimate load of the tested connections is increased by as much as 33 %, and 28 % for the slabs subjected to concentric and eccentric loading, respectively. However, the ultimate load and energy absorption capacity of the slab with UHPECC having a S value of 1d, where d is the effective depth are lower than those of the control slab. Three-dimensional nonlinear finite element models are developed to simulate the performance of tested slab-to-column connections and validated by experimental results. The parametric study shows that the n (=S/d) value greater than 3.5 has insignificant effects on the ultimate punching shear capacity of the slab. It is demonstrated that the proposed formulas faithfully estimate the ultimate punching shear capacity of slab-to-column connections constructed with different HPCs under concentric and eccentric loadings.