# Zero-force member problem (Statics)

1. Mar 25, 2013

### aero_zeppelin

1. The problem statement, all variables and given/known data
Determine the zero force members in the following truss

2. Relevant equations

- If only two members meet in an unloaded joint, both are zero-force members.
- If three members meet in an unloaded joint of which two are in a direct line with one another, then the third member is a zero-force member.

- If two members meet in a loaded joint and the line of action of the load coincides with one of the members, the other member is a zero-force member.

3. The attempt at a solution

Ok, I got 6 (there are 8 according to the solution) using the above rules:
HF, HI, OQ, QR, BC, and DE

The solution says that BE and LJ are also zero force members, but I have no clue why...

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2. Mar 25, 2013

### PhanthomJay

Not LJ, its IJ, why? If BC is a zero force member, that should tell you something about BE (and DE).

3. Mar 26, 2013

### aero_zeppelin

Ok, I had thought about IJ before but since the solution didn't mention it I didn't count it...

Now, for BE: since BC is a zero-force member, can we "ignore" it and then consider the other 3 with Rule #2?

4. Mar 26, 2013

### PhanthomJay

yes.

5. Mar 26, 2013

### aero_zeppelin

Thank you sir ;)