Since the bridge and all segments of it are static, the sum of the torques acting on any portion of the bridge you choose is zero for any pivot point you may choose. See if you can find a rigid portion of the bridge and a wisely chosen pivot to which you can apply this powerful fact.
Consider the triangular portion shown in bold and let x be the pivot. (This choice eliminates the torques
due to the tensions in the beams that attach at
point x.) Find the torques on this left hand
triangle (which can be considered a solid piece
because of the connections). Remember that
counterclockwise torque is positive. Assume
that the horizontal segment above is being
stretched, so that the force that the tension in
this segment exerts on the bold triangle is
directed to the right.
Express the torque in terms of T, L , and Fp.
Answer in terms of T and L :
Tt = (TL.sqrt 3) / 2
Summation Tx = -LFp - T sqrt[L^2 - (L/2)^2]
The negative value of the tension shows that the segment is actually under a compressible load.
