How to Identify Zero Force Members in a Truss Problem?

[usfz28]

I need to find all the zero force members, and solve for the other members. I am at school right now but I can definantly tell AB and AC are zero force members. When I get home I will see what else I can come up with. Also I cannot remember how to get the angled trusses Also All 3 downward forces are 20 kips

http://img.photobucket.com/albums/v625/BrockBlackZ/prob1.gif

 

[usfz28]

By=22.11 and Iy=57.89... Since Bx=0 then I guess BD and DG are zero force members, How about GJ? Also sicne AC is zero is CE, EH, HK also zero? I also think FI is zero too. I know there are a lot of zero force members in here just need some help finding them

 

[civil_dude]

Assuming pinned connections, the only obvious zero force members are ED, HK & KJ.

 

[civil_dude]

Since the lower right reaction is a roller, then FI will also be a zero force member. I would find your reactions and start at I.

 

[usfz28]

Why would ab and ac not be zero focer membes?

 

[Cyrus]

Go back and read when the assumption for zero force members is valid. If that does not help then report back.