Abstract
When the 2011 off the Pacific Coast of Tohoku Earthquake occurred, an associated tsunami struck the coastal area and a number of river structures were damaged. Two spans out of three of the Yanoura water-pipe bridge (Kamaishi city, Iwate Prefecture) were washed away by the tsunami. For prevention of important infrastructures such as water-pipe bridges, it is nessesary to reinforce them against tsunami. Therefore, detailed examination of tsunami attack on the Yanoura water-pipe is important. In this study, a vertical two-dimensional numerical simulation was applied to two longitudinal river profiles, focusing on the effect of the distance between the water-pipe and Yanoura road way bridge which is located just downstream of the water-pipe bridge. The results obtained in each case are compared in regard to horizontal forces, vertical forces and torque. According to the comparison, the effect of these forces upon the damage of water-pipe is discussed. As a result, it is suggested that an especially large torque contributed most considerably to the damage causing the water-pipe to be washed away. For verification of the results from 2D analysis, three-dimensional numerical simulation was also conducted. It is concluded that 2D analysis is sufficient to estimate the wave forces in each case.
