Experimental and theoretical study of GFRP hoops and spirals in hybrid fiber reinforced concrete short columns

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ORIGINAL ARTICLE

Experimental and theoretical study of GFRP hoops and spirals in hybrid fiber reinforced concrete short columns Ali Raza

. Qaiser uz Zaman Khan

Received: 29 April 2020 / Accepted: 30 October 2020 Ó RILEM 2020

Abstract Literature is deficient in exploring the structural behavior of concrete columns reinforced with glass fiber reinforced polymer (GFRP) bars and hybrid fibers. In the present study, the hybrid fiber reinforced concrete (HFRC) consisted of steel fibers and polypropylene fibers. A total of twelve GFRP reinforced HFRC (GHC) columns (250 mm in diameter and 1150 mm in height) were fabricated using longitudinal GFRP bars and transverse GFRP hoops/ spirals and tested to failure under different loading conditions. The testing results concluded that all the GHC columns presented similar failure modes with the rupture of GFRP bars and GFRP hoops/spirals. The decrease in the spacing of GFRP transverse reinforcement resulted in an improvement in the axial strength (AS) and ductility of GHC columns. The eccentricity of loading resulted in a significant reduction in the AS of GHC columns. The proposed

Electronic supplementary material The online version of this article (https://doi.org/10.1617/s11527-020-01575-9) contains supplementary material, which is available to authorized users. A. Raza (&) Department of Civil Engineering, Pakistan Institute of Engineering and Technology, Multan 66000, Pakistan e-mail: [email protected] Q. u. Z. Khan Department of Civil Engineering, University of Engineering and Technology, Taxila 47080, Pakistan e-mail: [email protected]

empirical model based on an experimental database of 270 fiber reinforced polymer reinforced concrete columns presented a good behavior for the experimental results. The comparative investigation solidly verifies the accuracy of the newly proposed empirical model for predicting the AS of GHC columns by assuming the compressive involvement of GFRP bars and the lateral confining pressure due to transverse GFRP reinforcement. Keywords GFRP bars  Hybrid fibers  GFRP spirals  Ductility  Confinement  AS model

1 Introduction The mechanical properties of the steel bars deteriorate in the humid environment leading to a decrease in the load-carrying capacity and serviceability of the reinforced concrete (RC) structures. To avoid corrosion, various protection methods are required causing a high initial cost. Glass fiber reinforced polymer (GFRP) bars are the most appropriate replacement for steel bars. GFRP bars have high tensile strength, lightweight, low density, high electromagnetic resistance, and most importantly the high corrosion resistance [1–4]. They are usually preferred in humid and marine environments to minimalize the maintenance costs and to maximize the serviceability of the concrete

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structures [2, 5–7]. The advanced research is focusing to minimize the brittleness of concrete. The literature portrays that the axial strength (AS) and ductility of col