Dynamic Characteristics Studies of an Ultra-long Suspension Bridge

This paper presents the experimental and analytical modal analysis of a two-span continuous steel box girder suspension bridge with a main span of 1650 meter. The field ambient vibration tests are carried out and the dynamic characteristics below 1.0Hz are identified using two output-only identification methods: the enhanced frequency domain decomposition and the stochastic subspace parameter identification. A 3-D FE modelling gives the analytical modal properties, which are then compared with those obtained from the experiments. A good correlation in the dynamic characteristics between the FE and the experiments verifies some assumptions involved in the structural design as well as in the dynamic analysis. Furthermore, vortex-induced vibrations are found and recorded during the construction of the bridge and the damping rations of the dominant modes are estimated using the decay of the responses.