On definition of the design resistance to compression of longitudinal reinforcement of tube confined concrete columns

Columns made of steel pipes, filled with concrete, are one of the few successful examples when concrete and steel are mutually and substantially help to resist force effects, which results in increased bearing capacity of the element as a whole. Tube confined concrete constructions have a number of significant advantages compared to reinforced concrete or metal ones. The main of them are high bearing capacity, rigidity and reliability, low labor intensity and high speed of building a frame. Eventually, all this leads to reduced consumption of material and financial resources for manufacturing. The promising areas for further improvement of steel tube confined concrete columns are preliminary lateral compression of the concrete core or its rational reinforcement. The paper presents the main results of experimental research studies on the bearing capacity of prestressed and traditional tube confined concrete columns with reinforcing of the concrete core. Based on these data it's concluded that the rational use of prestressing and high-tensile reinforcement in steel tube confined concrete columns has led to an increase in their bearing capacity up to 20 %. The authors have proposed formulas, which take into account the effect of a concrete and reinforcement grade, as well as the reinforcement ratio on the value of design resistance to compression of high-tensile reinforcement.