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IS 4998 Part 2 : 1992Guidelines for Cyclone Resistant Design and Construction of Buildings - Constructional Details

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ASCE 7 · AS/NZS 1170.2 · FEMA P
CurrentSpecializedCode of PracticeBIMStructural Engineering · Disaster Resilience and Retrofitting
PDFGoogleCompareBIS Portal
Link points to Internet Archive / others. Not hosted by InfraLens. Details
OverviewValues5InternationalTablesFAQ3Related

IS 4998:1992 Part 2 is the Indian Standard (BIS) for guidelines for cyclone resistant design and construction of buildings - constructional details. IS 4998 establishes the structural design criteria for reinforced concrete chimneys. It outlines procedures for evaluating dead loads, along-wind and across-wind forces, seismic actions, and thermal stresses caused by internal flue gas temperature gradients, alongside providing detailing guidelines for the chimney shell.

Provides constructional details for buildings to enhance their resistance to cyclone forces.

Overview

Status
Current
Usage level
Specialized
Domain
Structural Engineering — Disaster Resilience and Retrofitting
Type
Code of Practice
International equivalents
ASCE 7-22 · American Society of Civil Engineers (ASCE), USAAS/NZS 1170.2:2021 · Standards Australia / Standards New Zealand, Australia & New ZealandFEMA P-55 · Federal Emergency Management Agency (FEMA), USABS EN 1991-1-4:2005+A1:2010 · British Standards Institution (BSI), UK / European Committee for Standardization (CEN), Europe
Typically used with
IS 456IS 875IS 1893
Also on InfraLens for IS 4998
5Key values2Tables3FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes
! Across-wind loads due to vortex shedding often govern the structural design of tall chimneys and require dynamic analysis.
! Thermal stresses induced by temperature gradients across the concrete shell are significant and must be combined with wind or seismic load combinations.
! Special attention must be given to concrete mix design and cover to protect reinforcement from aggressive chemical exposure due to flue gases.
Frequently referenced clauses
Cl. 5Assessment of Dead LoadsCl. 6Assessment of Wind LoadsCl. 7Assessment of Seismic LoadsCl. 8Temperature EffectsCl. 9Structural Detailing
Pulled from IS 4998:1992. Browse the full clause & table index below in Tables & Referenced Sections.
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International Equivalents

Similar International Standards
ASCE 7-22American Society of Civil Engineers (ASCE), USA
HighCurrent
Minimum Design Loads and Associated Criteria for Buildings and Other Structures
Provides comprehensive methodologies for determining wind loads on buildings and other structures.
AS/NZS 1170.2:2021Standards Australia / Standards New Zealand, Australia & New Zealand
HighCurrent
Structural design actions - Part 2: Wind actions
Specifies procedures to determine wind speeds and resulting wind actions for structural design in a cyclone-prone region.
FEMA P-55Federal Emergency Management Agency (FEMA), USA
MediumCurrent
Coastal Construction Manual: Principles and Practices of Planning, Siting, Designing, Constructing, and Maintaining Residential Buildings in Coastal Areas
Provides guidance and best practices for construction in high-wind coastal zones, similar to the guideline nature of IS 4998.
BS EN 1991-1-4:2005+A1:2010British Standards Institution (BSI), UK / European Committee for Standardization (CEN), Europe
HighCurrent
Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions
Establishes the basis for calculating wind loads for the structural design of buildings and civil engineering works.
Key Differences
≠IS 4998:1992 is a guideline from 1992 and references IS 875 (Part 3) which uses a deterministic, 50-year return period approach. Modern codes like ASCE 7-22 use a more sophisticated, probabilistic approach with wind speed maps for different risk categories and mean recurrence intervals (e.g., 300 to 3000 years).
≠Modern international standards like ASCE 7-22 have a much stronger and more detailed distinction between loads on the Main Wind-Force Resisting System (MWFRS) and local loads on Components and Cladding (C&C), specifying significantly higher localized pressures for C&C, especially at corners and edges.
≠The calculation of topographic effects in IS 4998 (via the k3 factor in IS 875) is simplified. ASCE 7-22 and AS/NZS 1170.2 use more complex, multi-variable formulas (Kzt factor) that account for hill shape, height, and location on the feature, often resulting in higher amplification factors.
≠International standards provide more refined categories for internal pressure coefficients (e.g., 'enclosed', 'partially enclosed', 'open' in ASCE 7) based on specific opening criteria, whereas IS 4998/IS 875 uses broader permeability categories ('low', 'medium', 'high').
Key Similarities
≈All standards use a similar fundamental formula to calculate wind pressure, which is proportional to air density and the square of the wind velocity (P ∝ ρV²).
≈The design process in all codes begins with a 'basic wind speed' for a specific geographic location, which is then adjusted by a series of modification factors.
≈All standards employ modification factors to account for variables such as building height, terrain roughness, building importance (risk), and topography, although the specific values and calculation methods differ.
≈The concept of using pressure coefficients (or shape factors) to account for the aerodynamic effects of a building's geometry on wind loading is a common principle across all compared standards.
Parameter Comparison
ParameterIS ValueInternationalSource
Basic Wind Speed (Vb) Basis3-second gust speed at 10m height for a 50-year return period. Refers to IS 875 (Part 3).3-second gust speed at 10m height, but mapped for different Risk Categories (e.g., 300-yr MRI for Cat I, 700-yr for Cat II, up to 3000-yr for Cat IV).ASCE 7-22
Wind Pressure Formula (Simplified)Design wind pressure pz = 0.6 * Vz^2 (in N/m²). Refers to IS 875 (Part 3).Velocity pressure qz = 0.613 * Kz * Kzt * Kd * Ke * V^2 (in N/m²).ASCE 7-22
Risk/Importance FactorRisk Coefficient 'k1' applied to wind speed, ranging from 0.88 to 1.08 based on building life and importance. Refers to IS 875 (Part 3).Primarily addressed by selecting a wind speed map based on Risk Category. A separate Importance Factor (Iw) is applied in some load combinations.ASCE 7-22
Topography Factork3 factor, ranges from 1.0 to 1.36 for upwind slopes > 3°. Refers to IS 875 (Part 3).Kzt factor, calculated via formula. Can be significantly higher than 1.36 and applies to hills, ridges, and escarpments.ASCE 7-22
Internal Pressure Coefficient (Cpi)±0.2 (low permeability), ±0.5 (medium), ±0.7 (high). Refers to IS 875 (Part 3).GCpi = ±0.18 for 'Enclosed Buildings', ±0.55 for 'Partially Enclosed Buildings', based on specific opening criteria.ASCE 7-22
Regional Multiplier (Cyclonic Regions)Not explicitly a separate multiplier; cyclonic regions are covered by the higher basic wind speeds on the map.A Cyclone Importance Multiplier (Mc) is applied to wind speeds in cyclonic regions, ranging from 0.95 to 1.15 based on Post-Disaster Function.AS/NZS 1170.2:2021
⚠ Verify details from original standards before use

Key Values5

Quick Reference Values
minimum shell thickness150 mm
minimum vertical reinforcement0.25% of gross concrete area
minimum horizontal reinforcement0.20% of gross concrete area
maximum reinforcement spacing250 mm
minimum clear cover50 mm
Key Formulas
T_x = T_i - (T_i - T_o) * (R_x / R_t) — Temperature distribution across shell thickness
f_c = (N / A) + (M / Z) ± f_temp — Combined stresses due to axial load, moment, and temperature

Tables & Referenced Sections

Key Tables
Table 1 - Maximum Allowable Deflection
Table 2 - Temperature Gradient Assumptions
Key Clauses
Clause 5 - Assessment of Dead Loads
Clause 6 - Assessment of Wind Loads
Clause 7 - Assessment of Seismic Loads
Clause 8 - Temperature Effects
Clause 9 - Structural Detailing

Related Resources on InfraLens

Cross-Referenced Codes
IS 456:2000Plain and Reinforced Concrete - Code of Pract...
→
IS 875:1987Design Loads (Other than Earthquake) for Buil...
→
IS 1893:2016Criteria for Earthquake Resistant Design of S...
→

Frequently Asked Questions3

What is the minimum shell thickness required for an RC chimney?+
150 mm to ensure stability and sufficient cover for reinforcement.
What is the minimum vertical reinforcement required in the chimney shell?+
0.25% of the gross concrete cross-sectional area.
How are lateral loads handled in RC chimney design?+
Both wind (IS 875 Part 3) and seismic forces (IS 1893 Part 4) must be assessed, with across-wind vortex shedding being particularly critical for tall stack-like structures.

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