Issue 39

P. Král et alii, Frattura ed Integrità Strutturale, 39 (2017) 38-46; DOI: 10.3221/IGF-ESIS.39.05 38 Focussed on Modelling in Mechanics Inverse identification of the material parameters of a nonlinear concrete constitutive model based on the triaxial compression strength testing Petr Král, Petr Hradil, Jiří Kala Brno University of Technology, Faculty of Civil Engineering, Veveří 331/95, 602 00 Brno, Czech Republic kral.p@fce.vutbr.cz, hradil.p@fce.vutbr.cz , kala.j@fce.vutbr.cz A BSTRACT . The aim of this paper is to perform the inverse identification of the material parameters of a nonlinear constitutive model intended for the modeling of concrete which is known as the Karagozian & Case Concrete model. At present, inverse analysis is frequently used because it allows us to find the optimum parameter values of nonlinear material models. When applying such parameters, the resulting response of the structure obtained from a computer simulation is very similar to the real response of the structure based on the related experimental measurement. This condition then undoubtedly constitutes one of the progressive steps to refine the current numerical approaches. For the purposes of the inverse analysis performed in this paper the experimental data was obtained from the triaxial compression strength tests carried out on the concrete cylinders. K EYWORDS . Inverse analysis; Optimization; Objective function; Numerical simulation; Nonlinear concrete material model; Experimental data. Citation: Král, P., Hradil, P., Kala, J., Inverse identification of the material parameters of a nonlinear concrete constitutive model based on the triaxial compression strength testing, Frattura ed Integrità Strutturale, 39 (2017) 38- 46. Received: 11.07.2016 Accepted: 22.09.2016 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 sing nonlinear material models of concrete to examine the behavior of concrete structures exposed to static or dynamic loading currently constitutes a major move within the effort to approach the real character of and processes in the material during computer simulations. Current modern computing systems based on the finite element method, such as ANSYS [1], LS-Dyna [2], and Atena [3], offer a comparatively wide variety of nonlinear material models to simulate different conditions across the entire spectrum of materials. According to their respective properties, these models are applicable in both static [4-7] and dynamic [8-12] numerical simulations. The actual utilization of nonlinear material models of concrete within tasks of continuum mechanics nevertheless poses certain difficulties. One of such complications, forming the main subject of this paper, lies in the fact that the resulting computer simulation-based response of the structure is heavily dependent on the entered parameter values of the relevant nonlinear model of concrete. Thus, in any case where the parameter values of the employed material model were entered inappropriately, the eventual, computer-simulated response of the structure completely differs from the real response, and this condition constitutes an undesired effect in the given respect. To function properly, a large number of nonlinear U