# Solving this truss

1. Jan 21, 2013

### ajd-brown

1. The problem statement, all variables and given/known data

I need to find all the forces acting in the members of this truss.

2. Relevant equations

Sum x = 0
Sum y = 0
Sum Mom. at any point = 0

3. The attempt at a solution

i have tried using the method of sections and method of joints to solve this truss, but i cannot get any more values than the AF and AB, which = 25.9 and 12.99 respectively.

I dont want anybody to do it for me, i just need some help with the correct method, i think the fact that it is not statically determinate may have an impact, also does anybody have any idea as to how to improve this design/make it easier to solve? from experimenting in the program force effects, the addtion of the extra members on top of the truss decreased compressive forces dramatically. i will be making this truss out of 3mm square balsa wood, so compressive forces need to be minimised.

Thanks,

Anthony
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### truss.jpg
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2. Jan 21, 2013

### SteamKing

Staff Emeritus
Why do you think this truss is statically indeterminate?
You will need to know the dimensions of the truss in order to help you resolve the internal forces.

Hint: it appears that your truss is symmetric about point C in terms of geometry and loading. If you have found AF and AB, what forces will you find in the other end of the truss at ED and EH?

3. Jan 21, 2013

### ajd-brown

so this mean i can cut the truss in half, but what should i do with the central 25n load, should i half it or keep if the same?

as far as indeterminacy goes, i thought that because it does not satisfy m+3=2j (where m is number of members and j is number of joints,) that it is indeterminate, i take it that i am wrong.