PRACTICAL ANALYSIS METHOD OF REINFORCED CONCRETE FRAME STRUCTURES WITH CONSIDERATION OF CREEP AND CRACKING IN CONCRETE

The article is devoted to enhancing the practical method of reinforced concrete frame structure analysis with consideration of the creep and cracking processes in concrete. The proposed method is based on the usage of a linearized diagram of a bending moment and curvature relationship for reinforced concrete bending elements. The formulas for evaluation of the bending stiffness of reinforced concrete elements with consideration of creep and cracking of concrete are given. The proposed formulas are based on the linear creep theory that assumes a linear relationship between stresses and elastic deformations as well as between stresses and creep deformations. The algorithm for drawing of linearized diagrams "bending moment vs curvature" for reinforced concrete elements of rectangular cross-section with consideration of creep and cracking is described. The analysis of portal reinforced concrete frames used in the experimental research of other authors was made to verify the proposed practical method. Experimental research provided tests of frames by the short-term loads for the definition of the bearing capacity and by the long-term loads of the different intensities. According to geometrical dimensions, reinforcement schemes, and materials properties of the experimental frames the linearized diagrams "bending moment vs curvature" were drawn with the usage of the proposed algorithm. Tables with the comparison of bending moments values obtained by the analysis results with values obtained during experimental research are given. Statistic analysis of the ratio of theoretical values of bending moments to experimental values at the action of short-term and long-term loads shows good agreement with differences less than 10%.