the global stiffness of two 4x4 matrices of truss

How do I make a code to assemble these two 4x4 matrices to get the 6x6 global stiffness matric as shown?

clear all;
clc;
K1=[1 1 -1 -1;
    1 1 -1 -1;
    -1 -1 1 1;
    -1 -1 1 1];
K2=[1 -1 -1 1;
    -1 1 1 -1;
    -1 1 1 -1;
    1 -1 -1 1];
%here are the two matrices

Answer 1

[Fifteen12]

To add the matrices together, just arrange them by indices.

% Dummy values for k1 and k2
k1 = ones(4,4);
k2 = ones(4,4) * 2;

% Calculate stiffness matrix
K = zeros(6,6);
K(1:4, 1:4) = k1;
K(3:6, 3:6) = K(3:6,3:6) + k2

K = 6×6

1 1 1 1 0 0 1 1 1 1 0 0 1 1 3 3 2 2 1 1 3 3 2 2 0 0 2 2 2 2 0 0 2 2 2 2

You can make this more robust by using variables instead of hard coding the indices, but this minimal example shows the concept. Good luck with your finite elements!

[Mohammad]

thanks mate