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Re: hooked ABs[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: t.w.allen(--nospam--at)cox.net, seaint(--nospam--at)seaint.org
- Subject: Re: hooked ABs
- From: Rhkratzse(--nospam--at)aol.com
- Date: Tue, 5 Aug 2008 12:15:39 EDT
Thank you for your .02, Bill.
I'm wondering if *two* nuts are necessary at the bottom of a threaded rod anchor. Wouldn't *one* nut provide substantially the same anchorage as an embedded head (for residential shear wall anchorage, loaded primarily in shear)?
And while we're at it: I'm curious why/how Simpson's SSTB wiggly hold-down anchors are significantly better than J-bolts, since they too would seem to be subject to straightening and pullout. Bigger/stronger/deeper yes, but not conceptually different. (I'm not questioning Simpson's allowable loads, just trying to understand the mechanism.)
Ralph Hueston Kratz, S.E.
Richmond CA USA
In a message dated 8/5/08 9:01:29 AM, t.w.allen(--nospam--at)cox.net writes:
I think double nuts work as well if not better than a nut-plate-nut assembly. Sure, the latter has a larger truncated shear cone, but I believe the behavior of the embedded plate would tend to create a failure plane in the concrete quicker.
Just my two cents.
T. William (Bill) Allen, S.E.
Consulting Structural Engineers
V (949) 248-8588 • F(949) 209-2509
From: Andrew Kester, PE [mailto:akester(--nospam--at)cfl.rr.com]
Sent: Tuesday, August 05, 2008 8:26 AM
Subject: re: hooked ABs
I agree with Harold, I have never heard anything great about hooked ABs though they are still used all over the place. My boss stopped using them when I first started out of college about a decade ago because he read they "would fail by 'snaking' out of the house (wait, how did that much time just slip by!)...
Simpson in Jacksonville, FL (may have something sim. in TX or CA) has a one day seminar regarding their epoxies, bolts, etc. With audience participation, they drill holes in a big block of concrete and then after lunch you test them, even the epoxy anchors. Great demonstrations, as the epoxy would either shear cone fail the concrete or fail the rod in tension. The hooked L bolts always "snaked" out of the hole with the L straightening out.
If we have a connection at a foundation in particular, with any kind of uplift, we use all-thread rods with two nuts and a 2" SQ washer at the end. Nobody ever complains but if they do Simpson makes a PL1/4x2x2 I have seen at Home Depot. For really big uplift conditions at footings we will sometimes make those washers bigger or just use an embed plate that would have to fail in punching shear. We usually detail a couple of pieces of rebar sitting on top of the plate for a little feather in our cap.
Andrew Kester, P.E.
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803
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