Lateral cyclic behavior of interior two-way concrete slab-column connections reinforced with GFRP bars

In flat plates, the use of high-strength concrete (HSC) in the slabs, and the presence of shear reinforcement in the vicinity of columns are considered effective, economical, and practical solutions for enhancing the punching shear performance of slabs. This paper presents the first-ever experimental results for interior concrete slab-column connections reinforced with glass-fiber-reinforced-polymer (GFRP) bars subjected to a combination of gravity and lateral reversed cyclic loads. Four full-scale slabs measured 2500 x 2500 mm with a thickness of 200 mm, and 300 mm square column extending 700 mm above and below the slab surfaces specimens were constructed and tested until failure. The main test variables were (i) flexural-reinforcement type (GFRP and steel bars); (ii) slab's concrete compressive strength (NSC and HSC); and (iii) the use of GFRP shear reinforcement. All the tested specimens demonstrated adequate strength, deformation capacity, drift ductility indices, dissipated energy, and connection stiffness. The GFRP-reinforced NSC specimen without shear reinforcement showed adequate ability to withstand interstory drift up to 2.25% without punching failure. The GFRP-reinforced HSC specimen without shear reinforcement had a 33% higher lateral deformation and moment-transfer capacities compared to the GFRP-reinforced NSC specimen. The provision of GFRP-stirrups in the slab-column connection significantly influenced slab overall performance. The shear-reinforced specimen was able to sustain lateral drifts as high as 5% with no more than a 20% decrease in the moment carrying capacity. Moreover, the shearr-inforced slab was able to sustain the gravity load until the end of testing and only exhibited softer punching-shear failure with a gradual decrease in lateral loads.