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Concrete Anchors for largest Simpson Holddowns

Concrete Anchors for largest Simpson Holddowns

(OP)
Since the changes in the 2009 IBC for anchor rods in concrete (ACI 318 Appendix D), I have had trouble designing an anchor for the largest of Simpson's holddowns. Using the Simpson SSTB and SB anchors, the capacity of the anchor is less than 10k for a corner application in SDC C-F. The highest loads in a residence are generally in the corners, and are often higher than 10 kips if the house is narrow or has a lot of glass. What do you recommend for anchorage for holddowns in the 15 kip range? In most of the houses I'm designing, the concrete foundation walls are anywhere from 2' to 8' tall and 8" thick.

Thanks!
NHDSE

RE: Concrete Anchors for largest Simpson Holddowns

A few thoughts -

1. I thought a Simpson SB1x30 was good for 13-15kips.
2. Possiblly check for a post installed product, i.e. Hilti? (not sure that you would get better values)
3. Provide anchor reinforcement depending on the failure mode.
4. Try and check the design of the shear wall differently - Perforated Shear wall or Segmented or even FTOA.
5. Sharpen pencil on dead load
6. Design uplift forces as linearly varying across the wall and install multiply holddowns. Make sure you have a load path for this.

EIT
www.HowToEngineer.com

RE: Concrete Anchors for largest Simpson Holddowns

Stick it in the footing rather than the frost wall (assuming you have a frost wall) and size the footing appropriately. Or design the foundation so you can develop you anchorage properly. What would you do if it wasn't a wood or light gauge structure???

______________
MAP

RE: Concrete Anchors for largest Simpson Holddowns

Design a threaded rod from the hold down to an embedded bearing plate set in the footing. Should be able to develop one H*&& of a shear cone...

Mike McCann
MMC Engineering

RE: Concrete Anchors for largest Simpson Holddowns

You know I had footing on that list at some point, must have been distracted... damn phone calls getting in the way all the time...

EIT
www.HowToEngineer.com

RE: Concrete Anchors for largest Simpson Holddowns

RFreund:
Yup... we wouldn’t want real work interfering with anyone’s play on E-Tips. Turn your phone off. I’m sure the boss feels the same way. I’m sure he wants us spending even more time on Twitter and the shopping network, and the like, where we might really learn something. I’m always a bit surprised at how the number of posts decreases at the end of the work day, when people would be wasting their own time and electrons to continue to play here. Although, your list and thoughts were good ones, even without the footing; and your other posts and blog are always well thought out. I’m not just picking on you, you just gave the perfect opening for the above. smile

One of my earliest boss’ had an expression when he found us all bs’ing at one drafting table...; when I walk in here, all I want to see is a$$ holes and elbows, Get To Work. Of course, today you would substitute internet site or forum for drafting table. These darn computers and softwares have made us so efficient that we can now waste half our time on really important stuff, and the other half trying to understand why the software isn’t working, or how it arrived at that illogical result, and still not get anything done by the end of the day.

RE: Concrete Anchors for largest Simpson Holddowns

DH - Haha - I have yet to dislike one of you posts and you haven't let me down here. And similar to the others you have some very valid points.... "A$$'s 'n' Elbows "... I'll have to remember that one.

For the record, I was on lunch pacman

EIT
www.HowToEngineer.com

RE: Concrete Anchors for largest Simpson Holddowns

You may consider lapping the anchor rod with vertical reinforcement the stem wall. I know I've gotten 9-10 kip loads to work with #5 or #6 bars. AISC Design Guide 1 has a design example for calculating the required embedment. The rod will have to be fairly long +/-24". So depending on where the anchor is located within the 8" width, side-face blowout for deep embedment may become the controlling factor.

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