Rationalization of the parameters of the cylindrical bridge support (theoretical basis)

Abstract

The formulation and solution of the problem of durability and stability of a concrete support, which has an outer mesh cage reinforced with reinforcing ribs (frames) and an inner cavity is considered in paper. The contact stresses between the concrete core and the metal cage are determined, which, in turn, actually depend on the attributes of the mesh cage and the step of the reinforced ribs. The rationalization criterion based on minimizing the potential deformation energy is introduced. For the indicated task, the variables are the thickness of the mesh cage, the size of its cell, the step of the frames. Moreover, within the framework of the stated task it is also proposed the development of the approach in the formation of the criterion of the limit state of the material which variously resists to compression, stretching and shear (such as concrete). The approach is based on the presentation of the material diagrams (directly taken from experimental studies) in the form of a polynomial of the fifth degree. The coefficients of this polynomial are expressed through the generally accepted parameters of the stress-strain state, which, in turn, can depend on time, temperature, etc. The limiting value of the strain energy density is assumed as a criterion for the limit state. In this case, the aforementioned strain energy density depends on its particular values, calculated separately for strain of compression, stretching and shear. In addition, the criterion considers the nature of the stress-strain state by introducing the Lode-Nadai parameters into it. As a consequence, there were constructed limiting surfaces in coordinates which represent the principal stresses for the indicated classes of concrete. Moreover, recommendations for determining of the normalized values of the strain energy density are given and a logic-calculational algorithm for considering the transition from the limit state in the local area to the general collapse of the structure is proposed.