Buckling of Columns Subjected to a Central Force Produced by a Tensioned String

The paper is concerned with a new buckling problem of columns subjected to a central force produced by the tension of a string. The central force can be characterized by having a movable center fixed on the deformed axis of a column at its intermediate position. Equilibrium equations of the column, together with the boundary conditions and the conditions of continuity, lead to the characteristic determinant. The characteristic determinant yields the buckling load, and then the buckling mode. If the intermediate center is set at the midspan of the column, the characteristic equation yields a double root. The double root makes buckling mode indeterminate. This fact is an interesting aspect of the present buckling problem. The imperfection method is applied to discuss a possible buckling mode. Experiment of the column was conducted to check the theoretical prediction. The theoretical buckling load and the corresponding buckling modes are compared with the experimental results to find a good agreement between the theory and the experiment.