Solving a Truss Problem with MATLAB: Equilibrium Equations and Results

[CR19]

Ok, I've had a shot at this problem we've been given in MATLAB. Though I'm very new to physics forums.

I've attached the actual problem and also a few of my equilibrium equations.

I've written out the matrice in MATLAB but I'm guessing its incorrect as the answer I'm getting in Matlab is...

A =

Columns 1 through 12

1.0000 0 0 0.7807 1.0000 0 0 0 0 0 0 0
0 1.0000 0 0.6249 0 0 0 0 0 0 0 0
0 0 0 0 -1.0000 0 0 0 1.0000 0 0 0
0 0 0 0 0 -1.0000 0 0 0 0 0 0
0 0 0 0 0 0 0 -0.7807 -1.0000 0 0 0.7807
0 0 0 0 0 0 0 -0.6249 0 -1.0000 0 -0.6249
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 1.0000 0 0 0 0 0 0 0 0 0
0 0 0 -0.7807 0 0 1.0000 0.7807 0 0 0 0
0 0 0 -0.6249 0 1.0000 0 0.6249 0 0 0 0
0 0 0 0 0 0 -1.0000 0 0 0 1.0000 0
0 0 0 0 0 0 0 0 0 -1.0000 0 0
0 0 0 0 0 0 0 0 0 0 -1.0000 -0.7807
0 0 0 1.0000 0 0 0 0 0 0 0 0

Columns 13 through 16

0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
1.0000 0 0 0
0 0 0 0
-1.0000 0 1.0000 0
0 -1.0000 0 0
0 0 -1.0000 -0.7807
0 0 0 -0.6249
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0.7807
-0.6249 0 0 0.6249


b =

20
0
0
-10
0
-20
0
-10
0
20
0
0
0
0
0
0


x =

20.0000
-394.7389
-334.7389
631.6860
-493.1616
10.0000
12.4934
615.6834
-493.1616
0
12.4934
-583.6781
443.1882
10.0000
443.1882
-567.6755

Results:

x(Ha)=20 [kN]
x(Va)=-394.7389 [kN]
x(1)=-334.7389 [kN]
x(2)=631.686 [kN]
x(3)=-493.1616 [kN]
x(4)=10 [kN]
x(5)=12.4934 [kN]
x(6)=615.6834 [kN]
x(7)=-493.1616 [kN]
x(8)=0 [kN]
x(9)=12.4934 [kN]
x(Ve)=-583.6781 [kN]
x(10)=443.1882 [kN]
x(11)=10 [kN]
x(12)=443.1882 [kN]
x(13)=-567.6755 [kN]

I've written all the equilibrium equation from Horizontal forces Equation 1, Vertical Forces @A Equation 2...but the calculations which I performed by myself I got respectable answers.. But with MATLAB it doesn't appear to give me appropriate answers...

Can anyone help or point me in the right direction.

Many Thanks

 

[NateD]

Ans: The issue here is that your matrix A and vector b are incorrect. You need to make sure that the matrix A and vector b represent the equilibrium equations correctly. For example, you should have four equations in your matrix A and vector b representing the horizontal and vertical forces in each of the two directions. Also, make sure that the coefficients in the matrix A correspond to the respective variables in the vector b. Once you have these correct, the solution generated by MATLAB should be correct.

 

[oswaler]

I would first commend you for taking on the challenge of solving a truss problem in MATLAB. It is a powerful tool for solving complex equations and can save a lot of time and effort in calculations. However, as you have noticed, it is important to double check your results and make sure they make sense. In this case, it seems like there may be an error in your code or in the way you set up your equations.

I would suggest going back to your original equations and checking them for any mistakes. Also, try to simplify your code and make it more readable so it is easier to spot any errors. You can also try using different methods or functions in MATLAB to solve the problem and see if you get different results.

Additionally, it may be helpful to consult with a colleague or a tutor who has more experience with MATLAB and truss problems. They may be able to offer some insights or suggestions on how to improve your code.

Overall, solving problems in MATLAB can be challenging, but it is also a great learning experience. Keep working at it and don't be discouraged by initial mistakes. With practice and perseverance, you will become more proficient in using this powerful tool.