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ARTICLE

A Numerical Method for Estimating the Maximal Temperature Gradients Reached in Fire-Damaged Concrete Structures Based on the Parameter Identification

Dong Wei¹, Yinghua Liu^1,2, Zhihai Xiang¹

1 Department of Engineering Mechanics, AML, Tsinghua University, Beijing 100084, P.R. China
2 Corresponding author, Tel:86-10-62773751; fax:86-10-62781824; Email: yhliu@mail.tsinghua.edu.cn

Computer Modeling in Engineering & Sciences 2009, 46(1), 77-106. https://doi.org/10.3970/cmes.2009.046.077

Abstract

Taking advantage of the parameter identification, a new numerical method is developed in this paper to estimate the maximal temperature gradients reached in fire-damaged concrete structures. This method can avoid the hypotheses of temperature-time curve and fire duration usually made in conventional numerical methods, availably evaluate the depth and degree of fire damage of concrete structures and consider the effects of localized fire. A material model taking into account the properties of fire-damaged concrete is firstly proposed in the present research. The least-squares estimation and the Gauss-Newton method are used to identify the material parameters of fire-damaged concrete by means of the graded finite element. Then the maximal temperature gradients reached in concrete members are estimated according to the relationship between mechanical properties and temperatures of fire-damaged concrete. Furthermore, the error tolerance and error transfer in the parameter identification are presented in detail. The effects of different polynomial expressions of the material model, the number and different thicknesses of concrete layers, element types and Young's modulus-temperature (E-T) models on the estimations are thoroughly investigated. The results of numerical examples are in good agreement with those of the experiment, which validates the feasibility and effectiveness of the developed method.

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