EK429

The plastic design method is based on the following assumptions:

• The material has the capacity to undergo considerable plastic deformation without danger of fracture.
• Ductility of steel (that is, a long yield plateau) is important for the development of plastic zones (plastic hinges).
• Rigid connections must be proportioned for full continuity and must be able to transmit the calculated plastic moment.
• No instability (buckling) must occur prior to the formation of a sufficient number of plastic hinges, to transform the structure into a mechanism.
• The ratio between the magnitudes of different loads remains constant from the formation of the first plastic hinge to the attainment of the mechanism.
• Frame deformations are small enough to be neglected in the analysis.