# Exploring Analytical Hierarchy Process for Multicriteria Assessment of Reinforced Concrete Slabs
## 2 Materials and Methods
### Slab Selection Is Based on Their Type and Functionality  
Slabs are linear plane elements responsible for transmitting loads from external actions to the beams or the columns. These elements are mostly subjected to bending stress and must be designed, detailed, and built to attend to this internal stress.  
Figure 1: Survey workflow diagram.  
Although several types of slab already exist, these elements undergo constant changes. Their construction process frequently evolves to generate the most outstanding possible economy of materials and archive the architectural demand. Thus, among the various possibilities, we can highlight the most common ones: the slab on beams, the waffle slab, the flat slab, and flat slabs with drop panels, as shown in Figure 2. Slabs on beams are concrete blocks supported on the beams and are usually executed in one single step [13].  
The waffle slabs are composed of the cover and the ribbed section, formed by fillers that can be made of bricks, styrfoam blocks, or any form that allows for the execution of these elements with voids. This slab can be divided into a one-way or two-way slab, depending on the direction that it will be supported on the beams, i.e., if the load is being transmitted to the support in only one direction, it is classified as one-way; if it is sent in two directions, it is called two-way. Due to its voids, this type of slab enables large spans with less concrete when compared to the previous slab. However, its productivity can be affected by the assembly characteristics.  
Flat slabs are elements directly supported on the columns, and may or may not undergo a widening in the slab-column transition. According to [14], these slabs can be formed by the two previous types, i.e., solid or waffle, as shown in Figure 3. Characteristics of this type of slab include its high productivity compared to the constructive processes. Regarding acoustics, this type of slab can be described as advantageous, as presented in the study [15]. This manuscript investigates the relationship between the structural form of the slab and acoustics, and proves a good acoustic insulation of this type of structural solution.  
Figure 2: Most common types of slab.  
The construction techniques of the mentioned slabs differ from each other, causing variations in the production rates of each one. Additional differences between the models, such as the quantity of the utilized material and whether a model has better stiffness or less deformation, may also be statistically quantified. There are also subjective differences, such as the aesthetic suitability of the slab; in other words, a visual difference between the slab system designed by the engineer and what the architect visualized as the final product. For instance, there could be a reduction in the ceiling height due to the thickness of a waffle slab or its aesthetic perception in the absence of a ceiling. These differences between the types impact which slab best suits a specific project.  
Finally, there are flat slabs with drop panels and bend beams, which are types of slabs with insufficient thickness to resist the shear stress alone, thus requiring the inclusion of drop panels or bend beams to assist in resisting this effort by increasing the final thickness of the element. The difference between these two types is given by the region in which there will be an increase in thickness, with the first occurring only in the region of the pillar, and the second along the longer span.