Effect of Water Changes on Tank Bracings

How big is your tank? And frequent water changes won't cause the tank joints to weaken so much that they will have any noticeable effect in the short term. It might in the very very long term.
But this is only IMO...
P.S. How long/frequently are you going to do wc's (What do you mean by "I want to step up the Water changes until I can get additional filtration")
Otherwise I do not think that frequent water changes will destroy your tank unless you bash it while changing the water, or something.
Good luck though

That's actually a very good question! I would think it would, but I have no idea if it really does.
I hope someone else here knows the right answer!!

I think most of the stress that the tank would see resulting from a water change would be with the rate of change moreso than the amount or frequency of change. Most important, IMO, is the rate of fill. If you were to just dump 30% of the tanks capacity into the tank in a big splashy mess, it might stress the tank enough to become noticable after a few repetitions... However, I think that under any reasonable conditions waterchanges won't have an appreciable effect on the life of a tank... particularly when you consider that the tank and braces are likely rated for well over twice the maximum force that would be applied to it when full. In short, I really don't think that the extra stress from increasing the frequency or volume of water changes is a practical concern in the life of a tank.

A tank expansion and contraction from repeatedly removing and replacing the water would definitely affect the tank structure sooner then one might think. However to really affect the tank s expansion and contraction of joints one would have to almost completely empty a tank or do 100% water changes. Not even 75% on a large tank would contract the tanks geometric structure. If you listen carefully as a draining tank approaches 100% it will move on its base and make a stress sound. But how many people do 100% water changes? Doing 30 to 50% does nothing to change the tank structure and remains in a constant expanded position.