# Matplotlib compatibility patch for Pyodide
import matplotlib
if not hasattr(matplotlib.RcParams, "_get"):
    matplotlib.RcParams._get = dict.get

… in open thin-walled cross-sections

For open thin-walled cross sections the shear stress is defined by:

\[\tau = \frac{M_te_m}{\frac{1}{2}I_t}, \quad I_t=\sum_{i}\frac{1}{3}h_i t_i^3\]

This is treated in chapter 6.3.2 and 6.3.3 of the book Engineering Mechanics Volume 2 (Hartsuijker and Welleman, 2007).