Overhead Theater Loads

[smb4050]

Has anyone every run across design information on overhead theater loads? I've been asked to review if an existing theater steel truss roof system can safely support the installation of new higher capacity head blocks. The existing drawings do not show design loads. The building was built in 1974. Is there any information available on uniform loads to use for overhead support of theater equipment exclusive of catwalks? The rigging report I was given also mentions shock loads.

Thanks,

 

[jike]

For a new threatre, the Owner put us in contact with his rigger for the shows. We installed a pipe grid to support various light bars and special loadings hung from the roof framing. We worked with the curtain supplier for those loads.

 

[msquared48]

Are you talking about the loads to the grillage?

Mike McCann
MMC Engineering

 

[msquared48]

Back in '84 I did a high school theater in Anchorage, and, if I remember correectly, the grillage load (stage area) was 300 psf. This held all the curtains and special props. I will have to verify that though. The accoustic "clouds" were pretty light and outside of the stage area.

Mike McCann
MMC Engineering

 

[smb4050]

This for a high school theater also. I'm trying to find out if there is a industry standard uniform load for the overhead lighting, curtains, props, etc. which is suspended from the roof structure, so I am not sure if that's what is meant by the term grillage. To me 300psf sounds high. Of course the problem is these loads can and do change. I have a layout of existing light and curtain supports, and am in touch with the theatrical equipment supplier.

Thanks,

 

[msquared48]

The term "grillage" has to do with a metal support grid that is hung from the roof structure. It is in a "grid" pattern to allow for flexibility of placement of supports for the curtains, props, lighting, block snd tackle, etc., and is heavy in its own weight, irrespective of what it is supporting. Some of the curtains are 30 feet high or better. I will check on the loading.

Mike McCann
MMC Engineering

 

[msquared48]

This was probably done under the '70 UBC. The earliest I have is the '73 and for the "gridiron", which is the same as the grillage, the design live load listed is 250 psf (Table 23-C).

In addition, there is a separate chapter (39) dealing with theaters. You might try to get a copy to peruse from the library if there is not one in your office.

Mike McCann
MMC Engineering

 

[smb4050]

Mike,
Thank you for the reference.

Wow! I didn’t’ expect that kind of weight. The existing trusses are 40LH13 @ 8’-0 cntr’s spanning 68’ to 75’with a snow load of 27psf. These trusses are already near their allowable uniform loading and won’t safely support that much additional weight.

Thanks again,