I need a few sources of material that a middle school student could
access and understand as she researches how bridges are built to
withstand tsunamis. Could you find a few articles for me? Also,
anything that references the Golden Gate
bridge in this context would be very helpful.Dear coomer-ga;
Thank you for allowing me to answer your interesting question. Let me
address the second part of your question first and get that out of the
way.
In 1937 when the Golden Gate Bridge was completed there was very
little in the way of tsunami research. At that time the greatest
challenges of building the bridge were related to issues concerning
wind and earthquake resistance because of the high winds that prevail
in the San Francisco Bay and the frequency of tremblers in the region.
In truth, the original designers probably never took the issue and
probability of a direct tsunami impact into consideration because,
among other things, the bridge is some 220 feet above the water?s
surface (which is considered quite high for any bridge). For a tsunami
to have a dramatic impact on the Golden Gate Bridge it would have to
be the largest one ever recorded. Add to this the fact that the only
tsunami known to have occurred in the region took place in conjunction
with the 1906 earthquake and in that even the tsunami originated and
ran outward rather than came there from some other location. Even so
the event was relatively minor in comparison to greater events like
the one seen more recently in the Indian Ocean.
Tsunami Record from the Great 1906 San Francisco Earthquake
http://walrus.wr.usgs.gov/tsunami/1906.html
As for other bridges one of the leading research laboratories that
studies the effects of tsunamis on bridges is located at Oregon State
University in Corvallis. The O.H. Hinsdale Wave Research Lab is housed
in a hangar-like building in Corvallis and it is here that scenarios
are worked out by engineering experts to help determine what means of
resistance is needed.
TSUNAMI RESEARCH AT COLLEGE MAKING WAVES
http://www.nees.org/xcutting/news/press/osu/4348774p-4357664c.html
Since tsunamis are relatively rare and when they do occur they are not
typically the deadly variety we?ve seen in recent years, researcher
must rely on models and controlled experimentation based on some known
cases that were particularly devastating. One of those is the tsunami
that occurred in Messina Italy on December 28, 1908, the Monday after
Christmas weekend, when a major earthquake and subsequent tsunami
totally destroyed the city. Because of this terrible event researchers
have learned quite a bit about what bridges can, and cannot withstand.
STRETTO DE MESSINA
http://www.strettodimessina.it/Fattibilita_FAQ-e.html
The Akashi Kaikyo Bridge in Japan, the longest suspension bridge in
the world, and others benefited directly from the research and were
constructed to withstand a variety of forces including tsunamis.
WIKIPEDIA
http://www.worldwindcentral.com/hotspots/view_hotspot.php?id=1361
Using this model engineers were able to construct bridges using miles
and miles of cable attached to pylons, which were in turn attached to
anchorages, that allows for some subtle movement and makes the bridges
more resistant to collapse from the threat of great forces of wind and
water.
PBS: NOVA
SUPER BRIDGES
http://www.pbs.org/wgbh/nova/bridge/meetsusp.html
The truth is there are a lot of things about tsunamis that scientists
still don't know because there are so few recordings of the actual
tsunami inundation. Believe it or not the brightest engineers are only
now becoming more educated on the matter because of the advancement of
technology that previously prohibited us from creating scenarios and
studying them in such a way that they would benefit future
construction. Only recently, for example, were researchers able to
create what is believed to be the tallest man-made tsunami (an 8 foot
tall, 25 mph wave) in a tank at the Port and Airport Research
Institute's Tsunami Research Center in Yokosuka, Japan.
RED ORBIT
http://www.redorbit.com/news/science/159175/researchers_study_tallest_manmade_tsunami/
Dan Cox, Director of the Hinsdale Wave Research Lab I mentioned
earlier said in a recent interview with CNN that ?anything? (including
bridges) can be built to be tsunami resistant but at the moment the
methods we do know that seems to work best is simply cost prohibitive
in most cases, so the research goes on.
CNN.COM
http://edition.cnn.com/TRANSCRIPTS/0412/28/lol.01.html
Unfortunately even the concept of retrofitting structures seems to
take a back seat to costs:
?Cost is one of the most difficult impediments to tsunami-proofing
structures. Although the tsunami showed that Thailand is not immune to
these disasters, historically, they have occurred infrequently. In
addition, because this most recent earthquake relieved much of the
stress in the fault, it may be more than 100 years before the next
major tsunami occurs. With such a low level of risk, calculating
acceptable investments for elevating structures, refitting buildings
to reduce damage, and zoning people out of inundation regions may be
difficult.?
LESSONS IN ENGINEERING FROM THE TSUNAMI IN THAILAND
http://www.nae.edu/NAE/bridgecom.nsf/weblinks/MKEZ-6DFQZW?OpenDocument
This field appears to be open and a ripe field of research for great
young minds to consider. It is most likely that the youth of today,
like yourself, who will be the ones to ultimately solve the problem
for all of us. There is little man can do to prevent billions of cubic
tons of water from destroying a structure but the solution may not lie
in ?proofing? or resistance, rather in prevention in the first place.
Another hypothetical solution might be in future bridges that are
independent and capable or being swung open or retracted in such an
emergency. These are all certainly issues that bear more study. I
admire your interest in this subject, as I believe that it will be
sharp mind like yours that will eventually come up with the answers ?
hopefully in my lifetime.
I hope you find that my answer exceeds your expectations. If you have
any questions about my research please post a clarification request
prior to rating the answer. Otherwise I welcome your rating and your
final comments and I look forward to working with you again in the
near future. Thank you for bringing your question to us.
Best regards;
Tutuzdad-ga ? Google Answers Researcher
INFORMATION SOURCES
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8 January 2009 |
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