Max allowable loads for brackets on tank shell

[Soln]

I'm looking for a transparent method of determining allowable loads on tank shell by brackets, for example, a platform support bracket. I'm familiar with a method distributed by a tank mother company (C#!) that's been passed down; it calculates the max allowable moment, as M=1390t^2(6+6BL+(B^2)(L^2)). I'd like to know what's in the coefficient 1390, B=1.285/sqrt(Rt) is also used in API 650 Appendix P. I'm also familiar with a method published by Blodgett (Lincoln Book) that also uses undefined coefficients. Can anyone help me get to the root of the above mentioned methods to determine max shell loads? Can anyone provide a more transparent method, or direction to determine max loads/stresses myself?

 

[MJCronin]

SDK,

Many tank design companies handle this issue in a different way.....they develop a reasonable "standard clip" detail and require the use of the clip on all of thier ladder-platform attachments.

The "standard clip" would be slightly overdesigned, be load rated and be applicable for thin walled tankage.

Variations can be developed for special cases, such as tank made from non carbon steel materials.

 

[Soln]

That's a great policy, I'll use that myself. Is anyone familiar with a method they can share, using principles of strengths (avoiding ambiguous coefficients), to determine the allowable load for a specific shell clip? Sometimes I utilize reinforcing pads to distribute stress, but I need help establishing a method for determining allowable loads for specific shell thickness, radius, and clip configuration. Or, rather, a method for determining the stress imposed on a shell by a support clip (vice versa).
Thanks for the comment.

 

[compit]

As a tank inspector it is my experience that whenever a tank is designed with bracket welded direct to the shell, the exact location in regard to vertical and horizontal welds are not taken into account. As a result it can be common to find brackets welded inside the minimum permissible weld spacings as per 650 and 653. Just my 2 cents but if reinforcement pads were always used, there would be less stress on the shell and pad could easily be site cut to allow for required overlap.