What design philosophy does IS 11384 use?

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 This code's WSM approach is considered outdated, and a new LSM-based composite code from BIS is awaited.

IS 11384

: 1985

Code of Practice for Composite Construction in Structural Steel and Concrete

CurrentSpecializedCode of PracticeBIMStructural Engineering · Special Structures

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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

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

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.