Research On The Stability Of The Steel Member Wrapped By Carbon Fibre Under Axial Compressive Load And Bending Moment

Modern buildings advocate taking advantage of the green building materials, so the steel structural is used extensively. The failure modes of many members subjected to axial compressive forces and bending moments in steel structure are intensity or stability damage, the latter of which is the most interesting question concerned by people. Generally these problems are solved by some numerical methods. To deal with the above-mentioned problem, the analytical method will be sought when the section of component and force bearing status are both simple.Based on analytical ideas of computing elastic-plastic buckling of member under the axial compressive loads and bending moments, the analytical expressions of calculating the ultimate load of buckling about neutral axis with maximum moments of inertia for the H-shaped, the square/rectangular hollow section steel member with/without flange outsides wrapped by the carbon fibre and circular steel tube without/with outsides wrapped by the carbon fibre are derived in this paper. Furthermore, the results of the finite element are provided.In the calculating, the two situations of buckling in the compression side and in the both compression and tension sides of the steel member with pinned-pinned ends is discussed. Furthermore, the situation of yield region varying in the flanges or webs is considered respectively for the H-shaped, the square/rectangular hollow section steel member. For the thinness wall of the circular steel tube, the change of the plastic region along the wall thickness is no longer considered.Subsequently the analytical expressions of calculating the ultimate load of buckling about neutral axis with maximum moments of inertia for the H-shaped steel member with the initial geometrical defects whose flange outsides wrapped by the carbon fibre, subjected the axial compressive loads and bending moments, are formulated. The reinforcing effect of the member with the initial geometric defects and the perfect member by the carbon fibre is investigated. Given the both ends the different bending moments, the comparison study of the ultimate load of the member wrapped by the carbon fibre with initial geometrical defects and perfect member is presented. It is difficult to get the analytical solution of stability problem with the effect of the initial residual stress. By using the finite element method to solve the buckling of the H-shaped steel member with the pined-pined ends and with the initial residual stress, the discipline of the bending moments change with the ultimate load is discussed. Specially, the reinforced effect of the composite material with the larger bending moments is presented.By giving some parameters such as the ultimate load and the thickness of the elastic core, the curves of the bending moments versus the ultimate loads for buckling of the H-shaped steel member with the different slenderness ratios are in good agreement with the results obtained by the steel structural design codes. Then, the corresponding relationship curves of the bending moments versus the ultimate loads for the H-shaped steel member wrapped by carbon fibre are presented, and practical simplified formula of the ultimate load is obtained. To prove the simplified formula accuracy and provide the reference for the engineering design, the relationship curves of the bending moments versus the ultimate loads for the H-shaped steel member wrapped by carbon fibre before and after with the different sections size are enumerated respectively.Under the different ends bending moments, the nonlinear dynamic buckling analysis of the H-shaped steel member reinforced by the carbon fibre before and after, subjected by impact load and cyclic load, is given. Then, the ultimate load of the member under impact load and the cyclic horizontal ultimate load under cyclic load are obtained respectively. Finally, the effects of the boundary condition, the thickness of the carbon fibre and the Elastic modulus on the H-shaped steel member under dynamic load is discussed.