A kinematically exact finite element formulation of planar elastic - plastic frames A finite element formulation of finite deformation static analysis of plane elastic-plastic frames subjected to static loads is presented, in which the only function to be interpolated is the rotation of the centroid axis of the beam. One of the advantages of such a formulation is that the problem of the field-consistency does not arise. Exact non-linear kinematic relationships of the finite-strain beam theory are used, which assume the Bernoulli hypothesis of plane cross-sections. Finite displacements and rotations as well as finite extensional and bending strains are accounted for. The effects of shear strains and non-conservative loads are at present neglected, yet they can simply be incorporated in the formulation. Because the potential energy of internal forces does not exist with elastic-plastic material, the principle of virtual work is introduced as the basis of the finite element formulation. A generalized principle of virtual work is proposed in which the displacements, rotation, extensional and bending strains, and the Lagrangian multipliers are independent variables. By exploiting the special structure of the equations of the problem, the displacements, the strains and the multipliers are eliminated from the generalized principle of virtual work. A novel principle is obtained in which the rotation becomes the only function to be approximated in its finite element implementation. It is shown that (N-1)-point numerical integration must be employed in conjunction with N-node interpolation polynomials for the rotation, and the Lobatto rule is recommended. Regarding the integration over the cross-section, it is demonstrated by numerical examples that, due to discontinuous integrands, no integration order defined as `computationally efficient yet accurate enough' could be suggested. The theoretical findings and a nice performance of the derived finite elements are illustrated by numerical examples. 1997 2015-07-10 10:12:13 1033 plane frame, exact kinematics, plasticity, generalized principle of virtual work, finite elements ravninski okvir, točna kinematika, posplošeni princip virtualnega dela, plastičnost, končni elementi Elsevier Miran Saje 70 Igor Planinc 70 Goran Turk 70 Blaž Vratanar 70 UDK 4 519.61/.64:531.1:539.374 ISSN pri članku 9 0045-7825 DOI 15 10.1016/S0045-7825(96)01172-3 COBISS_ID 3 163169 OceCobissID 13 6695685 0 Predstavitvena datoteka 2015-07-10 10:12:14 CMAME_1997_.pdf 417767 Predstavitvena datoteka 2016-06-15 08:15:07