Series method for analyzing 3D nonlinear torsional divergence of suspension bridges

A simplified method for analyzing 3D nonlinear torsional divergence of suspension bridges is proposed in this paper. The geometric nonlinearity in the deflection theory and the three components of displacement-dependent wind loads are taken into account in the method. This method is a two-step process: the calculation of deflection response under the displacement-dependent wind loads, and the calculation of the critical wind velocity. The response under the displacement-dependent wind loads is calculated from Fourier series. The critical wind velocity is calculated by means of an iterative method. It is found that a small number of iteration cycles and Fourier coefficients are sufficient enough for convergence. The advantages of the proposed method are showed by a comparing the numerical results of this method with those obtained from the linear method and nonlinear finite element methods.