Experimental and numerical investigations on the influence of transverse beams and slab on the seismic behavior of non-seismically designed exterior beam-column joints

The study presents experimental and numerical results on two-dimensional and three-dimensional full-scale exterior non-seismically designed (NSD) reinforced concrete (RC) beam-column joint subassemblies subjected to quasi-static cyclic lateral loading. The tests were augmented by detailed 3D finite element modeling to obtain further information about the joint behavior. Through these systematic investigations and their detailed evaluation, clear conclusions could be drawn on the effect of transverse beams and slab on the overall seismic behavior of beam-column joints, where the joint core was devoid of transverse reinforcement. It was found that the presence of transverse beams enhanced both the ultimate joint shear strength and joint shear strength at first joint cracking. The crack development in concrete revealed that the diagonal joint shear cracks extended from the joint core into the transverse beams. The slab participation under flexure, when acting in tension, decreased with increase in drift due to intervening loss in joint stiffness, which was inconsistent with the observations in subassemblies where the joints were confined with transverse reinforcement. It was found that the inclined cracking in the transverse beams was caused due to joint shear stresses and aggravated due to torsional stresses when a slab was present. Normalized joint shear stress and principal tensile stress values were evaluated for first joint shear cracking and ultimate joint shear strength. These values may be useful for the seismic assessment of non-seismically designed beam-column joints with transverse beams and slab.