Dynamic behavior of statically preloaded concrete under uniaxial compression.

The analysis of experimental studies presented in the scientific literature indicates that the strength and deformability of concrete during its dynamic reloading may depend on the initial level of stresses caused by a previously applied static load. In this regard, the purpose of this study was to build improved models of concrete deformation of operating reinforced concrete structures of load-bearing systems of buildings and structures during their dynamic loading, taking into account the nonlinear elastic law of material deformation at the stage of loading with a static load, as well as changes in the parameters of viscous resistance during loading. As a physical model of the power resistance of concrete of loaded reinforced concrete structures with their dynamic additional loading caused by an emergency, we accepted the Kelvin - Voigt model for an elastic-viscous body. On the basis of the adopted model, variants of solving the differential equation of uniaxial compression of concrete with its dynamic additional loading from an arbitrary level of initial stresses acting in it from a previously applied static load are obtained. A step-iterative approach to determining the parameters of concrete state diagrams under static-dynamic loading conditions is proposed. Analysis of the obtained relationships between stresses and deformations shows that an increase in the level of initial stresses acting in a compressed concrete element at the time of application of a dynamic load leads to a decrease in the dynamic strength of concrete with the same action parameters. [ABSTRACT FROM AUTHOR]