Precast prestressed hollow core concrete slabs have been widely used in recent years. However, comprehensive finite element analyses for modelling the structural fire behaviour of this type of slab is too complicated to perform within hours. On the other hand, a simplistic analysis is too crude to capture the thermal expansion across the units. The aim of this paper is to present a simple computational method to be used in design for modelling the structural behaviour of hollow core concrete slabs in fires. The proposed model consists of a grillage system using beam elements to include the thermal expansion in both directions and to simulate the vertical cracking in the flanges, with the topping concrete modelled using shell elements. The simulation outcomes show good agreement with the experimental results.