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[Tyme2jam]

Any suggestions on mounting a truss system to a solid concrete ceiling for a 25x20 truss system with approx. 3000 pounds of gear on it? I am looking at some Hilti anchors. It will be a dance club. The ceiling is 12-14" thick. They have a few speakers anchored in now. Anybody, say stay away from this liability or is this a common problem for installs with easy solution that properly installed(key word huh) should be fine? I am thinking of having 8 - 12" 1/4 steel plates with a steel ring in the center made with 4 mounting points for the bolts, then suspending the truss with steel cable. Any suggestions welcome.

[Karl P(eterson)]

This isn't my main field of expertise, but I have been involved with rigging into concrete ceilings (in atrium's of large high-rises). We were required to use a special type of concrete anchor that were called spin-lock or something, google gives me this and this

Anyways, we used anchors at like a 10-1 safety ratio and verified that the overhead structure could support the weight at the point(s) we needed with the building engineering team. we did either a cluster of 4 or a cluster of 6 (I believe) anchors in some kind of special spread out pattern (to keep from causing an easy way to crack, i assume) bolted up a piece of steel that was fabed with a hang point, and off we went with your standard materials.

This may not in any way apply to you, but it may give you an idea.

Karl P

Note: In another job I remembered they needed to do some stress testing on the bolts and also had to grout them in after the fact, there should be minimal information about that on the site that i provided for you up there, but remember you do need to seek console of some people in your area who know the codes and the best way for you to do it in your situation.

[Mac Kerr]

It is definitely something that a structural engineer should look at. You need to know both if the ceiling can support the extra load, and if the concrete if of a rating that can hold the anchors. Is it a flat ceiling, or are there concrete beams? I think Hilti anchors in the side of beams can hold more weight, but a structural engineer will know for sure.

Mac

[Hal Bissinger/COMSYSTEC]

This is definately NOT something you should be involved with particularly if you have to ask how here. The consequences are too great and can result in your being put in jail for a very long time at the very least if people should die. This is not something I would want to be in any way involved with!

I suggest that you retain a structural engineer to design the installation and a licensed contractor to do the work. 3000 pounds is a lot of weight.

-Hal

[Tyme2jam]

Hal, you are correct in your post and I agree. I have hired an engineering frim to look at it.

[travisnie]

I'm a little late but it was a long weekend.
The common theme here is CYA (cover your a**).

As said 3000lbs is a lot of weight and if it comes down someone will die. This work will most definitely require a structural engineer. Even finding a good one can be difficult. Then a plan check and permits will be required. Not knowing your economic where abouts, I would venture around $5K in additional engineering plus added contracting & material expenses.

These things take time, especially the plan check. Be sure that your client is aware of and paying for these expenses usually in the form of an additional expense within a design/build contract. It is a hard lesson to do this kind of design work and see someone else put it in.

While dealing with the structural engineer, let him do what he is paid to do. You tell him the load, pick points on that load, and where it needs to be. That's it. I have found that the more suggestions I make, the lazier they become and then if it doesn't calc right they'll tell you that they just did what you asked. And to them, time is money.

I hope the rig is worth the trouble.
But most important, Be SAFE.

Travis

[jimmyktbone]

Direction to go:
Submit to the GC'S structural engineer your proposed mounting method.
Hilti anchors are the way to go, but you need them approved.
You don't need your own structural, that's what the GCs are paid for, unless this is a design/build. In which case, this'll cost you about 700-1000 bucks.
have fun, but be safe
jim

[Dan Fowler]

You should be able to find the pull out strengths of the Hilti bolts on their website or have them faxed to you from tech support.  I would put together an anchor design based upon those spec sheets and have a structural engineer review and stamp them.  This will be the most cost effective way to have your building connection designed.  (PE's will typically charge 400 to 500 bucks just for a stamp)

You DO NOT have to verify that the building roof will support your rig.  This is an issue that the GC/Owner's engineer should verify base upon your connection submittal.  Make sure you include a comment that the roof integrity needs verification by the architect/engineer/owner.  DO NOT install this rig until you have that verification, IN WRITING.  

Get everything in writing.

[Dave Miranda]

Tyme2jam

I agree with everyone else.  GET A STRUCTURAL ENGINEER!  Very happy to see you did.

Have you looked into a ground support solutions? Basically is 4 vertical Truss (you can anchor these into concrete) each truss has a motor on top so you can bring the "roof" or truss "grid" up and down.  Don't know the size of your venue or your budget.  You can even lease something like this from a staging company.  They set it up and take it out.

Good Luck!  dmiranda