for the roof truss as shown, it is pinned at point A and supposed by a roller at point H. determine the reaction at joint A and joint H.

Question

For the roof truss as shown, it is pinned at point $A$ and supposed by a roller at point $H$. Determine the reaction at joint $A$ and joint $H$.

This is one of the problem in our "statics of rigid bodies" midterm exam and actually our whole class didn't know how to get it... Please help us. (I don't find statics in the tags section that's why I use physics, which is closer I think)

and we are confused if this problem is about "moment" or parallel forces

moment formula= $fx(y)-fy(x)$

parallel forces $r=wl$ ($w$=weight)($l$=length)

This looks like it would be more on-topic at http://physics.stackexchange.com/ (they even have a "statics" tag!). — Arnaud D., Mar 27 '17 at 15:56

score 0 · Answer 1 · answered Mar 27 '17 at 16:20

As you are pinned at A you need to resolve each force into radial and tangential components around A. Find $\angle BAC$ to resolve the $55kN$ force. The reaction at $H$ has to balance the sum of the tangential torques because A cannot produce any torque. The reaction at $A$ has to balance the sum of the radial forces because H is on a roller and cannot resist radial force.

for the roof truss as shown, it is pinned at point A and supposed by a roller at point H. determine the reaction at joint A and joint H.

1 Answers1