Abstract
Voided slab systems were developed using segmented void formers such as spherical or oval plastic balls for two-way slab applications. This type of slab is expected to behave like a general two-way reinforced concrete slab because it has segmented voids, rather than the continuous voids of hollow core slabs. However, the structural behaviors of two-way voided slabs with segmented voids have not been clearly verified. Therefore, this paper analyzes the possibility of applying a donut-type two-way voided slab, which was investigated with a 12-point two-way bending test focused on global behaviors, including its load bearing capacity, flexural stiffness, ductility, deflection, and load distribution. In addition, the design method of a donut-type two-way voided slab was reviewed through the yield line method. The test results showed that one donut-type two-way voided slab acted like a conventional two-way reinforced concrete slab with the load distributed evenly between the different directions; however, another donut-type two-way voided slab with different characteristics showed uneven load distribution with different crack patterns. In addition, the yield line method could predict the load bearing capacities of the donut-type voided slabs with approximately 95% accuracy.
Highlights
A voided slab is a reinforced concrete slab in which voids reduce the slab’s weight
If the effect of the merged-type fixing device on the increased tensile reinforcement ratio is considered, the load bearing capacity of TF–D–M–P.P calculated by the yield line method is 1172 kN, an approximately 5% increase over
The application of the merged-type fixing device increased the load bearing capacity of the donut-type voided slab by approximately 5%, which was attributed to the improved tensile reinforcement ratio introduced by the legs of the merged-type fixing device
Summary
A voided slab is a reinforced concrete slab in which voids reduce the slab’s weight. In this slab, lightweight void formers are placed between the top and the bottom reinforcements before concrete casting to replace concrete in the middle of the slab. Corey (2013) reported that the flexural strength of a voided slab with spherical voids is the same as that of a solid slab with equal depth if the compression block used to apply the bending force to the slab sections does not enter the void zone; and the flexural stiffness of this voided slab is approximately 80–90% of that of the solid slab due to the cross-sectional loss caused by voids These results were demonstrated in analyses of twoway flexural capacities of voided slabs. Wondwosen (2014) conducted finite element analysis of a voided slab with spherical voids, and reported that the in-plane bending stiffness of the voided slab decreased by 20% compared to that of a solid slab with equal depth These researches focused on only the twoway flexural strength and stiffness of the voided slabs, without considering the load distribution through the different load-carrying directions. This study introduces the effects of donut-type voids and the fixing device, which holds void formers in place, on the voided slab’s structural behavior under twoway bending
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