Any nonlinear theories or finite elements have to be tested before they can be put into practice. Using the rigid body concept, this book provides simple rules for examining the validity of nonlinear theories and finite elements derived for structural members. The rules can be applied as well to testing the consistency of existing theories or computer analysis programs for nonlinear structures. Covers linear analysis and element quality test; nonlinear trusses and incremental constitutive laws; nonlinear analysis of planar frames; fundamentals of nonlinear theory of space frames; stiffness matrices for nonlinear analysis of space frames; theory and analysis on buckling of curved beams; and procedures for geometric nonlinear analysis. Provides numerous examples containing both analytical and numerical solutions. For mechanical, civil, and aerospace engineers.