Damage pattern and damage progression on breakwater roundheads under multidirectional waves

Abstract

An experimental model test study is carried out to investigate damage pattern and
\nprogression on a rock armoured breakwater roundhead subjected to multidirectional waves.
\nConcerning damage pattern, the most critical sector is observed to shift leeward with increasing wave
\nperiod. Taking angles relative to mean wave direction, the critical sector is observed in the sector 10°-
\n55° for short waves and in the sector 100°-145° for long waves. A probabilistic approach is developed
\nto predict for one typical roundhead geometry the damage distribution depending on the incoming
\nwaves and structural characteristics. The damage progression is observed dependent on significant
\nwave height and peak wave period, but not on the directional spreading and the spectral width of the
\nincident waves. Combining the results of both damage pattern and damage progression, a stability
\nformula for the distribution of damage over the roundhead is developed. Thus the formula also
\nconsiders the shifting of the critical sector due to increasing wave period which existing formulae do
\nnot include. Finally, analysing the damage produced by double peaked spectra, it is shown that the
\narmour may be designed by the formula when using the total significant wave height and an equivalent
\npeak period.