## 4 Results and Discussion  
The case study provided the application of the presented decision support model for identifying the most effective CLP improvement strategies and quantifying their impact on \begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **CLP Improvement Strategy** & **Improved CLP** & **Rank** \\ \hline S2 & Provide clear instructions to craftsmen on how to complete tasks before their execution & 0.5516 & 1 \\ S6 & Train laborers to achieve the latest concrete-pouring techniques & 0.5478 & 2 \\ S13 & Apply preventive maintenance to heating and air-conditioning systems to make sure & 0.5460 & 3 \\ S11 & Develop clear instructions about the equipment used to transport materials & 0.5452 & 4 \\ S9 & Hold regular meetings with laborers about schedule and remaining tasks & 0.5451 & 5 \\ S7 & Perform project team activities & 0.5446 & 6 \\ S16 & Hire cheap labor for daily housekeeping tasks & 0.5420 & 7 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Quantified impact and rank of the most effective CLP improvement strategies. Figure 8: Flow chart showing process of determining improvement strategies’ impact on CLP. Figure 7: FCM model of CLP with refined optimal weights. CLP for concrete-pouring activities in a building construction project. Experts' opinions and historical data were collected to model the complex CLP environment including the relationships among the factors affecting CLP, which are mostly interconnected. According to SSC weights derived from the responses of ten experts to the questionnaire survey shown in Figure 3, the most critical criteria for selecting CLP improvement strategies for the project under study are IC and IF, respectively. This means the first priority of the company is to implement strategies that have greater impact on CLP compared to other strategies. The second priority of the company is to implement strategies, which takes less time and involves lower costs compared to the project's scheduled duration and budget. In Table 3, strategy 11, \"Develop clear instructions about the equipment used to transport materials\", has the highest value of closeness coefficient. This strategy along with strategies S2, S13, S7, S6, S9, and S16 have closeness coefficients above the average. This means these strategies are the most effective CLP improvement strategies with respect to SSCs. The impact of these seven most effective strategies was quantified by developing an FCM model for CLP, implementing each strategy in the model, and determining improved CLP for each strategy. According to Table 4, strategy 2, \"Provide clear instructions to craftsmen on how to complete tasks before their execution\", improves CLP by 0.0206 and has the greatest impact on CLP. Recall that CLP is defined as the ratio of installed quantity (in cubic meters) to total labor work hours; therefore if concrete pouring requires 100 labor work hours per week, implementing this improvement strategy will increase the installed quantity of concrete by 100 \(\times\) 0.0206, or 2.06 cubic meters per week. This strategy is supported by [PERSON] and [PERSON] [11] and [PERSON] and [PERSON] [27], whose work identified \"Availability of clear work front\", \"Adequate job instruction\", and \"Clear readability of drawings and specifications\" as top strategies for improving CLP. Strategy 6, \"Train laborers to achieve the latest concrete-pouring techniques\", improves CLP by 0.0168 and is the second most effective in terms of impact on CLP. This strategy is supported by [PERSON] and [PERSON] [56] and [PERSON] et al. [57], who found \"Training crew\" and \"Expanding skilled laborers\" to be important strategies for improving construction productivity.