Forces in Truss Members (Statics)

cpmustang07

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

See attachment.
Edit: Point A is a pinned connection (has a reactionary force in X and Y direction). Point B is a roller connection (only has reactionary force in Y direction)

2. Relevant equations

Sum Fx=0
Sum Fy=0
Sum of Moments=0


3. The attempt at a solution


Find reaction forces at point A and D. Normally this wouldn't be an issue. I'd just find the reaction force of D by solving for the moment around point A. Then find A by knowing that the sum of forces in Y direction is 0. However, dimensions are not given in the problem. I have the answers, but I do not see how to get to them.

After finding reaction forces, isolate each joint and begin with joint with no more than two unknowns. Proceed until all forces are found.

Attached Thumbnails

 

PhanthomJay

These are all equilateral triangles...each horizontal member has the same length, L. What would be the perp. distance from the applied load to A?

cpmustang07

3*cos(60)*L, correct?

SammyS

Interesting way to say 1.5L, which is correct.

Phrak

No...

PhanthomJay

Why not?? If the length of each horizontal member is L, the perpendicular distance from the line of action of the applied load to A is 1.5 L.

Phrak

right. 1.5L to A and 1.5KN on D.

cpmustang07

Thank you for your help guys. I'll work on it again today and see if this different train of thought will get me through it. :)

I got it guys. Thank you. Apparently I'm really slow. ;)