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IS 1863:1979 is the Indian Standard (BIS) for rolled steel bulb flats. This standard specifies the nominal dimensions, mass, and sectional properties of hot-rolled steel bulb flats, which are highly specialized sections primarily used as plate stiffeners in shipbuilding and structural engineering.
rolled steel bulb flats
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Structural Engineering and Structural Sections
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Bulb flats offer excellent strength-to-weight ratios and their rounded edges make them easier to paint and maintain against corrosion compared to standard angle sections.
! Because bulb flats are highly specialized, structural engineers should verify availability and minimum order quantities with steel mills before specifying them for general building structures.
! Sectional properties provided in this standard are essential for structural steel detailing and creating accurate BIM profiles.
EN 10067:1997CEN (European Committee for Standardization), Europe
HighCurrent
Hot rolled bulb flats - Dimensions and tolerances on shape, dimensions and mass
Directly equivalent for defining the dimensions, sectional properties, and tolerances of bulb flats.
ASTM A131/A131M-19ASTM International, USA
MediumCurrent
Standard Specification for Structural Steel for Ships
Specifies material properties (chemistry, mechanical) for steels used in shipbuilding, including sections like bulb flats.
JIS G 3192:2014JISC (Japanese Industrial Standards Committee), Japan
HighCurrent
Dimensions, mass and permissible variations of hot rolled steel sections
Covers dimensions, mass, and tolerances for a range of hot-rolled sections, including bulb flats.
IACS UR W11IACS (International Association of Classification Societies), International
MediumCurrent
Normal and higher strength hull structural steels
Defines the material property requirements for shipbuilding steels, which bulb flats are made from, as accepted by major marine class societies.
Key Differences
≠IS 1863:1979 is a withdrawn standard, while international counterparts like EN 10067 and ASTM A131 are current and regularly updated.
≠IS 1863 references a single, obsolete structural steel grade (IS 226), whereas modern standards like ASTM A131 offer multiple normal and high-strength grades (e.g., Grade A, AH36, DH36) with specified low-temperature toughness.
≠Modern international standards separate dimensional requirements (e.g., EN 10067) from material property requirements (e.g., EN 10025-2), whereas IS 1863 was a single specification referencing a material standard.
≠Dimensional and straightness tolerances specified in IS 1863:1979 are generally looser than those in modern standards like EN 10067, which are tailored for automated fabrication.
Key Similarities
≈The fundamental geometric profile of a bulb flat, with a web and a bulb on one edge to increase bending stiffness, is consistent across all standards.
≈All standards identify the primary application of bulb flats as longitudinal stiffeners for plating in shipbuilding and other marine structures.
≈The manufacturing method specified or assumed for the product is hot-rolling in both the Indian and international standards.
≈Key controlling dimensions such as overall depth, web thickness, and bulb size are defined and have specified tolerances in all related standards.
Parameter Comparison
Parameter
IS Value
International
Source
Status
Withdrawn
Current
EN 10067:1997
Material Tensile Strength
410 - 530 MPa (from referenced IS 226)
400 - 520 MPa (for Grade A steel)
ASTM A131/A131M
Material Yield Strength
≥ 255 MPa (from referenced IS 226)
≥ 235 MPa (for Grade A steel)
ASTM A131/A131M
Low Temperature Toughness
Not specified
Specified for various grades (e.g., 27 J @ 0°C for Grade D)
ASTM A131/A131M
Depth Tolerance (for 200 mm depth profile)
± 2.5 mm
± 2.0 mm
EN 10067:1997
Straightness Tolerance (Camber)
≤ 0.20% of length
≤ 0.15% of length
EN 10067:1997
Standardized Depth Range
100 mm to 430 mm
80 mm to 430 mm
EN 10067:1997
⚠ Verify details from original standards before use
Key Values2
Quick Reference Values
mass density of steel7.85 kg/dm³ (or g/cm³)
common depth range80 mm to 430 mm
Tables & Referenced Sections
Key Tables
Table 1 - Dimensions, Mass and Sectional Properties of Rolled Steel Bulb Flats