Effect of Column Eccentricity on Beam-Column Joints Strengthened with Chamfers

Abstract

By installing unsymmetrical chamfers on the soffits of beams, it has been proved in the earlier studies to be effective for strengthening nonseismically designed beam-column joints (BCJs). To generalize this, this study aims to extend the strengthening strategy to BCJs having upper and lower columns of different sizes. Such column eccentricity is not uncommon in gravity-load designed structures. In this study, experimental studies were conducted on six 2/3 scale specimens designed for joint shear failure, including three interior and three exterior specimens. The performance of specimens with nonseismic detailing was compared with that of having joint shear reinforcements or strengthened with chamfers. All specimens were under constant axial load and were subjected to cyclic displacements until failure. Response of chamfer under cyclic horizontal displacement was studied by analyzing the strains in chamfer. First and foremost, column eccentricity has both positive and negative influences on BCJs when subjected to cyclic displacements. Chamfer contributes to joint shear capacity when it is in compression. This leads to formation of an additional strut within the chamfer. For exterior joints, this phenomenon becomes obvious, and performance is improved when displacement is applied in one loading direction only. Lastly, width of additional strut formed in chamfer is associated with chamfer size.