Structural performance assessment of light-weight floor systems using locally available CFB and CFS sections

Abstract

Studies, on the use of alternative materials to conventional reinforced concrete flooring have become increasingly important in modern construction. One encouraging option is a lightweight composite slab system using natural cellulose fibre cement boards supported by cold-formed steel purlins. In Sri Lanka, such fibre cement boards are locally manufactured and becoming popular in low-rise residential and commercial buildings. However, the lack of reliable mechanical property data for these boards presents a challenge to structural engineers during detailed design. To address this gap, a comprehensive experimental program was conducted at the University of Moratuwa to determine the mechanical properties of locally available fibre cement boards with thicknesses of 15 mm, 18 mm, and 20 mm. Tests were performed in accordance with BS EN 12467, BS EN 789, and BS EN 1383 to evaluate bending strength (along and perpendicular to the fibre direction), tensile strength, compressive strength (in-plane and perpendicular), and pull-through resistance. All tests were conducted under dry conditions using a Universal Testing Machine (UTM) in displacement-controlled mode. Characteristic strengths were calculated following the procedures in EN 14358. Based on the experimentally derived characteristic strengths, this research proposes a set of span tables for fibre cement boards supported by cold-formed “C” purlins as per the Eurocodes. These span tables offer a practical and cost-effective design tool for engineers and promote the use of sustainable, lightweight flooring systems in the local construction industry.