Experimental evaluation of the bearing capacity of concrete composite voided slabs

Voided slab systems in reinforced concrete structures are mostly produced with polystyrene foam placed under the slab. The main purpose of the voids in the slab is to reduce the weight of the slab. In this thesis, the behavior of a series of voided reinforced concrete slabs formed with polystyrene foam in the middle layer of the slab cross-section was investigated experimentally and analytically. In this context, 11 slab systems in which the amount of void changes is divided into two separate groups. While the first of the slabs was used as the control specimens without any void, four slabs were produced with voids. The slabs in the second group are additionally reinforced with shear reinforcement. The bottom and top layers of the voided slabs are made of solid reinforced concrete, whereas the middle layer consists of polystyrene foam and concrete. Slab length is 200 cm, width is 100 cm and thickness is 15 cm. Voided slabs are produced in three layers, each layer is 5 cm in height. In the preliminary study before the slab tests, an analytical study was carried out in ABAQUS software according to the concrete damage plasticity model (CDP) of concrete and elastoplastic behavior of steel. Slabs were tested according to the 3-point bending test method in which roller supports were placed at bottom of slab. The loading is applied with a uniform linear distributed loading in the middle of the span. Displacement readings were taken directly from the center of the slab span. In addition, mechanical tests of the concrete and steel used in the thesis were carried out. According to the results, when the void ratio increased, a decrease in the slab bending capacity and an increase in the total deformation were observed. At the same time, it was observed that the cracking type changed from bending to shear in case the void ratio was 20% or more. Despite the increase in voids in the first group of slabs, the initial stiffnesses remained approximately the same. In the second group of slabs in which shear reinforcements were used, the initial stiffness and ductile deformation increased compared to the first group. There was no significant decrease in the final load capacities of the slabs with the use of shear studs in the second group of slabs. In addition, the moment and deflection values obtained in the analytical study is found to be consistent with the experimental study. According to the experimental results, observations and analytical evaluation carried out within the scope of the thesis, it has been noted that a certain amount of void can be left in the slabs where shear stud is used and the slabs can be lightened without significant loss in ultimate load capacity.