Tuesday, November 15, 2011

Soft-story glass-walled condos


As we are aware, the seismic capacity of a soft-story condo approaches that of old brick in Christchurch.  From the Chile earthquake, the condos permanently tilt (must be abandoned) at 30-40 cm/s.  But Chile didn't have glass-walled condos!  Perhaps they are too smart.

With gw condos, we no longer have a nice brick or concrete infill.  Now, all the lateral stiffness must rely on the spidery columns.  And guess what?  They are useless!  What is the seismic capacity of such a beast?  Let's say 20 cm/s.  I believe this was easily hit by the Virginia earthquake on soft ground, as we would experience near the lake.  I can now update my earthquake scenario, in that these things will lose all their glass.  As we know, nothing will bother bank towers, since they pour the money into those things.


Gus said...

They aren't exactly just columns I the condos whown in that particular image... the interior core goes from bottom to top with walls between each of twelve units per floor. Then the outside is a hefty system of extruded aluminum anchored at top bottom and sides with the glass window inserts. We would really have to experience the big Toronto earthquake to find out.

Harold Asmis said...

Infill walls have been shown to help in earthquakes, but only if you alternate a full wall with windows. We must await a earthquake to satisfy our curiousity. :)

Anonymous said...

I think you have to differentiate between those buildings with a shear wall design right down to the foundation between those with parking below a massive transfer slab. The other point I would like to make is the condos down at the waterfront rest on bedrock not on the soft soils.

Harold Asmis said...

I'm happy with the 'standard' buildings with columns and shear walls down to the bedrock. Their seismic capacity is well over 50 cm/s.

Soft-story or transfer slab condos carry their own soft soil with them. It may not matter if they are on rock. They have a low seismic capacity, and I am confident that the glass-walled version is lower, simply because of some work done that shows full brick infill panels raises capacity.

Anonymous said...

Thanks for the response. I own a unit in 1 King West, a very slender building but of shear wall construction down to bedrock. The tower was actually used to seismically support the older Dominion Bank building. Do you think wind loads control the design of very tall buildings more than seismic loads?? By the way, our building has passive tuned damper on the top to control sway in heavy winds. Does that help us in the big one???

Harold Asmis said...

Shear wall to foundation is bank tower stuff. The seismic capacity (as shown by Mexico City) is huge, perhaps 80 cm/s. Considering that rock cannot physically go over 5-10 cm/s, you are safe.

Soft-story condos are a hazard. For some reason they pass static building code design, but have a serious dynamic problem.