On March 27, a shake-table simulation of twice the ground acceleration of the '94 Northridge CA earthquake was run in the Network for Earthquake Engineering Simulation
's Large Structures Laboratory at the University of Nevada
on a full-scale model of a strawbale housing unit developed in the wake of the devastating 2005 Kashmir 7.6 magnitude quake that killed nearly 100,000 people and left over three million homeless in Pakistan. Although the Earthquake Engineering Research Institute (EERI)
-sponsored test was intended to be to failure
, in the end the robust little straw house was still standing and structurally sound — check out the video footage below.
The quake-resistant buildings designed by PAKSBAB (Pakistan Straw Bale and Appropriate Building)
are intended to be affordable, energy efficient, and locally built with readily available materials.
Bamboo rods and nylon fishing net act as the reinforcement and tie-down system; the netting is wrapped under a soil-cement-encased gravel-bag foundation (made with old vegetable sacks), up both sides of the load-bearing baled-straw wall, and attached to the wooden top plates. The wall-tall bamboo, which also engages both the foundation and the top plate, is attached upright in opposing pairs on either side of the wall at frequent spacings and 'sewn' together through the bales, providing flexible resistance to out-of-plane forces. The whole assembly is covered with earthen plaster. The roofing is light corrugated steel. The hand-made structural straw bales — there are no posts or other bearing members — are smaller than those produced by automatic balers, which are rare in developing countries.
The plaster, as expected, experienced buckling and delamination, but there was no evidence of failure of the nylon net or bamboo.
There are some similarities between this system and the one devised by the Getty Seismic Adobe Project
. If you're into earthquake design (or just interested in watching buildings shake), check out the video there.