Load-Bearing Capacity of Short Concrete-Filled Steel Tube Columns of Circular Cross Section

Estimation of load strength of confined concrete tube elements is chracterized. with peculiar f features. Their concrete core and steel shell are in the state of spatial stress condition. which.in the course of loading varies both, quantitatively. and qualitatively. Thus, analytical description of. determining correlations and process of redistribution of loads between the components of this system is somewhat difficult. The proposed procedure of calculation of load-bearing.capacity of eccentrically. confined composite structure, concrete filled tube column, is based on non-linear strain. moqel. It takes into account spatial stress-strain state and collaboration of concrete core and.steel Practical implementation of this model is carried out by iterative calculation involving non-elastic strain of material and variation of coefficients of transversal strains of concrete and steel with increase in stresses, It is proposed to perform this calculation in two stages. At the first stage the diagrams of strain of concrete core and steel shell are plotted for axial direction of columns on the basis of calculations. At first the coordinates of parametric points of the required diagrams are determined, then the relative strain-stress data array is established. At the second stage, on the basis of known dependences of non-linear strain model, the load-bearing capacity of eccentrically confined column is calculated. Practical implementation of the proposed calculation procedure is aided by specially developed software. Comparisons of theoretical and experimental values of breaking loads for 110 centrally confined and 72 eccentrically confined column specimens evidence that the proposed procedure enables reliable estimation of their stress-strain state at any level of loading. The procedure can be applied for confined concrete tube columns manufactured by various technologies on the basis of concretes of various strength and types.