Fea Concrete Fire

Numerical Heat Transfer, Part A, 39:685^710, 2001 Copyright # 2001 Taylor & Francis 1040-7782/01 $12.00 + .00

FINITE ELEM ENT ANALYSIS OF COUPLED H EAT AND M OISTURE TR ANSFER IN CONC RETE SUBJECTED TO FIRE R. T. Tenchev, L. Y . Li, and J. A. Purkiss
School of Engineering and Applied Science, Aston University, Aston Triangle, Birmingham, B4 7ET, United Kingdom
A syst em of coupled transient differential equations governing heat, mass transfer, and pore pressure built up in porous media ( concrete) , subjected to intensive heating, is derived. Water vapor and liquid water are considered separately in the mass transfer formulation. The primary unknowns are temperature, water vapor content, and pore pressure of the gaseous mixture. A nite element formulation and corresponding owchart of computations of all required data are presented. The numerical example solved represents a cross sect ion of a concrete column exposed to re. The domain and time distributions of temperature, pore pressure, water vapor, and liquid water content are presented. Computed pore pressure is higher than those usually reported by other analytical studies. The in uence of some initial parameters ( permeability, initial water content, and porosity) on maximum pore pressure is investigated.

INTROD UCTION Concrete as a structural material comprises three different phasesösolid, liquid (water), and gaseous mixture (water vapor and air). The solid phase consists of cement paste and aggregate, both of which are porous. The cement paste contains very small gel pores (diameter about 2 nm) and capillary pores (about 1 mm). The products of hydration in the cement paste contain chemically bound water. The gel pores hold water absorbed on their large surface. The capillary pores may be fully ¢lled (saturated concrete) or partially ¢lled with water. The gel and capillary water is usually called free or evaporable water. The gaseous phase exists in the partially ¢lled capillary pores. When a concrete... [continues]

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