AN APPROACH OF REMOVING REDUNDANT ELASTIC SUPPORT FOR SOLVING STATICALLY INDETERMINATE STRUCTURE BY THE FORCE METHOD

The calculation characteristic of elastic support is analyzed in order to calculate the response of structure with redundant elastic supports by the force method. An approach of removing the restraining action of redundant elastic support is proposed, which aims at releasing the support conditions of springs at base and retaining springs as a part of the primary structure. In this way, the zero displacement condition at the base of springs in the actual structure can be utilized to establish the geometric compatibility equations in a more direct manner. The linear or angular flexibility coefficients in compatibility equations are equal to the absolute displacements of the released structure. The meaning of the equation is definite and concise. Spring deflection influences the calculation of the principal coefficients only. Treating the springs as axially-loaded elements, the principal flexibility coefficients can be evaluated by superimposing the flexibility coefficient of elastic support and the elastically restrained nodal displacement or slope produced by a unit force acting on the primary structure. The proposed method of removing redundant restraint is applicable for redundant axial elastic support, rotational elastic support and rigid support, which can standardize the process of calculation and improve the calculation efficiency for the Force Method.