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Seismic Restraint Question

Seismic Restraint Question

(OP)
I'm reviewing the support/seismic restraint of an art piece hung from a ceiling. The piece consists of about 50 small glass pieces weighing about 4 or 5 lbs each, supported by either 2 or 3 stands of steel wire. The whole thing weighs about 190 lbs. The length of the wires varies from about 2' to about 8'.

Now, the wires are designed to be vertical, which doesn't allow for any lateral restraint during a seismic event, however, the piece is located well above the level where it could hurt anyone, and has no chance of collapsing. While the individual pieces would likely swing back and forth, It has very little chance of injuring anybody.

The thing has the strength to resist swaying forces, and the actual displacements seem like no issue. My gut feel is to approve it.

Question: Does anyone have any suggestions or documentation allowing an installation like this to be laterally unrestrained? Even better if it's Canadian code/standard based.

Thanks in advance!

RE: Seismic Restraint Question

Any chance the individual thingys could smack into one another, shatter, and shower innocent babes with shards of glass? If not, I'd think that you'd be good to go in concept. If it's a public installation, I'd be inclined to run it by the AHJ for confirmation. I'm stymied to think of it but I'm pressure that I've run across an exception for something similar in the world of suspended services / ceiling.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Seismic Restraint Question

Can we call it a glass mass damper?

I would make sure your attachment can handle the lateral loads when the thing shifts sideways say by 1' (or whatever it is...)

RE: Seismic Restraint Question

(OP)
Well... this is where I get nervous.

Certainly a glass mass damper it is. Though it's the damping that gives it the potential to, as KootK says, smash into itself and rain glass shards.
There's no issue with the attachment points themselves. It's really just a question of the displacement.

I'm not sure if the AHJ would be much help, unless they have a definitive requirement for positive lateral displacement resistance... but perhaps they do.

RE: Seismic Restraint Question

We have to make some sacrifices in order to have art and beauty in our lives. Seriously. Otherwise we end up here: Link. Given that suicidal folks will get it done one way or another, I actually think that it expedites rescue efforts to have the attempts aggregated geographically.

But I digress. My personal thoughts on the matter don't help you get street legal with your array of ceiling mounted daggers.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Seismic Restraint Question

Ceiling Mounted Daggers :)

RE: Seismic Restraint Question

Looks like one of the bad guys in the new transformer movies.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Seismic Restraint Question

ASCE 7 13.5.1 allows suspended nonstructural components to be installed without lateral bracing provided they meet the following criteria:

1. The design load shall be taken as 1.4 times the seismic weight acting down with a simultaneous horizontal load equal to 1.4 times the weight.
2. Interaction effects need to be considered so that if the component impacts another object during an earthquake it does not pose a threat to life safety or cause failure of an essential component. See below for additional commentary.
3. The connection to the structure shall allow for a 360 degree range of motion in the horizontal plane.


RE: Seismic Restraint Question

(OP)
Deker, that's beautiful. Much obliged.

RE: Seismic Restraint Question

(OP)
UPDATE for anyone in the same situation in the future:

So after a bit of thinking and research, I've decided to insist that the artist provide a minimum of 3 wire supports per glass piece, each wire out of vertical, as well as rigid bar spacers between wires of adjacent glass pieces, located close to the top of the glass pieces.

We'll see how it goes over. It turns out this artist comes from a part of the world where they don't have earthquakes.

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