This code provides guidelines for the design and construction of composite floor systems made from precast concrete planks (hollow core or solid) and a cast-in-situ concrete topping. It covers material specifications, design principles for flexure and shear, interface shear transfer, and construction practices including handling, erection, and quality control. The standard aims to ensure structural integrity and serviceability of these hybrid flooring systems.
Provides guidance for the design and construction of composite concrete floor slabs using precast concrete planks acting compositely with cast-in-situ concrete.
Quick Reference Values
Minimum grade of concrete for precast planksM30
Minimum grade of concrete for cast-in-situ structural toppingM25
Minimum thickness of structural topping50 mm
Minimum clear cover to reinforcement in topping15 mm
Minimum bearing length for planks on support75 mm
Assumed density of hollow core slab for load calculationsUse manufacturer data or 75% of solid concrete
Key Formulas
τ_vh = Vh / (bi * li) — Horizontal shear stress at the interface
Vh = Asf * 0.87 * fy — Horizontal shear force for ultimate limit state
Practical Notes
Ensure proper surface preparation of precast planks (roughening) to achieve good bond and horizontal shear transfer with the cast-in-situ topping.
Pay close attention to propping requirements during construction. Props must be designed to support the weight of wet concrete and construction loads before the composite action is achieved.
Differential shrinkage between the precast plank and the in-situ topping can induce stresses and must be considered in design, especially for long spans.