The bending of prefabricated houses is also called structural instability. This means that when the load on the structure reaches a certain value, if a small interference force is added, the structural balance configuration will appear in a new form. Even if the small interference force is eliminated, the structure will not return to its original state. This situation is called structural instability or bending, and the corresponding load is called bending load or critical load. In modern times, structural stability theory focuses on bending forms (branch bending or extreme bending), bending modes and equilibrium paths after structural bending. There are three types of equilibrium states of any object: stable equilibrium state, unstable equilibrium state and random equilibrium state. After an infinitesimal deviation occurs near the equilibrium position, if the object can still return to its original equilibrium position, this state is called stable equilibrium; If the object cannot return to its original position after slightly deviating from the equilibrium position, but still deviates, this state is called unstable equilibrium state; The state of stochastic equilibrium is usually the transition from equilibrium to unstable intermediate or critical state.