# Life Cycle Assessment of Bridges Using Bayesian Networks and Fuzzy Mathematics
## 5 Discussion
### Case Environmental Impact
#### 5.1.2 Comparative Analysis of the Results of Fuzzy Comprehensive Assessment of LCA and Bayesian  
According to the conclusion of the assessment in Section 5.1.1 and the results of software analysis shown in Figure 7, the contributions to environmental emissions of SQ according to the software analysis can be ranked from high to low as follows: operation and maintenance (55.57%) > material manufacturing (26.64%) > construction and installation (14.73%) > disassembly and recycling (2.84 %) > survey and design (0.22%), and SQ's contributions according to the BNFC can be ranked from high to low as follows: maintenance and operation (55.73%) > material manufacturing (26.54%) > construction and installation (15.09%) > disassembly and recycling (2.84%) > survey and design (0.23%). \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Types of EC** & **Bridge Name** & **Analysis Value (kg)** & **V1** & **V2** & **V3** & **V4** & **V5** \\ \hline \multirow{3}{*}{GWP} & SQ & 141,068,691.53 & 0.23\% & 25.37\% & 15.31\% & 56.12\% & 2.97\% \\  & EH & 129,184,807.08 & 0.47\% & 25.24\% & 18.54\% & 53.88\% & 1.87\% \\  & SQ & 494,656.64 & 0.00\% & 68.41\% & 0.07\% & 31.52\% & 0.01\% \\  & EH & 536,917.19 & 0.00\% & 55.50\% & 0.06\% & 44.43\% & 0.00\% \\  & SQ & 757,716.26 & 0.19\% & 28.86\% & 2.97\% & 67.95\% & 0.03\% \\  & EH & 693,040.75 & 0.40\% & 27.94\% & 4.25\% & 67.36\% & 0.05\% \\  & SQ & 1,730,629.40 & 0.00\% & 59.34\% & 0.07\% & 40.58\% & 0.00\% \\  & EH & 1,768,574.83 & 0.00\% & 51.75\% & 0.08\% & 48.17\% & 0.00\% \\  & SQ & 3,395,256.84 & 0.17\% & 51.75\% & 0.08\% & 48.17\% & 0.00\% \\  & EH & 3,132,009.78 & 0.34\% & 53.61\% & 3.62\% & 42.38\% & 0.04\% \\ \hline \end{tabular} Note: \(\mathrm{V}_{\mathrm{i}}\) is the average value of five types of environmental influences, \(\mathrm{K}_{\mathrm{j}}=\mathrm{a}_{\mathrm{j}}/\mathrm{V}_{\mathrm{i}}\mathrm{K }_{\mathrm{j}}^{\prime}=\mathrm{K}_{\mathrm{j}}/\mathrm{\sum K}_{\mathrm{j}}\):  
\end{table} 
Table 6: Summary table of membership data of two cable-stayed bridge classification systems. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Impact** & **Bridge** & **GWP** & **AP** & **FEP** & **PMFP** & **WP** \\
**Factor** & **Name** & & & & & \\ \hline \multirow{3}{*}{\(a_{i}\)} & SQ & 0.96\% & 0.00\% & 0.01\% & 0.01\% & 0.02\% \\  & EH & 0.95\% & 0.00\% & 0.01\% & 0.01\% & 0.02\% \\  & SQ & 20.00\% & 20.00\% & 20.00\% & 20.00\% & 20.00\% \\  & EH & 20.00\% & 20.00\% & 20.00\% & 20.00\% & 20.00\% \\  & SQ & 0.0478\% & 0.0002\% & 0.0003\% & 0.0006\% & 0.0012\% \\  & EH & 0.0477\% & 0.0002\% & 0.0003\% & 0.0007\% & 0.0012\% \\  & SQ & 0.9567\% & 0.0034\% & 0.0051\% & 0.017\% & 0.0230\% \\  & EH & 0.9547\% & 0.0040\% & 0.0051\% & 0.0131\% & 0.0231\% \\ \hline \end{tabular} Note: \(\mathrm{V}_{\mathrm{i}}\) is the average value of five types of environmental influences, \(\mathrm{K}_{\mathrm{j}}=\mathrm{a}_{\mathrm{j}}/\mathrm{V}_{\mathrm{i}}\mathrm{K }_{\mathrm{j}}^{\prime}=\mathrm{K}_{\mathrm{j}}/\mathrm{\sum K}_{\mathrm{j}}\):  
\end{table} 
Table 7: Summary table of assessment factor weight data for two cable-stayed bridges. As shown in Figure 8, the contribution to environmental emissions of EH according to the software analysis can be ranked from high to low as follows: maintenance and operation (53.57%) > material manufacturing (26.38%) > construction and installation (17.81%) > disassembly and recycling (1.78%) > survey and design (0.46%), and EH's contribution according to the BNFC can be ranked from high to low as follows: maintenance and operation (53.57%) > material manufacturing (26.46%) > construction and installation (17.81%) > disassembly and recycling (1.70%) > survey and design (0.46%). Figure 8: Comparison diagram of research and analysis conclusions of EH environmental impact contribution. Figure 7: Comparison diagram of research and analysis conclusions of SQ’s contribution to the environment. Figure 9 shows that the conclusions obtained by the application software are basically consistent with those obtained by BNFC.