This study considers a wave impact load acting on a circular cylinder by breaking wave. The impact load due to breaking waves is not easy to measure due to large uncertainty in experiments. In this study, the impact load acting on the circular cylinder is measured by applying a breaking waves to a truncated circular cylinder. Force sensors and pressure sensors are applied to measure the impact loads with high sampling rates. Model test condition under steep wave is repeated 10 times and spilling and plunging wave tests are repeated 20 times. Based on the measured results and the high-speed camera images, the characteristics of impact load due to the breaking waves are discussed.
Severe impact loads damaging offshore structures can occur in heavy sea condition, and the wave impact load should be accurately evaluated for design of offshore platforms. Kjeldsen et al. (1986) reported that the impact load by breaking wave is relatively higher than an impact loads by general wave at the same wave height. The impact load due to the breaking wave should be estimated accurately, and model tests or analytic methods are applied to estimate it. Analytic methods were proposed by Von Karman (1929), Wagner (1932), Cointe (1989), and Goda et al. (1966). The slamming coefficient (Cs) and the curling factor (λ) were studied on the circular cylinder. Various model tests were performed because there is limitation of analytic methods which is mainly based on the potential flow and assumption of the slender circular cylinder. Irschik (2004) studied wave impact forces on the circular cylinder according to the inclined angles and the results of the model tests were compared with curling factors by Von Karman (1929), Wagner (1932), Cointe (1989) and Goda et al. (1966). Wienke and Oumeraci (2005) performed the experiment in a large wave channel and they summarized characteristics of impact force according to the shapes of incoming waves. Navaratnam et al. (2013) and Aashamar (2012) measured wave slamming forces on a jacket platform and compared them with analytic solutions of Wienke and Oumeraci (2005). Also, Navaratnam et al. (2013) and Aashamar (2012), Sawaragi and Nochino (1984) and Ros (2011) presented the scale effect of the slamming forces by model tests.