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Pumpstation Design:- Design of Liquid Retaining Structures

Pumpstation Design:- Design of Liquid Retaining Structures

Pumpstation Design:- Design of Liquid Retaining Structures

(OP)
Hi
I am currently designing a sewer pumphouse comprising a wet well and dry well, rectangular in shape.
The pumphouse is approximately 7.3m long x 3.930m Width x 4.1m Deep, effective dimensions.
I have computed all the loading scenarios on each of the walls of the pumphouse for the two worst scenarios i.e
when the wet well is empty and when it's completely full of liquid. The load types acting on the walls are active soil pressure, external water pressure and surcharge {wet well empty} while internal water pressure acts on the wet well walls when it's full ignoring passive earth pressure. In principle, these loads are triangular in nature as they act on the walls, varying from zero at the top to a ,maximum at the base of the walls. The roof slab to the two chambers is at the same level as the surrounding backfilled ground.
I considered the walls to be two-way spanning slabs that are continuous on all four sides in the analysis to determine the bending moments and shear forces. For this exercise, I used the elastic analysis method, after which I then redistributed the moments by 10%. I then performed a check of the results using the code method {to BS8110}. The results seemed reasonable, though the redistributed ones from the elastic method were generally higher than the code method.

I read a lot of reference texts on this topic, and I came across a worked example 6.1 by RD Anchor, "Design of Liquid Retaining Concrete Structures." I could not relate or find the source for the moment coefficients used in this example, which seem to be on a sliding scale, compared to moment coefficients used for elastic and code methods.
My problem is to compare and contrast triangular load pattern vs a uniformly distributed load (udl) that we normally use on slabs on a horizontal plane.
Could this be the source for the difference in moment coefficients stated above?
Which criterion should I apply in evaluating the Bending moments and shear forces acting on the walls?

RE: Pumpstation Design:- Design of Liquid Retaining Structures

I'm not sure where you are, but I suspect it's not in the states.
There are two publications that have moment and reaction (shear) coefficients worked out. One is by the Portland Cement Association and it pretty much stinks. The other is the out of date publication, "Moments and Reactions in Rectangular Plates" by the Bureau of Reclamation, Water Resources Division. It is a very good document. Someone around you has it, or it may be online. Most everyone I know that does these kind of calculations uses it, some the extent of entering all the data into spreadsheets and mechanizing it. It can be interpolated between length to width and load height parameters.
Even if you're only doing one of these, it's a worthwhile acquisition.

RE: Pumpstation Design:- Design of Liquid Retaining Structures

I would add that you shall in every case include the cracking limit state design in your project as well, which in such structures is very likely to be the most unfavourable effect (critical design).

Structural Engineer, PhD
Structural engineering software

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