Comparative study of reinforced-engineered cementitious composites and reinforced-concrete slab-column connections under a vertical monotonic load

The flat slab is a preferred choice for structural design because of its architectural and construction efficiency. However, flat slabs collapse frequently because of brittle punching shear failure of RC slab-column connections, which can be attributed to the low tensile strength and high tensile brittleness of conventional concrete. Engineered cementitious composites (ECC) have excellent tensile properties compared with conventional concrete. The failure modes of reinforced-ECC (RECC) slab-column connections were revealed in a recently published study by authors. In this study, three RC slab-column connections were tested further monotonically in a comparative study of RECC specimens. A specimen with a slab span of 700 mm and the reinforcement ratio of rho = 0.6% and 1.4%, and a 500-mm span specimen with a rho = 1.4% were used. The peak and residual specimen strengths were estimated and compared with the test results. The main conclusions were: (1) the punching shear failure of the RECC specimens was delayed significantly compared with the RC specimens. The RECC specimens experienced a flexural-triggered punching shear failure, with ductility ratios from 2.4 to 6.4, whereas the RC specimens usually have zero ductility. (2) The peak RECC specimen load was -2.0 times greater than that of the RC among the tested specimens. The peak strength of the RECC specimens was estimated by a yield-line mechanism, whereas the peak strength of the RC specimens was estimated by the punching shear-resisting mechanism. (3) The residual RECC load was -3.0 times greater than that of the RC among the tested specimens. The main contribution to the residual strength of the RECC specimens was by the vertical compound of axial force from steel bars that passed through the punching shear cone. The main contribution to the residual strength of the RC specimens was by the concrete cover spalling strength. (4) The comparative study verified preliminarily the feasibility of improving the punching shear performance by using ECC in slab-column connections.

Automated summary

The study examined the performance of reinforced-ECC (RECC) slab-column connections compared to traditional RC specimens. Results showed that RECC specimens exhibited delayed punching shear failure with higher strength and ductility ratios compared to RC specimens. The findings suggest the feasibility of enhancing punching shear performance in slab-column connections by using ECC.