Large Chain

[zcp]

I am looking at a fairly large canopy (19 ft x 18 ft) that cantilevers out from a building and is supported at the ends by a chain running back to the wall (about 9 ft up from the canopy).

Three questions:
1) Does anyone have a chain supplier that has large (14000 lbf working load or higher) chain that will handle being outdoors?
2) For the possiblity that the chain would need to be rigid (i.e. the case of wind uplift), has anyone found / used larger chain that has the links welded and if so, can you point me in the right direction?
3) Are there any suggestions that would provide the large chain "look" while acting as a rigid link for uplift?

ZCP

http://www.phoenix-engineer.com

 

[JStephen]

McMaster-Carr has SS chain shown up to 1" size/ 23,400 lb work load limit. Also listed as "not for lifting", for what that's worth. Similar items should be available from a local supplier somewhere. $118 a foot or so.

You could take two heavy angles, do some creative cutting, weld them angle-to-angle to make a "+" cross section with a chain look.

 

[Denial]

On your first question, the only time I needed large chain I went to a supplier of marine anchor chain. They have chains that will restrain a supertanker in a typhoon, and "outdoors" is no trouble either.

 

[14159]

Assuming you end up with a non-rigid chain:

The chain catenary forces will be very large compared to the reaction if the canopy is light. It would be unfortunate to get a call from the contractor that sounds like: "Hey. The chain's sagging 3 inches and we can't get rid of this sag by tightening because the end of the canopy just moves up!"

I've had this kind of thing happen before with cables due to the cable and turnbuckle weight. We had fairly large HSS columns about 15-ft apart, cantilevering up from embed plates. Between them was a relatively small cable that was placed there to resist 2-3 kip horizontal forces from an arched translucent canopy system. The contractor kept trying to turn the reduce the sag by tightening the turnbuckle but the column just kept moving toward each other (not by much, but it doesn't take much). I calculated the forces and couldn't believe how large they were -- it was completely counterintuitive. We ended up putting an HSS in there instead -- luckly we had a good relationship with the contractor and architect so there was little harm.

After that, we always made sure to investigate the "unloaded" case to make sure that it wasn't critical.

Another thing: I had a rod-supported canopy once and had the need for uplift resistance like you typed. I used a one-way moment end plate and it worked out well. Imagine an extended moment end plate with flange bolts only on the bottom side of the plate. I don't know if it'll fit your situation, but we found it to be useful for uplift and to hold the canopy down so that the rod sag could be reduced to a small-enough size.

14159

 

[zcp]

JStephen......thanks, I am putting this in the lifting category. Your angle idea sounds interesting and frightening at the same time.

Denial.....Do you or any of our boating friends out there have a suggested marine source that you have used before?

14159....good point on the catenary, in my line of work the aesthetics has to come first and the engineering / structural sometimes has to be the supporting actor. As far as your moment plate, it isn't the moment / stress that is at issue. It is the deflection of the long beam. I am also somewhat limited in the profile (back to aesthetics).

Back to the masses, has anyone welded or used chain welded rigid before? Some examples / stories would be great.

ZCP

http://www.phoenix-engineer.com

 

[dik]

You also might want to consider using Dywidag Threadbar for a tie

Dik