THE CREEP MODELING OF REINFORCED CONCRETE SHELL STRUCTURES WITH ACCOUNT OF ANISOTROPY OF PROPERTIES
One of the basic problems, which is solved on the stage design of reinforced concrete element, is the analysis of stress-strain state as well as determining of lifetime. The paper is devoted to the simulation of nonlinear creep of concrete structural elements taking into account the damage. High priority of the research theme is justified, the aim and goals are formulated. The paper proposes a combination of plastic model with fracture mechanics to simulate the behavior of concrete in accordance with its characteristics, including not only stress and strain, but also the degradation of its stiffness. The finite element method is used to solve the boundary value problem. Despite the wide spread of three-dimensional finite elements, for the sake of numerical simulation of thin-wall structures that are optimal for the use of special shell elements. The mathematical problem statement of creep of concrete structural elements taking into account the anisotropy of the material properties is presented. The creep problems of thin-walled structural members were solved by use of developed software. The deformations of the reinforced concrete slab supported by four corner columns are analyzed. Comparison of theoretical and experimental deflection values in the first weeks of the study showed that the error is up to 10%. After two months of research, this error decreases, varying from 2% to 7%. The analysis of the obtained results allows us to judge the effectiveness of the proposed model as a whole. The proposed model of thin-walled structures for creep allows to analyze the stress-strain state of reinforced concrete structures. The equation of state reflects the anisotropy of the material properties and takes into account the damage, which makes it possible to conduct a reliable assessment of the strength, stiffness and durability of reinforced concrete structures. The conclusions about the adequacy of the analysis of the reliability and durability of reinforced concrete structures.
Keywords: creep, long-term strength, reinforced construction, anisotropy, finite element method.
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