Stress-strain concrete model with double independent reinforcement

Abstract

Introduction. Being an integral part of the modern construction, concrete is a complex nonlinear material. Concrete strength and deformability depend largely on its stress-strain state. Such behavior is due to the complex and highly heterogeneous structure of the material. Among concrete and reinforced concrete structures of newly constructed and reconstructed buildings and structures, there are a large number of elements working in the conditions of the triaxial stress-strain state. Currently, there are high requirements in Federal Law No. 384-FZ for the calculation models of buildings and structures, including physical nonlinearity and plastic properties of materials. A phenomenological material model based on the plastic flow theory can serve as a tool that allows describing the physically nonlinear behavior of concrete under complex stress-strain conditions, as well as taking into account the above-mentioned requirements. Most models of concrete models implemented in “heavy” finite-element complexes oriented to universal application have a number of drawbacks that hinder the use of models. The main drawbacks include significant deviation of the strength/loading surface from the results of experimental data, incorrectly constructed dependence between material deformability and its stress state, no account of dilation and contraction, the presence of a significant number of singularity zones in the loading surface, the lack of algorithms for obtaining parameters used to describe the material behavior. The purpose of this work is to develop a model of concrete that can accurately describe the behavior of the material. Moreover, the model has to take into account main effects characterizing the stress-strain state of the material (dilation, contraction), it has to reflect the different behavior of the concrete under compression and tension and has to have a minimum number of singularity zones. Algorithms for obtaining all material model parameters should also be provided. Materials and methods. The results of analysis and systematic generalization of the data obtained from domestic and foreign sources on the theory of plasticity, concrete and reinforced concrete structures are used as the basis. Results. The model is implemented in the finite-element software package ANSYS which allows using the user-defined models of the material. The comparison of the laboratory tests results carried out for the concrete and reinforced concrete samples under different stress-train states with the results of numerical modelling. Conclusions. The stress-strain model of concrete presented in the paper allows rather accurate modelling of behavior of material under different types of stress-strain conditions in the framework of static simple short-term loading taking into account physical non-linearity of the material, considering different behavior under compression and tension, dependence of deformability of material on the type of stress-strain state, the effects of contraction and dilatation. The loading surface of the model contains a single singularity zone. The algorithms for obtaining all the parameters required for the material model are presented.