Relaxation of stress in elements of reinforced concrete structures

The calculation and prediction of the long-term safety of building structures is associated with the dynamics of the stress state of their composite elements and leads to relaxation problems for assessing the redistribution of stresses between the components that make up the structural element. In this study, reinforced concrete elements and the redistribution of stress from concrete to reinforcement are considered. To solve the corresponding relaxation problem an approach based on the concept of the strength structure of materials is proposed, which considers them as a union of their fractions (layers, fibers) with statistically distributed strengths. The loss of the ability of force resistance caused by loading by part of the fractions of the element entails a redistribution of stresses to its entire fractions. As a result of this, a nonlinear dependence of deformations on the design stresses arises, calculated under the assumption of equal strength of all fractions. For a material isotropic in strength, the relaxation problem is reduced to solving a linear integral equation conjugated with its linear rheological equation. The linear integral equation relatively structural stresses is reduced. After solving it, the desired stress is determined as the root of the algebraic equation connecting the structural and design stresses. The proposed approach significantly simplifies the obtaining of necessary for the long-term safety prediction of structures stress estimates in the components of structural elements.