Monday, November 9, 2009

RE: base plate design

Tanks can be overpressurized in more than a few ways.  
A tank can be overpresurized with air for testing purposes.  
LNG tanks need to have a minimum liquid level to avoid overpressurization also.  Inadequate or blocked venting is another cause.
LNG tanks can also exhibit "rapid phase transition". 
Fueling of tanks with inadequate venting can also be a source of overpressure. 
Flashing of vapors can overpressurize a tank. 

Tanks do what a tank would do and tried to take on a spherical shape as opposed to the original cylindrical shape. Whatever the source of the overpressure, the perimeter of the tank is anchored by the anchor rods and as the pressure increased the anchor rods fail in tension. 

Regards, Harold Sprague


Date: Mon, 9 Nov 2009 13:06:49 -0500
Subject: Re: base plate design

Do you mean the tanks were filled beyond the designed capacity for the anchors?
Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA
In a message dated 11/9/2009 9:41:21 A.M. Pacific Standard Time, writes:

How does tank pressure cause anchor bolt stretching?


--- On Sun, 11/8/09, Harold Sprague <> wrote:

From: Harold Sprague <>
Subject: RE: base plate design
Date: Sunday, November 8, 2009, 7:35 PM

Yes.  I have known of several failures for tank anchor rods.  The anchor rods stretch a long way.  This most commonly occurs when tanks are overpressurized. 

Regards, Harold Sprague

> Date: Sun, 8 Nov 2009 11:07:01 -0500
> Subject: Re: base plate design
> From:
> To:
> Highly neglected topic. No good single reference. The problem is the huge
> range of possibilities that can occur in: member section (shape and aspect
> ratios); load effects at the theoretical section end; local effects in the
> column, plate, rods, grout, concrete, welds; geometry of rod pattern; base
> shear (a topic in itself); elastic/plastic transition; flexible/rigid;
> assumptions...
> There was an interesting presentation at NASCC '09 in Phoenix, Better Base
> Plate Designs. I'll follow up if I can remember the researchers involved. I
> had a chat with them before I attended because I didn't want to waste my
> time. They reinforced the need for rigorous analysis. I believe that the
> work was supported by RISA Technologies for RISABase.
> I probably spend as much time with base plates as with the most complex
> connections in a structure. Lots of iteration and no single controlling
> case. I like to bracket my solutions to determine how much time to spend. If
> the best case and worst case are both within an order of magnitude, just go
> high. Quick method, to borrow a phrase from a colleague, "... round up and
> double ..."
> I'll repeat a question that I asked a while back:
> Has anybody ever known a structure failure due to base (steel/concrete) or
> anchor failure in the finished state (not during construction)?
> I have heard anecdotal stories but nothing confirmed as engineering failure
> vs overload, material or construction failures.
> Regards
> Paul
> --
> Paul Ransom, P.Eng.
> ph 905 639-9628
> fax 905 639-3866
> > From: "John J. Treff" <>
> > Does anyone have an example or a good reference for biaxial base plate desi=
> > gn? AISC Design Guide 1 deals only with uniaxial bending. Any references (=
> > books=2C manuals=2C papers=2C etc.)=2C suggestions or ideas on how to desig=
> > n biaxially (interaction of some sort or design separately for both axes an=
> > d then pick the worst case scenario) would be greatly appreciated.
> > From: "Adair, Joel" <>
> > Not that this will provide you with any guidance or understanding, but
> > RISA makes RISABase, which will handle biaxial bending, and just about
> > any other load combination you can dream up. We had it when I worked
> > -- Joel Adair
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