Lateral Buckling Finite Element Geometric Nonlinear Analysis Of WF-section Composite Beam Stiffened With CFRP

With the development of economic and scientific technology, the big-span structure is applied to various structures more and more. The bending rigidity and torsion rigidity of the big-span structures are relatively weak, because of their long spans. Especially when a concentrated load applied on the big-span structure, it will become instability because the structure has large bending and distortion. So, many scholars and engineers start to pay attention to this subject. Some structures' local or global stability cannot be guaranteed, because of wearing out with design and operation or being old, and so on. Pushing them over and rebuild will cause a very large economic loss. With abroad application of CFRP material in engineering in recent years, adopting CFRP material to strengthen structural in order to enhancing structural lateral torsional stability becomes the concerned subject too.In recent years, numerous domestic and international scholars do deep research on structures which stiffened with CFRP material and thin wall pole lateral torsional buckling which were applied with vertical loads. But studying fewer of lateral torsional bucking stability for thin wall pole structure which stiffened with CFRP material So, this thesis tries to do some lateral torsional buckling finite element analysis of WF section composite beam stiffened with CFRP strip.Stability is a kind of state. Structural instability failure is unexpected collapse of structural inner forces. The failure mode is more dangerous than the intensity failure. There are many types of structures instability failure. When vertical loads applied to a straight beam, the structure will have large bending and torsion and lose steady, this phenomenon is called lateral torsion buckling. The lateral torsional buckling of straight beam is bifurcate instability, the bifurcate load called critical load and it can be calculated due to the double characteristic of structural equilibrium state.In this thesis, the Updated Lagrange Formulation has been established and lateral torsional buckling analysis with geometrical nonlinear finite element to the one span and two spans WF-section composite beams stiffened with CFRP strip have been done. Adopting structures buckling eigenvalue to predict its academic bucking load,and then analyze structural deformation in the whole course with New-Rapson and try to get the bucking critical load. Through the lateral torsion buckling linear eigenvalue analysis and non-linear lateral torsional buckling finite element analysis to the single span and tow spans WF-section composite beam stiffened with CFRP strip which were applied with a concentrated force at the mid-span, we can included: First, the structures loss stability because its lateral torsion distortion;and second, the structural critical buckling load has been improved greatly if CFRP strip bonded to the top and bottom flange or bonded to the top flange at the mid-span;and last, the structural critical bucking load is related to the CFRP length, the CFRP strip width, the CFRP strip thickness and the CFRP strip location.