# Hybrid Methods for Selecting Precast Concrete Suppliers Based on Factory Capacity
## 3 Methodology
### Collect Data  
The process of collecting data for this study is described in detail in this section. Once the data collection exercise was completed, the criteria were identified to assess the precast suppliers. Different search engines were considered as data sources for this study. Such databases include Google Scholar, Web of Science, IEEE, ASCE, Springer, and Taylor and Francis. To retrieve the data, 15 keywords were utilized to locate the relevant documents. General terms such as bridges, highways, and construction projects were excluded from the search. The included keywords were appropriate and closely connected to the topic of this study. As a result, the search results were more refined and focused on the research topic. Such keywords included precast concrete, factors, productivity, performance, prefabricated, and challenges. The other inclusion criteria entailed selecting research materials written in English. Lastly, only peer-reviewed research materials published between 2000 and 2024 were selected for this study. Over 126 existing research materials were initially selected. This number dropped to about 22 research materials upon applying the above-described filters. To identify the criteria for selecting ready-mix concrete suppliers, data was collected through a multifaceted approach that included an in-depth literature review, construction site visits, and consultations with industry experts. This process yielded the 15 key factors presented in Table 2. Recognizing that the importance of these factors varies, this study's next objective was to determine which are most critical within the specific context of the Saudi construction market, as detailed in the following section. Figure 2: Radar chart of supplier performance profiles and overall ranks for WSM. The framework's methodology begins with a comprehensive initial pool of 15 potential criteria, as detailed in Table 2. Acknowledging that these factors are not of equal importance, the framework employs a systematic, multi-stage process to address this complexity. The first and most critical stage involves filtering these factors using the Delphi technique to identify the criteria most significant for differentiating between suppliers in the specific context of the Saudi market. This reliance on expert-driven input ensures that the model's conclusions are grounded in practical industry priorities, making the framework inherently flexible as it can be customized by any organization using its panel of decision-makers. A crucial distinction emerged from the iterative Delphi process: the separation of criteria into \"qualifiers\" and \"differentiators.\" The expert panel unanimously identified certain factors as non-negotiable, mandatory prerequisites. Specifically, Safety Standards (C15) and, to a lesser extent, Sustainability Practices (C13), were framed as 'pass/fail' gate-keeping criteria. In the Saudi Arabian construction industry, a supplier failing to meet fundamental safety regulations would be disqualified at the outset, never reaching a comparative evaluation. Similarly, sustainability is currently treated more as a compliance checkpoint than a primary variable for competitive ranking. Therefore, the nine criteria that emerged from this filtering process represent the core differentiators--factors such as cost, payment terms, and delivery performance--that decision-makers actively trade off against each other after a supplier has met the foundational requirements. The exclusion of qualifier criteria from the ranking model does not diminish their importance; it methodologically positions them as pre-screening conditions. Consequently, it is this refined set of nine differentiating criteria that proceeds to the next stage: quantitative weighting of their relative importance using the SWARA method.