Nozomi KENMOTSU
The Analytical Examination of the Tsunami Fluid Power of Acting on a Bridg
Kyuichi MARUYAMA and Yasushi TANAKA
The 2011 off the Pacific coast of Tohoku Earthquake on March 11 is an earthquake of the largest scale in the earthquake observed in Japan. The outflow of the bridge which is a kind of the material damage caused by this earthquake interfered with traffic of the vehicles for rescue or support, and made damage expand.It is predicted that Tokai, Nankai, Tonankai Consolidated Type Earthquake is generated in future.Because the problem like this is worried about by the earthquake, the solution to this problem becomes the urgent business.A lot of experiment and analysis about the bore have been performed, but there is the bridge to fall into even if a bore does not arrive at it.
Therefore it is necessary to examine the wave force to act on a bridge by a flow to elucidate the damage mechanism of the bridge. Therefore a purpose of this study is to analyze a fluid power of a tsunami acting on a bridge using fluid analysis.Furthermore, experiment on the flow, and compare the result of the experiment with the analysis; and of the validity of the fluid analysis examine.
At first I experimented on the flow on a condition same as analysis, but was not able to confirm the quantitative agreement with the analysis. However , I judged that there was validity of the fluid analysis because relations of speed and drag or lift accorded with analysis qualitatively .
And, about the influence by changing a condition in steady flow, I inspected it by fluid analysis. As a result, drag increased when inflow speed increased. On the other hand, when inflow speed increased, minus lift increased, but it was confirmed that ,lift decreased when inflow speed exceeded 4.6m/s. In addition, it was revealed that it was a result unlike the true phenomenon when I considered these damage forms.Therefore I examined a change of the wave force when water level increased over time. As a result, it was confirmed that drag decreased with increase in water level gently more, and ,lift suddenly increased. Furthermore, the rotary movement of the bridge girder occurs when water level continues rising at 0.05m/sThis does not have a true phenomenon and a difference.
According to the above results, water level increased at 0.055m/s, and the damage like the true phenomenon occurred when the inflow depth of the water became more than 11.62m.
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