NCIDQ IDFX Practice Exam

What type of concrete slab design is characterized by ribs and coffers?

1. Flat plate construction

2. Waffle slab construction

3. Post-tensioned construction

4. Double T construction

The correct answer is: Waffle slab construction

Waffle slab construction is characterized by its use of a grid-like pattern of ribs and coffers. This design involves creating a series of square or rectangular voids, which significantly reduces the weight of the concrete while maintaining strength and stability. The ribs provide support and distribute loads effectively, making waffle slabs suitable for larger spans and more extensive applications in commercial and industrial buildings. The coffered design not only aids in structural efficiency but also allows for aesthetic considerations, as the recessed areas can enhance the visual appeal of ceilings. This methodology improves insulation and reduces material costs, contributing to the overall efficiency of the construction process. In examining other types of concrete slab designs, flat plate construction features a uniform thickness without ribs, while post-tensioned construction employs tendons within the slab for increased strength, but lacks the distinct rib and coffer visual. Lastly, double T construction consists of pre-cast concrete elements shaped like the letter “T,” focusing on rapid assembly rather than the ribbed design characteristic of waffle slabs.