## 3 Initial Gap Measurement and Evaluation of New Bridge Expansion Joint Device  
Previously, it was difficult to use data when necessary, as they were managed in the form of reports and fields. By contrast, by using the NEXUS device, initial data can be accumulated, and the adequacy of highway bridge expansion joints can be checked and evaluated online at any time. To confirm this, we tested the initial data for the adequacy of the pre-setting after 300 days, when the initial drying shrinkage and creep deformation roughly converge; in this regard, it can be beneficial to use the initial gap database (D/B) for the three routes completed at the end of 2016. As the pre-setting of the expansion joint device is not consistent with the daily average temperature during winter and summer at the time of construction, it is essential to adjust the gap in advance such that it has an intermediate value at the reference temperature (average daily temperature of 15 \({}^{\circ}\)C). Figure 3: UI configuration of the analysis program: measurement point image; survey trajectory (link to GPS); front-view status; value of the joint gap. The route to be investigated has 302 expansion joint devices of three types, namely, rail type, steel finger type, and mono cell type (see Table 4). We converted the expansion gap and average temperature (obtained from the Korea Meteorological Administration) at 15 \({}^{\circ}\)C during the investigation and evaluated the adequacy of the pre-setting. After analyzing the initial values of the new bridges, we investigated some bridges that were not properly preset, potentially due to lacking gaps during summer (35-40 \({}^{\circ}\)C) or excessive gaps during winter (\(-\)15 \({}^{\circ}\)C) (see Figures 4 and 5). For example, the design temperature range \(\Delta\)T is from \(-\)5 \({}^{\circ}\)C to 35 \({}^{\circ}\)C in the pre-stressed concrete girder type expansion bridge design movement calculation standard. Therefore, the reference temperature for pre-setting can be seen as 15\({}^{\circ}\)C, which is the median temperature. In fact, the temperature at the time of construction of the new joint is under various temperature environments, not 15 \({}^{\circ}\)C, so pre-setting is performed at the time of installation to increase or decrease the spacing at the time of installation. The y-axis \"Percentage of the capacity of the new joint\" is to ensure that pre-setting was performed properly at the time of construction:  
1. After examining the joint gap and the average daily temperature on any day,
2. The joint gap converted into the reference temperature of 15 \({}^{\circ}\)C is expressed as a percentage of the capacity of the new joint. This value means the following: 1. If it is close to 50%, it means that it is installed in the middle of the absolute value of the joint gap. (If it is an expansion and contraction joint with a capacity of 100 mm, it represents 50 mm when the joint gap is 15 \({}^{\circ}\)C, which is the reference temperature.) 2. If it is near 10%, it means that it is installed at a small value of the absolute value of the joint gap. (In the case of an expansion joint with a capacity of 100 mm, it shows 10 mm when the joint gap is 15 \({}^{\circ}\)C, which is the reference temperature, so the joint gap is insufficient in summer.) 3. If it is near 90%, it means that it is installed at a large value of the absolute value of the joint gap. (If it is a 100 mm stretchable joint, it is 90 mm when the joint gap is 15 \({}^{\circ}\)C, which is the reference temperature, so the gap is exceeded in winter.) As such, if it is possible to investigate and analyze the expansion joint device gap while driving, without blocking a separate route, from the beginning, and to convert it into D/B in the bridge management system, by monitoring the changing trend, it is possible to take preemptive measures in case of emergency (such as when the gap narrows in a short time).