## 6 Conclusions  
This study presented a schematic data analysis and evaluation of modal identification procedures to obtain dynamic characteristics of civil structures (a suspension bridge and an overhead transmission line-crossing frame) using the ambient response. The band-limited white noise signal was used to simulate the ambient excitation source. The modal identification procedures included two types of output-only modal identification algorithms: the novel BSS learning rules (CP and GED) based on modern signal processing technology. The effectiveness and accuracy of both types of algorithms were investigated by numerical simulations and experiments in a suspension bridge. In addition, an engineering application of BSS methods was implemented in an overhead transmission line-crossing frame. On the basis of the presented results and interpretations, the main findings can be summarized as follows:  
* This study explored the feasibility of the novel BSS learning rules CP and GED in modal identification of a suspension bridge. Comparison of these two methods showed that the GED method was accurate; however, as the noise increased, the accuracy declined severely. Under a laboratory environment, GED is more applicable because this method has higher computing efficiency and accuracy than CP. However, the CP method has efficient mixed modal identification capabilities. The disadvantage of the BSS method is that the order of identifiable modes is limited by the number of sensors and cannot identify the mode which is not always well excited by ambient sources. * The CP and GED methods are capable of successfully identifying modal parameters of the crossing frame under ambient excitation, which further verifies the effectiveness of the identification algorithm in civil structures. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Mode**} & \multicolumn{2}{c}{**Input-Output (FRF)**} & \multicolumn{2}{c}{**Identified by CP**} & \multicolumn{2}{c}{**Identified by GED**} \\ \cline{2-9}  & \(f\) **(Hz)** & \(\xi\) **(\%)** & \(f\) **(Hz)/Error** & \(\xi\) **(\%)/Error** & **MAC** & \(f\) **(Hz)/Error** & \(\xi\) **(\%)/Error** & **MAC** \\ \hline
1 (1 st B) & 1.00 & 2.08 & 1.01/1.0\% & 1.98/4.8\% & 0.99 & 1.00/0\% & 2.16/3.8\% & 0.99 \\
2 (1 st T) & 1.22 & 3.19 & 1.25/2.5\% & 3.05/4.4\% & 0.84 & 1.21/0.8\% & 3.21/0.6\% & 0.89 \\
3 (2 nd B) & 1.59 & 1.04 & 1.52/4.4\% & 1.18/13.5\% & 0.92 & 1.60/0.6\% & 1.10/5.8\% & 0.98 \\
4 (2 nd T) & 2.25 & 1.22 & 2.26/0.4\% & 1.25/2.5\% & 0.96 & 2.28/1.3\% & 1.31/7.4\% & 0.99 \\
5 (3 rd B) & 4.44 & 0.59 & 4.47/0.7\% & 0.68/15.3\% & 0.89 & 4.43/0.2\% & 0.55/6.8\% & 0.91 \\  & CPU Time & & & 7.52 s & & 4.65 s & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Identification results of the crossing frame by CP and GED. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Mode** & \(f\) **(Hz)** & \(\xi\) **(\%)** & **Mode Shape 1** \\ \hline
1 st B & 1.00 & 2.08 \\
1 st T & 1.22 & 3.19 \\
2 nd B & 1.59 & 1.04 \\
2 nd T & 2.25 & 1.22 \\
3 rd B & 4.44 & 0.59 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Modal parameters of the crossing frame (by FRF method). **Author Contributions:** All authors discussed and agreed upon the idea and made scientific contributions. The original idea of the article was provided by [PERSON], and he also designed the methodology, realized its MATLAB program, and wrote the manuscript; [PERSON], [PERSON] ([PERSON]), and [PERSON] ([PERSON]) provided support throughout the entire study and revised the manuscript; [PERSON] gave suggestions for the theoretical analyses and tests. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the Science and Technology Research Project of State Grid, grant number 5200-202220092A-1-1-ZN. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable.