Lateral stability of reinforced concrete beams

The present study aims to investigate the effect of dimensions, steel contents, material properties, type ofloading and boundary conditions at supports on stability of rer.tangular reinforced concrete beams. Also, it aims to find a simple method to check the stability and to determine theratio between the failure (critical) moment and capacity moment of the section.In this study Finite Element Method was used with analysis of reinforced concrete section taking intoconsideration the nonlinearity of concrete and the presence ofcracks. A computer program was formulated and comparisonsbetween its results and the available experimental ones weredone indicating very good agreement.The critical bending moment and capacity moment of thesection for simply supported beams and cantilevers with different geometric dimensions were calculated underdifferent types of loads for different values of tension steel ratios and compression ones for different values ofconcrete cylinder strength and yield strength of steel. Theresults were presented as dimensionless charts showing therelation between the ratio of critical bending moment to capacity moment of the section and a slenderness parameter for the above variables. By fitting the curves in these charts a general equation for simply supported beams and another for cantilever were obtained with tables for their constants.Beams with different boundary conditions in both vertical andhorizontal planes were studied under different types ofloading and related to the simply supported beams underuniform moment loading.It was concluded that lateral stability of slender reinforced concrete beams depends on different variables suchas geometric dimensions (slenderness ratio), strength of materials, steel contents, type of loading and type ofboundary conditions. A simple method was obtained to check the stability of such beams and to determine the ritical load.