Theater Rigging - Engineer Seal/Sign? 4

[JAE]

I have a client who designs, fabricates and supplies theater rigging (pulleys, ropes, curtains, etc.) for theaters.

They are doing a project where the theater consultant is requiring their rigging shop drawings to be sealed by a structural engineer. It is listed in the project specs that this is a requirement.

The question I have is that I'm not sure this is really valid (requiring a seal). The structure of the theater itself (the roof, beams, etc.) have all been designed by the building EOR to support the rigging. The rigging itslelf isn't a "structure" but rather a proprietary product made up of pulleys, cables, controls, counterweights, etc.

A structural engineer like myself typically doesn't have the experience to seal "equipment" like this.

The rigging is warranted, certified by the supplier, etc. as a functioning, and guaranteed product.

Is the theater consultant off base here? Most states don't allow an engineer to "review" a shop drawing and seal it (plan stamping).

 

[msquared48]

i agree with you. Did a theater in Anchorage years ago and the stamp stopped at the gridiron. Nothing it held was our responsibility. Only the loading for which it was designed.

Stick to your guns here. They are trying to pass the buck.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[hokie66]

I don't think the theater consultant is off base by requiring the rigging to be certified by a professional engineer, but I agree that it would be unusual for that engineer to also be the building engineer.

 

[ImminentCollapse]

We did a library where the architect had this atrocious art piece suspended in the atrium, we only went as far as making sure the beams could handle it. Don't really know who sized the cables suspending it or the connections to the piece itself, I assume the architect.......

Another reason not to sleep at night in this profession.

 

[msquared48]

IC:

Love your handle - you're not into forensics are you? If you haven't already, you should really meet Ron.



Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[msquared48]

JAE:

Another thought here - what does your contract say to any design limitations, or requirements?

Also, I use a "shop stamp" for the shop drawings, never, but never a seal. I also only shop review what I have either reviewed with my own supplemental calculations, or specifically designed myself.

This request is tanamount to a structural stamp for a desk or moveable partition system designed by others to rest on a structural floor. Sorry, but from my perspective, it makes no sense.

Tell the client to have the supplier furnish the documentation he needs for the products. You have not designed them and cannot attest to their structural integrity.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[cntw1953]

If your client is in the business of "DESIGN/FABRICATION/SUPPLY", shouldn't he the one to certify his products? If requested upon, he shall hire someone qualified for perform design or design review on the rigging system and put his/her stamp on it? The structural engineer's responsibility stops with building and structural components, the rigging system is an "equipment" that is subjected to different standards. Am I off the base?

 

[JAE]

I think some might have misunderstood my original post.

The EOR of the building designed the roof structure to support the rigging.

The theater consultant (working with the AOR and EOR) wrote the specification for the rigging and in that spec requires a licensed engineer to seal the shop drawings of the rigging.

The contractor bid the job using a rigging sub-contractor.

The rigging sub-contractor submitted shop dwgs without an engineer seal.

The Architect rejected the shop drawings since they didn't have a seal.

The rigging sub is now looking to us to seal the shop drawings but the question I posed above is: [blue] Is the seal on the shop drawings really warranted since this is a PRODUCT and not a BUILDING design. [/blue]

Products are usually warranted, not sealed by an engineer.

And the other question I have is:[blue] Is the requirement for sealing rigging shop drawings a typical thing? A current thing? A future thing that's coming more prevalent?[/blue]

 

[JStephen]

If I understand the situation here, you didn't necessarily design the building or anything, but the rigging supplier is asking if you can furnish the PE seal for the rigging?

And, I assume this is something that is normally exempt due to industry exemptions (a manufactured item), but they are wanting a PE seal anyway?

If the work isn't obviously "structural" in nature, the consultant would probably accept a PE seal from other appropriate disciplines.

It might be worthwhile to ask that consultant if a review of the material would be acceptable as an alternative to sealing the material. That is, you can review their material, write up a brief report indicating that is or isn't okay as far as you see, and seal that report.

Keep in mind that when you get into weird stuff, there may not be anyone else better qualified to design it, either.

 

[msquared48]

For a shop stamp, all you are certifying is that the shop drawings were prepared in accordance with the design of the structure/item/whatever it is. Nothing more. On my shop drawing, I specifically state that the approval of the shop drawing does not absolve the preparer from any and all responsibility.

As for the "requirement", certainly not when I did my project. I guess you can ask for anything though in the world today. Getting it's another story. Look to the contract. If you were doing the building design, it would fall under the auspices of the IBC. Not so the rigging, etc.

Contractually, though, if this "requirement" was in the contract or specd/job description prior to you agreeing to the contract, you may be on the hook.

Considering everyone wants to pass the buck nowadays for lisability, I am not surprised they want a larger pocket available.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[doka1]

not that unusual, i would compare it to an engineer stamping a drawing for a contractor's work plan, i.e. shoring,or shielding and scaffolding on bridgework, or rigging (large underground structures for example).

I would assume in this situation you would make sure cables are properly sized, chainfalls, and whatever else may come with it. Analyze beams that the chainfalls are attached to.

 

[JAE]

JStephen, writing a report verses sealing the actual shop drawings was my first idea. Whether that would be acceptable we have yet to find. We haven't decided to take this on just yet - I thought I'd throw up this question here to see if others had ever been involved in designing rigging for a theater stage and sealed such shop drawings as an engineer.

Mike, this isn't a shop drawing stamp we're concerned about. The design professional of the building would use that. We are being asked by a sub-contractor to review their rigging design and seal their component of the structure.

Thanks for the replies so far - keep them coming if you have other thoughts.

 

[SlideRuleEra]

And the other question I have is: Is the requirement for sealing rigging shop drawings a typical thing?

Five years ago I was involved in building project that involved significant theatrical and audio/visual equipment

http://www.highoutput.com/index.html

The Architect/Engineer & Owner considered this portion of the work to be the equivalent to a "Design-Build" specialty contract. The A/E was not required to seal these drawings/documents.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[cntw1953]

I think ASME has provisions regarding to rigging/lifting device, a mechanical PE maybe is more familiar and better suit for this. But if you are competent in analysis and design, and familair with code requirements on rigging device, I don't see anything wrong for you to seal the drawing as consultant to the rigging contractor.

 

[msquared48]

JAE:

Ok. "We are being asked by a sub-contractor to review their rigging design and seal their component of the structure."

I guess that I am a little confused here as to what is meant by the "rigging design". Are you talking about the specific layout ot the rigging, that it provides the specified mechanical advantage for manual lifting of a certain load? Or are you talking the actual structural design of the pulleus and blocks? Or something else?

Is this something that you feel comfortable doing? If you are not comfortable with it, don't do it.

I can see that there is obviously structural design in this, but a bit out of the ordinary. More specialized.

Again, do you have to sign off on the actual structural design of the block and tackle, calculations provided by others, or only the rated capacity of the specific off-the-shelf equipment provided by the supplier - that it can lift the loads of the specs?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[SlideRuleEra]

A 1996 summary of this situation:

http://digitalcontentproducer.com/mag/avinstall_whose_law_anyway/

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[MikeHalloran]

IF I were a set/production designer, and were planning something structurally important, for example heavy scenery moving during a performance, platforms hung over the audience, or actors flying on cables, I'd sure want someone to check the plans to make sure that the right size cables, blocks, etc. were used and that they didn't stress the building interface in ways for which it wasn't designed.





Mike Halloran
Pembroke Pines, FL, USA

 

[JAE]

cntw1953: I'm familiar with ASME BTH-1 (Below the Hook provisions). I'm not sure all that applies - BTH-1 requires safety factors between 2 and 3.4 or so. The rigging sub told me they use SF = 7.

msquared48: The rigging we're looking at is a series of pulleys (blocks), cables, counterweights, knee braces to walls, and connections of these items to the structural beams overhead and the walls. The pulleys, or blocks, are manufactured items. Cables are aircraft type cabling (7 strand).
You are absolutely right that this is a very specialized area. There is some discomfort for us but at the same time, while it looks complex, it's really quite simple really.

Mike Halloran: The weird thing here is that the design team for the building is asking a very experienced rigging contractor to go get a structural engineer to sign off on their rigging when most all structural engineers don't know much about rigging. Seems like someone is just trying to check off a box somewhere and feel like they are improving safety and quality.

 

[sandman21]

When you design a gym the backboards are stamped by an SE but they do calc.s for the backstop.

We have several theaters in our office right now, I will ask a senior engineer about this issue tomorrow, and how it has been handled in the past.

 

[DaveAtkins]

This is somewhat akin to a precast concrete panel manufacturer stamping his shop drawings.

I see no problem with this if you can justify the design to yourself.

And you get paid an appropriate fee.

DaveAtkins