Analysis of Roof Truss for Wind Loads:

Next, we have to analyse the truss for the wind forces. As the wind pressure is 1.25 kN/m² of sloping roof area, the total wind load

W = Wind pressure × Sloping roof length × Spacing of truss

= 1250 × 5.59 × 4 = 27950 N

(a) Assume the wind blowing from left side. As the wind load acting at joints A and C is half that at joint G; we have the loads at joints A and C as 6987.5 N and at G as 13975 N. This is shown in Figure (c).

Figure (c): Wind Load Analysis (Wind Blowing from Left)

An reaction at the supports are calculated as follows: Taking moment of all forces about the point A

V_B × 10 =13975 × (5.59/2) + 6987.5 × 5.59

V_B = 7812 N

Now vertical component of wind loads is

W_T  ⋅ cos θ = 27950 × 2/√5   = 25000 N

∴ V_A + V_B = 25000 N ⇒ V_A = 17188 N

Also, H_A is equal and opposite to the horizontal components of the wind loads

∴ H_A = W_T sin θ = 27950 × 1/√5 = 12500 N

and is acting towards the left as shown in Figure (c). Knowing the loads and the reactions, the truss is analysed as before for member forces and these are indicated along with them in Figure (c) with their signs and direction arrows. (You have to check the calculations yourself.)