++++ ++++ ++++ ++++ ++++ Concept Question ++++ ++++ ++++ ++++ ++++ What new element is Castigliano’s Theorem introducing? 1. None, it’s just a particular case of the PMPE. 2. It’s a totally di?erent principle that allows to obtain solutions of elasticity problems with unprecedented accuracy and e?ciency in- cluding relativistic e?ects. ?U 3. F i = ?u i , when U can be expressed in terms of point displacements. 4. None, It’s just a useful tool to quickly ob- tain answers to speci?c questions such as: “What’t the displacement at a point?” with- out having to obtain the whole solution to the structural problem 1. ++++ None of the above statements 2. ++++ All of the above statements 3. ++++ All of the above statements but (2) 4. ++++ Statement (4) 5. ++++ DKDU The correct answer is ++++