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RE: Anchor Bolt Design for Vessel/Stack[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint-seaosc(--nospam--at)mail-list.com
- Subject: RE: Anchor Bolt Design for Vessel/Stack
- From: Harold Sprague <spraguehope(--nospam--at)hotmail.com>
- Date: Wed, 20 Mar 2013 11:09:19 -0500
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Bill, I have worked on this for quite a long time. I have tensioned anchor rods back when they were anchor BOLTS. Many other industries have tensioned anchor rods for a long time. There are a lot of other considerations that you will need to factor. There is also loss in tension that reduce the tension with time. There is the issue of breaking the bond with the concrete. If you don't, you will not have a reliable tensile force. There is also the method of how you measure the tensile force. Every industry does it a bit differently. The wind turbine industry has been using load indicating washers that are calibrated for a particular tension. The nuclear industry uses calibrated hydraulic bolt tensioners. I prefer to use calibrated hydraulic bolt tensioners. I have used this on projects from Louisiana to Alaska. Millwrights are accustomed to using hydraulic bolt tensioners. Riggers are also. Iron workers need to talk to the riggers. But I have used this for buildings and all kinds of applications. The first time was in 1976 when I had a tank that vibrated a lot in spite of my best calculations. An iron worker buddy offered a "fix" when he put a cheater bar on a spud wrench and "stretched" the anchor bolts. The vibration immediately stopped, and the light bulb went on above my head. The ACI 318 is still applicable although the ductility requirements may be moot since with appropriate tensioning there will never be a net change in the stress in the anchor rod. The applied tension of 70% of Fu is a bit generous for anchor rods. It is appropriate for high strength bolts because there will be no relaxation because steel is totally elastic. Concrete is less so because it needs to age. One of your thoughts may require a bit of a paradigm shift. This one is not very intuitive. The force at the base does not change with applied tension until the the applied tension is greater than the pre-tension. The concept is the same as any steel to steel connection that is in tension. Steel to steel connections that are bolted with bolts in tension are required to tension bolts to 70% Fu. When external loads are applied, the force in the anchor rod and the force at the anchor point does not change until the pretension force is exceeded. Therefore your statement "Anchor steel strength would also be calculated using total force (pretension + tension from lateral loads)." is not accurate. It has been my intention to publish an article about this for a while. Regards, Harold Sprague > From: bill(--nospam--at)polhemus.cc > Date: Tue, 19 Mar 2013 15:08:59 -0500 > Subject: [SEAINT-SEAOSC] Anchor Bolt Design for Vessel/Stack > To: seaint-seaosc(--nospam--at)mail-list.com > > Been awhile since I looked at this topic, and especially not in light of > ACI 318 App. D. > > Observations: > > 1. Pretensioning bolts is a good idea. The benefits include lessening the > possibility of bolt loosening and fatigue, and creating a sort of > composite behavior between the concrete foundation and the anchor bolts. > This is commonly done for anchoring tall slender structures such as > highway light standards. > > 2. If pretension is sufficiently applied, the base ring will be in > continual compression against the concrete (or grout). > > 3. Pretension to 70% of Fu appears ideal for this purpose. Truncated 1225 characters in the previous message to save energy. ------------------------------------------------------------------------- Post your message to the list by sending it to: SEAINT-SEAOSC(--nospam--at)mail-list.com. The email messages sent to the list will be saved in an archive on the World Wide Web. These archives are located at: http://archive.mail-list.com/SEAINT-SEAOSC To contact the list owner, send your message to: SEAINT-SEAOSC-list-owner(--nospam--at)mail-list.com. 5700 Ralston Street, Suite 300, Ventura, CA 93003 To unsubscribe, switch to/from digest, get on/off vacation, or change your email address, click here. <http://cgi.mail-list.com/u?ln=seaint-seaosc&nm=seaintma%40euken.net>
- Anchor Bolt Design for Vessel/Stack
- From: Bill Polhemus
- Anchor Bolt Design for Vessel/Stack
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