This part of the IS 1893 series focuses on the earthquake-resistant design of industrial structures and stack-like structures (chimneys, silos, cooling towers). It provides specific importance factors, response reduction factors, and guidance on dynamic analysis for structures with irregular mass and stiffness distribution.
Provides criteria for the earthquake resistant design of various types of industrial structures and stack-like structures.
Quick Reference Values
Importance factor (I) for structures storing hazardous materials1.5
Importance factor (I) for power plant structures1.5
Importance factor (I) for regular industrial structures1.0
Response reduction factor (R) for RCC chimneys3.0
Response reduction factor (R) for Special Steel Moment Resisting Frame5.0
Damping for steel stacks2%
Damping for concrete stacks5%
Key Formulas
Ah = (Z/2) * (I/R) * (Sa/g) — Design horizontal seismic coefficient
Vb = Ah * W — Design seismic base shear
Practical Notes
Industrial structures often have highly asymmetrical mass and stiffness distributions; a detailed 3D dynamic analysis is strongly recommended.
Ensure the operating weight of equipment, fluids, and stored materials is appropriately considered in the seismic weight calculations.
For tall stacks and chimneys, P-delta effects and soil-structure interaction often play a critical role and should not be ignored.