Performance Assessment of Exterior Beam Column Joint Retrofitted Using ECC

Abstract

The structural integrity is significantly depends on the behavior of beam-column joint during earthquake. The earthquake occurred in Nepal, India, Pakistan and Japan have been facing disastrous consciences attributed to failure of beam column joint. Adopted design philosophy in these countries lacks the ductile detailing in the past design which led to extensive cracks in beam column joint zone and failure occurs. This attracts the need on the research and development of repaid repairing techniques of damaged structural element. The confinement has been considered rapid repairing technique proven to be efficient in restoring original capacity. However, Engineered cementitious concrete (ECC) are the new composite techniques formulated using micro mechanics and exhibit straining hardening property, where previous composites such as FRP, steel fibers reinforced composites are limited to high compressive strength and strain softening tensile strain property. In the present dissertation, the effort has been made to implement the ECC as a retrofitting material to strengthen the initially distress beam column joint. Therefore, initially, the ECC has been developed to attain the higher tensile strain. Further, the beam column joint is damaged to obtain the complete and moderate initial damage levels which are calculated using Park and Ang damage indices model. The retrofitted specimens were subjected to quasi static cyclic loading (QSCL) under controlled deformation until failure. The initially damaged specimen has been retrofitted using ECC. The load-deflection relationship, ductility, stiffness and strength degradation, energy dissipation capacity and joint shear stress of controlled and ECC retrofitted specimens have been compared. The test results indicated that the use of ECC materials in the joint zone as a retrofitting material can enhance the joint shear stress capacity, stiffness and strength degradation, as well as the energy dissipation as compared to controlled specimens. However the performance of retrofitted specimen significantly depends upon the initial damage level of the beam column joint.