## 4 Results
### Comprehensive Membership  
Based on the mean and variance of the preliminary indicators (Table 8) and Equations (2) and (3), the parameter \(Z\) and the membership per indicator in \(\overline{A}_{D}\) and \(\overline{A}_{C}\) were calculated. The results demonstrate that the membership of social-technical indicators is 0.303\(-\)0.932 and 0.601\(-\)0.993, respectively, and the membership of economic sustainability indicators \(\overline{A}_{C}\) is 0.581\(-\)0.972 and 0.588\(-\)0.992, respectively. Regarding the greenness indicators, the results are 0.425\(-\)0.807 and 0.621\(-\)0.871, respectively. The scatter distribution of the membership value of \"designer-constructor\" is shown in Figure 1.  
As shown in Figure 1, some indicators are located at the top right areas, which indicates a larger membership. On the contrary, those indicators located at the bottom left have a smaller value. This distribution shows that designers and constructors have a consistent perception of the indicators. Besides, some of the indicators are located at the top left and bottom right of the figure. The discrete distribution is representative of the different perceptions between designers and constructors. Each point shows the extent to which designers and constructors have different attitudes towards a given indicator. For instance, the membership of indicator x\({}_{54}\) for constructors is 0.601, whereas its value for  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Code**} & \multicolumn{2}{c}{**Social-Technical Sustainability**} & \multicolumn{4}{c}{**Economic**} & \multicolumn{2}{c}{**Greenness**} \\ \cline{2-11}  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \\ \hline x\({}_{1}\) & x\({}_{2}\) & x\({}_{3}\) & x\({}_{4}\) & x\({}_{5}\) & x\({}_{27}\) & x\({}_{28}\) & x\({}_{36}\) & x\({}_{38}\) & x\({}_{39}\) \\ x\({}_{6}\) & x\({}_{7}\) & x\({}_{8}\) & x\({}_{9}\) & x\({}_{10}\) & x\({}_{29}\) & x\({}_{30}\) & x\({}_{40}\)designers is 0.303. This finding suggests that the indicator x\({}_{54}\) attracts more attention from constructors than that from designers. The comprehensive membership per indicator is calculated by using Equations (4) and (5) (\(n\) is 75). \(\lambda\) equals 0.75, which means that when the membership is less than 0.75, the indicator deserves exclusion. Consequently, the indicators for the sustainability of steel structures and their comprehensive memberships are derived, which is shown in Table 9.  
The indicators in Table 9 are classified into different dimensions, including social-technical sustainability (0.915), economic sustainability (0.804), and greenness (0.746). The social-technical sustainability dimension has the largest membership, which is ranked as the most important dimension. The \"bearing capacity of the structure\", \"investment amount\", and \"utilization of renewable energy\" are the most important indicators in the relevant dimensions, with their membership values being 0.993, 0.994, and 0.871, respectively. clearpage  
Figure 1: Scatter distribution of “designers-constructors” membership. Note: \(\mu_{C}\) and \(\mu_{D}\) represents the membership values of the indicators in \(\overline{A}_{C}\) and \(\overline{A}_{D}\), respectively.