## 5 Conclusions  
In the present study, a filtration-prediction model was proposed to decrease the short-period monitoring system cost of monitoring points of plate girder steel bridges. A double filter with polynomial prediction models was designed and evaluated in the time and frequency domains. In addition, a real monitoring system under different cases of dynamic loadings for the WonHyo highway bridge was used. The developed model performance was then evaluated by comparing its results with real measurements. The results of this study revealed the following. The filtration cycle process was used to eliminate the strain, displacement and acceleration measurements' noises in time domain. A double filter process was used; however, if the semi-static signals were contaminated, the cycle process of the filtration should be increased. In addition, the polynomial selection depends on the shape of the relationship between the measured and extracted responses of the bridge. In the present study, the second and first polynomial degrees were selected to illustrate the bridge behavior. This model was found to be suitable for the studied bridge, and it should be evaluated before being applied for other types of bridges. The application of this model to the WonHyo bridge shows that the moving average and wavelet filters were suitable to eliminate the dynamic noises of the measurements. On the other hand, the design stage of the model showed that the correlation between the observed and predicted values was high (R\({}^{2}\) = 0.95), while the model error was low for the semi-static (RMSE = 0.029 mm) and acceleration (RMSE = 0.0042 g) predictions in the time domain. In the testing stage, the model performance was low when estimating the acceleration (R\({}^{2}\) = 0.87), while the performance was still high (R\({}^{2}\) = 0.98) to predict the semi-static displacement. Moreover, the model error for the semi-static displacement and acceleration were small. The bridge frequency for the measured and predicted accelerations was equal in the model design and testing stages. In addition, the signals' time-frequency and time phase were highly correlated. The accuracy of the developed model in extracting the bridge damping ratio was 86.5% and 69% for the design and testing stages, respectively. These results indicate that the developed model could be effectively used to estimate the full behavior of the bridge using strain measurements only. Furthermore, the predicted displacement values were generally greater than the measured values, this implies that the model could be used as an early safety alarm. Finally, the capability of using the model for the entire bridge was evaluated and tested in the time domain of the \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Speed (km/h)**} & \multicolumn{2}{c}{**G1-disp. (mm)**} & \multicolumn{2}{c}{**G2-disp. (mm)**} & \multicolumn{2}{c}{**G3-disp. (mm)**} & \multicolumn{2}{c}{**G4-disp. (mm)**} & \multicolumn{2}{c}{**G5-disp. (mm)**} \\ \cline{2-11}  & **Disp.** & **Strain** & **Disp.** & **Strain** & **Disp.** & **Strain** & **Disp.** & **Strain** & **Disp.** & **Strain** \\ \hline
20 & 0.58 & 1.20 & 0.76 & 0.88 & 2.09 & 3.17 & 3.65 & 5.03 & 6.02 & 7.04 \\
30 & 0.39 & 0.73 & 0.91 & 1.25 & 2.23 & 3.38 & 3.78 & 5.25 & 6.18 & 6.95 \\
40 & 0.44 & 0.87 & 0.87 & 1.12 & 2.31 & 3.71 & 3.80 & 5.26 & 6.28 & 7.08 \\
50 & 0.35 & 0.84 & 0.98 & 1.36 & 2.32 & 3.43 & 3.81 & 5.27 & 6.24 & 6.73 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Semi-static estimated and observed displacements for girders G1 to G5. semi-static displacement. The results of this evaluation show that the model was suitable to predict the performance of the design point only. [PERSON] designed theoretical models, performed analysis, and wrote the original draft. [PERSON] revised and edited the manuscript. [PERSON] revised the manuscript. All authors have read and agreed to the published version of the manuscript. This work was supported by a 2020 Incheon National University Research Grant.