Stress-strain state and load ability of compressed pipe-concrete elements

In the article are presented the results of stress-strain state and the bearing capacity of compression pipe-concrete elements studies. The studies were carried by using a fractional-rational diagram of relationship between stress and strain proposed in the Eurocode for a compressed concrete core inside a pipe and a symmetrical two-line diagram with limited area of fluidity for any values of an arbitrary flexibility of element and eccentricity of compressive force. On the carried research basis has been developed an effective numerical technique for determining the stress-strain state and the bearing capacity of compressed pipe-concrete elements. In calculation technique constructing, the task solution is reduced to system of nonlinear algebraic equations solving, relative to the deformation level in the most stressed section of the compressed concrete core section and the position of the neutral axis in this section. The efficiency of the proposed calculation method has been verified by numerous numerical experiments. It is shown that depending on the element's flexibility and the compressive force's eccentricity, at the moment of bearing capacity loss, the operation of the steel pipe can be both elastic and elasticplastic, and this is determined only by calculations using the proposed general method. Keywords: concrete; steel pipe; «load-deflection» graph; deformation; stress; deflection; stress-strain state; bearing capacity; eccentricity.