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IS 11384:1985 is the Indian Standard (BIS) for composite construction in structural steel and concrete. This code provides guidelines for the design and construction of composite structures using structural steel and concrete. It covers the design of composite beams, slabs, and columns based on the Working Stress Method, including provisions for shear connectors and deflection checks.
Code of Practice for Composite Construction in Structural Steel and Concrete
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This code is based on the Working Stress Method. For modern Limit State Design, engineers often refer to international codes like Eurocode 4, pending the publication of a revised IS code.
! Proper design, detailing, and placement of shear connectors are critical for achieving the intended composite action between the steel and concrete elements.
! Consider the construction sequence carefully, as the steel beam alone must often support the wet concrete weight and construction loads before the composite action is effective, unless shoring is used.
EN 1994-1-1:2004European Committee for Standardization (CEN), Europe
HighCurrent
Eurocode 4: Design of composite steel and concrete structures - Part 1-1: General rules and rules for buildings
Covers design of composite beams, slabs, columns, and shear connections using Limit State Design.
AISC 360-22American Institute of Steel Construction (AISC), USA
HighCurrent
Specification for Structural Steel Buildings
Chapter I specifically addresses the design of composite members using LRFD and ASD methods.
BS 5950-3.1:1990British Standards Institution (BSI), UK
MediumWithdrawn
Structural use of steelwork in building. Design in composite construction. Code of practice for design of simple and continuous composite beams
Historically contemporary standard covering composite beam and slab design, sharing some older methodologies.
AS/NZS 2327:2017Standards Australia / Standards New Zealand
HighCurrent
Composite structures - Composite steel-concrete construction in buildings
Provides principles for the design and construction of modern composite steel-concrete buildings.
Key Differences
≠The primary design philosophy of IS 11384:1985 is the Working Stress Method (WSM), an outdated approach. Modern standards like Eurocode 4 and AISC 360 are based exclusively on Limit State Design (LSD) or Load and Resistance Factor Design (LRFD).
≠IS 11384:1985 provides simplified, empirical formulae for shear stud capacity. Modern codes use more complex, extensively researched formulae that account for more variables like stud ductility, concrete confinement, and slab reinforcement.
≠The treatment of long-term effects like concrete creep and shrinkage in IS 11384 is simplified, often recommending a multiplication factor for the modular ratio. Modern codes use more sophisticated models based on creep coefficients and shrinkage strains.
≠The partial safety factor system in the Limit State appendix of IS 11384 is less refined than the calibrated systems in modern codes. For example, Eurocode 4 distinguishes between different material factors for various components and failure modes (e.g., γM0, γM1, γM2 for steel).
Key Similarities
≈All standards are founded on the principle of composite action, where a steel beam and concrete slab are joined to act as a single structural unit, significantly increasing strength and stiffness.
≈The concept of an 'effective flange width' is used universally to define the portion of the concrete slab that contributes to the composite beam's strength, though calculation methods vary in detail.
≈All codes recognize the critical function of shear connectors (like headed studs) to transfer horizontal shear force between the steel section and the concrete slab to ensure composite behavior.
≈The distinction between propped and unpropped construction is a fundamental consideration in all standards, affecting how construction-stage and final-stage stresses are calculated.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Design Philosophy
Working Stress Method (WSM)
Limit State Design (LSD) / Load and Resistance Factor Design (LRFD)
EN 1994-1-1 / AISC 360
Effective Flange Width (Interior Beam)
Lesser of (Span/4) or (c/c spacing of beams)
Lesser of (L₀/4) or (beam spacing). L₀ is distance between points of zero moment.
AISC 360 / EN 1994-1-1
Partial Safety Factor for Steel (Yielding)
γ_m = 1.15 (in LSM appendix, from IS 800)
γ_M0 = 1.0
EN 1994-1-1
Resistance Factor for Steel (Flexure)
Not directly applicable in WSM. Corresponds to 1/γ_m ≈ 0.87 in LSM.
φ_b = 0.90
AISC 360
Minimum Degree of Shear Connection
Not explicitly specified as a minimum percentage; design can be for 'full' or 'partial' connection.
Generally required. E.g., ≥ 25% of full connection capacity.
AISC 360
Modular Ratio (m) for WSM
m = 280 / (3 * σ_cbc), where σ_cbc is permissible stress in concrete.
WSM is not the primary method. For serviceability, an effective modular ratio 'n_eff' based on creep coefficient is used.
EN 1994-1-1
Shear Stud Strength Basis
Tabulated allowable loads (WSM) or simple formula based on d², √f_ck, E_c (LSM appendix).
Lesser of stud steel strength (based on ultimate tensile strength f_u) or concrete crushing/cone failure strength (based on √f_ck, E_cm).
EN 1994-1-1
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Modular Ratio 'm'280 / (3 * σcbc)
Maximum longitudinal spacing of shear connectorsThe lesser of 4 times slab thickness or 600 mm
Maximum transverse spacing of shear connectors across flangeThe lesser of 3 times slab thickness or 450 mm
Minimum concrete cover over shear connectors25 mm
Maximum spacing of connectors in composite columns600 mm
Key Formulas
m = 280 / (3 * σcbc) — Modular Ratio for transforming concrete section to equivalent steel
N = Vh / Q — Number of shear connectors required for a given horizontal shear Vh
I_t = I_s + I_c / m — Moment of inertia of transformed composite section
Tables & Referenced Sections
Key Tables
No tables data
Key Clauses
Clause 6 - General Design Considerations (Effective Width)
It is based on the Working Stress Method (WSM). Permissible stresses are derived from the contemporary versions of IS 456 and IS 800.
How is the effective width of the concrete flange determined?+
The effective width on each side of the beam's web is the minimum of: 1/6th of the beam span, 1/2 the distance to the next beam, or 6 times the slab thickness (Clause 6.1.1).
What are shear connectors for?+
Shear connectors (like welded studs or channels) transfer horizontal shear forces between the steel beam and concrete slab, forcing them to act as a single, stronger unit (Clause 8).
Is this code still current for new projects?+
While technically still in force, the industry standard has shifted to the Limit State Method (LSM). This code's WSM approach is considered outdated, and a new LSM-based composite code from BIS is awaited.