This standard provides criteria for the structural design of reinforced concrete natural draught cooling towers. It covers the determination of loads (dead, wind, seismic, thermal), methods of analysis for the hyperbolic shell, and design requirements for the shell, top ring, bottom ring beam, and supporting columns. The code places significant emphasis on wind load analysis due to the unique geometry and height of these structures.
Criteria for the structural design of reinforced concrete natural draught cooling towers
Quick Reference Values
Minimum grade of concreteM20
Minimum clear cover to shell reinforcement40 mm
Minimum thickness of shell160 mm
Minimum vertical reinforcement in shell0.3%
Minimum horizontal (hoop) reinforcement in shell0.3%
Maximum spacing of hoop reinforcement300 mm
Key Formulas
Nφ = - (W(φ) + G(φ)) / (2 * π * r * sin(φ)) — Meridional membrane stress resultant
Nθ = - (qθ * Rθ) - (Nφ * Rθ / Rφ) — Hoop membrane stress resultant
Practical Notes
This code is from 1985 and may not cover all complexities of modern analysis. Designers often supplement it with international standards like ACI-ASCE 334.2R or detailed finite element analysis (FEA).
Wind load calculation is the most critical aspect of the design. For major projects, wind tunnel testing is highly recommended to validate or replace the static coefficients provided in the code.
Construction tolerances are extremely important. Deviations from the specified hyperbolic profile can significantly reduce the shell's buckling capacity.