The free vibration characteristics of a multi-span high-pier bridge with variable cross-sections were studied.The equivalent cross-sectional area and moment of inertia of the variable section beam were calculated, and the piers were simplified as elastic supports.Based on the Euler-Bernoulli beam theory, an analysis model of multi-span high-pier bridge with several elastic supports was established.The reaction forces of the elastic supports were regarded as unknown external forces on the beam, and the natural frequencies and mode shapes of the beam were calculated.The calculation results were in good agreement with the finite element results.Finally, the influence of the change rate of the beam cross-section, the height of the pier on natural frequencies and mode shapes of the beam were analyzed.The results provide a scientific reference for the design of multi-span high-pier variable-section bridges.
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