Floor support?

[kevin95695]

Threw this on the DIY forum, but not much help there.

I drew a 3D cutaway of our living room and the support structure of the floor.

2 questions: Left to right placement -- Should I spread the weight evenly over two floor joists or can it be offset as shown?

Second: If I use lally braces/jacks/columns as suggested by Minh (Reefugee), should I place them under the center of the stand (front-to-back), or towards the back of the stand to share the load with the existing piers?

There's got to be a structural engineer out there drinking beer and just itching to weigh in on this...

TIA!

 

[dots]

The main problem is liability, most won't because of that due to our litigous society.

Your missing a few items in your model. How old the house is, what the subfloor consists of? You mention piers, what is there spacing? The wall it is against, what is below that? How far is this from the perimiter of the foundation? What is the dimensions of the girders and the material, DFir or composite?

This is a 150g correct? Depending on the answers above, you may not need anything, but a little overkill never hurt.

Load distribution.......distributed evenly is always better, if you can support it evenly over the two, it will be better in the long run....can you move it to shown, maybe, but depends on your girder spacing.

Your stand design is going to have a big effect on it as well, if it a flat bottom, it will evenly distribute the load. If it is not and has a rim, or just four contact points, it will have localized points of stress in which the total static and dynamic loads will be transfered through contact point. Force=Mass/Area

As far as how much weight you have? What number to use, figure on 8lbs/gal, so 1200lbs and tack on some more for equipment and rock what not......so call it 2000lbs. At a minimum we should add about 500# for a factor of safety.......heck I heard about some HVAC guys doubling their loads for air handlers and then the Structural tripling that number..........if you estimate 2500lbs-3000lbs your probably in the ballpark. But I am guessing on this........liability thing remember.

I have a book with some beam tables in it and I will take a look at it, but took it to work.

I may be able to model this up for you quickly, if you give me the above information and run an F.E.A. (Finite Element Analysis) on it, which is simpler than what we had talked about before.

At the very least it will give you a "better" idea than a Wild Arse Guess.........In which I have a plenty.

By the way, would you really want advice from an engineer who has been drinking? If so, I will be sure to be wasted while doing the F.E.A. for you, we may even find you need to cut some holes in the floor to save some weight.

 

[kevin95695]

House built circa 1973. Floor is roughly 2" thick if you consider both the tongue-in-groove flooring and laminate surface. Piers are spread thin in my opinion -- The only ones that would be close enough to bear load are shown in second drawing. The wall is not load bearing, so relatively nothing beneath, except 2" floor. Way from perimiter. Girders/joists = 4"x6" old school regular grain wood. Yes 150g. And the little feedback I've gotten on the DIY forum is a consistent 'shock' regarding 48" spacing for floor joists, but yes, it is true. Keep in mind this is a house that is nearly 35 yrs old!

Thanks Doug, but I have NO idea what an FEA is... Or that other stuff either... Trying not to pester.

 

[dots]

Sorry, I can't help any more....so no problem.

http://en.wikipedia.org/wiki/Finite_element_analysis

This is the program I have been using for 3 years, it is a little more powerful than Google Sketch, (BTW the model you did looked pretty good.) I am definatly a fan of it and love it.

http://images.autodesk.com/adsk/files/autodesk_inventor_2008_technical_what_s_new.pdf

It talks about F.E.A., (pg 13), in it and shows the capabilities of the program.

I will get on it tomorrow hopefully.

 

[dots]

After reading your supplemental information, yes you will need to reinforce that floor, the combination of the age, spans, and materials used may not nessesarily cause the tank to fall through the floor, but there will most definatly be some deflection and possible fatique failure over time.

The best method are the jacks as you mentioned. When installing them, take extra care to distribute the point loads they create into distributed support by using a timber between the two. In addition, make sure the load they carry is transfered to the ground with a pier, preferably on a footing of some kind.

There was an excellent explanation Mihn provided for another person a while back, and I believe he had done the deed himself and would be an excellent resource on the specifics.

We won't need to run the modeling as I mentioned, but perhaps I will still do it just for fun this weekend. I need to practice it anyway.

Doug