# Deflection of aquarium glass

Hi all,

This is my first posting to this Forum.

I'm currently designing an all glass aquarium, and would appreciate any input from the resident experts.

The aquarium will measure 1.80m (length) x 0.72m (width) x 0.65m (water height). I have just completed the construction of a reinforced concrete stand, and a load test has shown a mid span deflection of 0.8mm with a load of 940kg.

I will be building the tank from 12mm thick normal float glass.

Is there a formula to calculate the maximum deflection (before failure) of a given length and thickness glass? I'm concerned if the bottom glass can accommodate the deflection of the supporting slab, and would also like confirmation that, if the glass will deflect to this degree (0.8mm), can it still be considered to be supported by the bottom slab (or should I treat it like an unsupported slab, spanning the 1.8m between it's ends.

Thank you for any replies.

Hennie

Sun, 02/05/2004 - 15:31

Hello Hennie,
There is a simple excel calculator for aquarium glass provided by Pilkington which I have used.
If you would like to send me your email address, I will send it to you as an attachment.
Kind regards,
Michael Guy
Glasshouse ltd.
United Arab Emirates.
glassco@eim.ae

Mon, 03/05/2004 - 13:30

Bye
Enrico

Wed, 05/05/2004 - 19:40

Hi guys, and thanks for the replies. I already have an Excel aquarium glass-thickness calculator, and it does give recommended glass thickness, and deflection of the glass at that thickness. I'm assuming that the deflection given will be less than the maximum deflection which that particular thickness of glass can tolerate.

It is quite easy (relatively speaking...) to measure the deflection of a piece of glass. It is more difficult to accurately measure the load (pressure) on that piece of glass. So... what I need to know (and cannot find anywhere on the Web) is what the MAXIMUM deflection of a given length and thickness of glass would be, before it breaks. Surely there must be a formula which one can use to calculate this, for a particular type or make of glass ???

Regards,
Hennie