Lessons about withstanding an earthquake
Mary-Sue Haliburton of Nepean, Ontario has this reflection on the earthquakes in Haiti and Japan...
The Haitian quake killed hundreds of thousands, but in Japan it was the tsunami which killed people. What was so different? The respective building codes of the two countries.
Though Japan was shaken by one of the most powerful quakes ever, now stated to be Richter 9.0, their many skyscrapers are still standing. This is a tribute to Japanese architecture and engineering. The buildings that were destroyed were houses and small wooden structures that were swept away by the ocean's power. Even right next to the quake zone, poured concrete buildings can clearly be seen in various videos to be undamaged structurally even if they were flooded temporarily.
The Japanese have lived with quakes and tsunamis for centuries if not millennia. They know what they are doing. Even if this tsunami was higher than their protective wall, their buildings withstood the shaking.
And if Haiti's new president is smart, he'll invite Japanese engineers to come to Haiti and give his planners and the NGOs with money some pointers on how to rebuild for safety and permanence.
In Haiti, the building codes were not adequate to handle a much lesser quake, which was 7.0 on the Richter scale. What killed so many people was the collapse of both houses and large buildings. I remember hearing a documentary -- was it on your show -- that Haitians didn't want straw roofs or even shingles because of concern about fire. So they rejected the straw-bale house.
But I was shocked to learn that homeowners would have two-foot-thick cement slabs put onto their houses as roofs instead. TWO FEET THICK ?? The weight must have been incredible.
It was the falling of these massive slabs that killed so many.
Many of the survivors were the occupants of tin shacks who were not able to afford these slab roofs. What house with that much weight on top could withstand a quake? Probably none. I would bet that none of the houses that fell had walls that were specifically engineered to tolerate the horizontal shaking forces under that much weight. Did they even have diagonal bracing? Would that have been enough? I'm guessing that the laws of physics were just ignored totally.
Obviously there is a great need for their new president Michel Martelly to learn the facts of earthquake-resistance engineering such as that practised in Japan. If the new government is better informed, then the people won't be at such fatal risk again from bad architecture.
I hope that Dispatches correspondent Connie Watson can find a way to raise this matter with Mr. Martelly. This knowledge would help his nation avoid repeating mistakes of the past in how they rebuild.
If people want cement -- and there are good reasons for using a fireproof material -- perhaps instead of slab roofs they should be using the inflatable dome structures. This is done by pouring the cement into a very large bag and then inflating it from underneath to make a dome-shaped space. When the cement sets, it's a seamless unit. As such, it should be resistant to damage from both hurricanes and quakes if the cement was properly mixed, with the new types of fibrous rebar substitutes included.
There are many other options for safe architecture, and Japanese expertise should be brought on board for Haitians to benefit from their long experience and insight.
Categories: Your Dispatches
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