Glass Fibre Reinforced Polymer (GFRP) Internally Reinforced Concrete Slabs in Fire

Abstract

During the past two decades, the civil engineering community has shown interest in applications of fibre reinforced polymer (FRP) reinforcement in concrete structures as an alternative to steel reinforcement because of enhanced durability. However, the performance of FRP in fire for applications in buildings demands more profound insights. The lack of adequate information on material characteristics at high temperatures for glass FRP (GFRP) bars creates uncertainty regarding the performance of GFRP reinforced concrete members in fire. This dissertation aims to characterize and understand the fundamental properties of GFRP reinforcing bars at high temperature and to evaluate the performance of GFRP reinforced concrete slabs in fire through full-scale fire testing and numerical modelling. This dissertation provides original and new insights to enhance the confidence of structural design engineers when considering fire resistance in design of GFRP reinforced concrete elements. The research is conducted in three separate but integrated streams: material testing, full-scale fire testing, and numerical modelling. Material tests are conducted on GFRP reinforcing bars to understand their behaviour including tensile strength and bond strength at high temperatures. Two sets of full-scale fire tests are studied to evaluate the performance of GFRP reinforced concrete slabs at the component level. The finite element (FE) numerical modelling includes both heat transfer analysis and structural analysis of GFRP reinforced concrete slabs, and incorporates the results of the material tests to estimate the fire resistance of GFRP reinforced concrete slabs. The FE model is validated against the results of the full-scale fire tests (Chapters 5 and 6). This thesis shows that existing prescriptive procedures, based on strength criteria alone, for evaluating the fire resistance of conventional structures are not applicable to GFRP reinforced concrete because such procedures fail to recognize that the design of GFRP reinforced concrete structures is governed by serviceability rather than by strength. Thus, more rational approaches for considering the fire resistance of GFRP reinforced concrete structures are developed which consider appropriate stresses in GFRP bars under service loads, the bond strength of the GFRP to concrete interface at high temperatures, and tensile strength at high temperatures. The objectives of the research are attained by enhancing the understanding of GFRP reinforcing bars and the performance of GFRP reinforced concrete slabs under heat effects.