Fibre reinforced polymer shear reinforcement for concrete members: behaviour and design guidelines

Abstract

This paper describes an experimental program conducted to examine the structural performance of fibre reinforced polymer (FRP) stirrups as shear reinforcement for concrete structures. A total of ten large-scale reinforced concrete beams were tested to investigate the contribution of the FRP stirrups in a beam mechanism. The ten beams included four beams reinforced with carbon fibre reinforced polymer (CFRP) stirrups, four beams reinforced with glass fibre reinforced polymer (GFRP) stirrups, one beam reinforced with steel stirrups, and one control beam without shear reinforcement. The variables were the material type of stirrups, the material type of the flexural reinforcement, and the stirrup spacing. Due to the unidirectional characteristics of FRP, significant reduction in the strength of the stirrup relative to the tensile strength parallel to the fibres is introduced by bending FRP bars into a stirrup configuration and by the kinking action due to inclination of the diagonal shear crack with respect to the direction of the stirrups. A total of 52 specially designed panel specimens were tested to investigate the bend and kinking effect on the capacity of FRP stirrups, along with two control specimens reinforced with steel stirrups. The variables considered in the panel specimens are the material type of the stirrups, the bar diameter, the bend radius, the configuration of the stirrup anchorage, the tail length beyond the bend portion, and the angle of the stirrups. Based on the findings of this investigation, shear design equations for concrete beams reinforced with FRP, appropriate for the Canadian Standards Association (CSA) code, are proposed. The reliability of the proposed equations is evaluated using test results of 118 beams tested by others.Résumé : Cet article décrit un programme expérimental dirigé afin d'examiner la performance structurale d'étriers en polymère renforcé de fibres (PRF) pour le renforcement en cisaillement de structures en béton. Un total de dix poutres en béton armé à grande échelle ont été examinées pour étudier la contribution d'étriers en PRF dans le mécanisme d'une poutre. Les dix poutres incluaient quatre poutres équipées d'étriers en polymère renforcé de fibres de carbone (PRFC), quatre poutres équipées d'étriers en polymère renforcé de fibres de verre (PRFV), une poutre renforcée d'étriers en acier et une poutre de contrôle sans renforcement en cisaillement. Les variables furent le type de matériau des étriers, le type de matériau pour le renforcement en flexion, et l'espacement des étriers. À cause des caractéristiques unidirectionnelles du PRF, une réduction significative dans la résistance de l'étrier, relative à la résistance en tension parallèle aux fibres, est introduite en fléchissant les barres de PRF en une configuration d'étrier, et par l'action de déséquilibre due à l'inclinaison de la fissure de cisaillement diagonale par rapport à la direction des étriers. En même temps que deux spécimens de contrôle renforcés d'étriers en acier, un total de 52 spécimens de panne...

A practical method for determining shear crack induced deformation in FRP RC beams

“…1), which includes a factor to account for the stiffness variation along the length of a flexural element: (1) where and are the gross and cracked moments of inertia, respectively; and and are the cracking and applied flexural moments, respectively.…”

“…Shear induced deformations are normally negligible at service load and are usually ignored when calculating the total deflection of FRP RC members. However, previous research indicates that i) the component of shear induced deflection can be larger when FRP materials are used as reinforcement [1], and ii) shear deformations can increase rapidly after the development of diagonal cracks, thus reducing considerably the overall stiffness of the element [2,3].…”

“…Despite of this, relatively few studies have examined in detail the shear behaviour of FRP RC beams (e.g. [1,[5][6][7]). …”

Serviceability Analysis of Rc Beams Reinforced With GFRP Bars- A Review

“…A reduction factor proportional to the modular ratio, E FRP /E steel , is typically applied to concrete shear contribution equations for conventional beams, although such an approach underestimates the shear strength in flexural members with larger amounts of FRP longitudinal reinforcement (Michaluk et al 1998) 22 .Shear failures occur in beams with FRP stirrups either by FRP rupture at the bend points or by shear-compression failure in the shear span of the beam. Failure from stress concentrations at stirrup bends may limit the effective capacity to as little as 35% of the strength parallel to the fibers (Shehata et al 2000) 23 . Multidirectional FRP grids can also be used as shear reinforcement (Bank and Ozel 1999; Razaqpur and Mostofinejad1999) 24,25 .…”

Seismic Performance of GFRP-RC Exterior Beam–Column Joints with Lateral Beams

“…During the past decades, many experimental investigations have been conducted to verify behaviour of different concrete elements reinforced with FRP materials (Brown and Bartholimew 1993;Shehata et al 2000;Alsayed et al 1999). These studies usually involved investigating the behaviour of individual FRP-RC members such as simply-supported beams, slabs, and columns.…”