Buffeting response of long-span cable-supported bridges under skew winds: Field measurement and analysis.

摘要

This dissertation mainly focuses on the development and verification of a modified frequency-domain method for buffeting analysis and the understanding of buffeting behavior of long span cable-supported bridges under skew winds, supported by a series of wind tunnel tests and field measurements.; The field measurement data of the Tsing Ma Bridge recorded during Typhoon Victor are analyzed for both wind structure and bridge response. It is demonstrated that for a long span cable-supported bridge located in a complicated terrain, typhoon-induced winds seldom attack the bridge at a right angle. Important wind characteristics such as mean wind speed and turbulence intensity vary along the bridge span.; To consider skew wind effects, a modified buffeting analysis method of long span bridges is developed in this dissertation based on the quasi-steady linear theory and the aerodynamic oblique strip theory in conjunction with the pseudo excitation method and finite element method. The modified method can naturally take into account the effects of inter-modes, multi-modes, and spatial modes as well as the interaction between bridge components.; To implement the modified method for buffeting analysis of a long span bridge, the six component aerodynamic coefficients, the flutter derivatives for a oblique strip of the bridge deck, and the aerodynamic coefficients of the bridge tower components are measured under skew wind conditions using specially developed wind tunnel rigs and techniques.; The comparison of buffeting responses of the Tsing Ma Bridge during Typhoon Sam is then conducted between the field and computation, and the comparison is found to be satisfactory in general.; It is also found through an extensive parametric study that the variation of bridge buffeting response is not monotonous with wind yaw and inclination. The maximum response may not occur in normal wind case. The influences of aerodynamic crosswind force, yawing and rolling moments on bridge response are rather small whereas the effects of flutter derivatives may be significant.