If it's encased in
concrete how is it going to work itself loose?
H. Daryl Richardson
----- Original Message -----
Sent: Tuesday, August 05, 2008 10:24
Subject: RE: hooked ABs
answer the SSTB part of your question, but I can answer the double nut
will lock together and stay in place. One nut will invariably come off unless
you bugger (technical term) the threads or weld the nut to the
T. William (Bill) Allen,
V (949) 248-8588 ?
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.)
Richmond CA USA
In a message dated 8/5/08 9:01:29 AM,
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
T. William (Bill) Allen, S.E.
V (949) 248-8588 ? F(949) 209-2509
Andrew Kester, PE [mailto:akester(--nospam--at)cfl.rr.com]
Sent: Tuesday, August 05, 2008 8:26
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
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.
ADK Structural Engineering,
1510 E. Colonial Drive, Suite 301
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