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Large Collector - Deck Connection Detail
3

Large Collector - Deck Connection Detail

Large Collector - Deck Connection Detail

(OP)
I was wondering if anyone had any ideas or comments on the attached sketch.

Background:

This is for an existing gym expansion. Basically I have two, three sided boxes. I need to collect the shear between them and dump it into a small shear wall. The collector will a large deep built up beam or truss. My concern is that if I simply extend the existing deck to the new beam with a plate than the contraction of the roof deck may cause problems with the collector (leading to some sort of induced LTB failure). Any comments on this or suggested details that would allow for exp/contraction but transfer vertical load and deck shear?

Thanks!!

EIT
www.HowToEngineer.com

RE: Large Collector - Deck Connection Detail

If the existing building worked as a 3-sided diaphragm, then do you need to transfer the force into the new shear wall? The new building can be built independent of the existing building?

RE: Large Collector - Deck Connection Detail

(OP)
Sorry that statement was misleading. We are removing the existing lateral bracing at that end of the building. (forget I said anything about 3-sided boxes).

EIT
www.HowToEngineer.com

RE: Large Collector - Deck Connection Detail

With the dimensions you are showing, I wouldn't worry about expansion/contraction. Plus, if the building is insulated, there should not be any appreciable temperature swings.

DaveAtkins

RE: Large Collector - Deck Connection Detail

Live load deflection of the two roofs will be a bigger concern. There appears to be a 5' difference between the roof elevations. Is there anyway to have the (n) collector directly above the (e) beam? Is the section drawn to scale with maybe 2ft between the (e) beam and (n) collector?

RE: Large Collector - Deck Connection Detail

(OP)
Thanks for the comments.

@wannabe ->Your dimensions are roughly correct. I suppose I could align them. What is your concern with deflection? What do you have in mind if they align. The existing will be removed and the new will carry both.

EIT
www.HowToEngineer.com

RE: Large Collector - Deck Connection Detail

wannabeSE makes a good point. But if the plate you use to connect one beam to the other is thin enough, it will allow the differential vertical deflection to occur.

DaveAtkins

RE: Large Collector - Deck Connection Detail

You may well get the flexibility that you need to handle the differential vertical deflection in that cantilevered bit of roof deck on the low roof.

Because you asked for it, I did my best to come up with a connection detail (below) that would transmit shear while accommodating expansion and contraction. I've never used it before and my general experience with these kinds of things is that they ultimately get gummed up somehow and do not function as intended.

Like Dave, I don't think that you need an expansion joint and you'll surely save yourself a ton of headaches by omitting it. Among other things, you'd require some kind of roofing detail with a double parapet and flexible cap.

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.

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