Infrastructure protectionMaking buildings more tsunamis-resilient

Published 6 February 2013

Often in disasters such as tsunamis, people escape the on-rushing wall of water by climbing to higher ground, called vertical evacuation. As people race to the third or fourth floor of a building, however, how do they know whether the building will hold up? Walls of water often carry with them cars, trucks, and 60,000-pound fully loaded cargo containers, transforming them into projectiles which slam into buildings with tremendous force. Most structural systems are designed to defy gravity, not a side kick from a shipping container. Engineers are now studying the impact of tsunami-carried debris in order to make buildings and other structures more disaster-resilient.

Anyone who has seen the movie “Impossible” or watched footage from the Japanese tsunami has learned the terror that can strike with little warning. In those cases, when there is no time to flee, there may still be time to reach higher ground, called vertical evacuation.

As you race to the third floor, however, how do you know whether the building will hold up? Walls of water are not the only danger. Another potentially lethal challenge is water-driven debris — such as 60,000-pound fully loaded cargo containers — transformed into projectiles. Often pulled behind semi-trucks on highways, these containers, which line port areas, well exceed the telephone-pole-size 1,000-pound default log assumed by most U.S. building-design guidelines.

A Purdue University release reportsthat a multi-university team lead by Ronald Riggs, a structural engineer at the University of Hawaii, has determined just what the impact could be and will present findings at an international conferencein June.

The goal is to supply structural engineers with information to design buildings in areas vulnerable to tsunamis.

Currently there are no scientifically tested guidelines. As those who survived the Japanese tsunami that swept thousands to their deaths can attest, no one had planned for such force.

Most structural systems are designed to defy gravity, not a side kick from a shipping container,” Riggs says. “An engineer can build what it takes to withstand the karate chop, but first the engineer has to know what forces to expect.”

This knowledge is vital not only for the buildings into which people might flee, but also for coastline storage tanks that could spew chemicals or other pollutants if damaged.

Riggs first began thinking about the problem as he examined damage to bridges and buildings following Hurricane Katrina. He noticed the cargo containers and barges that had been flung onto land in areas such as Biloxi, Mississippi. On another scientific excursion to Samoa, he says he saw a shipping container “whacked against a meeting hall — and there was no port anywhere nearby.”

These shipping containers are surprisingly ubiquitous,” Riggs says. The point was further brought home on TVs across the world that played and replayed footage from Tohoku, Japan, as tsunami-fed waters dragged cars, trucks, and shipping containers as much as six miles inland and then back out to sea in the drawdown.

They may have been moving only about 10 miles an hour, but given their weight, this is a significant load for a structure not made

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