The stiffness method for analysis presented in Chapter 3 for plane frames and in Chapter 4 for grid frames can readily be extended to the analysis of space frames. The plane frame or grid frame has three nodal coordinates at each joint. The space frame, however, has a total of six possible nodal displacements at each unconstrained joint; three translations along the X, Y, and Z axes and three rotations about these axes. Consequently, a beam element of a space frame has for its two joints a total of 12 nodal coordinates; hence, the resulting element stiffness matrix will be of dimension 12 x 12.
KeywordsTransformation Matrix Beam Element Global System Direction Cosine Local Axis
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