The paper presents a new beam-column element that combines computational efficiency with accuracy. The element uses only one monitoring section in each end inelastic zone of the structural member, but accounts for the spread of inelastic deformations under strain hardening response. It is, therefore, a variable inelastic zone model that combines the benefit of integrating the section moment-curvature response with the computational efficiency of concentrated hinge models for beams and columns. The element is more accurate than current distributed inelasticity models in simulating the monotonic and cyclic inelastic response of beams and columns under typical curvature distributions, while being much more cost effective. The element is also suitable for softening response, as long as a relation is available between the length of the softening zone and element response parameters.

In this paper, we have developed a half-space Peierls—Nabarro (HSPN) model to evaluate dislocation mobility on material surface. The free-surface induced size effect on the mobility of an edge dislocation in thin films is investigated by using the model. The thickness of the thin layer between the dislocation and the free surface significantly influences the mobility of the dislocation. The Peierls stress of the edge dislocation in a thin film may be expressed as a function of the thickness of the thin film. A closed-form solution is obtained for the scaling factor, defined as the ratio of the modified Peierls stress to the conventional one in bulk materials, which allows for the characterization of the size (depth) effect on the Peierls stress of the edge dislocation in the half-space. Depending on the core size of the dislocation, the Peierls stress of a surface edge dislocation is about 5% to 25% less than that found in bulk materials.