Inelastic Response of Frames to Dynamic Loads

A procedure of analysis is presented for determining the elastic-inelastic response of framed structures under dynamic loads. Application of Hamilton's principle in conjunction with the finite-element method leads to the basic dynamical equations of the system incorporating the plastic effects in the form of equivalent nodal forces. This approach also allows the more accurate treatment of the distributed loads and the distributed mass of the element than the usual geometrical method of lumping. In order to take into account stress reversal and strain hardening effects, an incremental theory of plasticity is used and the history of deformation of the entire structure is followed through. The material of the structure is assumed to obey the Mises-Hencky yield criterion and the plastic flow is governed by the Reuss-Mises inelastic stress-strain relationship.