I'm having difficulty understanding how the stiffness matrix for finite elements is obtained. I am only having a difficult time understanding how to obtain the matrix values for K from the given information, but understand how to do everything up to and after just get stuck on this.
I don't understand how the 8, -8 are obtained in the K11, K12, K21, K22 positions yet 3, -3 is obtained for K22, K23, K32, K33 following by the 18 in K33, K34, K34, K44.
Every direction I look at it falls apart at another section.
Though I just figured one thing out, but I'm not sure if it's correct or only works for this situation.
For $$ K^1 = 24/12 * 4 = 8 $$ For $$ K^2 = 24/8 * 1 = 3 $$ For $$ K^3 = 24/4 * 3 = 18 $$