# Effect of High-Temperature Pavement Paving on Fatigue Durability of Bearing-Supported Steel Decks
## 3 Field Monitoring
### Temperature Variation during the Paving Process  
All temperature sensors, excluding those monitoring ambient temperatures, were attached to the diaphragms. Hence, the monitored temperature data only represent the temperature characteristics of diaphragms. The thermal temperature variation of pavement and deck plate would be investigated based on the numerical results.  
The temperature histories monitored by TS-A1 (B1) to TS-A4 (B4), which are arranged below the pavement center, are shown in Figure 5a. The temperatures at different positions of the diaphragm are affected by the vertical thermal transfer; the vertical temperature distribution of the diaphragm exhibits hysteresis during the PGA paving process. With respect to the temperatures close to the deck plate (monitored by TS-A1 and TS-B1), there is a time lag before the increase induced by the paving sequence; however, the time intervals for other measuring points are negligible due to the hysteresis induced by heat transfer. The temperatures rise quickly after PGA paving, and then decrease at a slower rate.  
With respect to the temperature monitored at TS-A1, the maximum value of 95.2 \({}^{\circ}\)C appears at 25 min after PGA paving. The temperature monitored by TS-B1 reaches the maximum value of 93.2 \({}^{\circ}\)C at 22 min after PGA paving. Temperatures at the middle of diaphragm are much lower than those closest to the deck plate. Temperatures monitored by TS-A2 and TS-B2 reach their maximum values at 78 and 68 min after PGA paving, respectively. Additionally, the highest temperatures thereat are about 54.6 and 59.6 \({}^{\circ}\)C. TS-A4 and TS-B4 are both measuring points of ambient temperature: according to the monitored data from TS-A4, the ambient temperature near the OSDs increases from 27 to 30 \({}^{\circ}\)C, which is negligible. The monitored data from TS-B4 are not included in Figure 5 since it failed before PGA paving.  
Figure 4: Arrangement of temperature sensors and displacement meters (unit: mm).  
TS-A5 (B5) to TS-A8 (B8) were arranged below the paving edge, and the monitored data are plotted in Figure 5b. The monitored data from TS-A6 and TS-A8 are not included due to the failure of the sensors. Generally, the monitored temperatures below the pavement edge, excluding the ambient temperature, are lower than the temperatures below the pavement centerline. This could be attributable to two reasons: first, due to the transverse heat transfer, the temperature decreases gradually upon approaching the pavement edge [9]. Second, heat transfer below the pavement edge is much more complicated since there is a sidewalk closest to the pavement edge (see Figure 3). Apart from the heat transferred to the air, more heat tends to be transferred to the steel supporting the sidewalk, since steel has the greater thermal conductivity. The temperature monitored by TS-A5 reaches a maximum value of 47.3 \({}^{\circ}\)C at 108 min after PGA paving, however, the monitored data from TS-B5 change little, which might be due to measurement error. Meanwhile, due to the complex vertical and transverse thermal transfer, and the effect of the sidewalk, the temperatures at the middle and bottom of the diaphragm are similar.  
Overall, the temperature of OSD exhibits spatiotemporal variations during high-temperature paving. The temperature at different positions on the OSD shows distinct hysteresis due to heat transfer. Uneven temperature distribution might lead to complex deformation of the OSD, which will be discussed in the following sections.