Waffle slab design example pdf

French gardener, patented a design for reinforced garden tubs in 1868, and later patented reinforced concrete beams and posts for railway and road guardrails. Statements consisting only of original research should be removed. Focus has been on biaxial slabs and ways to reduce waffle slab design example pdf weight.

Several methods have been introduced during the last decades, but with very limited success, due to major problems with shear capacity and fire resistance as well as impractical execution. Most attempts have consisted of laying blocks of a less heavy material like expanded polystyrene between the bottom and top reinforcement, while other types included waffle slabs and grid slabs. Of these types, only waffle slabs can be regarded to have a certain use in the market. But the use will always be very limited due to reduced resistances towards shear, local punching and fire.

The idea of placing large blocks of light material in the slab suffers from the same flaws, which is why the use of these systems has never gained acceptance and they are only used in a limited number of projects in Spanish-speaking countries. In principle, fixing of the ellipsoids can be made in numerous ways, but using only the reinforcement meshes reduces superfluous material consumption and allows for an optimal geometrical proportion between concrete, reinforcement and voids. The voids are positioned in the middle of the cross section, where concrete has limited effect, while maintaining solid sections in top and bottom where high stresses can exist. Hence, the slab is fully functional with regards to both positive and negative bending. In principle, voided biaxial slabs act like solid slabs. Designing is consequently like for solid slabs, but with less load corresponding to the reduced amount of concrete.

Germany, Netherlands and Denmark, conclude that a voided biaxial slabs acts like as a solid slab. The voided biaxial slabs technology is directly incorporated in international standards as the Eurocodes, and various national codes such as the CUR in the Netherlands. The main difference between a solid slab and a voided biaxial slab refers to shear resistance. Due to the reduced concrete volume, the shear resistance will also be reduced. For a voided biaxial slabs with spheres the shear resistance is proportional to the amount of concrete, as the special geometry shaped by the ellipsoidal voids acts like the famous Roman arch, enabling all concrete to be effective.

This is only valid when considering the voided biaxial slabs technology. Other types of voided biaxial slabs have reduced resistances towards shear, local punching and fire. In practice, the reduced shear resistance will not lead to problems, as balls are simply left out where the shear is high, at columns and walls. The fire resistance is dependent on the temperature in the rebars and hence the transport of heat. As the top and bottom of the voided biaxial slab is solid, and the rebars are placed in the solid part, the fire resistance can be designed according to demands.

Due to the specific shape of the voids, there are no issues with internal pressure. ISO 140-4:1998, ISO 140-7:1998, ISO 717-1:1997 and ISO 717-2:1997 measuring impact and airborne sound. Monolithic, continuous and ductile structure. Simple, monolithic behaviour, uniform and continuous distribution of forces.

One way spanning decks are supported by a combination of walls and beams. This leads to rigid and inflexible structures. This type of structure should be used with care in seismic regions due to the risk of progressive collapse. As this floor type is made of complete prefab elements with no structural coherence, support moments are absent, resulting in increased material consumption.

Acts like a solid slab. Does not have the earlier problems with reduced resistances towards shear, local punching and fire. MMC with lightweight building envelopes. 1 kg recycled plastic replaces 100 kg of concrete.

Reduction of the foundation load. Reduction of columns section or their number. Lower concrete cost with an equal thickness. Savings in useful height on each level as there are no emerging beams.