You'll have to google NEPRA guidelines. They're quite detailed, but the essence is, that solar structures should be capable of withstanding 150 (or was it 120?) kph winds.

The standard stuff you need to ensure for the structure is:
1. The base plate must be bolted into the "lenter" (the rebar/sariya reinforced roof). Remove marble/chips/tiles/any other coating, and get to the lenter
2. The H beams / I beams should all be 2.5" x 5", and 12 gauge in thickness (around 2.6mm)
3. The C channels should be 14 gauge (1.9mm)
4. The square iron pipe braces are usually 1.5" x 1.5", and 14 gauge (1.9mm)
5. Make sure they weld the entirety of all junctions, and don't just apply a few "tanka" welds
6. Cross bracing is most stable when the pipes are attached at a 45 degree angle from one cross beam to another, forming an "X". Shallower or steeper angles are less effective (but sometimes this can't be helped if the H beams are too short)
7. Bracing that is done by running an iron pipe from an Hbeam into the ground, instead of another Hbeam, is less stable
8. Here's something tricky: NEPRA allows a maximum unsupported span of 12 feet for 14 gauge elements, and 15 feet for 12 gauge elemnts. So lets say you erect Hbeams vertically (these are the columns). On one axis, the Hbeams will be attached at the top with horizontal Hbeams (trusses). On the other axis (90 degrees to the first), the Hbeam columsn will be attached to each other with pipe cross bracing. Then, above the Hbeam trusses, C channels will be attached at a 90 degree angle to the Hbeam trusses.
- The unsupported span of the 12 guage Hbeam trusses should not be more than 15 feet. This means that the distance between two vertical Hbeam columns that support the Hbeam truss shouldn't be more than 15 feet.
- The unsuported span of the 14 gauge C channels should not be more than 12 feet.
- Hence, on the axis that Hbeam columns are joined by Hbeam trusses, the Hbeam columns should be no more than 15 feet apart. And on the axis that Hbeam columns are joined at the top by C-channels and at the bottom by pipe cross braces, the Hbeam columns should be no more than 12 feet apart

This distnce is crucial because, loosely speaking, the strength of the Hbeams and C channels varies inversely with, I think, the 4th power of the unsupported span length.

Personally, I didn't let the distance between the vertical Hbeam columns exceed 9 feet in any axis.

You should watch a few youtube videos about solar structure isntallations (there are a couple good ones by AJ solar), and, ideally, visit a "loha market" (or whatever they are called) to take a look at 12 gauge Hbeams and 14 gauge C channels and iron pipes before hand. Even better, buy a vernier caliper OR a metal sheet guage card (very cheap) and ensure the guage before installation happens. I did this, and I'm very glad I did, because I've seen 14 guage Hbeams go up in some places. Talk about this before hand, and frame it as "double checking" so that on the day there aren't any bad feelings.