I have a problem in the understanding of stiffness. For a simple cylinder with force acting axially, the definition of stiffness works ie Force per unit displacement. but what happens if the cylinder is bent, or even better a plate clamped on the edges with a UDL? In this case displacement would be different at different points, so how is stiffness calculated? PS : Is it like considering a dx area , calculating displacement and hence stiffness for it and then integrating for the entire area? But even then how would thickness be considered?