Applicability of the 500°C isotherm method in determining the strength of reinforced concrete beams after fire

Abstract

A procedure to estimate the residual bending moment and the shear load capacity after fire in reinforced concrete beams was evaluated. The calculation method is based on the 500ºC Isotherm Method, adopting the reduction coefficients proposed by Van Coile et al. (2014) for the steel yield strength. The proposed method validation was done from experimental results of 62 reinforced concrete beams available in the literature. It was possible to observe a good approximation of the analytical method with the experimental data. For the bending moment an average ratio M r ana / M r exp of 1.04 and standard deviation of 0.15 was found. For the shear force an average ratio V r ana / V r exp of 0.85 and standard deviation of 0.23 was found.

State-of-the-art review of the reliability evaluation of concrete beams exposed to fire

“…In this aspect, internationally known curves have emerged that aim to enable this standardization. An example is the ISO 834 fire (ISO 834:2019), the "standard curve" or "standard fire", which does not depend on the dimensions, purpose of the compartment or the thermal characteristics of the materials (Costa et al, 2004). It is worth mentioning that any extrapolation of conclusions about a standard fire to a real fire must be carefully analysed, as the behaviour of the standard curve is not faithful to the curve of a real fire (Costa and Silva, 2003).…”