Assessment of the stress-strain state of reinforced concrete elements with external reinforcement using a deformation model

Introduction. According to the recommendations, the calculation of reinforced concrete slabs with a steel profiled deck during the operational stage is performed based on the limit states. However, in order to solve a number of problems, it is necessary to know not only the limit state, but also the stress-strain state of the sections at each stage of loading. In SP 63.13330.2018, in addition to the calculation of normal sections based on the limit forces, there are also deformation methods with an analytical dependence of the curvilinear deformation diagrams of concrete in the form of ^σ_b = ^γ_b^E_b^ε_b. At the same time, the iterative methods used in the calculation of the maximum curvature of a bending element are quite time-consuming, even when using simplified deformation diagrams of concrete and reinforcement.

Aim. Development of an engineering deformation method for assessing the stress-strain state of reinforced concrete slabs with external reinforcement. Comparison of the results of calculation using the engineering deformation method and the method of calculation based on limit states.

Materials and methods. For a T-section element with external reinforcement, a system of nonlinear algebraic equations is written under the condition of dividing the vertical corrugations of the corrugated sheet into n layers, followed by the determination of stresses in an arbitrary layer as in multi-row reinforcement. The conditions of equality to zero of the sum of projections of all forces on the longitudinal axis and the sum of bending moments relative to the neutral axis are written depending on the position of the neutral axis in the design section.

Results. Examples and a comparison of the results of calculation of normal sections of reinforced concrete slabs with external reinforcement by the deformation method with the construction of the «moment-curvature» dependence and the method of calculation by limit states are given.

Conclusions. The proposed engineering deformation method provides a unified approach to calculation by limit states of the first group depending on the type of stress state: bending, eccentric compression at various eccentricities, and is distinguished by clear basic premises, greater simplicity and accessibility, both for designers and students.

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