Concrete Tank Moment Distribution
Concrete Tank Moment Distribution
(OP)
I'm designing an open-top rectangular concrete tank. The walls are fixed to a base slab and free at the top. I determined fixed end moments of the wall and slab using "Moody Tables". Now I want to perform a moment distribution to determine the final moment at the base slab/wall interface.
Question: How is the Distribution Factor determined for the wall with bottom fixed and top free?
-JCali
Question: How is the Distribution Factor determined for the wall with bottom fixed and top free?
-JCali






RE: Concrete Tank Moment Distribution
I am not sure how you can do the moment distribution. I would assume that you are looking at a 1' wide strip around the top of the tank and trying to look at it that way. I guess that isn't the approach that I would take. I think that you will find for many walls that you can just design as a cantilever and move on.
RE: Concrete Tank Moment Distribution
For your base moment (and horizontal wall steel away from the corners), use figures 21, 22 and 18 for plates with a fixed base and hinged edges. You can't use fixed edges unless your tank is square.
For your corner steel, use figures 1, 4, and 5. Keep in mind that your corner steel has to resist tension in addition to bending.
RE: Concrete Tank Moment Distribution
-JCali
RE: Concrete Tank Moment Distribution
Since the edges af the mat are connected to the walls, they will rotate with the base of the walls, and have the same moment. Figure 34 will probably give you different edge moments than your wall analysis. You'll have to adjust your mat analysis for the difference. As you can see, your analysis becomes pretty approximate, so be conservative.
Also, keep in mind that your mat may carry tension as well as bending as a result of the shear at the bottom of the wall.