Strength of centrally compressed concrete tube elements

Introduction. The increasingly large-scale use of compressed concrete tube elements in construction practice requires the development of methods for calculating their strength, taking into account the main features of their force resistance. The current design standards of a number of countries offer empirical formulas that ensure good accuracy in calculating axially compressed concrete pipe structures, but incorrectly take into account the distribution of forces between the concrete core and the steel pipe. This paper proposes a method that allows for a reliable assessment of the stress state of concrete and pipe. Materials and methods. The strength of short centrally compressed CTE can be determined using the method of limiting forces. The accuracy of calculations according to the proposed method depends on the correct determination of the coefficients of the material. Currently, heavy concrete, which has a dense structure, is usually used for pipe-concrete columns. For such concretes, it is proposed to take the values that are obtained after processing the results of experiments conducted under volumetric compression with a constant lateral pressure. To establish these values, a statistical analysis of the results of 232 experiments with short centrally compressed CTE made of heavy concretes of medium and high strength was performed. For each experiment, coefficient values were selected corresponding to the best match between theoretical and experimental destructive loads. Results. The methodology of the current standards does not allow to take into account the features of the concrete core in compressed CTE concretes of various types. In the proposed methodology, this issue is solved by appropriate selection of material coefficients. If there is a sufficient amount of experimentation with concrete CTE of a specific type, it is not difficult to find the values of the corresponding coefficients. Conclusions. The developed method for calculating the strength of short centrally compressed solid waste takes into account the main features of the force resistance of a tube-concrete structure and allows us to determine the distribution of forces between the concrete core and the steel pipe.