Stochastic Seismic Response Analysis Of Long-span Six-pylon Cable-stayed Bridges

Recently, as the main span and the number of pylons are increasing, multi-pylon cable-stayed bridges have been rapidly developed. Meanwhile, strong earthquake ground motion activities occur more frequently. The seismic study of multi-pylon cable-stayed bridges has become an unavoidable problem. Now. for multi-pylon cable-stayed bridges, there are less seismic studies and none of current seismic codes is accommodated. By contrasting to the demerit of the deterministic seismic response analysis method, the paper makes use of power spectrum density method, applying appropriate ground motion semi-empirical model, to study multi-support multi-dimensional stationary stochastic seismic response of JiaShao River-crossing Bridge. The main study is as following:1. Firstly, the dynamic characteristics of six-pylon cable-stayed bridges are analyzed. Comparing to other double pylons and multi-pylon cable-stayed bridge, the results show that characteristics of supporting system, quality and rigidity of both pylon and beam, boundary conditions make contributions to the dynamic characteristics of multi-pylon cable-stayed bridges.2. While one-dimensional, two-dimensional, three-dimensional seismic actions are applied to the JiaShao Bridge, the results show that three-dimensional couplings is obvious in large-span multi-pylon cable-stayed bridge, the response of three-dimensional excitation gives greater impact on the Jiashao Bridge.3. After analyzing the influence of the spatial variability effects of ground motions (wave Passage effect, coherent effect, local site effect) upon the seismic response of large span six-pylon cable-stayed bridge, characteristics of these effects are summarized. Besides, the Paper gives the distinctive characteristics of seismic response upon long-span six-pylon cable-stayed bridge.The results show that while the long-span multi-support structures are applied to multi-support multi-dimensional stationary stochastic seismic action, it is necessary to take consideration of three-dimensional couplings and spatial variability effects of ground motions. Thus, the reliability of structure in anti-seismic design can be ensured from the sense of probability and statistics.