Wind load calculations for Solar PV rooftop structures

Solar PV structures can be compared to a monoslope roof (only with lower height). I need to know how do civil engineers design foundations and rails/purlins. I am currently refering to IS 875. For wind load calculations I am not clear on how to obtain the s factor in the k3 factor formula (k3 = 1 + C . s.)
Also a clear example to calculate wind load for solar structures will be appreciated.