Experimental and theoretical investigation of column – flat slab joint ductility

Most modern seismic codes use ductility as one of the basic design parameters. Actually, ductility defines the ability of a structure or its elements to absorb energy by plastic deformations. Until the end of the previous century ductility was defined qualitatively. Most research works related to ductility are focused on structural elements’ sections. This study was aimed at complex experimental and theoretical investigation of flat slab–column joints ductility. It is one of the first attempts to obtain quantitative values of joint’s ductility for the case of high strength concrete columns and normal strength concrete slabs. It was shown that the flat slab–column joint is a three-dimension (3D) element and its ductility in horizontal and vertical directions are different. This is the main difference between ductility of elements and joint ductility. In case of flat slab–column joints, essential contribution to joint’s ductility can be obtained due to the slab’s confining effect. Based on experimental data, the authors demonstrate that flat slab–column joint’s ductility depends on the joint’s confining effect in two horizontal and vertical directions. Furthermore, the influence of slab load intensity and slab reinforcement ratio on the joint’s ductility is performed in this study. It is also demonstrated that the effect of the ratio between the slab thickness and the column’s section dimension on the ductility parameter is significant. Equations for obtaining a quantitative value of a flat slab–column joint’s ductility parameter were developed.