Quasi-static cyclic performance of RC exterior beam-column joint assemblages strengthened with geosynthetic materials

Abstract

The beam-column joints are the most critical and vulnerable part of the RC framed structures when subjected to earthquake load. The objective of the present study is to investigate the cyclic behaviour of seismic and non-seismic exterior reinforced concrete (RC) beam-column joints strengthened with innovative polymeric based geosynthetic materials. Two variants of geosynthetic material named geogrid and geotextile were used for strengthening the beam-column joints in the experimental program. In this strengthening protocol, two different types of strengthening patterns were used in which one was horizontal U-shaped pattern, and the other one was the diagonal cross (X-shaped) pattern. All the beam-column specimens were tested under the quasi-static cyclic loading with controlled amplitude to explore the cyclic performance on the parameters such as failure modes, hysteresis loops, load-deformation envelope curves, ductility, energy dissipation capacity, stiffness and strength degradation behaviour, pinching width ratio, damage index and joint distortion. The test results showed that the adopted strengthening schemes with geotextile and geogrid materials could successfully alter the failure of beam-column joints from shear to flexural and improved the ductile behaviour of the strengthened specimens. The load-carrying capacity and ductility-factor of the geosynthetic strengthened specimens significantly increased up to 48.4% and 37.8%, respectively when compared to the non-seismic control specimen, and it was highest in geogrid strengthened BCJs, especially in diagonal X-shape bonded specimen. The significant increment of energy dissipation capacity was also observed as 2.08 to 3.73 times for the strengthened specimens. Furthermore, the post-elastic performance and the joint shear strength of strengthened RC beam-column joints was also improved in comparison to the non-seismic control specimen. In addition, an analytical study was carried out to predict the shear strength contributions of externally bonded strengthening materials in the RC beam-column joint, which was compared with experimental findings. A good agreement was observed between the analytical and experimental results. Hence, the experimental and analytical study of the strengthened beam-column joints using geotextile and geogrid have confirmed that the appropriate bonding of these materials to the concrete can improve the seismic performance of the non-seismic exterior RC beam-column joints.