| It is well known that the correlation of span-wise distribution of fluctuating lift forces plays an important role on the gust response analysis in the frequency domain for horizontally long structures like long-span bridges. Generally speaking, it is difficult to measure the correlation property of the fluctuating lift force, the correlation of the approaching flow is used to replace that of the fluctuating lift force. However, recent researches point out that the correlation property of the lift force is not equal to that of the approaching flow, and the scale of the spatial correlation of the fluctuating lift force is much larger than that of the approaching flow fluctuations. While it had never been clarified why the correlation scale of the lift forces is larger than that of the approaching flow.Because of the complexity of the turbulence, it is difficult to analyze the influence of turbulence on fluctuating lift force. In this paper, a simplified method is put forward, that is to study the fluctuating lift force caused by one-point disturbance. It is found that the fluctuating lift force transmitted transversely from the original disturbance point.In this paper, a three dimensional mathematical transmission model of fluctuating pressures is put forward according to the fluctuating lift force model generated by one-point disturbance. Then it is simplified to a two dimensional model. As the transmission of the fluctuation lift forces are mutually independently, the fluctuating lift forces caused by successive disturbance of a same frequency at the same time are added to simulate the real fluctuating lift forces caused by turbulence. A new calculation method for the correlation of fluctuating lift force is put forward.The result of this paper is that when considering the second distribution of the lift force, the result of correlation of span-wise fluctuating lift forces according to the calculation method put forward in this paper fits that of the experimental result well.
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