Abstract:

The wind loads on the main arch of a long-span half-through arch bridge interfere with each other, and the buffeting response is in a coupled multimode. In this paper, based on the inherent modal coordinates of the structure, the nodal equivalent aerodynamic buffeting forces of the bridge are formularized by considering the wind speed varying with the main-arch height. Then, the spatial coherence of the disturbed wind spectrum of the main arch and the natural wind loads, as well as the multimode coupling of the responses of the main bridge and the main arch, is taken into consideration, and the coupled buffeting of the long-span half-through arch bridge in frequency domain is analyzed via the finite element method. Finally, with the Caiyuanba Yangtze River Bridge in Chongqing as an illustrative example, the power spectrum density and variance response of both nodal displacements and pulsed elemental internal forces of the bridge are obtained. The results show that  the high-order mode greatly affects the buffeting response of the long-span half-through arch bridge;  for such types of large-span half- through arch bridges, the horizontal and vertical pulsed wind-speed power spectra play an important role in the buffeting response, while the cross power spectrum of fluctuating wind can be ignored ; and  the CQC method con- siders the effects of multi-modal and modal coupling much better than the SRSS method.

Key words: arch bridge, aerodynamic coupling, buffeting response, finite element method