Flexural performance of concrete slabs reinforced with GFRP rebars

Abstract

The use of non-metallic fibre reinforced polymer (FRP) reinforcement as an alternative to steel reinforcement in concrete is gaining acceptance mainly due to its high corrosion resistance. High strength-to-weight ratio, high stiffness-to-weight ratio and ease of handling and fabrication are added advantages. Other benefits are that they do not influence to magnetic fields and radio frequencies and they are thermally non-conductive. However, the stress-strain relationship for Glass FRP is linear up to rupture when the ultimate strength is reached. Unlike steel reinforcing bars, GFRP rebars do not undergo yield deformation or strain hardening before rupture. Also, GFRP reinforcement possesses a relatively low elastic modulus of elasticity compared with that of steel. As a consequence, for GFRP reinforced sections, larger deflections and crack widths are expected than the ones obtained from equivalent steel reinforced sections for the same load. This paper presents a comparison of the experimental results with those predicted by the ACI 440 code in terms of; measured cracking moment, load-deflection relationships, ultimate capacity, modes of failure, stresses and crack width. This is to investigate the suitability of using the existing ACI design equations for predicting the flexural behaviour of samples reinforced with GFRP rebars. In this investigation, it appears that the ACI code equations on the whole over predict (i.e. crack widths and midspan deflection) the experimental results. On the other hand, the maximum experimental moment satisfies the ACI condition (i.e. unfactored design moment).