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RE: F1554 vs A36 threaded rods[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: F1554 vs A36 threaded rods
- From: Harold Sprague <spraguehope(--nospam--at)hotmail.com>
- Date: Fri, 7 Jan 2011 19:52:59 +0000
This is a good topic. Tom and I work in a bit of a different world. In anchoring process plant equipment, we need a reliable anchor force to preclude cyclic stresses and fatigue. To do that we routinely preload concrete anchor rods with hydraulic tensioners. We apply a defined preload on the anchor rods. If the bond on the shaft of the anchor breaks, the tension forces in the anchor are reduced. This is a bad thing in our world. |
For the anchorage of a PEMB, it should not matter. Regardless, I still advise against plate washers. I can cite a lot of references. The University of Texas performed the most germane studies for the Texas DOT. But then again, in a PEMB it should not make a substantive difference. An anchor plate washer in addition to the anchor nut is just a waste of time and money.
Regards, Harold Sprague
Subject: Re: F1554 vs A36 threaded rods
Date: Fri, 7 Jan 2011 14:29:47 -0500
You have brought up a good point regarding the threaded rods. However, there a few issues:
1. I don't thing the ACI 318 Appendix D is that accurate for deep anchors (18", 24") with a plate washer.
2. If the bond between the threaded rod and the concrete does not break, then the anchor is giving you a larger capacity than the cone. You might even be able to develop the rod in tension.
3. If the bond does break, then, you have the capacity of the cone.
Also, I have noticed that almost 99% of the anchors in Seismic Categories D and above, for columns along the perimeter of slab have brittle failure anyway. So, you would have to multiply the loads by 2.5. I feel a lot more confident with a deep threaded rod with plate washer.
Farzin S. Rahbar, SE
David C. Weiss Structural Engineer & Associates, Inc.
Sent: Fri, Jan 7, 2011 10:40 am
Subject: Re: F1554 vs A36 threaded rods
From a materials standpoint the materials are probably close enough. The problem is the threads. If you have performed an ACI 318 Appendix D design then the assumption is that with significant tension load the bond along the anchor bolt shaft is broken and all the force is delivered to the bottom head (nut, washer, or plate) which has enough bearing area to initiate the shear cone. This also assumes elastic stretching over the full length of the bolt. If the threads happen to prevent the shaft bond from breaking then you are trying to stretch over a very small length which may cause a brittle failure.
If your anchor bolts are small or most of your load is shear then I might not worry about it too much. If you have significant tension and you have large/long bolts then you may want to consider some type of bond breaker such as multiple wrappings with Teflon tape.
Thomas Hunt, S.E.
From: "Jeff Hedman" <jeff_h(--nospam--at)lrpope.com>
Date: 01/07/2011 10:22 AM
Subject: F1554 vs A36 threaded rods
I have a PEMB steel building project where F1554 headed anchor rods were specified to anchor the building to the foundation. However, these bolts were not ordered when they should have been and now due to time constraints the contractor wants to use A36 threaded rods with double nuts and a plate washer. At first glance I think this looks like it would be okay, yield stress and ultimate stress ranges are the same. However, I don’t have the ASTM publications that would tell me the difference between the two. This is an enclosed building so exposure to the elements is minimal. My questions are:
1. Are there any problems of using the A36 threaded rods instead of the F1554 rods that I should be aware of?
2. If A36 threaded rods are a problem, as another option, is it possible to get F1554 rods threaded the entire length and are they readily available?
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