## 3 Bridge and Monitoring System Descriptions  
In the present study, the developed model was used to evaluate the WonHyo bridge (steel plate girder) in Seoul, Korea. The monitoring system was designed to observe the bridge behavior under traffic loads. A three-wheel truck was used to assess the bridge performance. The monitoring system was designed and implemented by the A-Best Company. The WonHyo bridge is one of longest bridges crossing the Han river in Seoul. Figure 3 shows the plan of the studied span, the bridge cross section, the loading cases used and the monitoring system. The total length of the bridge is 1470 m, and its width varies between 14.0 to 20.0 m. In different sections, the bridge consists of different construction materials, such as reinforced concrete, pre-stressed concrete and steel. In the present study, the span between piers 7 and 8 (42.5 m long) was investigated. The main supporting elements of this span were six continuous steel plate girders (Figure 3a). The measurements were taken at the middle of the studied span. The bridge width at the mid-section was 14.0 m. Waterproof strain gauge sensors, a sampling frequency of 200 Hz (type WFLA-6-11-1L; TML Co., Tokyo Measuring instruments Lab., Japan, ([[https://tml.jp/eng/documents/strain_gauge/WFseries.pdf](https://tml.jp/eng/documents/strain_gauge/WFseries.pdf)]([https://tml.jp/eng/documents/strain_gauge/WFseries.pdf](https://tml.jp/eng/documents/strain_gauge/WFseries.pdf))), a high precision CDP-50 displacement meter, Tokyo Measuring instruments Lab., Japan ([[https://tml.jp/eng/documents/transducers/CDP.pdf](https://tml.jp/eng/documents/transducers/CDP.pdf)]([https://tml.jp/eng/documents/transducers/CDP.pdf](https://tml.jp/eng/documents/transducers/CDP.pdf))) and an ARF-10A accelerometer, Tokyo Measuring instruments Lab., Japan, ([[https://tml.jp/eng/documents/transducers/ARF-A_ARF-A-T.pdf](https://tml.jp/eng/documents/transducers/ARF-A_ARF-A-T.pdf)]([https://tml.jp/eng/documents/transducers/ARF-A_ARF-A-T.pdf](https://tml.jp/eng/documents/transducers/ARF-A_ARF-A-T.pdf))) were used to observe the strain (S), displacement or deflection (D) and acceleration (A) of the bridge girders, respectively. The dynamic test was first performed to investigate and measure the dynamic characteristics of the bridge by measuring and recording the actual impact frequency and the natural frequency (Figure 3b). To evaluate the performance of the bridge under static and dynamic loads, 16 strain sensors, 6 displacement sensors and 1 accelerometer sensor were attached at section A-A to monitor the bridge girders. The measurements of girder G6 were used to evaluate the model. The monitoring system was designed to measure the movements of the girders and the slab during a short time period (24 pm to 5 am, on 2015.09.04). Figure 4 shows the monitoring system components used to collect the data. The sensors were connected to the data acquisition devices. Then, the measured data were digitized in an AD converter and delivered through the Bluetooth module and access point (AP). The data acquisition device used in this study had one channel; each device was synchronized each time by a signal sender. A personal computer was used to store the data in real time and to control the sensor nodes (data acquisition devices). Figure 4: The structural health monitoring system. Figure 3: The WonHyo bridge (**a**) studied the span position and elevation and (**b**) the cross section, load case and monitoring system (G = girder, S = strain, D = displacement, A = accelerometer). estimating the semi-static and dynamic responses of the bridge. Additionally, there was no information loss from the original data, which accurately reflects the bridge behavior under dynamic load effects. Figure 7 shows the smoothed signals of the acceleration and the extracted dynamic responses for the accelerometer and strain (dynamic strain) measurements, respectively.