++++ ++++ ++++ ++++ ++++ Concept Question ++++ ++++ ++++ ++++ ++++ Why is the element sti?ness matrix singular in a ?nite element formulation? 1. So that it can accomodate rigid element dis- placements without introducing spurious nodal forces. 2. Because we made a mistake in the formula- tion, the sti?ness matrix should not be sin- gular. 3. Because we haven’t enforced any displace- ment boundary conditions (it’s a variational approach after all) ? ++++ Statement (1) ? ++++ Statement (2) ? ++++ Statement (3) ? ++++ Statements (1) and (3) ? ++++ DKDU The correct answer is ++++