Room- and elevated- temperature material properties of structural fire-resistant weathering steel

Abstract

The material behavior of structural component is critically important to resist the fire and other actions, especially for the structural parts directly exposed to fire. In this paper, the room- and elevated-temperature material properties of a newly developed fire-resistant weathering (FRW) steel with nominal yield strength f_y = 235 MPa are investigated by using an innovative heating method and conventional steady-state tensile testing method. The stress-strain curves and typical mechanical properties at elevated temperatures are obtained. Furthermore, the equations for reduction factors of Young's modulus, proof strength and tensile strength are proposed, and the thermal expansion characteristic parameters are determined via in-situ heating method. Based on the measured data, relevant equations for describing critical parameters are provided and compared with the available equations in the current standards. According to the experimental stress-strain curves and mechanical properties, the constitutive relationship at elevated temperatures based on the Ramberg-Osgood model is established and proposed. The goodness of fit for the stress-strain constitutive model is all above 96 %, which is consistent with the experimental curve. Therefore, the proposed constitutive model is sufficiently accurate for predicting the elevated-temperature stress-strain relationship of FRW steel. The research findings presented in this paper provide important reference for determining the material properties of FRW steel, and give valuable recommendation for the fire safety design of steel and composite structures.