Seismic Retrofitting of Columns with Lap Spliced Smooth Bars Through FRP or Concrete Jackets

Abstract

The effectiveness of RC jacketing or FRP wrapping for seismic retrofitting of rectangular columns having smooth (plain) bars with 180° hooks lap-spliced at floor level is experimentally investigated. The relatively low deformation capacity and energy dissipation of five unretrofitted columns is found not to depend on lap length, if lapping is not less than 15 bar-diameters. Six columns cyclically tested up to ultimate deformation after RC concrete jacketing demonstrate force and deformation capacity and energy dissipation sufficient for earthquake resistance, regardless of the presence or length of lap splicing in the original column. Another ten columns cyclically tested to ultimate deformation after wrapping of the plastic hinge region with CFRP show that FRP wrapping of the splice region is more effective than concrete jackets for enhancement of the deformation and energy dissipation capacity of old-type columns with smooth bars lap-spliced at floor level, provided that wrapping extends over the member length sufficiently to preclude plastic hinging and early member failure outside the FRP-wrapped length of the column.

Bond behaviour of substandard splices in RC beams externally confined with CFRP

“…lap length l b =20-35d b , where d b is the bar size) [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Despite the extensive researchefforts,relatively littleresearch has focusedon developing appropriate analyticalmodels for the strengthening of column splices using FRP materials.…”

Flexural behaviour of reinforced concrete jacketed columns under reversed cyclic loading

“…The validity of the proposed analytical model for predicting the flexural response of RC jacketed members under cyclic loading was examined by comparing the moment -curvature histories derived by the analytical model with those for the specimens studied by Bousias et al [10]. The decision to select this experimental study was based not only on its scope, but also on the fact that it provides detailed test results in terms of moment -curvature curves.…”

“…The effectiveness of the RC jacketing intervention method has been verified by studying the response of 44 specimens from 11 experimental studies [1][2][3][4][5][6][7][8][9][10][11], which constitute the experimental database of RC jacketed members compiled by the authors [12]. A key issue related to the response of the composite cross section is the interaction between the existing cross section and the outer shell (jacket).…”

Fibre-reinforced polymer strengthening of substandard lap-spliced reinforced concrete members: A comprehensive survey

“…Cantilever columns have been extensively tested in the past (Priestley et al 1992, Saadatmanesh et al 1996, Saadatmanesh et al 1997b, Saadatmanesh et al 1997a, Seible et al 1997, Xiao and Ma 1997, Haroun et al 1999, Ma and Xiao 1999, Chang et al 2000, Ma et al 2000, Chang et al 2001, Saatcioglu and Elnabelsy 2001, Haroun et al 2003, Elnabelsy and Saatcioglu 2004, Sause et al 2004, Schlick and Breña 2004, Yalçin and Kaya 2004, Bousias et al 2006, Bousias et al 2007, Breña and Schlick 2007, Youm et al 2007, Chung et al 2008, Eshghi and Zanjanizadeh 2008, Harajli 2008, ElGawady et al 2010, Bournas and Triantafillou 2011, Kim et al 2011. Column specimens are usually cast on a stiff concrete block simulating the structure's foundation, as shown in Figure 1.…”