# Exploring Analytical Hierarchy Process for Multicriteria Assessment of Reinforced Concrete Slabs
## 2 Materials and Methods
### Methodology  
The development of this research began with a literature review aiming to analyze and define the criteria used in the decision-making process of the studied problem. This survey was carried out using the following databases: Compendex, ScienceDirect, Google Scholar, Wiley, and SpringerLink, searched in the English and Portuguese languages, with the emphasis on scientific articles published between the years 2001 and 2022. The following research questions can be asked at this stage: Which criteria do professionals in theArchitecture, Engineering, and Construction (AEC) industry believe impact the decision of which slab to adopt in each project? This survey highlighted the following criteria:  
* Structural performance: Capacity of slabs to support the applied loads, considering the displacement of the slab as a function of the span (serviceability), the internal forces as bending moment (resistant capacity), and the durability of the element;
* Productivity/constructability: Related to the simplicity of the construction process, directly proportional to the execution time and the allocated labor resources;
* Cost: Monetary value associated with the cost of the materials used in the slab's construction (concrete, steel, and formwork), as well as the value of the execution;
* Appearance: Related to the aesthetic when integrating the structural element and the architectural concept;
* Waste generation: Environmental impact generated by construction waste;
* Thermal/acoustic comfort: Related to the performance of the slab concerning the thermal comfort provided by the heat transmission of the slab and the acoustic comfort offered by the insulation of noise between floors. Other criteria, such as the type of structural system, can be applied in research that covers more types of construction, such as warehouses and large buildings, among others. However, because this research is limited to residential and commercial buildings, these factors do not have as significant an impact as the others that are listed. This choice is made as this type of building is more used and common in several cultures [31]. With the selected criteria, and based on the five slab alternatives (slab on beams, one-way waffle slab, two-way waffle slab, solid flat, and waffle flat), it is possible to develop a criteria tree for the presented problem, as shown in Figure 5.  
For the construction of judgment matrices, because the criteria are divided into two categories, quantitative (structural performance, productivity and cost, and waste generation) and qualitative (appearance and thermal/acoustic comfort), the assembly of the matrices was divided between the machine learning analysis and the Delphi methodology, respectively. For the subjective criteria, to apply the Delphi research methodology, it is necessary to follow a sequence of scientifically validated steps that include an elaboration of the system to be adopted and the flow that will be used, as presented in Figure 6.  
Once the method was chosen, 12 specialists were selected and divided as follows: four builders, four structural engineers, and four architects. The decision was made on the premise that each professional has unique perspectives and priorities that influence the decision-making process. For example, the engineer will prioritize the structural performance, the builders will prioritize the minimum cost, and the architects will prioritize the structure's appearance in the edification. The heterogeneity of this sample aims to provide a more holistic view of the process. The experts were selected based on their academic backgrounds and extensive market experience. The study included four architects, all of whom are university professors. Figure 5: Criteria tree of the problem (The asterisks indicate the sub-classifications of the slabs. The varying colors in the arrows enhance visibility for better comprehension). Figure 6: Flowchart applied to the Delphi method.