Detail Question

[NewbieStruct]

We have prototypical steel buildings that has steel joists at 6'-0" o.c. We have an interior brace frame that lies in between two joists. In our details, we have that shows the location with both the steel beam and steel joists. We specifically say that the steel deck to attach steel deck per our general notes. There is section in the general notes that specifies the attachment to roof support members. Lately, we are getting RFI(s) saying since we have steel joists on either sides of steel beam, is it required to attach to the steel beam. This is basically because the steel joists have some camber on them and the steel beam sometimes is lower than the deck.

We have done similar projects where we don't even have the note but shown on a detail that the steel deck is top of a beam. This makes be scared that some contractors might not even sent a RFI and not attach to the steel deck. What happens in such a case during a lateral event? Who is to blame?

My question is "Are our notes not sufficient ?" Do we need to make it any more clearer?

 

[jayrod12]

If your joists sit on your beam. How would it be possible for the deck to attach directly.

 

[NewbieStruct]

The joists bear on the exterior walls like the beam. The joists and beam are parallel to each other. The detail shows steel deck sitting on the top of steel joists and steel beam. The regular spacing between the joists is 6'-0". The beam also acts as a joist. The beam is in between the two joists spaced at 6'-0" o.c. so the beam to joist spacing is approximately 3'-0". Attached view for clarity.

 

[KootK]

In my opinion, you do need need to make it clearer. The fact that your detail is being routinely misinterpreted is evidence of that I'd say. More importantly, I feel that your design should be adjusted to solve the recurring constructability issue. You could:

1) Weld a deck support angle to the side of the beam flange that matches the joist camber.

2) Camber the beam. Sometimes this can cause problems for your brace connections however.

3) Space joists 6' either side of the beam to allow the deck to flex more between joists and make it more obvious that a deck connection is required.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[NewbieStruct]

Could not attach in previous post

 

[NewbieStruct]

Kootk, So saying "Attach steel deck to steel beam per general notes is not sufficient" in your opinion. What about the buildings that are already built (4-5 years old)? We did not get such an RFI before. It started happening in the last 6-7 months.

 

[KootK]

I feel that the note is not just insufficient but remiss if it's directing builders do do something unduly difficult or impractical. You could add a note saying "site cast deck and beam of monolithic molten steel". It's clear but it ain't gonna happen.

The situation with the existing buildings is complex and, if there are problems, there will be issues to be resolved between you, your contractors, the owner, and perhaps your respective legal council.

-If the contractor didnt't connect the deck per your note and didn't query you on it, then they may be in trouble.

-If the contractor forced the deck down, made the connection, and it subsequently ripped off, then you might be in trouble.

-If the camber was modest, the contractor/fabricator made use of the natural beam camber, and the deck wasn't too thick, perhaps the connection was made successfully and nobody's in trouble.

Now that you're aware of the problem, I'd certainly take steps to avoid future problems.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

What kind of camber are you experiencing on your joists. Generally I've found that standard joist camber does not affect the ability to fasten the deck to any steel beams that run parallel to the joists. That also assumes the beam is a good 4 feet clear of any adjacent joists. Then the deck usually has enough flexibility to be pushed down to accommodate.

I've never had an RFI come in regarding this and I don't think I've ever put much thought into it. Do you indicate via section or plan notes that the top of these beams should match the top of the joist? Or did you just leave the beam low to match the rest of the steel? If the latter, then you must provide something to make up for the joist seat depth, an angle, or a tube or something.

 

[SteelPE]

jayrod,

The erector will most certainly have problems. Just because you never received an RFI doesn't mean they are not having problems, you just don't know what they are doing to solve the problem (like taking a saw to the deck and cutting the high rib). On longer joists I will indicate that the joist (say 40'+) next to the beam is to receive 1/2 of the SJI recommended camber. This is to give the erector a chance at getting the deck down.

Newbie,

I have never done anything more than indicate diaphragm attachment schedules on my plans. I have never noticed a problem in the field either. I have received questions in regards to the answer above which has caused us to add the note on our drawings in certain instances. Seems to me you may have some inexperienced guys out there right now.

 

[jayrod12]

I would hope that anyone reviewing the steel installation would catch them cutting the deck flutes. As I said, there hasn't been RFI submitted and I've never noticed issues on site. Take from that what you will.

Am I being naive? Maybe, but if they're having difficulty on site with this, I would expect them to notify me. If I ever caught one of the steel erectors modifying steel or deck on site without my direction there would be loads of hell to pay.

 

[NewbieStruct]

Thanks. My boss is going to add notes to our plans to make it more clearer on the drawings.

 

[XR250]

Most buildings I see have a bar joist 6" from the exterior wall and then an adjacent edge angle. How is that any different as the edge angle likely was not cambered.