Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 11233:1985 is the Indian Standard (BIS) for design and construction of radar antenna, microwave and tv tower foundations. This code of practice provides guidelines for the geotechnical and structural design of foundations for self-supporting communication towers, including radar, microwave, and TV towers. It covers site investigation, load calculations, design criteria for stability against overturning and uplift, and specifies requirements for various foundation types like isolated footings, rafts, and piles.
Code of practice for design and construction of radar antenna, microwave and TV tower foundations
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This code is dated (1985). Always use the latest versions of IS 875 (Part 3) for wind loads and IS 1893 (Part 4) for seismic loads on telecommunication towers.
! Uplift resistance is frequently the governing design factor for tower foundations, especially for isolated footings under high wind conditions.
! The weight of the inverted frustum of soil above the footing is critical for calculating uplift resistance. Ensure proper compaction and consider the soil's submerged unit weight if the water table is high.
TIA-222-HTelecommunications Industry Association (USA)
HighCurrent
Structural Standard for Antenna Supporting Structures and Antennas and Small Wind Turbine Support Structures
Directly covers the design of tower structures and their foundations, including geotechnical considerations.
EN 1997-1:2004European Committee for Standardization (CEN)
MediumCurrent
Eurocode 7: Geotechnical design - Part 1: General rules
Provides the framework for geotechnical foundation design used for towers in Europe, used with EN 1993-3-1.
CSA S37-18Canadian Standards Association (Canada)
HighCurrent
Antennas, towers, and antenna-supporting structures
Comprehensive standard for the design, fabrication, and erection of towers, including detailed foundation requirements.
AS 3995-1994Standards Australia (Australia)
MediumCurrent
Design of steel lattice towers and masts
Covers the design of lattice towers, including principles for foundation design similar to IS 11233.
Key Differences
≠IS 11233:1985 uses the Working Stress Method (WSM), applying global factors of safety to loads. Modern international standards like TIA-222-H and Eurocodes use the Limit State Design (LSD) or Load and Resistance Factor Design (LRFD) philosophy, which applies partial safety factors to loads and material resistances separately.
≠IS 11233 allows a blanket 25% increase in the safe bearing capacity of soil for wind load conditions, which is a practice discontinued in modern codes like TIA-222-H, where load combinations directly account for transient loads.
≠The Indian standard is significantly older (1985) and lacks the detailed guidance on modern geotechnical investigation techniques, seismic analysis, and foundation types (like micropiles) that are present in current international standards.
≠IS 11233 provides prescriptive values for parameters like the angle of rupture for soil uplift (30 degrees). Modern codes like Eurocode 7 and TIA-222-H emphasize site-specific geotechnical analysis to determine such parameters.
Key Similarities
≈All standards recognize the same fundamental failure modes for tower foundations: overturning, sliding, uplift, and excessive settlement/bearing failure.
≈The basic methodology for calculating uplift resistance using the weight of the foundation and an inverted cone or frustum of soil/rock above it is a common principle across all standards.
≈All codes require consideration of foundation design under multiple load cases, including operational (normal) conditions and maximum storm (survival) conditions.
≈The types of foundations covered are largely similar, including isolated pad footings, combined footings (rafts), and deep foundations like piles and drilled piers.
Parameter Comparison
Parameter
IS Value
International
Source
Design Philosophy
Working Stress Method (WSM)
Limit State Design (LSD) / Load and Resistance Factor Design (LRFD)
TIA-222-H
Factor of Safety against Overturning (Normal Condition)
2.0
Uses Load and Resistance Factors (e.g., resistance factor φ = 0.75 for overturning) rather than a single global FoS.
TIA-222-H
Factor of Safety against Uplift (Soil, Normal Condition)
2.0 (on weight of soil cone)
Uses LRFD with resistance factor φ = 0.75 for uplift resistance of soil. The effective safety factor is embedded in load/resistance factors.
TIA-222-H
Permissible Increase in Soil Bearing Capacity for Wind Load
25% for soil, 50% for rock.
Not permitted. Load factors in LRFD combinations account for the low probability of simultaneous maximum loads.
TIA-222-H
Assumed Angle of Rupture for Soil Uplift Cone
30 degrees to the vertical.
To be determined by geotechnical investigation; 30 degrees may be used as a preliminary assumption if justified.
TIA-222-H
Minimum Depth of Foundation
1.5 meters below ground level.
No absolute minimum specified; depth is governed by frost penetration depth, soil stratigraphy, and overturning calculations.
TIA-222-H
Consideration of Buoyancy
Full buoyancy to be considered if water table is above the base of the foundation.
Full buoyancy is considered based on design ground water level determined by the geotechnical report.
CSA S37-18
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Factor of Safety against Overturning (Normal Loads)2.0
Factor of Safety against Sliding (Normal Loads)1.5
Factor of Safety against Uplift (Weight of footing + soil)1.5
Factor of Safety against Bearing Capacity (Normal Loads)2.5
Permissible Total Settlement (Raft Foundation)75 mm
Permissible Angular Distortion (Tilt)1/500
Key Formulas
Stability Check (Overturning): Restoring Moment / Overturning Moment ≥ 2.0
Uplift Resistance Check: (Weight of Foundation + Weight of Soil Cone) / Uplift Force ≥ 1.5