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IS 15498:2004 is the Indian Standard (BIS) for cyclone resistant design and construction of composite structures - code of practice. This code of practice provides guidelines for the cyclone-resistant design and construction of composite structures, including those combining steel, concrete, masonry, and timber. It covers crucial aspects like site selection, structural form, load calculation, and detailing of key elements like roofing and connections. The standard is intended for use in cyclone-prone coastal regions of India to enhance building resilience and safety.
Lays down provisions for the cyclone resistant design and construction of composite structures.
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Disaster Resilience and Retrofitting
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Roofing systems are the most vulnerable component. Special attention must be paid to the anchorage of roofing sheets, using cyclone washers and ensuring sufficient fasteners as per Clause 9.
! Connections between different structural elements (e.g., roof truss to wall, wall to foundation) are critical points of failure and must be robustly designed for wind uplift and shear.
! Avoid complex building shapes and large overhangs. Simple rectangular or square plans perform better under cyclonic winds as recommended in Clause 7.
ASCE 7-22American Society of Civil Engineers (ASCE), USA
HighCurrent
Minimum Design Loads and Associated Criteria for Buildings and Other Structures
Provides comprehensive wind load determination methods, including for hurricane-prone regions, which are fundamental to the design process.
AS/NZS 1170.2:2021Standards Australia / Standards New Zealand, Australia/New Zealand
HighCurrent
Structural design actions - Part 2: Wind actions
Specifies wind actions for design, with specific, detailed provisions for cyclonic regions, making it highly comparable.
EN 1991-1-4:2005 + A1:2010European Committee for Standardization (CEN), Europe
MediumCurrent
Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions
Defines the procedure for calculating wind loads on structures, forming the basis for design, similar to the loading part of IS 15498.
EN 1994-1-1:2004European Committee for Standardization (CEN), Europe
MediumCurrent
Eurocode 4: Design of composite steel and concrete structures - Part 1-1: General rules and rules for buildings
Focuses on the design of composite members and systems, which IS 15498 applies specifically to a cyclonic context.
Key Differences
≠IS 15498 is an integrated code of practice, combining cyclone loading principles (referencing IS 875) and composite construction guidelines. International practice typically separates these into a dedicated loading standard (e.g., ASCE 7) and a material design standard (e.g., AISC 360 for steel/composite).
≠The basis for basic wind speed (Vb) differs significantly. IS 875 (Part 3) uses a 50-year return period, whereas ASCE 7-22 uses risk-category-dependent return periods (e.g., 700 years for standard buildings) resulting in higher design wind speeds.
≠The wind zoning map in IS 875 is simpler, with six zones for the entire country. In contrast, ASCE 7 and AS/NZS 1170.2 provide more granular wind speed maps with more detailed contour lines and special wind regions.
≠Terrain and exposure categories are defined differently. IS 875 has four terrain categories, while ASCE 7 uses three primary exposure categories (B, C, D) with different definitions and corresponding exposure coefficients (Kz).
Key Similarities
≈All standards use a fundamental formula to convert wind velocity into a reference pressure, typically proportional to the square of the velocity (e.g., IS `Pz = 0.6 * Vz^2`, ASCE 7 `qz = 0.00256 * Kz * Kzt * Kd * V^2`).
≈The concept of using external (Cpe) and internal (Cpi) pressure coefficients to determine the net design pressure on building surfaces is a common methodology across all listed standards.
≈All codes account for the dynamic nature of wind by applying a gust effect factor (G or Gf) to the design, which considers the structure's size, frequency, and turbulence.
≈The use of importance factors (or risk categories) to increase design loads for critical structures like hospitals and shelters is a shared safety principle.
≈The principle of ensuring a continuous load path from the cladding to the foundation to transfer wind forces is a fundamental requirement in IS 15498 and all equivalent international standards for wind design.
Parameter Comparison
Parameter
IS Value
International
Source
Basic Wind Speed Return Period (Standard Buildings)
50 years (per IS 875 Part 3)
700 years (Risk Category II)
ASCE 7-22
Wind Pressure Formula Constant
0.6 (for pressure in N/m² from velocity in m/s)
0.00256 (for pressure in psf from velocity in mph)
ASCE 7-22
Number of Terrain/Exposure Categories
4 Terrain Categories
3 Exposure Categories (B, C, D)
ASCE 7-22
Topography Factor
k3 factor, ranging from 1.0 to 1.36 based on upwind slope.
Kzt factor, calculated with a more complex formula considering hill shape, height, and location.
Which primary code is used for wind load calculation?+
IS 875 (Part 3) is the primary code referenced for all wind load calculations (Clause 6.2).
What importance factor should be used for a cyclone shelter?+
An Importance Factor (k4) of 1.30 should be used for cyclone shelters and other post-cyclone emergency buildings (Clause 6.2.2.1).
What does the code recommend for building openings like doors and windows?+
Openings should be minimized, located away from corners, and equipped with strong, operable shutters capable of resisting wind pressure and impact from flying debris (Clause 7.4).
Are there specific guidelines for connections in composite structures?+
Yes, Clause 8 provides guidelines for connections, emphasizing that they must be designed to be stronger than the members they connect and capable of transferring all induced forces like uplift, shear, and overturning moments.