Composite slabs are gaining wide acceptance in many countries as they are faster, lighter and economical in construction buildings. The ultimate behaviour of steel-concrete Lightweight composite slab system with hollow box beamis experimentally investigated in this paper. The strength of composite slabs system relies on the bonding action between the concrete and the steel deck, the shear connections and the cross sectional resistance of steel beam. However, structural behaviour of composite slab is complex phenomenon and therefore experimental study is often conducted to establish the strength of the structure under ultimate load capacity. The main objective of this study is to determine the structural behaviour of lightweight composite slab system with hollow box beam, compare the analysis and design method according to Eurocode 4. Total of two specimens are examined in order to obtain failure mechanism of the composite structure under full load capacity. A new design approach of composite slab for roofing system is proposed in this study and compared to experimental result. The comparison shows good agreement between experiment and theoretical results
