Experimental Investigation on Behavior of Reinforced Concrete Beam Column Joints Retrofitted with GFRP-AFRP Hybrid Wrapping

Upgradation to higher seismic zones of several cities and towns in the country has necessitated in evolving new retrofitting strategies. Recent earthquakes have demonstrated that most of the reinforced concrete structures were severely damaged during earthquakes and they need major repair works. One of the techniques of strengthening the reinforced concrete structural members is through external confinement by high strength fiber composites which can significantly enhance the strength and ductility which will result in large energy absorption capacity of structural members. Fiber materials are used to strengthen a variety of reinforced concrete elements to enhance the flexural, shear, and axial load carrying capacity of elements. Beam-column joints, being the lateral and vertical load resisting members in reinforced concrete structures are particularly vulnerable to failures during earthquakes and hence their retrofit is often the key to successful seismic retrofit strategy. The existing reinforced concrete beam-column joints which were designed as per code IS 456:2000 must be strengthened since they do not meet the requirements given in the ductility code IS 13920:1993. In this paper an attempt has been made to study the behavior of reinforced concrete beam-column joints retrofitted with glass-carbon hybrid fiber sheets. Three exterior reinforced concrete beam-column joint specimens (control) were cast and tested to failure. Two specimens had reinforcement details as per code IS 456:2000. The other specimen had reinforcement details as per code IS 13920:1993. An axial load was applied on the column. Push and pull load was applied at the free end of the cantilever beam till failure. The failed two beam-column joint specimens designed as per code IS 456:2000 were retrofitted with GFRP-AFRP/AFRP-GFRP hybrid fiber sheets wrapping to strengthen the specimens. The performance of the retrofitted beam-column joints was compared with the control beam-column joint specimens and the results are presented.