Earthquake-safe Housing for Iran, Haiti and Elsewhere
Jonathan I. Katz
The recent tragedies in Bam (Iran) and Haiti raise the question of earthquake-resistant construction in poor, hot regions, in which housing ust be built by local people using mostly indigenous materials.
One possible solution begins with cargo containers. These steel boxes (the commonest size is 2.6 m X 2.6 m X 12 m) are available all over the world in great numbers and at modest cost (about $2000 new, but much less when used). It is easy to cut holes in them for windows, doors and flues with a hacksaw. They each can carry up to 30 tons, and are often stacked several high, so their steel frames can support loads of over 100 tons.
By itself, a cargo container is unlivable in a hot climate. Its thin steel walls and roof absorb sunlight and the inside becomes lethally hot on a sunny day. At night it is cold. It must be combined with the traditional mud bricks or masonry, which have a large heat capacity and thermal impedance. The container can be a shell around which brick walls and concrete or brick roof are built. This combines the insulating properties of the bricks with the structural properties of the steel; in an earthquake the bricks collapse, but the ductile steel shell keeps them from falling on the people inside.
If steel reinforcing rods and concrete are available a roof can be poured in place on top of the container. If not, then a mud brick barrel vault or series of domes can be built instead, or bricks, or adobe simply laid across the top of the container. The steel roof of the container will protect the inhabitants from collapse.
These composite structures combine the advantageous mechanical properties of steel (available at low cost in the form of used cargo containers) with the advantageous thermal properties of mud brick, concrete or masonry. If people would replace their present unreinforced masonry structures with the same materials outside a frame consisting of one or more cargo containers, the enormous death toll of earthquakes (more than half the population of Bam, and hundreds of thousands in and around Port au Prince) would be much reduced.