ANALYTICAL SOLUTIONS ON ULTIMATE BEARING CAPACITY OF A SQUARE CFRP-STEEL TUBE MEMBER WITH INITIAL IMPERFECTION

Based on Ježek method for computing the elastic-plastic buckling of the member under axial compressive loads and the bending moments, and considering the initial imperfection, the analytical expressions are derived for calculating the ultimate load of buckling about the neutral axis with the maximum moment of inertia for a square steel tube member with flange outsides wrapped by carbon fibre. Using the elastic-plastic finite element method and the theory of nonlinear buckling, the impact by initial geometric imperfections on the square steel tube member wrapped by carbon fibre is analyzed and the numerical solutions for ultimate bearing capacity are obtained. By comparing with the values of the finite element method (FEM), it shows that the analytical method proposed is valid. The calculation results show that when the value of moment is given, only the ultimate bearing capacity of the member reinforced by the carbon fiber among the three member always keeps a higher figure. When the given moment is small, the ultimate bearing capacity of a bare steel member is higher than that of a steel member reinforced by the carbon fiber with the initial geometric imperfection. When the value of the bending moment increases gradually, the ultimate bearing capacity of the former reduces faster than the latter.