This code provides guidelines for the design and construction of floors and roofs using a system of precast reinforced concrete joists and planks. It outlines requirements for materials, design principles (using Working Stress Method), manufacturing, erection, and the application of in-situ concrete topping to achieve a composite slab.
Design and Construction of Floor and Roof with Precast Reinforced Concrete Planks and Joists - Code of Practice
Quick Reference Values
Minimum grade of concrete for precast unitsM20
Minimum grade of concrete for in-situ toppingM15
Minimum clear cover to main reinforcement15 mm
Minimum thickness of structural concrete topping40 mm
Minimum end bearing of joist on masonry75 mm
Maximum size of coarse aggregate in topping12.5 mm
Key Formulas
M = σst * Ast * j * d — Moment of resistance (Working Stress Method)
Practical Notes
This code is based on the Working Stress Method of design, which is largely superseded. For modern projects, designers should adapt the principles to the Limit State Method in conjunction with IS 456.
Careful handling, transportation, and erection of the precast units are critical to prevent cracking or damage. Ensure specified bearing lengths and propping arrangements are strictly followed.
Composite action between the precast units and the cast-in-situ topping is fundamental to the system's strength. The top surface of precast units must be clean and intentionally roughened to ensure a good bond.