Revisit the Tsunami Hydrodynamic Force on the Front Face of Onshore Structure

Abstract

Great tsunamis passing through structures in some cases cause structural damage by the hydrodynamic force. Although there are many empirical methods to estimate hydrodynamic force which are expressed with a function of flow depth, flow velocity or Froude number, the predicted hydrodynamic forces exhibit considerable scatter. In order to investigate the characteristics of the hydrodynamic force acting on the front face of a structure and propose the prediction method of the hydrodynamic force induced by a tsunami, we have carried out three dimensional numerical simulations of tsunami passing a structure.

Large-scale experiments on tsunami-induced pressure on a vertical tide wall

“…The run-up force is observed during the transition between the impulsive and quasi-steady hydrodynamic forces and occurs due to the effects of the flipped water mass resulting from the bore impact. In a series of numerical studies (Kihara et al, 2012;Takabatake and Kihara, 2014;Takabatake et al, 2013), we have also observed the three-phase pressure pattern exerted on structures. A local maximum pressure was observed during the transition between the impulsive and quasi-steady phases, and we presumed that this local maximum pressure is caused by convergence of the upward flow accelerated by the continuous burst of the incident flow in low areas on the wall and the downward flow accelerated by gravity in high areas.…”

“…Bredmose et al (2009) referred to this pressure as "reflective pressure." In a series of numerical studies (Kihara et al, 2012;Takabatake and Kihara, 2014;Takabatake et al, 2013), we observed that a local high pressure occurred in this phase. We suggested that this local high pressure was caused by the convergence of upward flow, accelerated by the continuous burst of the incident flow in low areas, and downward flow, accelerated by gravity at high areas on the wall.…”

“…For all six cases, the period of the flow was approximately 90 s. As shown in early studies (e.g., Fukui et al, 1963;Takabatake and Kihara, 2014), the pressures exerted on a tide wall are affected by the characteristics/conditions of both bore and continuous flow. The conditions of the bore which relate to the pressures would be the traveling speed, the height, and the slope of the water surface of the bore.…”

“…Early studies showed that the pressure distribution on the wall is approximately hydrostatic in form when the flow reaches a quasi-steady state (e.g., Palermo et al, 2009Palermo et al, , 2013Takabatake and Kihara, 2014). As shown in Figs.…”

Large-scale experiments on tsunami inundation and overtopping forces at vertical sea walls

“…This three phase time history is observed experimentally by Nouri et al (2010), Palermo et al (2013), Kihara et al (2015) and numerically by Takabatake and Kihara (2014). Kihara et al (2015) examine the impulsive, intermediate and quasistatic phases of tsunami loading on a wall in the laboratory.…”