F. Hokes et alii, Frattura ed Integrità Strutturale, 39 (2017) 7-16; DOI: 10.3221/IGF-ESIS.39.02 7 Focussed on Modelling in Mechanics Selecting the objective function during the inverse identification of the parameters of a material model of concrete F. Hokes, J. Kala Faculty of Civil Engineering, Brno University of Technology, Veveri 331/95 Brno 60200 hokes.f@fce.vutbr.cz , http://www.fce.vutbr.cz kala.j@fce.vutbr.cz , http://www.fce.vutbr.cz A BSTRACT . Selecting the correct objective function is the critical precondition for a successful optimization task. The validity of this condition is also required when optimization algorithms are needed for the inverse identification of the unknown parameters of nonlinear material models of concrete, where experimentally measured load-displacement curves can be conveniently applied. In such cases, the objective function expressions can be formulated as the difference between the functional values of the curves or via comparing the characteristic features, which comprise the area under the curve and also the maximum functional value. The proposed article brings a study of the influence of the different formulations of the objectives functions to achieving optimum in the inverse analysis using genetic algorithm. The numerical part of the study was performed in the ANSYS computational system with use of multiPlas library of elasto-plastic material models from which the model based on formulations of Menetrey and Willam was chosen. K EYWORDS . Identification; Objective function; RMSE; Optimization; Sensitivity analysis. Citation: Hokes, F., Kala, J., Selecting the objective function during the inverse identification of the parameters of a material model of concrete, Frattura ed Integrità Strutturale, 39 (2017) 7-16. Received: 11.07.2016 Accepted: 21.09.2016 Published: 01.01.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he application of advanced nonlinear constitutive models of building materials can be described as the approximation of mathematical modelling methods to the real behaviour of structures. Such efforts are, however, often complicated by the existence of a wide set of input parameters for such nonlinear models. Interest in the phenomenon of nonlinear behavior of concrete is in order of a wide range of use of this material in scope of many researchers. However, the construction of a correct constitutive relationship which is able to express this nonlinear behaviour for various types of loading appears to be problematic [1]. One of the basic problems which arise when formulating a material model for concrete is the different responses of the material to tensile and compressive load [2]. For this reason, several approaches are used for the mathematical description of the behaviour of concrete. One of these approaches involves the use of theory of plasticity [3]. Applications of theory of plasticity to the description of the T

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