How do I find the force in each beam of a truss problem?

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In summary, the conversation is about finding the force in the 4 beams of a truss using the Method of Sections. The person is unsure of how to cut the truss and solve for the forces, and the other person suggests looking at the left section and summing moments to solve for the forces in members 1, 2, and 3. They also mention the importance of identifying zero force members and offer to help show how to solve the problem on paper.
  • #1
Zaza669
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http://www.siz.co.il/my.php?i=oogytirin1tt.jpg

I have to find force in 1. 2. 3. 4. Beam.
How can i do that?

Thanks
 
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  • #2
What have you tried? Are you not familiar with method of joints?
 
  • #3
No. I have to use Method of section. I have no idea how to cut the 4 beam together.
 
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  • #4
Zaza669 said:
No. I have to use Method of section. I have no idea how to cut the 4 beam together.
Oh that's unfortunate. But you don't want to cut more than 3 members. Try looking at the left section of the truss cutting thru members 1, 2, and 3. Then sum moments about the lower left hand corner to solve for the force in member 3. Then you can use the sum of forces in x direction and in y direction = 0 to solve for for force in member 2 and 1. Force in member 4 should then be obvious maybe.
 
  • #5
PhanthomJay said:
Oh that's unfortunate. But you don't want to cut more than 3 members. Try looking at the left section of the truss cutting thru members 1, 2, and 3. Then sum moments about the lower left hand corner to solve for the force in member 3. Then you can use the sum of forces in x direction and in y direction = 0 to solve for for force in member 2 and 1. Force in member 4 should then be obvious maybe.

Can you show me on the paper how to solve that?
Thanks
 
  • #6
Zaza669 said:
Can you show me on the paper how to solve that?
Thanks
You should become familiar with identifying zero force members. Otherwise, see attached. Sum moments about A to solve for F3. There's going to be a lot of zeroes in that equation...
 

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

A truss problem is a structural engineering problem that involves analyzing the stability and strength of a truss, which is a framework of beams or bars used to support a structure. It is important to solve because it ensures that the truss can safely withstand the applied loads and prevent structural failure.

2. What are the steps involved in solving a truss problem?

The steps involved in solving a truss problem are:

  1. Identifying the type of truss and its support conditions
  2. Drawing a free-body diagram to determine the external forces acting on the truss
  3. Applying equations of equilibrium to solve for the internal forces in each member
  4. Checking for stability and strength by analyzing the internal forces in each member
  5. Making necessary adjustments to the truss design if it does not meet the required stability and strength criteria

3. What are the common assumptions made when solving a truss problem?

The common assumptions made when solving a truss problem are:

  • The truss is a two-dimensional structure
  • The joints are frictionless and can only support axial forces
  • The members are connected by ideal pins or hinges, allowing for rotation but no translation
  • The truss is loaded only at the joints
  • The members are made of a rigid, homogeneous material

4. What are some methods used to solve a truss problem?

Some methods used to solve a truss problem are:

  • Method of joints: solving for the internal forces in each member by analyzing the equilibrium at each joint
  • Method of sections: solving for the internal forces in a specific section of the truss by cutting it and analyzing the equilibrium of the cut section
  • Direct stiffness method: using matrix operations to solve for the internal forces in each member

5. What are some factors that can affect the stability and strength of a truss?

Some factors that can affect the stability and strength of a truss are:

  • The type and arrangement of the truss members
  • The geometry and size of the truss
  • The material properties and quality of the truss members
  • The loading conditions and applied forces
  • The support conditions and boundary conditions

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