Narrow Results

The force from a tsunami will damage buildings, such as houses, bridges, and many other coastal infrastructures. The impact and drag force of a tsunami depend on the scale and the characteristics of the tsunami as well as the infrastructures' characteristics.

This study was conducted using physical modeling to determine the effect of openings and protection on buildings to reduce the effects of a tsunami attack. The openings were symmetrical about the front and rear walls and were oriented in the direction of the tsunami. Barriers with dimensions that were the same width and three times higher than the building and of various lengths were used to simulate protection against a tsunami.

The results indicated that the force on the buildings depends on but is not linearly correlated to the opening. The barrier upstream of the building significantly reduced the force depending on its distance to the building and the surge Froude number; however, the openings still play an important role in reducing the force on a protected building. Simple equations for practical use are proposed to calculate the tsunami force on a building with openings with or without protection.

Compared with circular, square and diamond piers, the N60 pier proposed in our previous study has been numerically proven to be effective in reducing tsunami force. The relatively stronger vortices behind the N60 pier are responsible for the not-small-enough tsunami force on the N60 pier. The asymmetry in shape makes the N60 pier fail to reduce flood force because flood propagates in the opposite direction of tsunami bore. A series of new type piers named $\mathrm{\text{N}}\alpha -\beta$ are proposed to further improve the anti-tsunami ability of the N60 by computational fluid dynamics (CFD) method among which the N60-60 pier is proven to be most effective in reducing tsunami force, and its tsunami force mitigation mechanism is analyzed numerically. Further, the physical experiments were conducted to validate the N60 pier and the new type pier N60-60. Results show that compared with circular, square and diamond piers, the N60 pier is indeed capable of reducing tsunami force, and compared with the N60 pier, the new type N60-60 pier is capable of further reducing tsunami force. The order of magnitudes of tsunami forces on piers is: N60-60 $<$ N60 $<$ circular $<$ diamond $<$ square.

Tsunami caused by Tohoku earthquake in 2011 had flooded many oil storage tanks, and these tanks brought many secondary damages on coastal area by fires. In order to reduce those secondary damages, an idea of using a mooring line to check the drift of the oil storage tank was proposed. This research examines an effective mooring system that restrains the motion of a floating tank in tsunami flow. A series of hydraulic experiments were carried out under some different mooring conditions in order to discuss the characteristics of tank motion. Furthermore, this study discusses the characteristics of a drag coefficient to obtain an equation to estimate the fluid force on a semi-immersed cylindrical tank.