Truss Analogy for the Design of FRP- Retrofitted RC Exterior Beam-Column Joints

Abstract

It is now generally accepted that beam-column joints are critical regions in reinforced concrete (RC) frames designed for inelastic response to severe seismic attack. Inadequately detailed joints, especially exterior ones, have been identified as critical structural elements that may fail prematurely due to high shear stresses [1]. Strengthening of RC joints is a rather difficult task. A variety of techniques have been applied to joints, with the most common being the construction of RC or steel jackets. The rehabilitation of RC columns jacketed with carbon fibre-reinforced plastic (FRP) composites for improving shear strength, confinement, and ductility has received considerable attention in recent years. An extensive test on 18, 2/3 scale exterior joints was carried out by Antonopoulos and Triantafillou [2]. Ghobarah and Said [3], developed design methodology for fibre jacketing to upgrade the shear capacity of existing beam-column joints in RC moment resisting frames. Smith and Shrestha [4] carried out a concise but systematic review of experimental research on the strengthening of RC connections with FRP in addition to an evaluation of the effectiveness of the strengthening schemes. Smith and Shrestha noted that four different types of deficiencies have been introduced into connections that require strengthening with FRP. These are shear strengthening, anchorage strengthening, shear and anchorage strengthening and plastic hinge relocation. Recently, Shrestha and Smith [5] reported the results of a detailed experimental investigation on the FRP strengthened RC beam-column connections subjected to monotonic loading and compared these results with their proposed analytical model. The aim of this study is to fill the gaps that exist in the current state of knowledge for the FRP strengthening of joints worldwide. In this paper, a truss analogy proposed by Hwang and Lee [6] for unstrengthened exterior beam-column joints has been further developed to cover the shear strength of FRP-strengthened joints. The method is checked against numerical analyses that are calibrated with available experimental results. The numerical analysis is extensive and is performed with the latest version of ANSYS software.