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fizzy (Mechanical)
16 May 08 7:13
Hi All,

Pls can someone tell me how to calculate the anchor bolt load required to overcome saddle movement as a result of seismic load using ASME VII div 1. I'm working on a horizontal vessel of abt 15tonnes.
Helpful Member!  gr2vessels (Mechanical)
18 May 08 21:58
Anchor bolting calculations are done mostly by Dennis Moss's Pressure Vessel Design Manual, chapter 3. This is acceptable calculation for vessels designed to ASME VIII. It will be very difficult however, to separate all the loads acting on saddles and design the bolts only for seismic loads. After all, it always boils down to bolt shear and bolt tension, hence having all the loads calculated and the saddles sized, then get the minimum required bolting area dividing the load to the allowable stress and then divide it to the number of anchor bolts and there you go, select the corresponding bolt with the calculated cross section area. I also suspect that you need to re-phraze a bit your question, to clarify what help you really need;- perhaps you would distinguish the saddle and anchor bolts calculations for a 15 t vessel in a very active seimic area or located in a low seismic active area. Also, the bolt loads are never required to overcome the saddle movements, rather the anchor bolts prevent the saddle movement (other than that required for thermal expansion).
Please come back,
cheers,
gr2vessels
fizzy (Mechanical)
20 May 08 8:00
Hi gr2vessel,
Thanks for your reply. Like you said the anchor bolts are to prevent the saddle movement rather than overcome its movement.
The vessel is to be placed in a pit which means wind loads wouldn't act on it, just seismic and possibly bouyancy when the pit is filled with water. I've designed the saddles using finglow but not too sure on the type of bolt and thickness of base plate required. I'll be happy if you could give me some tips on how to calculate for bolt anchorage to prevent the vessel movement as a result of seismic movement. The vessel will be located in a low seismic active area.
In terms of the bouyancy case, can i simply use the upthrust acting on the vessel to determine the bolting and possibly the base plate thickness.
gr2vessels (Mechanical)
20 May 08 18:53
fizzy,
The Moss's book is very detailed on the design of saddles, including the design for seismic loads, it will answer all your questions in detail. However, I'm unable to email a copy of it to you because of strict copyright restrictions. The only way out is for you to purchase a copy on-line, take my word that is a valuable investment for many years to come. Do you have access to a design software like Compress or PV Elite? You can get the best available calculation done on a trusted software recognised all over the world, to not mention that the software gives you the ability to optimise the size of your saddles, including bolting.
fizzy (Mechanical)
21 May 08 4:21
Thanks, gr2vessels.

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