Confined Concrete in Fiber-Reinforced Polymer Partially Wrapped Square Columns: Axial Compressive Behavior and Strain Distributions by a Particle Image Velocimetry Sensing Technique

Abstract

Strengthening existing reinforced concrete (RC) columns using a partial wrapping strengthening technique (PWST) by fiber-reinforced polymer (FRP) strips has been widely implemented. However, compared with the confinement mechanism of confined concrete in columns strengthened with the FRP full wrapping strengthening technique (FWST), the confinement mechanism of confined concrete in FRP partially wrapped columns is less understood. This paper presents the results of an experimental investigation into the behavior of confined concrete in FRP partially wrapped square columns under axial compression. The effects of FRP strip width and thickness on stress–strain behavior were thoroughly investigated. The novel particle image velocimetry (PIV) non-contact strain sensing technique was adopted to measure the strain in the specimens. Results show that the axial strains as well as the hoop strains are generally larger at the mid-plane of adjacent FRP strips than those at the mid-plane of each FRP strip, and considerable variation in hoop strains along the height of the specimens was observed. Comparisons between the experimental results and predictions by existing design-oriented stress–strain models were carried out to examine the accuracy of the models. A new design-oriented stress–strain model is proposed for confined concrete in FRP partially wrapped square columns and the comparisons between laboratory results and predictions from the proposed model show that the proposed model is superior to the existing models.

Confinement Effect of Reinforced Concrete Columns with Rectangular and Octagon-Shaped Spirals

“…Many models have been developed based on experiments to predict the strength and behavior of RC columns and concrete cylinders with shear reinforcement [11][12][13][14][15][16][17][18]. Extensive research has also been conducted not only on conventional crossties, but also on interlocking spirals to suppress lateral expansion of core concrete and buckling of longitudinal reinforcement, as well as shear reinforcement of RC columns using Fiber-Reinforced Polymer (FRP) [19][20][21][22][23][24][25][26][27].…”

Bond strength prediction of the composite rebars in concrete using innovative bio‐inspired models

“…Some researchers have investigated the properties and application of such materials. [1][2][3][4][5][6][7][8][9] The glass fiber-reinforced polymer (GFRP) bars are considered important alternatives. The most important reasons to choose it can be: (a) the high chemical strength of these bars, (b) the high ratio of strength to the weight of GFRP bars, (c) the high economic efficiency, and (d) the high resistance to rust.…”

“…Nowadays, fiber‐reinforced polymers are used as suitable materials for reinforcing concrete. Some researchers have investigated the properties and application of such materials 1‐9 . The glass fiber‐reinforced polymer (GFRP) bars are considered important alternatives.…”

Design-oriented axial stress–strain model for partially fiber-reinforced-polymer-confined normal-strength concrete

“…Although the studies of the partially FRP-confined concrete columns are limited compared with the FRP fully wrapped columns, it can be concluded from the existing researches (Garyfallia et al, 2015; Guo et al, 2018; Hany et al, 2015; Mai et al, 2018; Pham et al, 2015) that the confinement mechanism between the two FRP schemes is significantly different. If the theoretical methods initially developed for FRP fully wrapped columns are directly applied to FRP partially wrapped columns, the confinement effect provided by FRP strips may be overestimated due to the existence of the unconfined regions between two adjacent FRP strips.…”