Global imperfections (also called Δ – effect)
- are a (global) displacement of action line (of normal force) due to rotation of the bar.
- This effect is important for structures where the nodes are moving significantly under the effect of the loads.
- It results in additional moment in bars
Local imperfections (also called δ – effect)
- are the relative (local) deformation of the element in relation to the reference line between the end points. A bar doesn’t remain straight between the end points.
- This effect is important in of very slender elements.
- It results in additional deformation in bars
Diamonds can take global imperfections into account, but not local imperfections.