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

Dexin Duan,Qingfeng Xu,Jian Yang,Weidong Liu,Lijun Ouyang,Wanyang Gao

doi:10.3390/polym14020346

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.

Highlights

The following subsections give the details of the thermal properties of concrete and Fiber-reinforced polymer (FRP) bars and the boundary conditions considered in the heat transfer analysis, while the modeling of the temperaturedependent constitutive laws of the material and bond properties of concrete and FRP bars at ambient and high temperatures for the mechanical analysis will be provided in detail
Due to the lack of information available in the literature, the bond–slip model proposed by Aslani [79] is still used in the finite element (FE) model to define the local constitutive law of the GFRP bar-to-concrete interface at high temperatures
The reason for choosing these fire tests for validation is that all the material properties required to define the constitutive models of GFRP bars and concrete at high temperatures are reported in detail in their original studies

Summary

Introduction

A large number of studies have been conducted on the performance of FRP bar-reinforced concrete (referred to as FRP-RC for simplicity) members at ambient temperature [1,2,3,4], and the related design provisions have been specified in the current design guidelines [5,6]. Under high-temperature exposure in a fire, the material properties of FRP bars and concrete as well as the bond behavior between them will usually be significantly reduced [11,12], possibly leading to a significant reduction in the load-carrying capacity of the FRP-RC members [13,14]. Fire performance of the FRP-RC members is an essential issue in the design process and should be properly considered to meet the requirements specified in the current design guidelines [5,6]

Methods

Results

Conclusion