Models of Concrete and Reinforcement under Explosive Loads

In this article, the mathematical models of structural materials describing their dynamic properties are considered for calculating building structures for the action of dynamic loads. Physical and mechanical properties are described related to reinforcing steel and concrete under the action of explosive loads, as well as the influence of the loading rate and other factors on the deformation diagram of steel and concrete. The analysis is carried out concerning the reasons for the increase in the resistance of concrete and reinforcement under rapidly increasing loads. The relevance of the topic is determined by its compliance with the main goals and objectives of the Russian state policy in the field of improving the safety of buildings and structures when exposed to explosive loads. The article describes the methods of mathematical description of the structural materials behavior under the action of explosive loads. A simplified method for modeling the dynamic properties of reinforcing steel and concrete by multiplying the calculated resistance by the dynamic strengthening factor, as well as a more time-consuming method based on the equations of gas-hydrodynamics and implemented in the LS-DYNA software package, are considered. The authors used the method of taking into account the dynamic strengthening of reinforcing steel and concrete based on the nonlinear behavior of materials using diagrams with a piecewise linear description. Dynamic hardening was considered using hardening factors. The purpose of the study is to compare the results of numerical calculation according to the method proposed by the authors with the data obtained during the experimental program Blind Blast Test. The calculation was carried out by the finite element method using the Lira 10.12 calculation complex. The DYNAMICS+ system was used to simulate the load from the action of an external explosion. The experimental model is a reinforced concrete slab reinforced with ASTM Grade 60#3 rods. The results of numerical calculation showed high convergence with the experimental program. The use of the method of accounting for the dynamic hardening of reinforcing steel and concrete, based on the nonlinear behavior of materials using diagrams with a piecewise linear description, is the most optimal model that allows to get a fairly accurate solution and at the same time is acceptable from the point of view of labor intensity. This article is of interest to design engineers engaged in the calculation of structures for explosive loads.