correct stiffness matrix of 1d 3dof bar element

.gitconfig

@@ -6,6 +6,10 @@
 	br = branch
 	ci = commit
 	mylog = log --pretty=format:'%h %s [%an]' --graph
+  lg1 = log --graph --abbrev-commit --decorate --date=relative --format=format:'%C(bold blue)%h%C(reset) - %C(bold green)(%ar)%C(reset) %C(white)%s%C(reset) %C(dim white)- %an%C(reset)%C(bold yellow)%d%C(reset)' --all
+  lg2 = log --graph --abbrev-commit --decorate --format=format:'%C(bold blue)%h%C(reset) - %C(bold cyan)%aD%C(reset) %C(bold green)(%ar)%C(reset)%C(bold yellow)%d%C(reset)%n''          %C(white)%s%C(reset) %C(dim white)- %an%C(reset)' --all
+  lg = !"git lg1"
+  changes = show --stat --oneline
 	pushall = push --recurse-submodules=on-demand
 [core]
 	quotepath = off

src/fem/K.java

@@ -34,8 +34,8 @@ public class K extends Matrix{
 	 */
 	public static Matrix bar3(double L, double ki){
 		return new Matrix(new double[][]{
-				{ 7, 56,  1},
-				{56, 16, -8},
+				{ 7, -8,  1},
+				{-8, 16, -8},
 				{ 1, -8,  7}}).times(ki/(3*L));
 	}