structural help needed

[hurricane_redbone]

If you look on page 6, you will see the top of my tank. it has 6 holes in it so light can come through and feeding but still maintaining the strength of a cubic structure. but I was thinking that If i ever need to put something large in the tank or maybe when my fish are bigger and i need to pull a fish out for some reason, or the worst nightmare, catching a fish that doesnt want to be caught; it might be nice to have a larger hole at the top so i can have more freedom especially in chasing the lil bastards to a corner. so heres my question:
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|___|___|___|
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If this is the tank ^, what would have the strongest structure if i cut one of the bars away to make a larger hole.

option 1:
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|___|.....|___|
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option 2:
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|___|_______|
|_______|___|

I think 1 is the best way to go, what do you all think?

 

[ammerman19]

you are right deinitely option #1

 

[portabuddy]

I say #1 aswell, you have the front to back support and with the two ther bars giveing you side to side support i say cut the middly one away...

 

[IITUFFTOBEATII]

but I was thinking that If i ever need to put something large in the tank or maybe when my fish are bigger and i need to pull a fish out for some reason, or the worst nightmare, catching a fish that doesnt want to be caught; it might be nice to have a larger hole at the top so i can have more freedom especially in chasing the lil bastards to a corner

I wouldn't cut it at all, do you really anticipate your fish not being able to fit through those spaces before you realize they need to be moved? Option 1 is the only option but wont help you corner a fish any more than the current configuration. Your option 2 will not work, consider the load path, either it will not hold, or none of the bracing was needed in the first place

If you do decide to cut the middle piece out (option 1) you might as well cut them from the other two bays as well because they will be useless without the center one connecting them

edit: just to elaborate a little on why option two won't work: you eliminate any bracing in the short direction where it is more critical because the longer walls will have larger stresses and keep the bracing on the short walls which have relatively smaller stresses. If the tank does not fail with this configuration than there is no need for bracing on the short walls. I wouldnt be willing to test this if it were mine.

I do think the bracing is a good measure and I wouldnt cut any of it, just have to plan appropriatly to not need to put in or remove anything that wont fit through the openings, they look plenty big to me

 

[IITUFFTOBEATII]

I know its a little late for this bit of info but the corners of your bays should be rounded, square corners cause stress concentrations which can lead to fatigue, cracks, and possible failure

 

[hurricane_redbone]

I know its a little late for this bit of info but the corners of your bays should be rounded, square corners cause stress concentrations which can lead to fatigue, cracks, and possible failure

Im not worried about that, the top fits on perfectly square, cracking would only occur if there was a vertical force. but its all horizontal stress on the would. I dont think this wud be a problem.

 

[hurricane_redbone]

I wouldn't cut it at all, do you really anticipate your fish not being able to fit through those spaces before you realize they need to be moved? Option 1 is the only option but wont help you corner a fish any more than the current configuration. Your option 2 will not work, consider the load path, either it will not hold, or none of the bracing was needed in the first place

If you do decide to cut the middle piece out (option 1) you might as well cut them from the other two bays as well because they will be useless without the center one connecting them

edit: just to elaborate a little on why option two won't work: you eliminate any bracing in the short direction where it is more critical because the longer walls will have larger stresses and keep the bracing on the short walls which have relatively smaller stresses. If the tank does not fail with this configuration than there is no need for bracing on the short walls. I wouldnt be willing to test this if it were mine.

I do think the bracing is a good measure and I wouldnt cut any of it, just have to plan appropriatly to not need to put in or remove anything that wont fit through the openings, they look plenty big to me

thanks for the help. I knew option 1 was the only way to go, i just put up number two to suggest that if anybody knew any other way to go they cud just draw it out.

But its good to see someone else is on the same page as me, I was also thinking that removing the middle one will pretty much make it so the side walls have almost no bracing, and worst case scenario, if too much pressure builds up, it could cause the middle bracing to break sideways, leaving the whole tank unsupported and making my living room very wet.

I guess if i needa move anything really big in and out ill have to lower the wat level to like half and take the top plate off...

 

[IITUFFTOBEATII]

cracking would only occur if there was a vertical force. but its all horizontal stress on the would. I dont think this wud be a problem.

Its the stress in the members that causes the stress concentration, in this case it will be the tension force exerted by the walls of the tank, which is horizontal not vertical. Because it is one piece the stress distribution will cause concentrations at the corners, as the short brace supports the long walls it will elongate and some of this stress is transferred to the long brace supporting the short walls, and the same is true for the other direction. With out making them seperate pieces this is unavoidable. What is traditionally done in manufacturing is to make the corners at the intersections round to make the stress distribute in a less critical manner. It may never be a problem for your tank, just something to consider if you ever decide to build another in the future.

 

[IITUFFTOBEATII]

if too much pressure builds up, it could cause the middle bracing to break sideways, leaving the whole tank unsupported and making my living room very wet.

with the middle cross member removed there would never be any sideways force in the middle braces. There would be no bracing in the long direction at all except the rails of the top piece along the edge.

I guess if i needa move anything really big in and out ill have to lower the wat level to like half and take the top plate off...

thats seems like a much better idea than changing your design, stick to the plan