Yermolenko D. Volumetric stress-strain state of concrete filled steel tube components

Object - work of concrete filled steel tube (CFST) elements and their behavior under loading; aim - to solve the problem of assessing the stress-strain state and calculation of carrying capacity for CFST elements, considering their real physical and mechanical properties, geometrical parameters and the way of transmission of load; methods - the theories of elasticity and plasticity, structural mechanics methods; experimental researches; mechanic, tensometrical and digital photogrammetric methods; numerical methods; newness - the new theory of assessing the stress-strain state of CFST elements has designed accounting volumetric work of core and case. It makes possible to estimate the influence of different components at contact forces and considers the peculiarities of work of materials in CFST components under loading. It was constructed the generalized model of core as a cylindrical body of cross section with loading on lateral surface and end sections. It was engineered finite elemental model of compressed CFST elements. It was received the new experimental data on the work of compressed CFST elements depending on length, way of loading, type of contact between CFST components and eccentric quantity of compressive force. It was used for the first time the digital photogrammetric method to calculate and estimate the strain state of the experimental samples and fixate all process of deforming to destruction; results - it was solved the problem in estimating of stress-strain state considering the real work of the materials in CFST components at cross section based on a model of a composed body. It was defined the influence of discrete factors, specifically the type of contact interaction of core with case, length of CFST elements on changes of stress and strain in CFST under compressing loading. It was proved experimentally reasonability of taking the system of bodies "core - case" as a calculating scheme of CFST. It was developed the engineering methodology of calculating of carrying capacity of CFST elements. The results of studies were introduced in normative document of designing CFST constructions; branch - building.