This standard provides guidelines for the cyclone-resistant design and construction of Pre-Engineered Steel Buildings (PEBs). It supplements IS 875 (Part 3) by introducing a cyclonic importance factor (k4) and provides specific local pressure coefficients and detailing practices for PEB components like frames, cladding, and their connections to ensure safety in cyclone-prone areas.
Provides guidelines for the cyclone resistant design and construction of buildings utilizing pre-engineered steel structures.
Quick Reference Values
Cyclonic Importance Factor (k4) for structures within 50km of coast in 55 & 50 m/s zones1.15
Cyclonic Importance Factor (k4) for post-cyclone importance structures1.30
Minimum Base Metal Thickness (BMT) for roof and wall cladding0.5 mm
Minimum grade for primary frame connection boltsGrade 8.8
Minimum grade for secondary connection bolts (purlins, girts)Grade 4.6
Minimum design life for permanent buildings50 years
Maximum permissible drift at top of columns under serviceability loadsH/150
Key Formulas
Vz = Vb * k1 * k2 * k3 * k4 — Design wind speed at height z
pd = 0.6 * Vz^2 — Design wind pressure in N/m^2 at height z
F = (Cpe - Cpi) * A * pd — Wind force on a surface element
Practical Notes
The introduction of the cyclonic importance factor 'k4' is a key requirement of this code and significantly increases the design wind speed compared to a standard IS 875 (Part 3) analysis.
Failures in PEBs during cyclones are often initiated at the cladding level. Meticulous design and specification of cladding fasteners as per Clause 7 are critical.
Pay close attention to the local pressure coefficients for edges and corners (Table 3 & 4), which are much higher than general surface pressures and govern the design of fasteners and local framing in those zones.