What physical phenomena can be neglected when modelling concrete at high temperature? A comparative study. Part 2: Comparison between models

• Published in: International journal of solids and structures Vol. 48; no. 13; pp. 1945 - 1961
• Main Authors: Gawin, Dariusz, Pesavento, Francesco, Schrefler, Bernhard A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15-06-2011; Elsevier
• Subjects: Analytical and numerical techniques; Applied sciences; Building structure; Buildings. Public works; Concrete structure; Concretes; Construction (buildings and works); Degradation; Exact sciences and technology; Flux; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Heat transfer; Heating; High temperature degradation of concrete; Hydro-thermo-chemo-mechanical phenomena; Mathematical models; Modelling; Numerical model; Physics; Simplification; Solid mechanics; Structural and continuum mechanics; High temperature degradation of concrete; Hydro-thermo-chemo-mechanical phenomena; Numerical model; Constitutive equation; Hygrothermal variation; Hydro-thermo-chemo-mechanical; Heat flow; Thermomechanical properties; Chemical degradation; High temperature; Modeling; Axial symmetry; Mass transfer; Transport process; Thermochemical properties; Concrete construction; Concrete; phenomena; Heat transfer; Damaging
• ISSN: 0020-7683; 1879-2146
• DOI: 10.1016/j.ijsolstr.2011.03.003

The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of concrete exposed to high temperature. Several possible simplifications in modelling of heat and mass transport phenomena in heated concrete are considered and their effect on the results of numerical simulations is analyzed.
In part I of the companion paper, the physical phenomena, and heat and mass flux and sources in a concrete element were studied, both during slow and fast heating process, to examine the relative importance of different flux components. Then, the mathematical model of concrete at high temperature, developed by Authors in the last 10
years, was briefly presented and for the first time all the constitutive relationships of the model are summarized and discussed in detail. Finally, the method of numerical solution of the model equations was thoroughly presented.
In this part of the paper a brief literature review of the existing mathematical models of concrete at high temperature and a summary of their main features and physical assumptions is presented first. Then, extensive numerical study is performed with several simplified models, neglecting a chosen physical phenomenon or flux component, to evaluate a difference between the results obtained with the simplified models and with the reference model. The study concerns hygric, thermal and degradation performance of 1-D and 2-D axisymmetric concrete elements during fast and slow heating. The analysis will allow us to indicate which simplifications in modeling of concrete at high temperature are practically and physically possible, without generating excessive differences of the results with respect to the full reference model.