Help understanding how to determine Compress or Tension in Truss

[NoobeAtPhysics]

Homework Statement

A small square truss shown is supported by a pin joint at I and a roller at A. Label all members of the
truss by Z (for zero force member), C (for compression) or T (for tension).

Homework Equations

The Attempt at a Solution

So this was an exam question on a past test and I have troubles understanding how to calculate this in a fast manner.

I usually just use method of joints for each member and determine it that way. But I don't know how to determine tension/compression by looking at a truss. I've asked a couple people but I never understand what they mean...

What is your guy's approach/thought process when solving this problem?

My next exam is coming soon and I really hope to get a better understanding of this!

Thank you very much.

 

[SteamKing]

Start at the free end, point E, where the 100 N force is applied. What do you get for members DE and EF?

 

[NoobeAtPhysics]

DE is compression and therefore EF is in tension

 

[SteamKing]

Good. Now work back towards the wall.

 

[Nickie]

I understand your concerns and will provide guidance on how to determine compression or tension in a truss. First, let's define what compression and tension mean in this context. Compression is a force that pushes or squeezes a member of the truss, while tension is a force that pulls or stretches a member.

To determine whether a member is experiencing compression or tension, you can use the method of sections or the method of joints. For the method of sections, you would cut the truss into sections and analyze the forces acting on each section. If the forces are directed towards the cut section, then the member is in compression. If the forces are directed away from the cut section, the member is in tension.

For the method of joints, you would analyze the forces at each joint of the truss. If the forces acting on a joint are pushing away from the joint, then the member connected to that joint is in tension. If the forces are pulling towards the joint, then the member is in compression.

Another helpful approach is to visualize the truss as a series of triangles. In a triangle, the longest side will experience the most tension, while the shortest side will experience the most compression. This can help you quickly identify which members are in tension or compression.

In summary, to determine compression or tension in a truss, you can use the method of sections or joints, and also consider the length and orientation of the truss members. With practice and understanding of these concepts, you will be able to quickly determine the forces acting on each member of a truss. Good luck on your exam!