In this lecture, we'll cover the following:

• Visualising bending moments across the evaluation grid using heat maps
• Interpreting finite element outputs: $(M_x)$, $(M_y)$, and $(M_{xy})$
• Converting raw moments into practical design moments using the Wood and Armer method
• Comparing practical design approaches with principal moment analysis
• Implementing an interactive plotting tool to explore different moment components

In this lecture, we move from data preparation to visualisation, using previously computed stress resultants to generate heat maps of bending moments across the structure. We focus on understanding which moments are most meaningful for design, particularly the need to account for the torsional component $(M_{xy})$ rather than relying solely on $(M_x)$ or $(M_y)$. To address this, we introduce the Wood and Armer method, which combines bending and torsional effects into equivalent orthogonal design moments, ensuring that torsion consistently increases reinforcement demand in a practical and conservative way.

We also contrast this with a more rigorous but less practical approach based on principal moments, where bending is evaluated on rotated planes with no torsion. While mechanically sound, this method is not suitable for typical slab reinforcement layouts due to varying orientations. Finally, we implement an interactive visualisation tool that allows us to explore different moment components—including both raw and design-adjusted values, building directly on earlier plotting functions.

Next up

In the next lecture, we will turn to extracting shear forces, where we will encounter and resolve some practical challenges related to data averaging at shared nodes.