Don't know how to make the loop works with variable
Show older comments
Sorry new to all of this.
Whenever I try using 'Lb' as a range (from 0 to 15000 with load step of 1000) that I want the program to calculate for each, errors keep showing, and it won't continue with the calculations.
Thanks in advance.
%CALCULATIONS OF THE LATERAL TORSIONAL BUCKLING
%---------------
Cb = 1;
Lb = 0:1000:15000;
if (Sxt/Sxc >= 0.7)
FL = 0.7*Fy;
elseif (Sxt/Sxc < 0.7)
if (Fy*Sxt/Sxc >= 0.5*Fy)
FL = Fy*Sxt/Sxc;
elseif (Fy*Sxt/Sxc < 0.5*Fy)
FL = 0.5*Fy;
end
end
%CALCULATIONS OF THE LIMITING LATERALLY UNBRACED LENGTH FOR THE LIMIT STATE
%OF YIELDING, mm
Lp = 1.76*ry*sqrt(E/Fy);
%CALCULATIONS OF THE LIMITING UNBRACED LENGTH FOR THE LIMIT STATE
%OF INELASTIC LATERAL TORSIONAL BUCKLING, mm
Lr = 1.95*rt*(E/FL)*sqrt((J/(Sxc*h0))+sqrt(((J/(Sxc*h0))^2)+(6.76*(FL/E)^2)));
%CALCULATIONS OF THE NOMINAL MOMENT (Lp < Lb <= Lr)
if (Iyc/Iy > 0.23)
R1 = Mp/Myc;
elseif (Iyc/Iy <= 0.23)
R1 = 1;
end
for Mn2 = Cb*((R1*Myc)-(((R1*Myc)-(FL*Sxc))*((Lb-Lp)/(Lr-Lp))))
if (Mn2 < R1*Myc)
disp('Mn2 = Cb*((R1*Myc)-((R1*Myc)-((FL*Sxc)*((Lb-Lp)/(Lr-Lp)))))')
Mn2 = Cb*((R1*Myc)-(((R1*Myc)-(FL*Sxc))*((Lb-Lp)/(Lr-Lp))));
elseif (Mn2 >= R1*Myc)
disp('Mn2 <= R1*Myc')
Mn2 = R1*Myc;
end
end
%CALCULATIONS OF THE NOMINAL MOMENT (Lb > Lr)
if (Iyc/Iy <= 0.23)
R1 = 1 & 'J = 0';
end
R2 = sqrt(1+(0.078*(J/(Sxc*h0))*(Lb/rt)^2));
for Mn3 = Cb*pi*pi*E*Sxc*R2/(Lb/rt)^2
if (Mn3 < R1*Myc)
disp('Mn3 = Cb*pi*pi*E*Sxc*R2/(Lb/rt)^2')
Mn3 = Cb*pi*pi*E*Sxc*R2/(Lb/rt)^2;
elseif (Mn3 >= R1*Myc)
disp('Mn3 = R1*Myc')
Mn3 = R1*Myc;
end
end
if Lb <= Lp
disp('Mn = Mn1')
Mn = Mn1
else if Lb > Lp && Lb <= Lr
disp('Mn = Mn2')
Mn=Mn2
else Lb > Lr
disp('Mn = Mn3')
Mn=Mn3
end
end
plot(Lb,Mn)
7 Comments
Walter Roberson
on 20 Jan 2020
R1 = 1 & 'J = 0';
What is the intention of that line?
Ahmed Sayed
on 20 Jan 2020
Walter Roberson
on 20 Jan 2020
R1 = 1;
J = 0;
maybe.
Ahmed Sayed
on 20 Jan 2020
Walter Roberson
on 20 Jan 2020
for Mn2 = Cb*((R1*Myc)-(((R1*Myc)-(FL*Sxc))*((Lb-Lp)/(Lr-Lp))))
if (Mn2 < R1*Myc)
disp('Mn2 = Cb*((R1*Myc)-((R1*Myc)-((FL*Sxc)*((Lb-Lp)/(Lr-Lp)))))')
Mn2 = Cb*((R1*Myc)-(((R1*Myc)-(FL*Sxc))*((Lb-Lp)/(Lr-Lp))));
elseif (Mn2 >= R1*Myc)
disp('Mn2 <= R1*Myc')
Mn2 = R1*Myc;
end
end
You have for Mn2 so Mn2 is a for loop variable. You are then altering that variable inside the for loop. That is not going to have the result you expect. You make the same mistake for Mn3 slightly further on.
What is the point of that code anyhow? If Mn2 is less than a certain value then you set Mn2 to... the exact same value it already was.
Perhaps you should be doing something like
Mn2 = min( Cb*((R1*Myc)-(((R1*Myc)-(FL*Sxc))*((Lb-Lp)/(Lr-Lp)))), R1*Myc );
Ahmed Sayed
on 20 Jan 2020
Walter Roberson
on 20 Jan 2020
Any time you have
for VARIABLE = ROW_VECTOR
end
then after the loop, VARIABLE will be a scalar (there is an obscure exception to this.)
Accepted Answer
Image Analyst
on 19 Jan 2020
1 vote
It says
Unrecognized function or variable 'Sxt'.
Error in test (line 5)
if (Sxt/Sxc >= 0.7)
so that means that before that line, you need to define Sxt, Sxc, Fy, and any other variables that have not been defined.
15 Comments
Ahmed Sayed
on 19 Jan 2020
Edited: Image Analyst
on 19 Jan 2020
Image Analyst
on 19 Jan 2020
Can you make it easy for us and hard code in the values for those 6 parameters you ask for? I don't know what to enter.
Ahmed Sayed
on 19 Jan 2020
Ahmed Sayed
on 19 Jan 2020
Edited: Ahmed Sayed
on 19 Jan 2020
Image Analyst
on 19 Jan 2020
The error says
Error using ^ (line 51)
Incorrect dimensions for raising a matrix to a power. Check that the matrix is square and the power is a scalar. To perform elementwise matrix powers, use '.^'.
Did you try it's suggestion of using dot caret?
Also, after you do that there are problems with this line
else if Lb > Lp && Lb <= Lr
did you really mean "else if" (highly unusual) or did you mean "elseif" (more likely)? And secondly, Lb is a 16 element row vector, not a single number, so "Lb > Lp && Lb <= Lr" is a logical vector of 16 true or false values. What is your intent there?
Ahmed Sayed
on 19 Jan 2020
Image Analyst
on 19 Jan 2020
Still not sure what you want to do, but maybe you should make that last if block inside a for loop over the 16 elements of Lb:
fprintf('Mn1 = %f. Mn2 = %f. Mn3 = %f.\n', Mn1, Mn2, Mn3)
Mn = zeros(1, length(Lb));
for k = 1 : length(Lb)
if Lb(k) <= Lp
fprintf('Mn = Mn1 = %f. And Lb(%d) = %f.\n', Mn1, k, Lb(k))
Mn(k) = Mn1;
elseif Lb(k) > Lp && Lb(k) <= Lr
fprintf('Mn = Mn2 = %f. And Lb(%d) = %f.\n', Mn2(k), k, Lb(k))
Mn(k) = Mn2(k);
elseif Lb(k) > Lr
fprintf('Mn = Mn3 = %f. And Lb(%d) = %f.\n', Mn3, k, Lb(k))
Mn(k) = Mn3;
end
end
plot(Lb,Mn)
title('Lb vs. Mn', 'FontSize', 15);
xlabel('Mn', 'FontSize', 15);
ylabel('Lb', 'FontSize', 15);
grid on;
Is that what you're looking for?
Ahmed Sayed
on 19 Jan 2020
Edited: Ahmed Sayed
on 19 Jan 2020
Image Analyst
on 20 Jan 2020
You're welcome. So if we're done here and this answers your question, what we like people to do is to click the link to "Accept this answer". It gives answerers "reputation points" for helping you.
Ahmed Sayed
on 20 Jan 2020
Edited: Ahmed Sayed
on 20 Jan 2020
Walter Roberson
on 20 Jan 2020
>> R1 = 1 & 'J = 0'
R1 =
1×5 logical array
1 1 1 1 1
That is going to throw off anything that depends upon R1. You probably need
R1 = 1;
J = 0;
Ahmed Sayed
on 20 Jan 2020
Image Analyst
on 20 Jan 2020
What exactly is your intent when you do this:
if (Iyc/Iy <= 0.23)
R1 = 1 & 'J = 0';
end
Is it not to set R1 to 1, and J equal to zero, like Walter said?
When I ran your code, Mn3 was NOT a 16 element vector like Mn2.
It might help if you thoroughly document each line of code. If I had written this code, there would be a comment line before every 1 or 2 lines of code. Often, believe it or not, if you describe what you're doing in words, it will let you see what you're doing wrong. Plus it helps us to help you. Right now all I see is an alphabet soup mess of a program. So, since I have trouble following it, I can only have tunnel vision and examine one small chunk at a time. Hence I don't know if Mn, Mn1, Mn2, Mn3, etc are vectors or scalars. All I see is what they are and have no idea if that's what they're supposed to be or not.
Ahmed Sayed
on 20 Jan 2020
Walter Roberson
on 20 Jan 2020
You should probably have a vector of R1 and vector of J, one for each entry in Lb, and you should probably be using logical indexing to do your calculations
mask = lcy./ly < 0.23;
R1(mask) = 1;
J(mask) = 0;
More Answers (0)
Categories
Find more on Analysis and Verification in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
