On-site wave-wind observation and spectral investigation of dynamic behaviors for sea-crossing bridge during tropical cyclone

Abstract

The dynamic behaviors of a sea-crossing bridge during a tropical cyclone event which passed through the bridge site in September 2015 are simulated using in-situ observation wave and wind data. The hourly observation data during the cyclone event at the bridge site including averaged wind speed, turbulence intensity, direction, significant wave height, mean period, spectral variations are recorded. The wave and wind spectra are analyzed from raw data and are fed to a frequency-domain framework for response modeling. The stochastic wave actions considering foundation geometry, diffraction effect, wave coherence and second-order quadratic wave force transfer functions are considered using boundary element methods and the wind actions including buffeting loads, aerodynamic stiffness and damping are modeled based on stationary buffeting theory. Results reveal that the maximal structural response occurs near the cyclone eye wall while the storm center is still 80–100 km away but experiences sudden drop when the cyclone eye reaches the bridge site. Deck responses are much more sensitive to wind, but wave dominates the tower and base force responses. Second-order wave load is found to be critical to responses because the sum-frequency wave force could undesirably coincide with the bridge eigenfrequencies.