Experimental investigation on seismic performance of reinforced concrete beam-column joints with and without adequate ties at joint region

Abstract

Beam-column joints are identified as potential critical components of reinforced concrete moment resisting frames subjected to seismic lateral loading. Severe damage within a joint panel may trigger deterioration of the performance of reinforced concrete beamcolumn connections. A comprehensive study has been carried out to investigate the seismic behavior of beamcolumn joints with and without adequate ties at joint region. Seven half-scale specimens of reinforced concrete beam-column joints were constructed considering three types of categories. These test categories were a) joint region with and without seismic ties, b) application of conventional and seismic stirrups in the joint region and c) different column to beam cross-section ratios which were considered to observe their effects on the performance of beam to column joint. The specimens were subjected to cyclic incremental moment with sustained gravity load. Different crack patterns were observed for different categories of specimens. Specimens without ties at joint region showed diagonal cracking at joint; on the other hand, control specimens with ties experienced vertical cracking at the faces of the joint where the beams framed into the joint. The experimental data obtained in four deflection controlled cycles were used to study overall performance of the beam to column joint. Loaddisplacement as well as moment-rotation characteristics of the joints were obtained. At the same time, maximum loads, load at first crack formation, maximum as well as residual deflections and stiffness were measured or observed. Finally, the test results of beam-column joints with and without seismic ties at joint region were compared. The specimen with non-seismic stirrup detailing and without ties at joint region performed poorly. The reinforced concrete beam-column joints with seismic ties at joint region showed improved performance with respect to absorbed energy, relative resisting moment and secant stiffness.