Multidimensional Arrays Global stiff matrix

2020 9 8
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更新时间：2020 9 8
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Do anyone know how to make a Multidimensional Arrays GSM, cause I have already make a 2x2 Local Stiff matrix. But I am confuse on make a GSM with for loop. And here is my code for LSM and vaeiables. Thank you
%Step 1 Discretize
%Assign Variables
E = young;
A = area;
L = leng;
F1 = F;
Num_elements = no_e;
l = L/Num_elements ;
K = E*A/l ;
%step 2 Local Behavior
% Form local stiffness Matrixes
LSM = zeros(2, 2, Num_elements);
for x=1: 1: Num_elements
LSM(1,1,x)= K(x,1);
LSM(1,2,x)= -K(x,1);
LSM(2,1,x)= -K(x,1);
LSM(2,2,x)= K(x,1);
end
%Step 3
%Assemble Global Stiffness Matrix (GSM)

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0 个投票

Substitute this portion of your code:
LSM = zeros(2, 2, Num_elements);
for x=1: Num_elements
LSM(1,1)= K;
LSM(1,2)= -K;
LSM(2,1)= -K;
LSM(2,2)= K;
end
With this one:
LSM(1,1)= K;
LSM(1,2)= -K;
LSM(2,1)= -K;
LSM(2,2)= K;

更多回答（1 个）

0 个投票

Here is the GSM created in loops:
LSM(1,1)= K;
LSM(1,2)= -K;
LSM(2,1)= -K;
LSM(2,2)= K;
GSM = zeros(Num_elements);
for ii=1:Num_elements-1
ROW = ii + [0 1];
COL = ROW;
GSM(ROW, COL) = GSM(ROW, COL)+LSM;
end

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Shing Kwan Tang
Shing Kwan Tang 2020-9-8
do the COL and ROW need to put the number i want. cause when I run the code, it give me an error say that
lab_2_part_3(50, 60, 55, 60,5)
Unable to perform assignment because the size of the left side is 2-by-2 and the size of the right side is 2-by-2-by-5.
Error in lab_2_part_3 (line 38)
GSM(ROW, COL) = GSM(ROW, COL)+LSM;
my whole code is like this ;
function [ displacements, external_Forces] = lab_2_part_3(E ,A ,L ,F1 ,Num_elements)
%Step 1 Discretize
%Assign Variables
E = young;
A = area;
L = len;
F1 = force;
Num_elements = no_ele;
l = L/Num_elements ;
K = E*A/l ;
%step 2 Local Behavior
% Form local stiffness Matrixes
LSM = zeros(2, 2, Num_elements);
for x=1: Num_elements
LSM(1,1)= K;
LSM(1,2)= -K;
LSM(2,1)= -K;
LSM(2,2)= K;
end
%Step 3
%Assemble Global Stiffness Matrix (GSM)
GSM = zeros(Num_elements);
for y=1:Num_elements-1
ROW = y + [0 1];
COL = ROW;
GSM(ROW, COL) = GSM(ROW, COL)+LSM;
end
%Step 4
%Apply Boundary Conditions
F1 = [60 ; 0 ; 0 ];
LSM = GSM (1:end-1 ,1:end-1);
% Step 5
%solve for unknown displacements
mini_U = LSM \ external_Forces;
%step 6
% Analyze and find Reaction Forces
displacements = mini_U;
external_Forces = [60 ; 0 ;0 ; -60];
end

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