New Opening in Existing Tilt Up Wall

[JNEnginr]

I know this question has been asked several times, but I didn't quite find the answer i was looking for, so I'll have at it one more time.

Existing Tilt up wall, 30ft tall by 20 ft wide panel. Not a Shear Wall. Have original construction drawings. I know where the rebar is located, its in small groups as opposed to spaced evenly throughout the wall, I imagine for knock out panels. SMall opening was cut in wall without asking anyone for permission. And of course, they cut through the rebar group, like (4) #8 bars, (2) EF.

So I'm going to reinforce, no questions asked, putting a steel tube on each side of the opening. The opening is about 10 ft from the bottom of the panel, so I'm going to bolt there, to the wall and to the slab, then I'm going to run it up past the opening and bolt it again. I'm aware of the cracking at the corners and all that as well.

My initial response would be to run the tube all the way to the roof, and let the tube do all the work for wind/seismic loads. But what happens if I don't run the tube all the way up, but just say, 5ft above the opening and bolt? (Not my call mind you) Then I'm trying to create a composite section, right? And need to do a shear flow calc? Am I trying to develop the either total or partial tensile strength of the tube into the epoxy set bolts?

Thanks

 

[ishvaaag]

In my view, whatever be your intent, you may model your changes in a program and check how it behaves under the code hypotheses. You may ensure the composite action probably included in such model checking for the behavior and strength of the connectors.

 

[JNEnginr]

Anyone else have any insights?

 

[canwesteng]

I don't see a problem with treating it as a composite section and doing all the required checks. I would probably frame around the entire opening though.

 

[KootK]

I don't see this as composite. I see a single, simple span flexural member consisting of a steel tube for the lower segment, concrete panel for the upper segment, and a flexuarl/shear splice somewhere where the two meet. I'd connect the tube at the top of the opening and at the top of the tube and get the splice done as a simple couple formed by the connections. With this strategy, your bolts would see only tension and compression as a result of flexural action. Any bolt shear would be due to gravity effects etc.

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.

 

[msquared48]

I would run the tube section to the underside of the immediate floor or roof structure, making sure the lateral forces are distributed to the diaphragm.

Mike McCann, PE, SE (WA)

 

[JNEnginr]

Thank you for all your responses,

MS, I agree, I would run it to the ceiling, but my colleague is saying that they don't want to run it all the way up.

Koot, I agree with what you are saying, that's how I originally did my calc, I just wanted to see if other people agreed. I didn't think Shear flow was an issue.

So would most agree that Shear flow has nothing to do with this problem?

Solution would be to analyze the moment at the start and stop of the opening (top and bottom of it), then provide a steel section capable of withstanding said moment, then take the max moment, turn it into a couple, the design bolts for max tension/compression force, which the bolt would see as shear.

I'm just not positive about the "d" I use to get the couple. If the wall is 8" thick, and an hss10x4 is being used, would I say d = distance from center of wall to center of tube, so 8/2 =4 plus 10, so d = 14?

 

[KootK]

I'm just not positive about the "d" I use to get the couple. If the wall is 8" thick, and an hss10x4 is being used, would I say d = distance from center of wall to center of tube, so 8/2 =4 plus 10, so d = 14?

Using the strategy that I suggested, "d" would be the distance between the fastening at the top of the opening and the fastening at the top of the column. Five feet by the sounds of it. In my mind, the trickiest bit is checking the concrete panel above the opening for it's role in things. You'll need to exercise some judgment with regard to effective widths etc.

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.