Hydrothermal model for predicting fire-induced spalling in concrete structural systems

Abstract

A one-dimensional numerical model to predict fire-induced spalling in concrete structures is presented. The model is based on pore pressure calculations in concrete, as a function of time. Principles of mechanics and thermodynamics are applied to predict pore pressure in concrete structures exposed to fire. An assessment of the possibility of tensile fracture is made by comparing the computed pore pressure with temperature-dependent tensile strength. The pore pressure calculations are coupled with heat transfer analysis to ensure that the loss of concrete section, resulting from spalling, is accounted for in subsequent heat transfer analysis. The validity of the numerical model is established by comparing temperature, pore pressure, and concrete spalling predictions with results from fire tests. The computer program is applied to conduct case studies to investigate the influence of concrete permeability, tensile strength of concrete, relative humidity in concrete, and heating rate on fire-induced spalling in concrete members. Through these case studies, it is shown that permeability, tensile strength of concrete, and heating rate have a significant influence on fire-induced spalling in concrete. It is also shown that relative humidity has a marginal influence on fire-induced spalling in concrete.