Simplified prediction of wind-induced response and stability limit of slender long-span suspension bridges, based on modified quasi-steady theory: A case study

The Hardanger Bridge is currently under construction in Norway. It will have a main span of 1310 m and a girder that is only 18.3 m wide, which implies that wind-induced vibration is a major concern in the design. Buffeting response and flutter analysis of the Hardanger Bridge are treated in this paper. The self-excited forces are modelled using aerodynamic derivatives obtained from free vibration tests, quasi-steady theory, and a suggested modified quasi-steady theory. The stability limit predicted using aerodynamic derivatives corresponded well with the wind tunnel results, while the quasi-steady theory severely underestimated the critical mean wind velocity for the section model used in the wind tunnel tests. A new set of modified quasi-steady coefficients are suggested, where the experimental results of the aerodynamic derivatives are used to obtain frequency-independent model coefficients. The critical velocities predicted by the modified quasi-steady coefficients differ only by 4-5% from estimates based on the aerodynamic derivatives. The response predicted by the suggested simplified aerodynamic model is also presented, and the results indicate that adequate estimates are achieved.