Finite Element Analysis in Matlab

E_steel=200*10^6; %kPa

L_deck=12; %m

%E=26; kips

E=115.654; %kN

%H=18; kips

H=80.068; %kN

for i=1:25

u(i)=i;

F(i)=0;

end

%Tower shaft AC:

A_AC=7.540*10^-3; %m^2

I_AC=5.438*10^-5; %m^4

%Tower shaft BC:

A_BD=1.814*10^-2; A_DC=A_BD; %m^2

I_BD=3.367*10^-4; I_DC=I_BD; %m^4

%Cables

A_cab=7.069*10^-4; %m^2

I_cab=0;

%Bridge deck

A_br=1.232*10^-2; %m^2

I_br=2.219*10^-4; %m^4

%Area

A(1)=A_AC;

A(2)=A_BD; A(3)=A(2);

A(4)=A_cab; A(5:7)=A(4);

A(8)=A_br; A(9:11)=A(8);

%Inertia

I(1)=I_AC;

I(2)=I_BD; I(3)=I(2);

I(4)=I_cab; I(5:7)=I(4);

I(8)=I_br; I(9:11)=I(8);

%Applied force vetor

F=F';

F(6)=-E;

F(9)=-E;

F(12)=-E;

F(14)=H;

%length

L_AC=sqrt(7.0^2+1.0^2); L(1)=L_AC;

L_BD=sqrt(1.0^2+0.5^2); L(2)=L_BD;

L_DC=sqrt(6.0^2+3.0^2); L(3)=L_DC;

L_CE=sqrt(6.0^2+6.0^2); L(4)=L_CE;

L_CF=sqrt(9.0^2+6.0^2); L(5)=L_CF;

L_CG=sqrt(12.0^2+6.0^2); L(6)=L_CG;

L_CH=sqrt(15.0^2+6.0^2); L(7)=L_CH;

L_DE=3; L(8)=L_DE;

L_EF=3; L(9)=L_EF;

L_FG=3; L(10)=L_FG;

L_GH=3; L(11)=L_GH;

%Theta

theta_AC=180-atand(7.0/1.0);

theta_BD=180-atand(7.0/3.5); theta_DC=theta_BD;

theta_DE=0; theta_EF=theta_DE; theta_FG=theta_DE; theta_GH=theta_DE;

theta_CE=360-atand(6.0/6.0);

theta_CF=360-atand(6.0/9.0);

theta_CG=360-atand(6.0/12.0);

theta_CH=360-atand(6.0/15.0);

theta(1)=theta_AC; theta(2)=theta_BD;

theta(3)=theta_DC; theta(4)=theta_CE;

theta(5)=theta_CF; theta(6)=theta_CG;

theta(7)=theta_CH; theta(8)=theta_DE;

theta(9)=theta_EF; theta(10)=theta_FG;

theta(11)=theta_GH;

%ID_array

ID_AC=[u(19) u(20) u(21) u(16) u(17) u(18)];

ID_CE=[u(16) u(17) u(18) u(5) u(6) u(7)];

ID_CF=[u(16) u(17) u(18) u(8) u(9) u(10)];

ID_CG=[u(16) u(17) u(18) u(11) u(12) u(13)];

ID_CH=[u(16) u(17) u(18) u(14) u(25) u(15)];

ID_DC=[u(1) u(2) u(3) u(16) u(17) u(18)];

ID_BD=[u(22) u(23) u(24) u(1) u(2) u(3)];

ID_DE=[u(1) u(2) u(4) u(5) u(6) u(7)];

ID_EF=[u(5) u(6) u(7) u(8) u(9) u(10)];

ID_FG=[u(8) u(9) u(10) u(11) u(12) u(13)];

ID_GH=[u(11) u(12) u(13) u(14) u(25) u(15)];

ID=[ID_AC; ID_BD; ID_DC; ID_CE; ID_CF; ID_CG; ID_CH; ID_DE; ID_EF; ID_FG; ID_GH];

kff=zeros(25,25);

kbeam=0;

%Element AC

for i=1:11

C=cosd(theta(i));

S=sind(theta(i));

kbeam(1)= E*A(i)/L(i)*C^2 + 12*E*I(i)/L(i)^3*S^2;

kbeam(2)=E*A(i)/L(i)*C*S - 12*E*I(i)/L(i)^3*C*S;

kbeam(3)=-6*E*I(i)/L(i)^2*S;

kbeam(4)=-E*A(i)/L(i)*C^2 - 12*E*I(i)/L(i)^3*S^2;

kbeam(5)=-E*A(i)/L(i)*C*S + 12*E*I(i)/L(i)^3*C*S;

kbeam(6)=-6*E*I(i)/L(i)^2*S;

kbeam(7)=E*A(i)/L(i)*S^2 + 12*E*I(i)/L(i)^3*C^2;

kbeam(8)=6*E*I(i)/L(i)^2*C;

kbeam(9)= -E*A(i)/L(i)*C*S + 12*E*I(i)/L(i)^3*C*S;

kbeam(10)=-E*A(i)/L(i)*S^2 - 12*E*I(i)/L(i)^3*C^2;

kbeam(11)=6*E*I(i)/L(i)^2*C;

kbeam(12)= 4*E*I(i)/L(i);

kbeam(13)=-kbeam(3);

kbeam(14)=-kbeam(8);

kbeam(15)=2*E*I(i)/L(i);

kbeam(16)=kbeam(1);

kbeam(17)=kbeam(2);

kbeam(18)=-kbeam(3);

kbeam(19)=-kbeam(10);

kbeam(20)=-kbeam(8);

kbeam(21)=kbeam(12);

kele(1:6,1)=kbeam(1:6);

kele(2:6,2)=kbeam(7:11);

kele(3:6,3)=kbeam(12:15);

kele(4:6,4)=kbeam(16:18);

kele(5:6,5)=kbeam(19:20);

kele(6,6)=kbeam(21);

kele= triu(kele.',1) + tril(kele);

array=ID(i,:);

for n=1:6

for m=1:6

kff(array(n),array(m))= kff(array(n),array(m))+kele(n,m);

end

end

end

kff;

F;

xf=kff\F;

I have the errors at line 8 and line 9. How to fix them ? . Thanks

[the cyclist]

Please post the entire error message you get.

Answer 1

[KSSV]

It is not an error, it is a warning. You need to initialize the variables which you are using in loop.

Replace the lines:

for i=1:25
    u(i)=i;
    F(i)=0;
end

with

u = 1:25 ; 
F = zeros(size(u)) ; 

If you want to use a loop, which is not required:

u = zeros(1,25) ; 
F = zeros(1,25) ; 
for i=1:25
    u(i)=i;
    F(i)=0;
end

[LUAN NGUYEN]

thank you