Experimental fire testing of large‐scale glass fibre‐reinforced polymer‐reinforced concrete beams with mid‐span straight‐end bar lap splices

Abstract

Summary Adopting glass fibre‐reinforced polymer (GFRP) rebars as a replacement of conventional steel reinforcement in different infrastructure applications is mainly attributed to its corrosion resistance and considerable lightweight‐to‐high strength ratio. However, the use of FRP rebars in construction is still limited due to the degradation of its mechanical properties at elevated temperatures. The experimental work presented in this paper aimed to investigate the structural fire behaviour of concrete beams reinforced with GFRP bars having lap splices at the beam mid‐span. Four identical 2750‐mm long concrete beams with cross‐sectional dimensions of 300 mm × 350 mm were experimentally examined under four‐point flexure bending. A 60‐mm thick concrete cover was used on the bottom, front and back sides of all beams. Two beams were tested as control specimens in ambient condition, while the other two beams were exposed to standard fire while subjected to a transverse load equivalent to 40% of the beam ultimate design moment. Experimental results show that concrete beams sustained the applied loads for a minimum of 53 minutes in standard fire conditions. Also, both test beams failed due to slippage of the spliced bars when the temperature measured at the top of the middle bar approached its glass transition temperature.

Load ratio effects on the structural fire behaviour of glass fibre‐reinforced polymer‐reinforced concrete beams with mid‐span bar lap splices – Experimental study

“…Accordingly, the cracks were deliberately developed in the two beams of the present study to allow direct heat penetration into the beam cross‐sections as a more conservative scenario. This was in anticipation to negatively affect the fire resistance time of the two beams tested in this study in comparison to that of the other identical beams subjected to about 50% reduced load level, which were tested by Nour et al 14 Before the commencement of the fire tests, all thermocouples cables, load cell, and the displacement transducer were checked after being connected to the Data Acquisition system.…”

“…The study presented in this paper considered four identical large‐scale GFRP‐reinforced concrete beams: two were experimentally examined as part of this study, and the other two beams were tested in a prior related study conducted by Nour et al 14 All beams had cross‐sectional dimensions of 300 mm wide × 350 mm high and 2750 mm total length, with 2200 mm clear span. Each beam was reinforced with three 20‐mm diameter GFRP bars as longitudinal reinforcement and 10‐mm diameter steel stirrups spaced at 150 mm along the entire length of the beam.…”

“…The service moment and ultimate design moment of the beams were calculated at 23.6 and 31.6 kN.m according to the CSA‐S806‐12 design standard, respectively. For the two identical concrete beams tested by Nour et al, 14 about 40% of the beam ultimate design moment was applied during the fire tests. This specific low load level was deliberately selected so that the applied load was below the calculated cracking moment of the beams to avoid the development of cracks before the commencement of the fire test.…”

“…Accordingly, the main objective of the research study presented in this paper is to investigate the effects of increasing the applied load level on the fire resistance of GFRP‐reinforced concrete beams having mid‐span bar lap splices. The results obtained from this study have been compared with those obtained for identical beams but subjected to only a 40% load ratio, which were examined in the prior related study conducted by Nour et al 14 …”

“…Limited research has been conducted on the structural fire behaviour of GFRP‐reinforced concrete beams, with almost none addresses the behaviour of beams having bar lap splices. To the best of the authors knowledge the only study in the available literature that investigated the fire behaviour of large‐scale concrete beams reinforced with GFRP bars and having mid‐span lap splices is that conducted by Nour et al, 14 in which the beams were subjected to constant load level. Accordingly, the main objective of the research study presented in this paper is to investigate the effects of increasing the applied load level on the fire resistance of GFRP‐reinforced concrete beams having mid‐span bar lap splices.…”