Ductility and moment redistribution capacity of multi-span T-section concrete beams reinforced with GFRP bars

Abstract

Glass fibre reinforced polymer (GFRP) bars are being increasingly used to reinforce concrete members as an alternative to steel, particularly in harsh environments, owing to their main advantages that include high strength, low self-weight, electromagnetic transparency and non-corrodibility. However, besides being relatively expensive, GFRP bars have low elasticity modulus and exhibit linear elastic behaviour until failure, thereby providing no contribution to structural members’ ductility. This paper presents experimental and numerical investigations about the flexural behaviour of continuous concrete beams reinforced with GFRP bars, in particular on their capacity to redistribute internal forces. Small-scale flexural tests were carried out on 7 two-span beams with T cross-section: the main parameters analysed were the GFRP reinforcement ratio and the confinement level in critical zones of the beams, namely at the central support. The behaviour of the beams was analysed and compared in terms of serviceability and failure responses. The numerical investigations included the development of non-linear finite element (FE) models of all beams tested. After validation and calibration with the test data, a comprehensive parametric study was performed, in which the effects of (i) the span, (ii) the cross-section geometry, and (iii) the longitudinal GFRP reinforcement ratio on the moment redistribution capacity of full-scale continuous beams were evaluated. Results obtained show that moment redistribution occurs and that elastic analyses are considerably conservative. The confinement of the concrete at critical cross sections may be a good solution to enhance the plastic hinge ductility and consequently, the moment redistribution in GFRP reinforced concrete beams.