New Vestibule in Existing Lobby - Curtain Wall Connection

[Nat]

Hello! I'm working on the renovation of an office tower (6 floors) and one component is adding a new interior vestibule to the lobby. The vestibule (7'-0" x 13'-0") will be storefront with a gyp bd ceiling. The proposed design includes adding (2) posts at the interior corners, anchored to the slab to carry the framing for the canopy/ceiling... pretty straightforward. The connection at the exterior curtain wall is my concern. Rather than adding (2) more posts in front of the cw, the proposed design attaches to the horizontal mullion of the curtain wall. A structural engineer walked the project and said that horiz mullion is structural, but I was not present at the meeting and there is no documentation from the SE. The load of the ceiling and canopy is not a lot, but I tend to err on the conservative side. Should I push for the SE to sign off on the connection detail or am I overthinking this?

Just a note - I work for a design-build contractor and the proposed design is coming from the construction division... they are pushing back against having the SE come in due to time and budget.

Thanks in advance!

 

[RLGA]

If you know the manufacturer of the curtain wall system, contact them. They probably did the design calculations for the system (these systems are usually delegated design and not designed by the project's structural engineer). They can probably tell you what it can support if anything.

 

[steveray]

The SE is going to sign off on it one way or the other....

 

[Nat]

Thanks for the comments. I did push back and will be having the SE design the connection.

 

[Mark K]

This is not a building code question.

Sounds as if the construction division is trying to play engineer. Are they used to working with engineering consultants or is there attitude that he is just another sub?

Sit down with the structural engineer and discuss the concerns of the construction division and then hear what he recommends. Remember you brought the engineer on board for his expertise. Pressuring the engineer to sign off on a detail sounds as if you are not willing to respect the engineers expertise.

Be aware if the engineer is not listened to it is more likely that you will have problems down the road.

 

[steveray]

It's a design build......

My answer: Well when you are done designing it, you can build it.....

 

[ADAguy]

Curtain walls are typically designed for wind, seismic and attachment to the buildings structure. Superimposing a load not initially accounted for may lead to unintended consequences.