Having trouble calculating reaction forces for this truss.

In summary: Both beams are loaded in a similar fashion, except the latter beam requires an extra equation in addition to the equations of static equilibrium in order to solve for the reactions at the supports. In the case of the latter beam, we must know how the beam deflects under load, and we cannot calculate that unless we know some additional structural details beyond the spacing of the supports.
  • #1
Comfy
12
0

Homework Statement


Calculate reaction forces for truss. Truss is attached in picture.

Homework Equations



ΣFx=o
ΣFy=0
ΣM about reaction point=0

The Attempt at a Solution


attached in picture
 

Attachments

  • 1462768412577-223762192.jpg
    1462768412577-223762192.jpg
    10.8 KB · Views: 488
  • 1462768369827508814578.jpg
    1462768369827508814578.jpg
    17.5 KB · Views: 459
  • 1462768436719370329048.jpg
    1462768436719370329048.jpg
    31.8 KB · Views: 492
Physics news on Phys.org
  • #2
Comfy said:

Homework Statement


Calculate reaction forces for truss. Truss is attached in picture.

Homework Equations



ΣFx=o
ΣFy=0
ΣM about reaction point=0

The Attempt at a Solution


attached in picture
Unfortunately, the attached images are almost entirely illegible. :frown:

If you want some help, either write out your calculations or post better images. :wink:
 
  • #3
SteamKing said:
Unfortunately, the attached images are almost entirely illegible. :frown:

If you want some help, either write out your calculations or post better images. :wink:
This truss is statically determinate now, and should be solvable, right? That is why I don't understand why I am having trouble solving for the support reactions.
 

Attachments

  • 20160509_001153.jpeg
    20160509_001153.jpeg
    16.8 KB · Views: 461
  • 20160509_001201.jpeg
    20160509_001201.jpeg
    9.5 KB · Views: 479
  • 20160509_001214.jpeg
    20160509_001214.jpeg
    21 KB · Views: 490
  • 20160509_001352.jpeg
    20160509_001352.jpeg
    11.8 KB · Views: 476
  • #4
Comfy said:
This truss is statically determinate now, and should be solvable, right? That is why I don't understand why I am having trouble solving for the support reactions.

What makes you think this truss is statically determinate? You're still trying to calculate four reactions using only two equations of statics.
 
  • #5
SteamKing said:
What makes you think this truss is statically determinate? You're still trying to calculate four reactions using only two equations of statics.
I
SteamKing said:
What makes you think this
SteamKing said:
What makes you think this truss is statically determinate? You're still trying to calculate four reactions using only two equations of statics.
I have more than 2 equations, I have sum of forces in y and sum of moments about any of the supports. It is statically determinate because 2 (11 joints)=17 members+5 reactions. What do you mean by 2 equations of statics?
truss is statically determinate? You're still trying to calculate four reactions using only two equations of statics.
I have 4 equations Sum of forces in y direction and the
 
  • #6
Comfy said:
I

I have 4 equations Sum of forces in y direction and the
Your last post came out garbled. Can you repeat?
 
  • #7
SteamKing said:
Your last post came out garbled. Can you repeat?
I have more than 2 equations, I have sum of forces in y and sum of moments about any of the supports. It is statically determinate because 2 (11 joints)=17 members+5 reactions. What do you mean by 2 equations of statics?
 
  • #8
Comfy said:
I have more than 2 equations, I have sum of forces in y and sum of moments about any of the supports. It is statically determinate because 2 (11 joints)=17 members+5 reactions. What do you mean by 2 equations of statics?
You can write only one equation involving the sum of the forces and one equation summing the moments about one convenient reference point.

You cannot write, for example, one moment equation where you sum moments about point A and another equation where you sum moments about point H.

This beam is statically determinate:


simple-beam-dist-load.png


This beam is statically indeterminate:


upload_2016-5-9_8-26-53.png


Both beams are loaded in a similar fashion, except the latter beam requires an extra equation in addition to the equations of static equilibrium in order to solve for the reactions at the supports. In the case of the latter beam, we must know how the beam deflects under load, and we cannot calculate that unless we know some additional structural details beyond the spacing of the supports.
 

1. How do I calculate reaction forces for a truss?

To calculate reaction forces for a truss, you will need to use the equations of static equilibrium. These equations state that the sum of all forces in the x direction and the sum of all forces in the y direction must equal zero. By applying these equations to the truss, you can solve for the reaction forces at each support.

2. What information do I need to calculate reaction forces for a truss?

To calculate reaction forces for a truss, you will need to know the external loads acting on the truss, the geometry of the truss (lengths of each member and angles between them), and the location of the supports.

3. How do I know if my calculated reaction forces are correct?

To verify the correctness of your calculated reaction forces, you can apply the equations of static equilibrium to the truss. If the calculated reaction forces satisfy these equations, then they are correct. You can also compare your results with those obtained from other methods or software.

4. What if my truss is not in static equilibrium?

If your truss is not in static equilibrium, then it means there is an error in your calculations or assumptions. Double check all the input data and equations used in your calculations. If you are still having trouble, seek help from a peer or a professional.

5. Can I use a computer program to calculate reaction forces for a truss?

Yes, there are many software programs available that can calculate reaction forces for a truss. These programs use numerical methods and complex algorithms to solve for the reaction forces. However, it is still important to have a basic understanding of the equations and principles involved in order to interpret and verify the results obtained from the software.

Similar threads

  • Engineering and Comp Sci Homework Help
Replies
2
Views
1K
  • Mechanical Engineering
Replies
1
Views
705
  • Engineering and Comp Sci Homework Help
Replies
2
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
7
Views
3K
  • Engineering and Comp Sci Homework Help
Replies
5
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
987
  • Engineering and Comp Sci Homework Help
Replies
2
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
4
Views
830
  • Engineering and Comp Sci Homework Help
Replies
1
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
5
Views
3K
Back
Top