11.3  The rod by virtual work

The rod \(-(EAu')' = f\), fixed at \(x = 0\) and loaded by \(P\) at \(x = L\). Internal virtual work \(\int_0^L N\,\delta u'\,dx\) equals external virtual work \(\int_0^L f\,\delta u\,dx + P\,\delta u(L)\), with \(\delta u(0) = 0\) because the support cannot move. Linear elements, assembly, and comparison with the exact solution. The Galerkin reading as a short aside.