Solving Truss Equations: Find Force in Members EA, EF and EG

In summary, the problem involves finding the forces in members EA, EF, and EG in a truss structure, given the loads and pinned supports at points A and G. The methods of sections and joints are used to analyze the structure, and the author has also taken into account the dimensions of the members to decompose the forces. However, the problem becomes more complex due to the external static indeterminacy of the truss, which requires additional analysis of deformation and boundary conditions. The author also mentions using an app or program to solve the problem, as the manual calculations can be tedious and time-consuming.
  • #1
arestes
80
3

Homework Statement


Find force in members EA, EF and EG given the loads shown. A and G are pinned supports.

Homework Equations


Three equations of equilibrium for sections (method of sections) 2 equations for any node (method of joints).
I also used the dimensions to decompose member forces.

The Attempt at a Solution


I started by analyzing the entire truss to get something about the reactions. I found both VERTICAL components of A and G to be 13 kg-f and 17 kg-f respectively, the horizontal components fulfill : $$A_x + G_x =15 $$

Then I made a cut through BF, CF and AE and evaluated moments about F to get:
$$ \frac{32}{\sqrt{17}}AE=128-4A_x$$

All my other attempts involve the other unknowns and I can't still get them together. What would be the quickest way without throwing in a bunch of equations till I finally reach the answer?
*** I need to teach this and I can't see the "trick" if there is one, so I can teach whatever that trick is supposed to tell me.
BTW,I put this onto an android app and got the solutions. It was painful to input all the data. Do you recommend a particular app or program for these problems?
 

Attachments

  • truss 1.jpg
    truss 1.jpg
    48.2 KB · Views: 439
Physics news on Phys.org
  • #2
Truss is externally statically indeterminate because you have 4 unknown reaction forces and just three equilibrium equations, and to solve it by hand calcs is as bit tedious because it requires deformation and boundary conditions analysis. I wonder who makes up these problems?
 
  • Like
Likes arestes

1. What is a truss and why is it important to solve its equations?

A truss is a structure composed of connected triangles that is used to support a load. It is important to solve its equations in order to determine the forces acting on each member and ensure that the truss can withstand the applied load without collapsing.

2. How do I find the force in a specific member of a truss, such as EA, EF, or EG?

To find the force in a specific member of a truss, you need to use the method of joints. This involves analyzing the forces acting at each joint of the truss and using the equations of equilibrium to solve for the unknown forces in each member.

3. What is the equation for calculating the force in a truss member?

The equation for calculating the force in a truss member is F = P * sin(theta), where F is the force in the member, P is the applied load, and theta is the angle between the member and the applied load.

4. Can I solve truss equations using a computer program or do I need to solve them by hand?

Yes, you can solve truss equations using a computer program. There are many software programs available that can perform the calculations for you and provide a visual representation of the truss and its forces. However, it is still important to understand the principles and equations involved in solving truss problems by hand.

5. Are there any assumptions or simplifications made when solving truss equations?

Yes, there are a few assumptions and simplifications made when solving truss equations. These include assuming that the truss is a perfect geometric shape, that all joints are pinned and can only support axial forces, and that all members are rigid and can only resist tension or compression forces.

Similar threads

  • Engineering and Comp Sci Homework Help
Replies
2
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
1
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
1
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
3
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
4
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
13
Views
3K
Back
Top