Analysis of waffle composite slabs

For few decades and since the well-known composite slabs consisting of reinforced concrete poured on corrugated steel sheeting was achieved, the use of composite structures has grown widely However and since this type of slabs acts as a one-way slab due to the ribs configurations in the steel sheeting, some problems have been created such as having two parallel heavily loaded beams in each panel while the other two perpendicular beams are almost unloaded; which is uneconomic. The steel sheeting stiffness is always satisfactorily high in one direction and relatively low in the other which requires the use propping due to the relatively high loaded beams during the construction stage. For the above reasons and others, the idea of using two-way (or waffle) composite slabs was brought up. Carrying out such research required firstly choosing the most appropriate finite element modelling technique in representing the two-way or waffle composite slab and comparing its behavior to that of one-way. Three modelling techniques named real shape, equivalent and grillage models were tested and represented by two and three-dimensional finite element techniques to detect the best of them. Since no previous experimental, numerical or empirical results of waffle composite slab analysis were yet available to evaluate the modelling results, it was necessary to study also the behavior of the well-known one-way composite slab using the prementioned modelling techniques. After the best finite element model was achieved, an extensive parametric study in which many influencing parameters such as slab aspect ratio, slab boundary conditions, steel sheet depth, corrugation cell aspect ratio and its orientation were tested, was carried out in order to investigate the overall behavior of two-way composite waffle slab under different conditions. Many encouraging results and recommendations were obtained opening the door for this new configuration of composite slabs.