Using MathCAD to find point of zero shear

[Carnegie]

I'm trying to set up an equation in MathCAD to find the point of zero shear in a sheet pile wall. It returns an imaginary number. If you look on step 5 of the attached pdf it returns an answer of y-12.87ft when reduced to a workable quadratic equation. I'm trying to skip this step and solve for y. Does anyone have any suggestions? Thanks.

 

[Carnegie]

Here are the links

 

[Carnegie]

And yet another...

 

[Carnegie]

Ummmm K. looks like I solved my own problem. If you look on the attached screed grab of the Mathcad sheet you'll notice I added F5 and didn't subtract it. Now the sheet works. You gotta watch those pluses and minuses gang.

 

[IRstuff]

In the future, please post a real worksheet. Debugging a picture is often futile.

TTFN

FAQ731-376

 

[GregLocock]

loading xml files into mathcad v4 is a bit futile as well!

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Carnegie]

I wasn't sure you could post a sheet. You can peruse what I did if you like. it's a MC version 14. Just drop the "z" off the file extension to bring it back to an earlier version.

 

[jghrist]

Dropping the "z" does not allow opening in Version 13.

 

[Carnegie]

My mistake. I guess it only works if you have v.14. I know you can take v.13 files and add the "z" and turn it into a v.14 file but apparently not the other way around.

 

[IRstuff]

z means that it's compressed.

TTFN

FAQ731-376

 

[miecz]

Carnegie-

The cantilever sheet pile analysis in the Pile Buck Steel Sheet Piling Design Manual includes a "pivot point", below which the passive pressure reverses to the active side of the sheet. Your formulas don't seem to reflect a pressure reversal and result in a less consevative depth of embedment.

 

[Carnegie]

Thanks. These formulas were written by the NYSDOT Geotechnical Dept. I imagine the exclusion of the pressure reversal is compensated for by a much lower allowable stress of 25 ksi.

 

[Carnegie]

Here's the manual. You may like to look at it.

 

[Carnegie]

Thanks for keeping me up on my game. That's why I like to post things here. Please look at first paragraph, part B, page 9.

 

[miecz]

Oh, I see. The NYSDOT formulas use a so-called simplified method, and requires the resulting depth of embedment to be increased by 20% to account for the simplification. There is no pivot point in the simlified analysis. If you want to have a look at the conventional method, you can find it at SlideRuleEra's web site, in the US Steel Sheet Piling Design Manual