Saturday, January 30, 2010
Earthquake resistant buildings for Haiti
diagram non-copyright R.Lawson
After the earthquake in Haiti I looked at earthquake predictions, then at earthquake engineering - making buildings more earthquake resistant. It is impossible to make a building earthquake-proof, but we can decrease the likelihood that it will crush the occupants. Buildings in seismic zones should be made to seismic specifications, but it is possible to retrofit existing buildings in an affordable way.
It's not rocket science, its triangulation.
In the above, diagram (a) above shows a conventional modern concrete building, with the floors hung from a few vertical concrete pillars. When the earthquake (e) shakes the ground, the pillars crack at (d), and the whole building collapses, concertina style. The structure is supposed to be stabilised by the walls, but they shake out with the tremors.
The solution is to triangulate the corners with robust concrete or wooden beams, as in (c). This is not difficult or expensive, and this triangulation should be included in the Haiti reconstruction. Interestingly, traditional timber framed buildings are earthquake resistant. It is good to use timber, so long as it is replaced, as all timber contains an equivalent mass of CO2 taken out of the atmosphere.
I have a feeling that the main block to earthquake resistance and engineering is denial.