Holes in Deck Support Angles 2

[jike]

When we have a deck support angle expansion bolted to a CMU wall with 1/2" diameter expansion bolts, the steel detailer normally provides 11/16" diameter holes. I assume that this is so that he can install the anchors thru the angle. Isn't this hole considered oversized since it exceeds the diameter of the anchor by more than 1/16"? Doesn't the angle have to drop down to bear on the bolts?

Should a plate washer with a 1/16" oversized hole be added and welded to the angle?

 

[SlideRuleEra]

The washer you descibe is good practice. The holes are oversized, but the safe load capacity of the anchors themselves (installed in a CMU wall) is too low for the oversize holes to be a limiting condition.

http://www.SlideRuleEra.net

 

[JAE]

For a Hilti Kwik Bolt, the recommended hole dia. is 9/16" (the anchor fits through a standard hole). Why let them oversize at all?

 

[jike]

JAE, good point. I need to check and make sure that they are using Kwik bolts not sleeve anchors.

Thanks again!

 

[Lutfi]

I think the detailer is coming from the old days where they used to place the anchors in the concrete and the anchors had tendency to shift around. There is no excuse for that these days.

I think 1/16 inch larger hole is plenty enough. They can use the shelf angle as template.

Regards,


Lutfi

http://www.cdeco.com

 

[tweedledee]

I had the same problem also recently with epoxy anchors in CMU.
The contractor used larger holes in the deck support angle so they could temporarily support the angle at each end. Then they drill the CMU holes through the pre-drilled steel holes (like a template). This saved them setting out the holes on the wall prior to placing the deck support angle.

BUT, the problem is this,.. if the anchors are installed at uneven elevations relative to each other, then some bolts will be supporting more load than you had designed for!!. i.e. the load will get to the highest anchor first.

The ASD spec gives very clear rules for oversizing. For your 1/2" bolt, a maximum of 1/16" larger than the diameter is permitted.

In my case, since the angles were fabricated with the holes, I requested that they use a larger anchor, or a welded 1/4” washer plate with the correct size hole at every anchor.