Loading calculation.
In this video wind load calculation for the roof truss is covered.
Latest IS code, i.e. IS875 Part 3 : 2015 is followed.
Following elements are included;
Vb = design wind speed at height z, in m/s,
k1 = probability factor (risk coefficient) (table 1),
k2 = terrain roughness & height factor (table 2),
k3 = topography factor (6.3.3),
K4 = importance factor for cyclonic region (6.3.4),

As per IS 875- part 3 (2015)
Wind Load = F = (Cpe -- Cpi) x A x Pd
Pd = Kd x Ka x Kc x pz
pz = 0.6 Vz2
Vz = Vb x k1 x k2 x k3 x k4