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).

 

[Ron]

JAE...it's not all that unusual, even though it is a "product". An engineer who specializes in rigging might be willing to do something like this, but most of us in the building related side would typically not do something like this. One problem we've found with this is that most mechanical engineers who do analysis other than HVAC design are usually "industry captive" and are not licensed. It is fairly rare to find a licensed mechanical engineer who does not specialize in HVAC.

About 10 years ago we did a rigging analysis for the PAT/Field Goal net for the Jax Jaguars that is cable supported. It was truly a structural function with some "machine" implementation. Was it mechanical? Was it structural? Well...a little of both. Fuzzy area.

I have two clients for whom I do analysis of their "designs" and I sign and seal shop drawings. One of them produces custom structures and the other produces stairs and rails (somewhat a "product"). My condition on all of this is that if I ask for a design modification, it has to be done. If I ask for a change in the drawings (notations, spelling, format) it has to be done. When the drawing matches my analysis, I'll sign and seal it....otherwise, no dice. For one of these clients it has worked well for 25 years. For the other, I'm into my 2nd year and so far, so good. I will not do a shop drawing "review" and sign and seal it. I do calculations on every one that I sign and seal. Sometimes the calcs are just rudimentary checks on repetitive items...I have to do enough that I feel comfortable answering questions about them, in the event I'm asked.

 

[JStephen]

Unless an ME is working specifically in the crane or rigging fields, they won't know any more about that stuff, and likely less, than SE's. It's not like we took courses in cableology. Even someone working in the rigging industry won't necessarily be familiar with aircraft cable and similar lightweight items.

ASME BTH isn't applicable, but is a good example of what goes on. It's an ASME document, therefore it should be ME specifically, but then all the design equations are right out of AISC-05.

Past experience with the field would help largely to know if there were any standards applicable to it. You could conceivably have building code or OSHA rules relating to it. Possibly fire considerations as well.

 

[southard2]

This is a bit unusual but the EOR and/or Architect have a right to demand a signed and sealed design. The sub and contractor bid the job knowing such now they have to fulfill their contractural obligations. Its really that simple.

For you to sign and seal the shop drawings you will have to be able to show via calculations that it works. I'd charge by the hour since there isn't anyway of knowing how long it will take. I'd tell them take it or leave it. I'd think you'd be able to find load ratings for the individual components such as the pulleys, ropes, chains, etc... On your calculations and/or shop drawings you could qualify that things such as curtains haven't been designed. Just make sure the client knows it will costs alot.

Don't shout in this in the theater (I mean Florida) or pretty soon they will be requiring Florida Product Approval. Of course that might be nice since it would be a one time design.

Thanks for bringing this topic up. For years I have tried, and always failed, do be able to get anyone to tell me the weight of the rigging over stages. So I've always overdesigned the roof and beams like crazy.

John Southard, M.S., P.E.

http://www.pdhlibrary.com

 

[doka1]

southard is on the right path, as an engineer for a construction company i do this on a regular basis as stated earlier. I am not proving the actual crane designed to life the structure, I analyze the situation and break it down, and show calculations for every step. for example, for a crane pick i would start with of course making sure the crane is capable of the pick at the particular radius, check line count, ground pressure calcs on the crane pads to make sure the crane doesn't tip. Then i would analyze the rigging rigging, check cable sizes, temporary welding required, and shackles. I bundle my calculations (which show all assumptions and factory of safety)and all the product and equipment spec sheet into a report. In some instance you are required to write a narrative on the logistics of the operation and include in the report.

As a structural engineer these are all elementary calculations, but the fact that you are supporting things from a building your SPECIFIC area of practice would help further. I would have a pretty simple analyzation of the beam, where some of you structural engineer would get pretty detailed into it.

 

[msquared48]

I do not seal shop drawings, calculations yes, but never shop drawings. I markup and verify shop drawings, and fix a shop stamp to each issue of them, approved or otherwise. Thats all.

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

 

[ishvaaag]

Here in Spain anytime the local Fair comes (12 October, by the way) the owners of the stands for the fairground and any of the passtimes are required to have a certificate (usually by an architect, but remember we here do the structural design still most times) of the safety of the installation, in order to ensure public safety. For some that should be like salmon's season, I never did any anyway. On the other hand I must say that I don't remember a single accident on this matter here in my 30 yr long practice that made the news (not that there have not been but surely not gruesome or would likely have heard off). In sum, as soon the safety of something becomes in doubt, someone is asked to check and undersign.

As long as you think is proper of you making such kind of work and they pay enough, spend the necessary time and let them know that this is never to be a matter to pass you the liability without proper review. If, on the other hand, it is some kind of standard product, I think it unusual the provider is not delivering it with a proper warranty of it, even installed, except that by being mean on them they have not payed them for reviewing that their design is in accord with their specs. Or they are being astute, providing a design without signing it, if something happens, they are not the structural designers (this may be the case) but are merely selling parts (not that uncommon, in the micropile -or prefab- field they are more experienced, provide the alternative design, come to show what they do with structural design very acquainted with the thing, sell the standard products, do and to some extent control the installation by themselves and yet... the architect must approve and sign the works, they are NOT signing what they are selling and providing even if they have more experience in the field).

If the contractor have allowed them such easygoing entry in the work, must not be surprised that there was a cost that he had not counted on; furthermore, since the system would be propietary, I still feel the one making the review, to keep them in the hook in spite of any reviews one makes, ask that they certify the quality, the behaviour and workmanship of anything that they provide in accord to their "propietary" (but who knows if deceivingly unwarranted) product design. For if it can be thought as a product will come under different rules and they must both warrant the product and, for one thing like this, the standard installation, or that has had an installation according to their standard.

 

[ImminentCollapse]

"Is the seal on the shop drawings really warranted since this is a PRODUCT and not a BUILDING design."
What did the spec say for the rigging? We usually specify what items require a seal. If it wasn't in the spec, then I don't know how it can be required at this stage (pun unintended)

"Is the requirement for sealing rigging shop drawings a typical thing? A current thing? A future thing that's coming more prevalent?"
For something out of the ordinary, yeah, rigging maybe, but could be a slippery slope. Do drop ceilings need a seal? chandaliers, art pieces, HVAC components etc....

 

[FFENGINEER]

Wouldnt this be akin to fall protection, i.e. safety engineer? They are usually structural type engineers.

 

[ESGconnector]

JAE, we are structural engineers and we specialize in entertainment rigging. This is a common requirement, which we address almost daily. You can contact me directly if you need additional information.

 

[ESGconnector]

Here's a pre-emptive apology...guess I should have worded my last post more carefully. Seems almost impossible to answer accurately and avoid it seeming like a solicitation.
The engineering seal requirement has been around and growing for about the last 5-7 years. It seems apparent that specilty equipment specifiers often are not registered design professionals and shift liability in this manner. However, in practice it is appropriate to have such things checked by an engineer experienced in this specialty discipline, because even structures specifically built for performance can be introduced to new or increased loading conditions for which it may not have been originally designed. We also see this frequently in renovation projects. Hope this helps.

Entertainment Structures Group

 

[dicksewerrat]

I gess that I would also look at the OSHA Fall protection, Rigging and Crane sections. Some of these things pick people up or lower them down. Then send it all off to a specialist.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[paddingtongreen]

If this were just a one time rigging job, it would be up to the rigging contractor, but as a piece of the permanent building equipment, the requirement is reasonable. It is not an "off-the-shelf" job, it is a system using off-the-shelf parts that may be used often. As a Structural Engineer, I rely on the documentation certifying the raw materials, but I do certify the assembly/structure that we build with the material.

When an Engineer seals a document there is an implicit certification that she is qualified in that discipline. An engineer with the appropriate learning and experience should seal the documents.


Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[steve1]

I see this as akin to pipe support engineering where the engineer selects components from a catalog of standard components such as clevis's, rods, and clamps, and ensures that each has the strength to resist the design load. The pipe support engineer may or may not also be responsible for determing the design load on the support and the capacity of the structure that the support is attached to.

In your case you would need to determine the load on each component and ensure that it has adequate capacity. I would think that you would also need to determine the load that will be applied to the buiding structure and ensure that it is less than that for which the building was designed to handle as you mentioned in your OP.