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# Using MathCAD to find point of zero shear

## Using MathCAD to find point of zero shear

(OP)
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.

(OP)

(OP)

### RE: Using MathCAD to find point of zero shear

(OP)
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.

### RE: Using MathCAD to find point of zero shear

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

### RE: Using MathCAD to find point of zero shear

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

### RE: Using MathCAD to find point of zero shear

(OP)
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.

### RE: Using MathCAD to find point of zero shear

z means that it's compressed.

### RE: Using MathCAD to find point of zero shear

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.

### RE: Using MathCAD to find point of zero shear

(OP)
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.

### RE: Using MathCAD to find point of zero shear

(OP)
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.

### RE: Using MathCAD to find point of zero shear

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

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