Linear Interpolation & Programming of Stiffness of Pile Group

Question

Good Morning MathCAD Group,Would anybody be kind to help me with the attached files. In the first file, I have pasted the table I'm trying to interpolate and MathCAD interpolation code that I have written, that I think is not working. I have in the table three different values that need to be interpolated before arriving at the correct answer.My second file is trying to program the stiffness of a pile group with a battered pile at different angles.Would anybody please help. Thank you.Regards,Boyer

Werner_E · Accepted Answer

I had a second look at your interpolation routines and they are definitely wrong. For instance all those routines don't consider the argument SR.ratio - it will be overwritten by the routine with a vector and is gone forever.

What you need is a 2D-interpolation, doing interpolation in two directions.

See the attached file where I included some routines for 2D- and even 3D-interpolation and showed how to use them in case of your first table. Feel free to try one of the three cubic spline interpolations as well ich that seems appropriate.

You can avoid the manipulations I did with your Table_1 if you provide the data in the correct way from the very beginning. We need the row and column header values as vectors and the pure data matrix without column and row headers, sorted that way that row and column headers are in ascending order.

Werner_E · Answer

I'm trying to interpolate and MathCAD interpolation code that I have written, that I think is not working.

I don't see any Mathcad errors in your first file. So why do you think its not workin? What did you expect?

My second file is trying to program the stiffness of a pile group with a battered pile at different angles.

Here the first error is the sum and the using of the vector index i. All variables you use in that expression are single constant scalars. You are calculating a sum from 1 to n (20) and treat all those variables as if they are vectors consisting of 20 values each - they aren't. I understand that n is te number of piles you have, possibly arranged in a rectangle. But I see no attempt to assign each of those piles a different E.p, A.p, etc. So its unclear what you expect that sum to be and which values you are trying to sum up.

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