Abstract:
Over the last decade the world has seen three major tsunamis strike the coasts of
Indonesia, Samoa, and Chile. These tsunamis have caused significant losses of life and
property on the coastal cities of these and nearby countries. The NEES (Network for
Earthquake Engineering Simulation) Housesmash project was created to look at some of
the specific effects of the inundation phase of a tsunami. Specifically the Housesmash2
project, which was conducted at the O.H. Hinsdale Wave Lab at Oregon State University,
looked at several different hazards and mitigation techniques for tsunami resilient design.
Some of the research from this project will be presented in the following two
manuscripts, each based on a small part of the project.
The first manuscript looks at the effect of small finite width engineered seawalls
which can be used as a mitigation technique to reduce tsunami induced loads such as
hydrodynamic drag by deflecting the incoming water over and/or around the wall, thus
reducing the bore energy. In this experiment 5 unique wall heights, cross shore locations,
and wave heights were systematically varied to determine the effects of each. From this,
the most and least important factors can be determined, which will help to design walls
that are the most efficient in reducing tsunami loads. The tests showed that seawalls can
substantially reduce the hydrodynamic loads, a reduction factor as big as 0.1(90%
reduction) was observed during testing. These results agree very well with published
field reconnaissance reports from the 2004 Sumatra tsunami. To make this research
useful for design engineers, equations were developed to predict the reduction in
hydrodynamic load on a structure. These equations use the offshore wave size, bore
height, wall height, and location to determine the reduction factor.
The second manuscript looks at the potently catastrophic effects of debris impact,
specifically impact from shipping containers. For this experiment 1:25 scaled shipping
containers were built to 7 different weights corresponding to 45% to 112% of scaled
weight of the ISO (International Organization for Standardization) legal limit of
30,400kg. During this experiment the mass, cross-shore starting location, starting
orientation, and offshore wave height were varied to better understand the effects of each.
Impact forces were recorded on a 1:25 scale model of a proposed tsunami evacuation
facility with open columns on the ground level. The containers were tracked as they
traversed across the beach and impacted the structure using newly developed optical
methods. Several published methods of predicting impact forces were tested against the
experimental data showing the accuracy of each. In addition new methods for predicting
impact forces are proposed based off of further analysis of the data set recorded.
