|
 An inspection of Thai villages and ports struck by tsunami waves has uncovered some engineering lessons that might reduce casualties and destruction in future oceanic upheavals, according to a Johns Hopkins researcher.
Robert A. Dalrymple, an internationally recognised expert on water waves and coastal engineering, was part of a nine-member team that recently toured southern Thailand, examining landscape and structural damage in areas that had been battered by waves up to 10 metres (more than 30 feet) high when the tsunami struck on December 26th. The research trip to Thailand , along with similar expeditions to Sri Lanka and India , was organised and funded by the American Society of Civil Engineers, in cooperation with the Institution of Civil Engineers.
The American Society of Civil Engineers is preparing a detailed technical report, but Dalrymple said team and personal observations in post-tsunami Thailand led him to compile a list of general lessons for builders in coastal areas where future tsunamis may occur:
Elevated structures survive better
The waves were powerful enough to smash through a building's ocean-facing wall and break out the opposite side, and high enough to inundate a second-story level. Elevated buildings that allowed the moving water to pass through the lower level with little interference fared better than those with solid first-floor walls. Taller buildings that allowed people to reach heights above the wave's crest helped reduce casualties.
Materials matter
Reinforced concrete structures were more likely to survive the wave forces. In general, masonry (brick) and wooden structures did not fare as well.
Orientation is important
Walls facing the ocean, allowing perpendicular impact from the waves, sustained more damage. Walls oriented in the direction of the flow sustained less.
Strong foundations are necessary
In addition, landscaping or other features can protect the foundations against scouring, which is soil erosion caused by the moving water. Seawalls can be a very effective way to reduce wave damage. The structures must be continuous, however, with no gaps for pedestrian crossings. Also, such structures should not slope inland, allowing waves to slide up and over the walls like a skier.
Debris in the flow is hazardous
Many tsunami victims were injured or killed by debris pushed along by the powerful waves. Debris can be minimised if vehicles are parked and heavy items stored on the inland side of buildings. Ports are particularly vulnerable to tsunami waves. Boats and piers in a harbour hit by a tsunami have little protection.
Dalrymple said several questions raised during the trip require further research. These include why the height of the tsunami varied dramatically along the coast of Thailand and how engineers can construct a mathematical model of wave forces as they pass through coastal structures.
http://www.ce.jhu.edu/dalrymple/dalrymple.html
http://www.ce.jhu.edu
http://www.asce.org
•Date:
1st March 2005 • Region: Various •Type:
Article •Topic:
Buildings and facilities
Rate this article or make a comment - click
here
|
