Buffeting Response Analysis Of Large Span Cable-Stayed Bridges For Largest Single Cantilever Stage

The issue of wind induced vibrations of long span bridges has become one of the main dominating factors in design due to the longer span and higher flexibility. Among the various vibrations buffeting response, a forced random vibration excited by turbulence flow, is the objective of this paper. The buffeting could be excited in any wind speed, though it could not induced the instability collapse such as flutter, the comparatively large buffeting responses may cause safety and comfort of vehicles and pedestrians and may cause the structure damage due to fatigue. In erection state, the buffeting with large amplitude also needs to be controlled in order to secure the personnel and equipments from danger. Therefore, bridge buffeting responses have drawn more attention and in this way have become one of the primary research topics.Based on a long span cable-stayed bridge, the linear buffeting analysis for single largest cantilever erection stage is conducted and the following contents are included:1. According to the characteristics of the cable-stayed bridge and natural wind field, feasibility analysis of three-dimensional fluctuating wind field simplification is conducted by simplifying the three-dimensional gusty wind field into multiple single dimensional gusty wind fields and compiling simulation program using harmonic synthesis method.2. The time domain transformations are conducted for buffeting loadings caused by static wind and gusty wind. The calculating of buffeting forces is achieved by quasi-steady aerodynamic model proposed by Scanlan while considering the influence of aerodynamic admittance. Established the largest single cantilever construction stage structure of the equation of motion and Newmark method which belongs to direction integral method, the solving program is established.3. The linear buffeting analysis in time domain for a cable-stayed bridge in single largest cantilever erection stage and the influence of aerodynamic admittance to the results are conducted. Based on this, a comparison is made with results obtained in the wind tunnel tests and thus the precision of the calculating results could be verified.4. A conclusion is made and some items that should be noticed, short comings, and the issues to be solved are discussed.