ABSTRACT
This chapter introduces an alternate procedure known as the direct stiffness method, which is suitable for computer implementation. The direct stiffness method can be easily understood by considering the analogy between the procedures used to develop in the direct stiffness method and to calculate the second moment of area of composite areas. The coordinates used in the direct stiffness method are similar to the coordinates used in the stiffness method. In a structure where many elements with different orientations meet at a node, it becomes necessary to transform the element stiffness matrix along the local axes to the common global axes of the structure so that the structure stiffness matrix can be developed. Conjugate means that the force and displacement vectors only produce work in the direction of displacement. The force–displacement equations of the elements in global coordinates are assembled to get the force–displacement equations of the structure.
