Creating Global Stiffness matrix

Hello,

I am quite noob in Matlab. I am trying to add two matrix to create a global stiffness matrx.

k1 =

10150000 -5000000 -3750000 2000000 -6400000 3000000

-5000000 12400000 3000000 -10000000 2000000 -2400000

-3750000 3000000 3750000 0 0 -3000000

2000000 -10000000 0 10000000 -2000000 0

-6400000 2000000 0 -2000000 6400000 0

3000000 -2400000 -3000000 0 0 2400000

k2 =

10150000 -5000000 -3750000 2000000 -6400000 3000000

-5000000 12400000 3000000 -10000000 2000000 -2400000

-3750000 3000000 3750000 0 0 -3000000

2000000 -10000000 0 10000000 -2000000 0

-6400000 2000000 0 -2000000 6400000 0

3000000 -2400000 -3000000 0 0 2400000

I will find a global stiffness matrix(K) (8X8). How can I find this matrix?

[the cyclist]

Do you have any information on the formula you want to use to combine these matrices? You have given us two 6x6 matrices. (Actually, k1==k2, so really only one matrix.) How do you propose to make one 8x8 matrix out of two 6x6? I mean, conceptually, not in MATLAB. We can help you with the MATLAB part, if you help us with the conceptual part.

[Alpha Boy]

K1 =

k2 =

I have to sum up 2X1 with 2X1, 2X5 with 2X5...

[chitra lekha]

I am in the same platform as you

[Daniyal Raja]

sem question my g

[Mohammad Hamad Sheikh]

dany boss wht u donig here

Answer 1

[the cyclist]

If I've understood correctly, then

K = zeros(8);

vec1 = [1 2 3 4 7 8];
K(vec1,vec1) = K(vec1,vec1) + k1;

vec2 = [5 6 7 8 3 4];
K(vec2,vec2) = K(vec2,vec2) + k2;

gives what you want.

Because K starts out as all zeros, the addition with k1 could have been written

K(vec1,vec1) = k1;

but I thought it might be easier to see what was going on this way, and also that k1 and k2 are being treated symmetically.

[Alpha Boy]

Yes, you are correct! But how can I do it in Matlab?

[the cyclist]

Uh, what? That is literally the exact MATLAB code to do it.

[the cyclist]

I'm assuming you've defined k1 and k2, such as

k1 =[
    10150000    -5000000    -3750000     2000000    -6400000     3000000
    -5000000    12400000     3000000   -10000000     2000000    -2400000
    -3750000     3000000     3750000           0           0    -3000000
     2000000   -10000000           0    10000000    -2000000           0
    -6400000     2000000           0    -2000000     6400000           0
     3000000    -2400000    -3000000           0           0     2400000];


k2 = [
    10150000    -5000000    -3750000     2000000    -6400000     3000000
    -5000000    12400000     3000000   -10000000     2000000    -2400000
    -3750000     3000000     3750000           0           0    -3000000
     2000000   -10000000           0    10000000    -2000000           0
    -6400000     2000000           0    -2000000     6400000           0
     3000000    -2400000    -3000000           0           0     2400000];

[Ruairi Kavanagh]

how would i would i change this code if i had 8 matrices fo 4x4 that needed to fit into a 6x6 matrix