SIMPLE FINITE ELEMENTS FOR NONLINEAR （简单的非线性有限元素）.pdfVIP

SIMPLE FINITE ELEMENTS FOR NONLINEAR ANALYSIS OF FRAMED STRUCTURES Reijo KoUHIA Rakenteiden Mekanii :ka, Vol. 23 No 4 1990, s. 3 - 49 SUMMARY: In this study a finite element method for both geometrically an Q materially nonlinear analyses of space frames is developed. Beams with both soliQ and thin- walled open cross-sections have been considered. The equations of equilibri~m have b een formulated using an updated incremental Lagrangian description. Ih e elements developed can undergo large displacements and rotations, but the incremen t .a l rotations are assumed to be small. The material models adopted are elasto-plastic, t e mperature dependent elasto-plastic and visco-plastic models with special reference to J.netals. Also computationally more economical formulations based on the relationship b e t ween stress resultants and generalized strain quantities have been presented. In the case of thin- walled beams the torsional behaviour is modelled u sing a two parametric d eplanation model, where the angle of twist and its derivative have independent appr oximations . This approach yields the average warping shear strai n s directly from the di splacement assumptions and no discrepancy between stress and strain fields exists. INTRODUCTION Frames are common load carrying systems in engineering constructions . E ffective use of high strength materials and the tendency to optimazed constructions re sult in thin and slender st ru ctures. Due to the slenderness and increased imperfection sensitiYi ty the stability problems become