I have gone through Beam Element analysis in several books on FEA. 80% of books have a particular Stiffness matrix, while a very small number of books have a matrix which is subtly different in sign. http://www.flickr.com/photos/66943862@N06/7195680680/in/photostream/lightbox Most books have the 2nd matrix in the photo above. A couple of books have 1st one. Likewise the loading matrix is also slightly different. Corresponding to the first one, the loading matrix is F*L/12 [ 6 -L 6 L]T While the majority have F*L/12 [ 6 L 6 -L]T Which method is correct?