Abstract:

When structures are stressed at relatively low levels, the applied stress is linearly proportional to the induced strain ‐ elastic deformation. When the applied stress exceeds the elastic region, plastic deformation takes place. In this case, the applied stress is no longer proportional to the strain. This paper presents the nonlinear analysis of steel structures. The results show that the lower bound of the plastic limit state can be determined according to the internal forces. When the loads increases, the plastic deformation will appear on the lower and upper edges at one or several nodes of the steel plate. The plastic deformation is developed in the steel plate until completely perfected. The load at that time is lower bound of the plastic limit state.