Abstract: A multi-support motion generation program was developed in Fortran based on the power spectrum input according to harmonic composition method. Shanghai Minpu Bridge, which is the longest double-deck long-span highway cable-stayed bridge, was taken as example to study the seismic response of the bridge under multi-support excitations. A fine finite element model with beams and shells was built on the basis of platform Abaqus. The eigenvalue analysis and the time history analysis under nonlinear multi-support excitations were performed based on the geometrical nonlinear static analysis to get the dynamic characteristics as well as the variations of the internal forces in the main towers and the subsidiary piers and the axial forces of the web members (vertical, oblique and squint web members). The results show that the lateral shear force in the pier column below the subsidiary pier beam distribute uniformly. It increases with the distance from the main tower, so does the lateral moment. The axial forces of the web members of side span between upper and lower decks vary significantly, especially the vertical and oblique members near the pier top. The axial forces in the squint web members are well distributed and those at the pier top and at the mid-span are relatively small. The axial forces in the vertical and oblique web members at mid-span are small, and those in the other web members vary little.

Key words: bridge engineering, double-deck cable-stayed bridge, multi-support excitations, seismic response, nonlinear time history analysis