How to: percentage of slope

mdbdesign · 发表于 2022-7-6 09:57:25

Happy New Year to everybody.

As per sample pdf file, need to calculate rise as per slope (%) shown on dwg.
I am doing it first time and don't want to confuse myself.
Only data I got is: % of slope, length of center line (already sloped I hope) and elevations but not in every turn.
Any suggestion, especially from pipe guys?(any lisp or spreadsheet is very welcome:))
sample.zip

irneb · 发表于 2022-7-6 10:08:27

Sorry, I don't do piping that often. But I do understand the concept. The % slope basically gives you the tan of the angle: I.e. Y/X. So a 2% slope = 0.02 = 2 / 100. If the centre-line-length is simply the X, this would be very easy: length * (slope / 100) ... thus in lisp (* length (/ slope 100)).

If the centre line length is the "already" sloped length, I'm assuming you mean it's the length of pipe as installed (not dimension on plan). Thus it would be the R in the calculation ... uhm, to try and remember trigonometry ... that means you've got R and the tan's value. Now you need to obtain the sin to get hold of the Y from the R. So: Length * Sin (ATan (Slope / 100)) ... or again in lisp: (* Length (Sin (ATan (/ Slope 100)))).

This then gives you a positive value of Y. I.e. you've got the level difference between the 2 endpoints of the pipe. Then you simply need to add or subtract from one end's level (depending on direction of fall).

ReMark · 发表于 2022-7-6 10:13:22

I came across a lisp routine at the Cadalyst magazine website if you are interested. It's called the Slope Annotation Tool and is described as a....

"Routine that calculates the percentage slope from one point to another given the elevation spot data."

Perhaps it could be used to obtain the information you are looking for?

pBe · 发表于 2022-7-6 10:25:16

Is this anything like contour slope interpolation?
Apoligies for my ignorance on piping

ReMark · 发表于 2022-7-6 10:28:35

I always thought that the percentage of slope was calculated by subtracting one invert elevation from the other and dividing by the overall length of pipe. Am I wrong?

ReMark · 发表于 2022-7-6 10:41:30

No, I believe it isn't.

irneb · 发表于 2022-7-6 10:45:04

I think we may be missing the OP's request. His pipe runs are a lot like a drainage pipe run's invert level calculation: he has a start level, a slope (already set at 2%) and the length of the pipe. From this he wants to label the ending level. What I'm not sure of is if the pipe's length is measured in plan view or in section. E.g. if the pipe is 5000 mm long in plan at a slope of 5% - that would make the actual piece of pipe 5006 long. Conversely a 5000 long pipe in section at 5% would be 4994 mm in plan. Given with these types of slopes the difference is minute, but with a pipe run which could be quite long and have multiple junctions you'd want to be as accurate as possible.

irneb · 发表于 2022-7-6 10:55:19

Here's a reasonable compromise. The attached spreadsheet calculates from a starting level. Given a % slope (negative slopes for sloping down) and a length. I've also included rounding up/down to the nearest mm depending on if sloping upwards or downwards (so a level of +2345.3 when sloping upwards always errs on an increased slope to become +2346, and a level of +2345.6 when sloping down becomes +2345). The slope % stays constant unless you modify it at any one of the pipes - then it continues to use that slope %.

There are 2 tabs in the spreadsheet one for when the lengths are measured in plan, the other when they're measured in section (i.e. the pipe's physical length). You can clearly see the discrepancy between the 2 measurements - using the same slopes & lengths in both gives a last level of +1871 when measured in plan, but in section a level of +1890.

Note the spreadsheet's made for use in metric mm. There may be needed some modifications if you're using another measuring unit (most probably the roundup / -down would need some changing). As would the cell formatting to show in fractions for inches.
Pipe Levels.zip

mdbdesign · 发表于 2022-7-6 10:58:07

Sorry guys, I was not able to answer, something wrong with internet connection.
Thank you for spreadsheet, will test it now.
So far I find out that length of pipes is shown with slope included but not every corner is mark with elevation. Will still need to use spreadsheet from IMEB. Thank you all for help.

[编程交流] How to: percentage of slope

发表回复

精选推荐