Abstract
The rise in urbanisation and subsequent demand for infrastructure accelerates the use of concrete as a construction material. Conventional design practices need large member sizes to fulfil architectural and structural requirements. Hence, the size of structural members such as slab, beam, column, etc., significantly affects the quantity of concrete used. This calls for the need to optimise the use of concrete to reduce the self-weight of structure. The present study explores the possibility of biaxial voided slabs as a substitute for conventional reinforced concrete slabs. A typical biaxial voided slab eliminates concrete from the middle of the floor slab by introducing voids and it leads to a significant reduction in self-weight, about 30–50%. However, these voids reduce the sectional area of slab concrete, which leads to a reduction in flexural stiffness and shear resistance. The behaviour of the biaxial voided slab subjected to two-way flexure is discussed. Experiments are carried out to determine two-way flexural behaviour of the two-way slab with sphere shape voids by adopting 16-point loads. The obtained experimental results of strength and serviceability criteria are compared for slabs with and without voids. It is found that the flexural capacity of the two-way slab with biaxial voids is the same as a solid slab, with a minor reduction in its flexural stiffness. Furthermore, an analytical study is carried out based on the yield line analysis to predict the flexural capacity of the slab and compared with experimental results. It is evidenced that 16-point load is equivalent to 89% of uniformly distributed load and the flexural capacity of void slabs can be predicted by using yield line analysis as used in the conventional solid slab.
Keywords
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Abbreviations
- A st , b :
-
Area of bottom reinforcement;
- A st , t :
-
Area of top reinforcement;
- C :
-
Force in concrete per unit width of slab;
- d :
-
Overall depth of slab;
- d e :
-
Effective depth to bottom reinforcement;
- d ′ :
-
Effective depth to top reinforcement;
- f cm :
-
Mean concrete cube compressive strength;
- f st , b :
-
Stress in bottom reinforcement;
- f st , t :
-
Stress in top reinforcement;
- l :
-
Overall length of slab;
- l e :
-
Effective length of slab;
- m :
-
Ultimate moment capacity per unit width of slab;
- m x :
-
Ultimate moment capacity per unit width of slab in x-direction;
- m y :
-
Ultimate moment capacity per unit width of slab in y-direction;
- P u :
-
Theoretical or experimental ultimate load (16-point load);
- T b :
-
Force in bottom reinforcement;
- T t :
-
Force in top reinforcement;
- x u :
-
Neutral axis depth at ultimate;
- x ̅ :
-
Depth of resultant compressive force in concrete;
- W n :
-
Theoretical ultimate load (UDL) of solid slab based on YLA;
- W u 1 :
-
Equivalent UDL of ultimate load without considering self-weight of slab;
- W u 2 :
-
Equivalent UDL of ultimate load inclusive of self-weight of slab;
- δ u :
-
Mid-span deflection of slab corresponds to ultimate load.
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Acknowledgements
This work was supported by the Department of Science & Technology, India (SR/S3/MERC/0040/2012). The authors wish to acknowledge the assistance and facilities offered by the technical staff, Structural Engineering Laboratory, IIT Madras.
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Sagadevan, R., Rao, B.N. (2021). Experimental and Analytical Investigations on Two-Way Flexural Capacity of Biaxial Voided Slab. In: Adhikari, S., Dutta, A., Choudhury, S. (eds) Advances in Structural Technologies. Lecture Notes in Civil Engineering, vol 81. Springer, Singapore. https://doi.org/10.1007/978-981-15-5235-9_18
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