The buffeting theory [1] refers to the computation of the response of a structure to wind turbulence. Here, the structure is a suspension bridge, modeled using the theory of continuous beam. The frequency domain approach is used. No modal coupling is introduced. The present scr ipt computes the lateral, vertical and torsional response. A multi-modes approach is used. This scr ipt is designed for those who already have some knowledge in the field of random vibration analysis. The present scr ipt is a simplified version of the one used in [2], on a real bridge.