Solving Truss Problems: Need Help!

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In summary, the conversation involves a person seeking help with solving a truss problem and getting the reactions of the trusses. They have found the reactions at A and B, but their equations are not working out. Another person suggests using moments to find the missing reactions and explains the process. The conversation also mentions a 50kN force that was not taken into account in the moment equation.
  • #1
Joelllllll
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Need help with trusses!

Hey guys
So I'm trying to solve this truss problem and get all the reactions of the trusses
I've done it so many times but my equations never work out and I get crazy answers :\
I've found the reactions at A and B
Ax=-50kN
Ay=72kN
By=128kN
My answers for tryingto solve it are
Pac=-90kN
Pad=104kN
Pce=6.66kN
Pcd=-177.3kN
Pde=-295.5kN
Pdb=132.4kN
I just can't see where I went wrong?
Can someone help me out here?:(
Thanks
 

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  • #2


I found Ax= -50 too, but I found Ay=96kN and By=104kN.

To find Ay and By I used moments. Taking the moment around A you find the equation.

Ma = 100kN(2.25m) + 100kN(4.25m) - By(6.25m)

When you solve this I get By = 104kN. From their you just take 200kN - 104kN and that gets you Ay=96kN.

I think this should help you get on the right track from here.
 
  • #3


What about the 50kN force?
Why didn't you use that in your moment equation?
 

What are truss problems?

A truss problem is a type of structural engineering problem that involves analyzing and designing a framework of interconnected beams and rods to support a load or weight. Truss problems often involve finding the forces acting on each member of the truss in order to determine its stability and efficiency.

What are the steps for solving truss problems?

The steps for solving truss problems may vary depending on the specific problem, but generally they involve:

  1. Identifying the unknown forces in the truss
  2. Applying equilibrium equations to each joint in the truss
  3. Solving the equations to find the unknown forces
  4. Checking the stability of the truss by ensuring that all forces are in equilibrium
  5. Calculating the efficiency of the truss by comparing the actual forces to the theoretical maximum forces

What are some common assumptions made when solving truss problems?

Some common assumptions made when solving truss problems include:

  • The truss is made up of straight, rigid members that do not deform under load
  • Joints are assumed to be frictionless and able to rotate freely
  • The weight of the truss is negligible compared to the applied loads
  • All external loads are applied at the joints of the truss

What are some techniques for simplifying truss problems?

There are a few techniques that can be used to simplify truss problems, including:

  • Method of joints: This involves analyzing the forces at each joint in the truss to determine the unknown member forces
  • Method of sections: This involves cutting the truss into smaller sections and analyzing the forces acting on those sections
  • Zero force members: These are members that do not carry any force and can be removed from the truss to simplify calculations

What are some common mistakes to avoid when solving truss problems?

Some common mistakes to avoid when solving truss problems include:

  • Forgetting to include all forces acting on a joint, such as reactions from supports
  • Neglecting to consider the direction of forces, which can result in incorrect signs and values
  • Using incorrect units or not converting units correctly
  • Assuming that all members in the truss are in tension, when some may actually be in compression

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