Fire Performance of FRP-RC Flexural Members: A Numerical Study

Abstract

Fiber-reinforced polymer (FRP) bars are increasingly used as a substitute for steel reinforcements in the construction of concrete structures, mainly due to their excellent durability characteristics. When FRP bar-reinforced concrete (referred to as FRP-RC for simplicity) members are used in indoor applications (e.g., in buildings), the fire performance of FRP-RC members needs to be appropriately designed to satisfy safety requirements. The bond behavior between the FRP bar and the surrounding concrete governs the composite action between the two materials and the related structural performance of the FRP-RC flexural member that will be affected when exposed to fire. However, there is a lack of reliable numerical models in the literature to quantify the effect of bond degradations of the FRP bar-to-concrete interface at high temperatures on the fire performance of FRP-RC flexural members. This paper presents a three-dimensional (3D) finite element (FE) model of FRP-RC flexural members exposed to fire and appropriately considers the temperature-dependent bond degradations of the FRP bar-to-concrete interface at high temperatures. In addition, the thermal properties of concrete and FRP bars are considered in the heat transfer analysis to predict the cross-sectional temperatures of the FRP-RC members under fire exposure. In the FE model, the mechanical properties and constitutive laws of concrete and FRP bars at high temperatures in addition to the bond degradations between them have been properly defined, thereby accurately predicting the global and local structural responses of the FRP-RC members under fire exposure. The proposed FE model has been validated by comparing the FE predictions (both temperature and midspan deflection responses during fire exposure) and the full-scale fire test results reported in the literature. The validated FE model is then used to study the effects of bond degradations on the global and local structural responses of the FRP-RC members under fire exposure. It is proved that the temperature-dependent bond degradations need to be considered to achieve accurate predictions of the failure mode and deflection responses.

A Critical Review on Glass Fiber-Reinforced Polymer Bars as Reinforcement in Flexural Members

“…Researchers also presented numerical models to understand FRP-reinforced structural members' behavior under fire. The finite element (FE) analysis presented by Duan et al accurately predicted the thermal response of FRP-reinforced concrete structures [27]. FE model presented in this research also predicted the anchorage failure of FRP-reinforced members at a high temperature which was a typical mode of failure in fire tests discussed in the literature.…”

“…The fiber-reinforced polymer bar, popularly known as FRP bar [31], can be manufactured using uninterrupted fibers enclosed in the polymeric-resin matrix [32]. The main purpose of a fiber is to carry a load, and the resin will act as a binding material [33,34], which transfers this load to fibers [27,28]. Fibers are protected by resin.…”

Influence Of Helical Confinement On Crack Development In RCC Beams

“…Non-destructive test software [10] and piezoelectric sensors [23] were used to determine the recorded wavelengths to produce technical images of the contained concrete. During the experiment [11], sensors measured the amplitude (A), which was recorded for each picture.…”

Fire Behavior of GFRP-Reinforced Concrete Structural Members: A State-of-the-Art Review

“…Aslani (2018) calibrated the parameters of the modified BPE (mBPE) model (originally proposed by Cosenza et al (1996) for ambient temperature) for three types of GFRP bars (sand coated, ribbed, and with a rough surface) based on experiments by Katz et al (1999) at temperatures up to 230 ºC. These bond laws considered the effects of concrete strength, cover thickness, bar diameter, and embedment length on the maximum bond stress at ambient temperature, and more recently were implemented in a numerical study by Duan et al (2022) (reviewed in Section Modelling of thermomechanical behavior). Solyom et al (2020) assessed the adequacy of the mBPE and CMR models (the latter proposed by Cosenza et al (1995) for ambient temperature) to describe the pre-peak bond behavior of a ribbed GFRP bar up to 300 ºC, concluding that the latter model was better suited for that purpose.…”