How Do I Determine the Force of Flowing Water

Question

How Do I Determine the Force of Flowing Water

PBW2 (Civil/Environmental)

(OP)

16 Sep 04 08:31

I need to analyze a pipe hanger that will be located along the bottom of a bridge. I need to determine what force the river flow will have on the pipe during a flood. I've been told to use 3 fps as the velocity of flow.

The pipe is 8" and carries water. I've been racking my brain but can't seem to find the correct formula.

Thanks for any help.

gbam (Civil/Environmental) · Answer 1 · 2004-09-16 11:31:58

Grab your old hydraulics book and look through the momentum equation, etc... You may have to derive the procedure inorder to fully understand it.

LHA (Civil/Environmental) · Answer 2 · 2004-09-16 13:49:54

Momentum will give you a force at various points. You will then have to analyze torque/moment and compare to pipe material specs.

But first, work on that velocity...use a flow versus cross sectional area analysis. For that you will need depth. For that, Manning's on the section might do, but I would do a HECRAS run on it. During your design flood, the water most likely will greatly exceed 3 fps. That is the most important prerequisite. I don't think you should seal your conclusions without a better velocity.

dicksewerrat (Civil/Environmental) · Answer 3 · 2004-09-16 18:46:28

What about ice floes? They have ripped more stuff from under bridges than just water. They bring an impact, point load to the party. Then think about debris.

cvg (Civil/Environmental) · Answer 4 · 2004-09-16 19:38:07

not just ice, how about other floating debris such as trees?

PBW2 (Civil/Environmental) · Answer 5 · 2004-09-20 12:07:39

RE: How Do I Determine the Force of Flowing Water

PBW2 (Civil/Environmental)

(OP)

20 Sep 04 12:07

Thanks for the response.

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How Do I Determine the Force of Flowing Water