Stressbars (Traverse Strapping) Question

[Mentzer]

I am planning my next tank, stand etc just now.
The tank shall be 96" long x 36" wide x 26" deep, made from 12mm glass.
I know the tank/water depth is the primary factor with regard to water pressure/stress, but is there a mathematical formula to calculate the width, spacing and number of "stress bars" or "traverse strapping" required?
Right now I am thinking about three in total.
Two (one each end) of 4" wide a few inches in from either end and, the critical one, 8" wide centred. All 12mm glass as per the tank construction. Any comments or suggestions welcomed. Thanks

 

[CHOMPERS]

I think you have the right idea. Go back to the formula or calculator to see how three braces will help. At each brace, it effectively is equivalent to dividing the tank at that point. In other words, with three braces you can do the equations as four smaller tanks.

And for those here in the US, 12mm is aprox. 1/2 inch.

 

[CHOMPERS]

Oh, by the way, space the bracing out evenly. The ends don't need to be braced so close. They serve as their own bracing.

 

[Phixer]

I am planning my next tank, stand etc just now.
The tank shall be 96" long x 36" wide x 26" deep, made from 12mm glass.
I know the tank/water depth is the primary factor with regard to water pressure/stress, but is there a mathematical formula to calculate the width, spacing and number of "stress bars" or "traverse strapping" required?
Right now I am thinking about three in total.
Two (one each end) of 4" wide a few inches in from either end and, the critical one, 8" wide centred. All 12mm glass as per the tank construction. Any comments or suggestions welcomed. Thanks

This can get deep. Use the hydrostatic pressure formula to determine how much pressure you are working with. Then you will need to figure the max deflection of you material.

Too much to type in here but if you have determined the material is capable of withstanding the hydrostatic pressure for your dimensions you will need to find the max safe deflection rate. Almost always greatest deflection at center of window. I dont know what the specs for 12mm glass is, you will want to get this from the MFG. If the glass is thick enough no bracing is required however the deflection rate is reduced significantly with the addition of one center cross member. For the other sides (each side of the center cross member) no more bracing is required if the safe deflection limit is not surpassed. If the defection is still greater than what the window is rated at you will need to add more cross members spaced evenly until the deflection for each section in between cross members is below the limit the material can safely handle. The more you add the safer it will be however as long as the max deflection is not exceeded in any area you will be fine.

 

[macktab]

I agree with jovial, and a struct analysis is required to determine a custom design. Plate bending formulas have been derived by industry engineers to estimate maximum stresses and deflections for various plate width/depth ratios and corresponding deflections for several boundary support conditions, I have a copy. And it gets involved. I assume u r thinking glass.

We could also use the "observational" approach, looking at the performance of marketed and sucessful designs in practice. I have a 55G tank 48x13x20high circa 1976 that uses 3/8" (9.5mm) glass without a center support and is super tight to date. Without calc's I would look at the spec's for say, AGA tanks website, which gives pretty good idea of number of braces for given tank dimesions/glass thickness.

I dont intend to dilute the need for performing a specific calculation, it might be fun . But my gut feeling is that you wouldnt want to go more than 30in without a top brace, using substantial brace material thickness.

 

[Mentzer]

Interesting posts.
Thanks guys.

PS. I did think of equidistant spacing as you suggest Chompers, the major thing that would be problematic is that I really need to have
36" gaps ( or 30" at least) otherwise it would be very difficult getting at 36" micropeltes out the tank if required....