COMBINED DEFORMATIONS 2 Methods to study composite deformation s-Principle of superposition (Analysis of external forces: External forces are reduced along the centroid of section and resolved along principal axes of inertia 2Analysis of internal forces: Determine the internal-force equation and its diagram corresponding to each external force component and the critical section Analysis of stresses: Plot the distribution diagram of the stress in the critical section, do the superposition of the stresses and establish the strength condition of the critical point2、Methods to study composite deformation s—Principle of superposition ①Analysis of external forces：External forces are reduced along the centroid of section and resolved along principal axes of inertia. ②Analysis of internal forces：Determine the internal-force equation and its diagram corresponding to each external force component and the critical section. ③Analysis of stresses：Plot the distribution diagram of the stress in the critical section，do the superposition of the stresses and establish the strength condition of the critical point. 11