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Author Topic: Suspended Load Safety, When to hire a Structural Engineer?  (Read 2083 times)

Scott Carneval

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Suspended Load Safety, When to hire a Structural Engineer?
« on: November 25, 2015, 01:06:22 pm »

As a systems integrator we have rigged dozens of speakers, truss, lights, etc., but most times we have had the advantage of working on a construction project with an architect and engineering firm involved. In other cases we typically have open beams available for rigging. I've suspended from concrete several times, but always with an architect's blessing and typically after the ceiling has been x-rayed to identify post-tension cables if necessary. 

We're about to quote a project where we'll need to rig a pair of 90lb speakers from a concrete ceiling.  The building is about 30-40 years old and although I've asked for as-builts several times, my requests seem to fall on deaf ears.  I'm confident that the ceiling can support two 90lb speakers, but I also realize the risk in suspending a load over humans, especially children.  I don't know if there is post-tension cable installed, so at the very least I would want to have it x-rayed.

I guess my question is, at what point should I involve a structural engineer to get stamped drawings? On one hand it seems rather silly for 'only' a 90lb load, but I would feel more than just silly if a speaker fell on somebody. 
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Keith Broughton

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Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #1 on: November 25, 2015, 01:58:14 pm »

As a systems integrator we have rigged dozens of speakers, truss, lights, etc., but most times we have had the advantage of working on a construction project with an architect and engineering firm involved. In other cases we typically have open beams available for rigging. I've suspended from concrete several times, but always with an architect's blessing and typically after the ceiling has been x-rayed to identify post-tension cables if necessary. 

We're about to quote a project where we'll need to rig a pair of 90lb speakers from a concrete ceiling.  The building is about 30-40 years old and although I've asked for as-builts several times, my requests seem to fall on deaf ears.  I'm confident that the ceiling can support two 90lb speakers, but I also realize the risk in suspending a load over humans, especially children.  I don't know if there is post-tension cable installed, so at the very least I would want to have it x-rayed.

I guess my question is, at what point should I involve a structural engineer to get stamped drawings? On one hand it seems rather silly for 'only' a 90lb load, but I would feel more than just silly if a speaker fell on somebody.
I'm sure you're insurance company would opt for engineering oversight and I'm sure you would feel better as well.
90 pounds falling can hurt humans, children or otherwise. ;)
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Cailen Waddell

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Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #2 on: November 25, 2015, 02:02:48 pm »

Scott,

In my experience, for small loads, there are modest costs.  We had to get an engineer to check a recent art installation (artist wanted to hang 300# of concrete from the ceiling) and the costs including a detail drawing were, I think, around $400. 

The other alternative I have seen in quite work is subbing the rigging to a rigging company who keeps a structural engineer on staff or on retainer.  That sometimes can be cheaper... 

I am always appreciative of contractors who make every attempt to do things safe, so as an end user - thanks! 


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Scott Carneval

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Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #3 on: November 25, 2015, 02:57:34 pm »

Scott,

In my experience, for small loads, there are modest costs.  We had to get an engineer to check a recent art installation (artist wanted to hang 300# of concrete from the ceiling) and the costs including a detail drawing were, I think, around $400. 

The other alternative I have seen in quite work is subbing the rigging to a rigging company who keeps a structural engineer on staff or on retainer.  That sometimes can be cheaper... 

I am always appreciative of contractors who make every attempt to do things safe, so as an end user - thanks! 


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Thanks Cailen.  Do you mind sharing the name of the person or firm you used? $400 is a fraction of what I was expecting to pay.

I know that safety is nothing to take lightly. I'm familiar with all of the proper hardware and rigging techniques, but I just want to make sure we're covering all of our bases here.
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Cailen Waddell

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Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #4 on: November 25, 2015, 02:58:38 pm »

Let me see what I can find...


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Cailen Waddell

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Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #5 on: November 25, 2015, 03:03:01 pm »

Lysaght & associates. In Raleigh on st. Mary's st.  I should mention, I never saw a bill for the work, was just told this is what it costs.  Give them a call though... And good luck. 

Also one of the ballet schools we have had a dad who is a structural engineer.  His firm is large and does a lot of work for live nation...  They are familiar with what we do.  I can ask him if this is something they would look at, but it may be a different scale than they are used to


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Scott Carneval

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Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #6 on: November 25, 2015, 03:10:17 pm »

Lysaght & associates. In Raleigh on st. Mary's st.  I should mention, I never saw a bill for the work, was just told this is what it costs.  Give them a call though... And good luck. 

Also one of the ballet schools we have had a dad who is a structural engineer.  His firm is large and does a lot of work for live nation...  They are familiar with what we do.  I can ask him if this is something they would look at, but it may be a different scale than they are used to


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Thanks! If you don't mind reaching out to the ballet Dad to see if he's interested, it sounds like this would be something he's familiar with, albeit on the smaller side of things. We haven't secured the job yet, but I know we're within budget and we're spec'ing a Danley system, so I don't anticipate the client finding a better/cheaper solution.  I would love to build a relationship with someone locally as I'm sure we'll continue to run into this issue. 

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ProSoundWeb Community

Re: Suspended Load Safety, When to hire a Structural Engineer?
« Reply #6 on: November 25, 2015, 03:10:17 pm »


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