Shake Test II

Ian writes:

As some of you may recall, we tested a scale model cob building that Steve Lay and others built on a siesmic shake table a few weeks ago at the University of British Columbia. The building received a massive pounding, but did not simulate an earthquake as it was supposed to, due to problems with the hydraulics. Despite the massive pounding, the building received only minor damage.

With the hydraulics repaired, we successfully conducted our tests on Sept. 20th. The model, which was about 6 ft diameter and 5 ft high, easily handled a 7.4 richter quake with only minor cracks. And this was after the previous pounding that certainly compromised the structure. This quake simulated a particular quake in California that was particularily destructive to buildings.

Finally, the building was given a 2 g force shake, something closer to a 9 richter and at the epicenter. As was expected the building was shaken apart. This would be a very rare quake and no building would easily survive this level of shaking forces. Amazingly, despite such a violent shake, the building remained standing, though large chunks of cob had fallen away from the building. Anyone inside would have survived as the roof remained in place and no large cob fell inward.

There was considerable rocking of the building from side to side which points to the importance of tying/keying in the building to the foundation well, although I expect that the failure would then be the mortar in the stone foundation. Another interesting observation was the amount of shearing, probably at horizontal layers that were not tied together so well. Embedding bamboo dowels or something like this throughout the walls would greatly reduce this type of failure. I am not an engineer so we will have to await their report. The engineers however were very impressed by cob's performance and now have some good data and video footage to explore ways to increase cob's strength for those of us in earthquake zones.

The following images show the damage after the highest level of shaking.

Roof.... at last!

Apologies for the lack of posts. With the push before the grand opening, updates got forgotten. Photos did not however!




Rafter framing begun.




Charles's beautiful corn relief sculpture.




Rafters and sky.




The team on the roof.




Cobbing between rafters.




Nancy and Julie - Carpenter volunteers!




Kay cobs between rafters.




Final rafter design.




Tossing cob.




Steve installs reclaimed cedar decking.




Cedar over beams from inside.




David applying StoneHemp plaster to interior.




Plaster covering cob.




Finishing details.




A Steve/Ian handshake on completion of roof decking.

Shake Test!

It was an interesting day at the UBC Earthquake Lab yesterday!

Approx. 70 people came out to witness the shaking of "Frida," our little cob model. Media and city officials were in attendance.

The intent was to subject Frida to a large earthquake that was recorded inthe Mojave Desert, beginning at 1/4 intensity, then 1/2, and finally full strength, recording failure after each test.

The first test started well. However, technical difficulties with the shake table hydraulics resulted in the table repeatedly contacting the bumper pads, delivering massive shocks and subjecting the model to excessive forces. Frida however took it all in stride. The building separated from the table surface, but stayed intact. After repeated shocks, only minor cracking of the plaster was observed around window and door frames, with one crack visible on the interior. Although different than the forces experienced during an earthquake, the ground acceleration was off the scale. Thus, despite the table malfunction, much was learned from the test.

Repairs are being made to the table, after which another attempt at the actual tests will be made. Although already damaged, the model is expected to perform well. Media covering the event included CBC French TV (aired Thursday night at 6pm), a small piece in the Province, and CBC Radio's "Sounds Like Canada" (air dateTBD).




Setting-up "Frida" for testing (placing roof sensors).




Kristi and Kay with model.




Kay and Steve tighten roof plate bolts prior to testing.




Kay and Steve - Frida's proud parents.




An eager crowd awaits the tests.




Dr. Carlos Ventura and technician in control room.




Post-test: Kay checks interior for cracks.




Post-test: slight damage of doorframe and lower wall.




Post-test: Cracks (marked with marker).

Volunteer Appreciation Party

Last Friday we had a great turnout to our Volunteer Appreciation evening. A big thanks to all who attended and all of those who helped but couldn't make it. Many prizes, much food, fun, and music were had!




Enjoying food and good company.









Troubadour / Volunteers!





Cob Creatures! Yours to take home!





Cute Cob!

Almost to height!

Hooray! After much help from our excellent volunteers, we are nearly finished the walls!
Only a couple of inches all around to go.




Lintel in place over window and walls getting higher.





Ian measures and inserts roof plate anchors (steel rods).





Reinforced lintel gets cobbed-in.





View of structure including sculpted window.





View from other side, with "corn cob" sculpted windows and roof-plate anchors visible.





Corn cob window from inside - in progress (glass under styrofoam).





Driftwood and ? built into the wall!





Rainy day tarp set-up and Kay and Linda with helpers.