The design basis, in the open.
Every Vasistron structure is designed to the site it will stand on and ships with a design report that states the wind pressure, the section sizes and the foundation loads. This page sets out the codes, the materials and the method, so a consultant can check the report line by line.
IS 875 Part 3 basic wind speed
India is divided into six basic wind speed zones. Hyderabad and most of Telangana sit at 44 m/s. The design pressure also depends on terrain category, height and topography, so two sites in the same zone can need different steel.
- 33 m/s
- Zone 1: parts of Kerala, Karnataka interior, south Tamil Nadu
- 39 m/s
- Zone 2: much of the Deccan plateau, Maharashtra interior
- 44 m/s
- Zone 3: Hyderabad and most of Telangana, Delhi, Gujarat interior
- 47 m/s
- Zone 4: Chennai and the Tamil Nadu coast, Kolkata, Rajasthan north
- 50 m/s
- Zone 5: Andhra and Odisha coast, Gujarat coast, Uttarakhand
- 55 m/s
- Zone 6: Andaman and Nicobar, Saurashtra coast, north-east border
Steel, coating, fasteners
Pre-galvanised coil suits most inland sites. Hot-dip galvanising after fabrication protects cut edges and is specified near the coast or in industrial atmospheres. GI versus HDG, explained.
- Structural steel
- IS 2062 E250, or [S350GD] for cold-formed sections IS 2062 / IS 1079
- Pre-galvanised coil
- [275] gsm zinc, both faces IS 277
- Hot-dip galvanising
- [65–85] µm average, post-fabrication IS 4759 / ISO 1461
- Fasteners
- SS304 bolts, nuts, washers and module clamps IS 1367 for mechanical properties
- Anchor fasteners
- SS304 or HDG, sized from foundation pull-out
- Site welding
- None. All holes punched at the works.
From inputs to a stamped report
- 01 Inputs Site coordinates, module datasheet, layout, roof or soil data, any client specification.
- 02 Wind pressure Basic wind speed from the IS 875 Pt.3 zone map, factored for risk (k1), terrain and height (k2), topography (k3) and importance (k4 where applicable). Pressure coefficients for the tilt and edge zones.
- 03 Member design Purlins, rafters and posts checked for bending, shear, deflection and buckling under dead, wind and imposed loads to [IS 800] / [IS 801].
- 04 Foundation Driven post embedment from soil parameters, or ballast weight from uplift. RCC pedestal design for carports. Existing purlin check for rooftop.
- 05 Report and drawings Design report with the figures used, general arrangement, foundation layout and bill of materials, issued in [3] working days.
What we check before dispatch
- Coil test certificate against the order (grade, zinc mass).
- Section dimensions and hole positions against the drawing, first-off and every [50] pieces.
- Coating thickness by magnetic gauge on HDG batches, [5] readings per piece.
- Bundle contents against the bill of materials, labelled by roof zone or table.
- Fastener grade certificates filed with the dispatch note.
Engineering questions
- GI or HDG: which should I specify?
- Pre-galvanised (GI) coil at [275] gsm suits most inland sites and keeps cost down. Hot-dip galvanising after fabrication to IS 4759 gives a thicker coating and protects cut edges, and is the better choice near the coast or in industrial atmospheres.
- Which IS codes apply to solar structure design?
- IS 875 Part 3 for wind loads, IS 800 for steel design, IS 2062 for structural steel, IS 277 and IS 4759 for galvanising, and IS 1893 where seismic checks are required.
- What wind speed do you design for?
- The basic wind speed for the site from the IS 875 Part 3 zone map, between 33 and 55 m/s, adjusted for terrain, height and structure class. The design report states the figures used.
Send the site coordinates and a layout. The design report comes back with the price.
Drawings and a priced bill of materials back in [3] working days. Or call +91 93478 15712.