Abstract: A mathematical model for calculating the vertical displacement and bending moment of a long floating bridge under moving load is established based on the elastic foundation beam theory. On this basis, according to the displacement reciprocity theorem and the influence line theory, the calculation method of floating bridge with the longitudinal connection gaps under moving load is deduced and proved by introducing the concepts of gap angle and angle influence line. The method can be used to calculate the displacement and force of floating bridges with longitudinal connection gaps under moving load. The results indicate that the increase in connection gaps leads to the increase in draft of floating bridge. At the same time, the bending moment of bridge span and the force at the connection decrease. With the increase in load moving speed, the maximum draft and the connection force will increase. The influences of longitudinal connection gaps and load velocity on the deformation and force of floating bridge structure can not be ignored. The reasonable connection gaps are very important to optimize the structure of floating bridge. In the process of passing floating bridge, the vehicles must pass at a limited speed and load to ensure the safety. The calculated results have good consistency compared with the numerically calculated and model test results in Ref.［16］.

Key words: floatingbridge, elasticfoundationbeam, influenceline, connectiongap, movingload