Assessment of random wave pressure on the construction cofferdam for sea-crossing bridges under tropical cyclone

Construction cofferdams for sea-crossing bridges can be damaged or even collapsed due to extreme wave loads under tropical cyclones. To enhance a better understanding of the random wave pressure on the cofferdam, wave gauges and pressure transducers were installed on a real cofferdam for sea-crossing bridge to measure the random wave pressure during Typhoon Dujuan in 2015. The first order diffraction theory was used to calculate the wave pressure numerically. The measured and numerical results were compared in the frequency domain and discussed in terms of pressure spectrum, pressure spectral characteristics, transfer function and maximum wave pressure. The main conclusions are: (1) the wave diffraction and water depth affect the dominant frequency range, zeroth moments and peak spectral value of wave pressure spectrums on the cofferdam; (2) the maximum wave pressure on the up-wave side of the cofferdam is up to 2.2 times that on the down-wave side; (3) the secondary peaks were observed in pressure spectrums under tropical cyclone; and (4) the numerical model based on the first order diffraction theory could not capture the secondary peaks and overestimate the wave pressure energy near the primary peak frequency.