Blocking between joists seats 2

[WWTEng]

I am concerned about roll-over of joists seats on a project (40LHs, spanning 68’, with horz shear = 780# joist seat). I found this thread to be useful.

http://www.eng-tips.com/viewthread.cfm?qid=301328

So I have decided to place HSS blocking between the seats but I was wondering if I can run this detail by folks here to see if it makes sense. I am using a 5” high HSS to match the joist seat and then asking it be simply tack welded to the seat.

 

[frv]

Why aren't you transferring the lateral load from the deck angle directly to the precast concrete panels? This is where the lateral load gets resolved anyway. The blocking is serving no function as shown.

 

[SteelPE]

Or you could just give the joist mfr the required roll over capacity.

 

[WWTEng]

frv,

I was just thinking about that actually. I can always ask for another embed plate from the precaster and save the cost of steel and welding.

 

[WWTEng]

SteelPE,

I have done that in the past but they always comeback with a comment that there is going to be x" lateral movement at the top of the joist and want me to approve that, which I have never felt comfortable with.

 

[spats]

You totally misunderstand JAE's comment in the earlier post on how he is using the blocking. As frv said, the blocking you show serves no function.

WWTEng, you must be a young/inexperienced engineer in an office where you have no support from other engineers. Your frequent, recent posts tell me this... unless you don't want to ask because you're afraid you'll look stupid. If there is somebody in your office you can bounce this stuff off of, that would be your best choice. The only stupid people are those that won't ask.

 

[UcfSE]

You don't need another embed to attach the deck angle to the wall, which is what I would do also. You can bolt the angle to the wall.

 

[DHKpeWI]

According to the book "Desgining with Vulcraft" joist seats have a roll-over capacity of 1,900 pounds.

 

[DHKpeWI]

I can send a few pages of this section if you would like.

 

[WWTEng]

UcfSE,

the precaster has no problem proving a 6x6 (@4' oc) plate at this location if I ask for it. But why would you prefer a bolted connection rather then a welded connection? Also, I was thinking that I would only weld the angle to the embed and not to the joist, to allow for any thermal movement of the deck.

DHKpeWI:

Thanks a lot for the info. Is it possible for you to post that info here!

 

[UcfSE]

I would prefer a bolted connection because it can be coordinated after the walls are cast, rather than trying to have a lot of embeds hit all in a line without being too high or low for the angle connection. Maybe I'm just used to high wind areas, but 4ft oc sounds like a long way to go to get embeds to work for the wall out of plane reaction.

 

[DHKpeWI]

WWTEng

See attachment.

 

[msquared48]

If the steel deck is welded to the edge collector at the PC panel and the deck is alto welded to the top flange of the joist, how are the seats going to roll over?

I think you are visualizing a problem here that does not exist.

Mike McCann
MMC Engineering