There seems to be many situations where an inelastic analysis needs to be performed on a frame structure. In the last decades, the subject has received much interest from many researchers, especially for seismic applications. Different models have been proposed for the frame element to represent its inelastic behavior, among which, the one component models with inelastic springs are widely used. In such models, each frame member is represented by an elastic element, with several nonlinear springs, mostly located at the ends of the element. These models suffer several deficiencies, mentioned in the context. To overcome such deficiencies, a new approach is suggested for the construction of inelastic stiffness matrix of the frame element. In the proposed method, some virtual inelastic springs are attached to the elastic element. Such springs model plasticity in the strain states beyond the rigid body modes of the element. The stiffness matrix of the frame element, obtained through this procedure, is compared with the conventional ones for its priority.

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