Rename to sum_previous or something like that and change the book to is_included, etc.

np and pd both have cumsum, but these are not lower bound.

• cumulative
• running
• snowball

Create class for Rebar Geometry.

Many functions rely on a simple bw, h input for column section. These should be changed to use the ConcreteColumn class instead.

The ZAtMax* functions need to be reworked not using ZfromP. Rather, need to refactor using the calculated c or strain at d functs to give more precise Z values.

These two functions are not actually necessary for the process --- Pmax and Pmin are calculated directly.

Planning on a PyQt6 interface with ability to input geometry and see realtime PM diagram. Coming soon...

Call it ConcreteColumn instead.

Although it could also be used for a wall section too, it's main focus is columnar analysis.

Problem:
The Z@P function is currently broken. And it's sensitive to the initial bounding Z values.

Background:
My previous VB code reversed Z signs for compression and tension. That part needs to be updated.

Thoughts:
This method uses Bisection Method for root finding. It shifts the PM graph vertically by a distance PDiff to align the PDiff value with the X axis. Values for P range from Pmax (compression) to Pmin (negative, tension). Z values range from about 1.5 (Pmax) to -50 to -75, maybe even -100, depending on the bar ultimate strain. Z simply relates the strain at d to ey of the bar.

Need to revise the get c list approach, which was formerly based on VBA and it's limitations.

• Need to update the @prop.
• Add class methods for effective area
• Centroid of effective area