The Effect of Voids on Flexural Capacity of Reinforced Concrete Slabs

The voided reinforced concrete slab system is mainly produced with polyester foam placed mostly at the bottom of the slab. The aim of the voids is to reduce the weight of the slab. In this paper behavior of the voided reinforced concrete slabs in which voids placed at the mid-height of the slab cross-section, is examined analytically. A series of models were created to come up with a lightweight slab. Two distinct slab models were analyzed using the ABAQUS software. In the first group, slabs had three layers, in which bottom and top layers were of solid reinforced concrete, but the mid layer was of voided unreinforced concrete. In the second layer, in order to increase the contact between top and bottom layers of the slab, crossties were utilized, and the mid layer was reinforced accordingly. Since all the layers were 5 cm thick, the total thickness of the slabs were 15 cm. Slabs were 100 cm wide and 200 cm long. They were simulated the three-point bending test. Concrete damaged plasticity material model (CDPM) for concrete and elastoplastic material model for steel was selected. From the results it was found that moment capacity decreased with the increase in the volume of the voids. There was a sudden decrease in strength after reaching the yield strength in voided slab without a crosstie. In addition, crossties enabled the reduction of the weight of the slabs without significant decrease in moment capacity.