I haven't got a clue, but I do recall an afternoon in my structures lessons - something to do with imagining an archway but horizontal and compression, transfer of loads, being stonger under load etc etc. No need to bore you with it
Lol, you b****y chancer
.
An afternoon? Your entire structures lessons
were an afternoon. Tops!
Parallel axis theorem ol' boy: it's to do with the respective inertias (resistance to rotation about the axis of mass of a body in that direction in space): looking on plan, a crinkle-crankle or circular wall has a greater inertia than a straight wall of equal thickness, by virtue of their respective extremities being further away from their neutral axes of the whole than that of a straight one.
For rectangles, I = bd^3/12 + AH^2 for each element of the body. That's why a ruler is easy to bend when held flat, not so easy when you turn it on edge.
And that is why SEs should deal with structural matters, not surveyors