Reduced-Order Modeling of Composite Floor Slabs in Fire. I: Heat-Transfer Analysis

This paper presents a reduced-order numerical modeling approach for the analysis of heat transfer in composite floor slabs with profiled steel decking exposed to fire effects. This approach represents the thick and thin portions of a composite slab with alternating strips of shell elements, using a layered thick-shell formulation that accounts for both in-plane and through-thickness heat transfer. To account for the tapered profile of the ribs, layered shell elements representing the thick portion of the slab adopt a linear reduction in the density of concrete within the depth in the rib. The specific heat of concrete in the rib is also proportionally reduced to indirectly consider the heat input through the web of the decking, because the reduced-order model considers thermal loading only on the upper and lower flanges of the decking. The optimal ratio of modified and actual specific heat of concrete in the rib is determined, depending on the ratio of the height of the upper continuous portion to the height of the rib. The reduced-order modeling approach is validated against experimental results.