Tsunami Loadings on Structures: Review and Analysis

Abstract

The 2011 Great East Japan Tsunami has altered our traditional concepts for estimating loadings on structures. Prior to this event, we generally understood that reinforced concrete structures -those often used for critical coastal facilities -could withstand tsunami actions. This is no longer the case. Many concrete buildings and coastal protective structures (seawalls, coastal dykes and the like) failed due to the 2011 Tsunami. In this paper, the existing design guidelines are reviewed. We point out that some of the force-estimation methods recommended in the guidelines are rational, while others are not. Then we introduce a methodology to evaluate building's global stability emphasizing the effect of buoyant force. Buoyancy reduces the net structural body force; thereby reducing the restoring forces to resist sliding and overturning failures. Buoyancy force is an upward pressure force under the building, which is caused by an increase of pore-water pressure in the soil by excess water weight on the ground surface; therefore it takes a finite time to build up. We demonstrate that the effect of buoyancy force depends on 1) duration and depth of tsunami inundation, and 2) burial depth of the building. We also note that if and when a building interior is flooded (due to breakaway walls or windows), the flooded water increases the effective body force (weight); hence producing a stabilizing effect. Example calculations are given to demonstrate the importance of the delayed action of buoyancy force and breakaway walls and windows.

Implementation of Tsunami Evacuation Maps at Setubal Municipality, Portugal

“…A study focused only on the tsunami vulnerability in the Setubal urban area [52] showed that the 1755 tsunami would potentially affect 481 buildings and 923 residents (equivalent to about 0.8% of the total for the municipality [52]). An author [53] presented new formulas to include damage on the buildings; however, that was not considered in this research. Still, the tsunami vulnerability study [52] showed that there are two buildings in the moderate vulnerability class, 26 in the low vulnerability class, and 453 buildings in the very low vulnerability class.…”

Performance-Based Tsunami Engineering via a Web-Based GIS Data Explorer

“…momentum flux), Max (hq 2 ), and the maximum overturning moment Max (h 2 q 2 ). Further, the time history of flow conditions allows us to estimate impact forces of floating debris, as well as buoyancy forces and scour effects [7]. Quick access to the time-series data in this direct fashion makes it possible to analyze many hazard scenarios, important since each scenario has some probability of occurrence.…”

“…The accelerating rate of construction of critical infrastructure in coastal zones requires a better understanding of design methodology for tsunami-resistant structures. To analyze the performance of buildings and infrastructures in a tsunami scenario, it is necessary to know not only the maximum runup heights and inundation zone, but also the time histories of flow depth and velocities at a location of interest within the inundation zone in order to evaluate tsunami-induced forces, moments, soil instabilities, and buoyancy forces [7]. Time series data required for analysis of buildings and infrastructures are much more difficult to compute than the relatively straightforward determination of maximum inundation limit, further complicating the process and often necessitating high performance computing resources [8].…”

Modelling of tsunami-induced bore and structure interaction

“…Note that in the case of the immediate impact on the structure, no additional force is applied -for example, drag force. The hydrodynamic 'drag' forces indeed occur in real tsunami events (Yeh et al, 2014) and these affect the structure when surrounded by a 'steady' fluid flow with relatively constant velocity (FEMA, 2011). However, in this simulation, the hydrodynamic drag was not so significant ( Figure 14) due to the application of a single stroke solitary wave where the most dominant effect was the highly transient impulsive pressure immediately following the impact of the leading edge of the arriving water mass.…”