ABSTRACT
The suspension bridge with separated girder and tower has characteristics of unequal height at the bottom of the towers, shorter girder’s length than the two towers span, setting the ground-anchored hangers and so on. Based on nine groups of spatial finite element models, the modal analysis of Aizhai Bridge is carried out from three aspects: boundary conditions for separation of girder and tower, ratio of suspension length to span, and installation of hangers anchored in ground. The structural dynamic behaviors are summarized and the influence of three factors on the structure performance is also established. Its seismic performance is analyzed through elastic and plastic time history analysis in longitudinal and transverse direction. The results of the analysis show that the change of the boundary conditions has a little influence on structure vibration modal and seismic load on tower, but it has a great influence on the lateral displacement of the girder in midspan. Ratio of suspension length to span has a great influence on the tower’s displacement and internal force, the girder’s bending behavior and torsion vibration, but it has a limited influence on the fundamental frequency and displacement of the main cable. The installation of ground-anchored hangers can improve the structure’s rigidity, and reduce the cable’s vibration obviously.
