Help Reviewing a Gymnasium Roof System 1

[EagleCreek11]

I have a local roofing contractor that wants to make sure this roof system is adequate to support his roofing operation. At this time, I do not know a whole lot about the project, such as age of the structure, depth of the roof filler, if any reinforcement is present, etc... I only know what I can see from these pictures. Obviously, I cannot make any type of recommendation yay or nay regarding his loading requirements, however; I would like to see if anyone who reads these has ever seen this type of roof system. It appears to be an arched (or more like a bowl, as the system slopes downward at the middle) concrete deck supported by a metal deck, which is supported by banded steel rods (looks like at least 7 to 9 rods...). Photos are attached.

If you have seen this type of system, could you provide some input on the design and construction? What do I even call this system? I cannot imagine the deck is not capable of resisting a minimum construction live load of 20psf. Thanks in advance!

 

[BAretired]

Very unusual! Can you get structural drawings?

 

[HTURKAK]

What kind of roofing operations? More than repairing water proofing?

It is hard to imagine the structural system supporting such a heavy roof . The second picture implies concrete layer under the WP.
Can you post structural drwgs and some pictures above the suspended ceiling ?
My first impression is the roof supporting str is 3D truss system rather than a shell str.




Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[EagleCreek11]

It is my understanding that the contractor is simply putting a new felt back membrane system on this roof (likely a PVC roofing material, unsure).

I do not have any structural or architectural drawings. We have requested, but this contractor is simply bidding the work and had concerns about the structure and wanted to know if he needed shoring for his roofing operations. I have not been to the site to determine if large cracks in the concrete/overlay material are present, or if the steel has any issues.

I have not seen this type of roof design, and without having been there, I am unsure if a 3-D truss system is present. Should the contractor be awarded this project, it is my hope some drawings can be located!

 

[dik]

Is he removing the existing?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[EagleCreek11]

dik.... It is my hope that he would remove the existing waterproofing and replace, but I am not sure.

To be honest, I was referred this project by another structural engineer this morning and this is all the information I have. This post is more trying to understand the roof system and to see if anyone has observed or designed a system like this.

 

[driftLimiter]

Seems like there is a catenary or membrane effect in this roof. Very interesting. I would be looking at the original design and anchorage at the ends of those rod bundles to see if they were accounting for lateral thrust. Seems like those rod bundles wouldn't make very good beams but they would make excellent cables.

 

[dhengr]

EagleCreek11:
The overhead view of the roof surface suggests that that might be (probably is) a shallow hyperbolic paraboloid surface. They work well at spanning large column free areas and are a fairly light roof structure. The support systems, walls, buttresses, etc. should give some hints as to the structure. The school, or the municipality should have some plans or know who the Arch. or SE were.

 

[JAE]

This might be some type of cable tension structure - possibly similar to the La Villita Assembly Hall in San Antonio, Texas.
The one photo you show suggests that the perimeter eave has a concrete beam that would serve as a compression ring with cables (internal to the concrete?) providing some type of catenary tension support for the main roof area.

 

[jerseyshore]

Found this article while searching what dhengr suggested.

https://www.designingbuildings.co.u...lic paraboloids,construct thin 'shell' roofs.

Would be really cool to see the original drawings even though I'm sure that's very unlikely. Check the old boiler room or random file cabinets, never know.

 

[ALK2415]

might be some sort of catenary structures (from 60's)
you might need to redo the structural calculations for the added weight

see Cable Structures by H. Max Irvine page 223

Catenary roof system

Also found this roof detail for Olympic Saddledome, Calgary (Alberta)
Link

 

[EagleCreek11]

Thank you all for the information to this point in time. Should I find additional information, I will share! In the event I get to work with this contractor on this project, I may post the information I discover (if I remember!). Should anyone else view this and have additional information regarding this type of system, I would love to read it!