Force around an opening

[slickdeals]

Folks,

I have a situation for which I need a creative solution. What you see in the attachment is a leg of a tilt up panel, through which the owner needs to run a 10" dia. pipe for stormwater.

I am required to evaluate if he can do it, meaning provide some alternate way to transfer the forces around the opening and then down the foundation.

Does anyone have a similar experience?

Thanks

 

[DaveAtkins]

I would add a vertical WT each side of the opening to reinforce what is left of the concrete.

DaveAtkins

 

[slickdeals]

@Dave,
Thanks for the suggestion. I am trying to get some more understanding of how the force flow is achieved.

As in how does the force transfer from the concrete to the steel member, and then back into the concrete? I am essentially making up for the area of lost concrete, but how long does the member need to be/ how should it be connected and such?

 

[youngstructural]

If the force is purely axial, you can just introduce a section of steel pipe, dry pack grouted fully around solid into an oversized hole. This, however, will not work in uplift without some re-jigging...

The crushing strenght of the tube also needs to be considered for annular deflection. You can use mining tunnel pipe deflection formulae for this purpose.

Hope that helps!

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[hokie66]

IMHO both you and the owner should know better. Surely there is a better location for the pipe.

 

[msquared48]

I would design the panel as an "L" shaped panel, attaching the edge to the next panel and transferring the force from the 2' leg to the adjacent panel, avoiding the issue here. I would make the 2' leg containing the 10" diameter hole an infill, non-bearing panel.

From my tilt-up design experience, it just looks to me that there will be too much reinforcing required and too little structural space to utilize, especially considering shear reinforcing too. I can see two layers of #5 at 4 to 6" on center with ties, even if the hole is not there.

Mike McCann
MMC Engineering

 

[JStructsteel]

msquared, why the ties in the leg? Are you saying the #5's with ties due to the hole, or before the hole? Are the ties only there for shear forces?

 

[youngstructural]

I normally design tilt-up legs less than 600mm wide as Mike suggests... I cannot speak for Mike, however I would usually have two layers of D (or HD) 12 (or 16) bars with R6 stirrups at 150 crs. That's very similar to Mike's sugggestion, except metric, and I would use them before the hole. With the hole I would be looking to do a specific check, however I would default to Hokie's position if the column experienced ANYTHING other than simple compressive loading.

Essentially you're treating the leg as a column. This has always been a point of annoyance for me: When is a tilt-up panel a wall, and when is it a column? I have never found a code that will draw a line between column vs. wall dimensions or aspect ratio, despite having looked for this guidance for a long time. I have always tried to treat any tilt up panel as a column if I believed the behaviour would be more likely to be column-like, or it it has a thickness to width ratio of less than 1/4.

And yes, the stirrups are for the shear capacity, but also for confinement. If you have a slender panel all around, then they are also to permit ductile plastic hinge formation at high seismic loads.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...