CALCULATION METHOD OF COMBINED BEAMS

Abstract

was proposed to perform the calculation with taking into account nonlinear properties of material similarly to the reinforced concrete beams calculation with layer-by-layer division of section by height but taking into account the presence of two layers along the section width. In this case, an iterative approach is used with a sequential increase in the magnitude of strains in the marginal compressed fiber of the combined section. Bernoulli hypothesis is used, i.e. it is considered that the strains along the section height are distributed according to a linear law, and the stresses in each layer considered along the section height are determined according to the material diagram. At the same time, the stresses in the reinforced concrete plates and in the stone part are different at the same height in the cross section due to the difference in diagrams of these materials. For the calculation simplification the material diagram is accepted in the form of Prandtl diagram. It is shown that, due to the presence of two different materials in the cross section, there can be four possible cases for the height of a compressed zone determining. It depends on the ratio of the value of deformations in the marginal fiber specified at iterations to the maximum deformations of the layers (stone part and reinforced concrete plates). The height of compressed zone in each case is determined from the quadratic equation solution. It is shown that the iterative calculation converges very quickly. At the same time, the accuracy of calculations by the approximate method is sufficient for carrying out practical calculations. An algorithm for the iterative calculation of the combined beam is given.