Creating Global Stiffness matrix

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Alpha Boy
Alpha Boy 2020-7-4
评论： Ruairi Kavanagh 2023-4-23
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?
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Daniyal Raja
Daniyal Raja 2022-11-24
移动：the cyclist 2022-11-24
sem question my g

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回答（1 个）

the cyclist
the cyclist 2020-7-5
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.
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the cyclist
the cyclist 2020-7-5
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
Ruairi Kavanagh 2023-4-23
how would i would i change this code if i had 8 matrices fo 4x4 that needed to fit into a 6x6 matrix

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