Determination of the Support Reactions:

By the fixed support A there are vertical and horizontal reaction V_A and H_A, at the sliding support B there can only be a vertical reaction V_B.

Since there are no horizontal components of loads

we have         H_A = 0

Taking moments of all forces about A, we see in which

V_B × 10 = 7700 × 2.5 + 7700 × 5 + 7700 × 7.5 + 3850 × 10

⇒         V_B = 15400 N

As Σ V = 0,

V_A + V_B = 7700 × 4 = 30800 N

∴          V_A = 15400 N

Knowing the external loads and the support reactions, now you can find the force in the members of the roof truss, either by 'method of joints' or 'method of sections'. The forces as calculated are shown along with the members with their directions (signs, + ve tension or- ve compression) in Figure 8(b). You are required to verify these calculations.