Load Capacity

That tower design belongs in next week's Caption This!

The closer the tanks are to the tip of the that thing, the greater chances of it falling. See if there are any cracks in the ledge or test it generally. Placing a strong column beneth it would develop its stability greatly. 1300 lbs. is quiet a weight for such a column (also given the dimensions). So my gut would tell me that its not safe. Try to place the tanks as close to the vertical column in your picture, and also construct another column right below the location of the tank(s) on the the ledge.

My gut also tells me that a 50% increased load may not be safe. Remember simple concrete has tremendous compression strength but lousy tensile strength. A cantilever design has forces of both compression and tension in it. Whatever re-bar steel configuration that resides inside this construction and any possible fasteners to any part of this cement are handling the tension in this design. We cannot see how the likely re-bar skeleton is configured to make a real estimate. This leads to me to my initial comment that you will be increasing the stress load by such a large percentage of the original load that I would be hesitant to just add this much of a load. Don't forget, at some time there will probably be additional forces (wind load, service worker, etc.) on this structure than the static loads you are now considering to increase.

I also wonder about your footing in wet weather possibly tipping the tower over. When you add all of this additional mass on only one side, you may no longer have the center of mass of the whole tower over your footing.

My option would be to remove the existing tank & replace it with a rectangular or square one, this will allow you to install it closer to the back of the platform allowing you to increase the volume without increasing the leverage, if the tank is made for you, you could have it made say 5ft wide 3ft deep & 6ft high. without knowing anything about that tower,what it was built for or the loadings it was built for, just from experience I would say it would have no problem holding three times what you are proposing.

If you are doubtful of the loading put a support under the front.

NB always wear a hard hat.

Bazzer

First off THANK YOU for including pictures..I wish more people did that when asking a question here. You actually don't have enough information. If that tower was originally designed as it's being used it probably was designed to a higher specification. Without knowing that you're guessing, that's what can contribute to a disaster. I wouldn't suggest you add more weight without further design information.

Should you however want my input I suggest the following..

by providing extra supports at the end,as shown in figure and allowing for proper transfer of load to the new columns, by making proper connection b/w beam and column, will serve your purpose . Since load will be distributed to four columns instead of two columns. So columns will be able to take the extra load on the slab irrespective of the earlier design.Now slab is simply supported by the beams on three sides, so bending moments will be maximum below the point load(water tank 100 gal) . since extra load added is less (50 gal) than the existing one , we can presume that design of slab would have done for the existing condition . so no problem as far as bending of slab is consider. but check for increased shear due to addition of extra load , whether provided depth of slab is sufficient to take care of shear. Since you do not have any detail of the reinforcement provided, check the shear capacity of slab by taking reinforcement required for existing load i.e moment produced by the existing tank (100 gal ,alone) on the slab . At last calculate the load coming on the beam and check whether beams is safe against moment and shear , since at present, its a cantilever beam (main reinforcement would have provided at the top and minimum reinforcement at the bottom) . since extra supports are provided max moment will be at the bottom and at the middle of the beam , so check for load carrying capacity of the beam for minimum reinforcement. Note : (assume minimum grade of concrete as per code and steel grade as per your decision depending on the experience of usage in your area or minimum reinforcement as per code for all calculations ) . By this you can draw conclusion , whether to upgrade the existing one or new structure to be built .

It looks like there is the space but no platform directly between the two columns..

My gut says it's ok, but my brain wants to climb all over it with some friends and see it I could budge it.. scientificly

That lump of concrete (4'x5'x about average 1¼') weighs more than 2500 lbs: the existing water tank holds 800 lbs of water and you want to add another 400 lbs of water. I'd say you'd get away with it easily: put both tanks as close as you can to the pillar or use a single new tank which you can place close to the pillar.

My Gut feeling is: NO, dont do it.

If you must, get this thing well propped. The reason for a big NO is, that this thing does not looks properly maintained and looks compromised. You dont seems to have sufficient data and a structural engineer to evaluate this structure.

As said by so many others here, dont do it.

Fareed