Strength calculation method for cross-section of reinforced concrete flexural member using curvilinear concrete stress diagram of EN-2

Abstract

This article is continuation of earlier work of the author. A practical method for cross-section strength calculation of flexural reinforced concrete members with rectangular compression zone using curvilinear concrete stress-strain diagrams of Eurocode 2 (EN-2) is presented in this article. The method can be used for strength calculation of members with flanges and reinforcement in compression zone as well. Curvilinear EN-2 stress diagrams are readily superseded by polynomials that can be easily integrated are proposed by the author. It gives opportunity for mathematically accurate, without changing of curvilinear diagram by arbitrary diagrams, determination of value and location for resultant of concrete compression zone stresses and location of neutral axes as well. Calculation is performed for any chosen strain of the layer subjected to the maximum compression. The said strain may be of greater or less value in comparison to that corresponding to the concrete strength. In this way the maximum strength of the member can be estimated when the compression zone strain value varies within chosen interval. The method is suitable in both cases for the members which are commonly (not abundantly) and abundantly reinforced if the neutral axes is located within the cross-section, i. e. within the interval up to the centre of the tensile reinforcement cross-sectional area. Strength of members reinforced with high strength reinforcement which is not sufficiently prestressed or not prestressed at all can be determined by calculation. Formulae can be used for calculation of stress-strain state in persistent situations (not ultimate ones) and for calculation of steel prestress value as well. Rectangular compression zone parameters required for member strength calculation using curvilinear stress diagram are presented in the article. Results obtained by the proposed method are compared with the results obtained using EN-2 formulae.