# Bridge Expansion Joint in Road Transition Curve: Effects Assessment on Heavy Vehicles
## 4 Test Results and Discussion
In this sense, several simulation analyses were performed using the linear quarter-truck model described in [32] to estimate the dynamic load increment for the heavy vehicles' characteristic speed range running on the examined road (i.e., 80-120 km/h). The results of the simulation analyses (Figure 19) show higher DLC values, increasing vehicle speed in analogy with literature studies [34; 37]. The DLC calculation was performed considering just a limited segment having a total length of 100 m: 50 m before and 50 m after the BEJ1. Comparing the DLC obtained for two different alignments (i.e., 1 and 3), the highest values were found for Alignment 3, whose unevenness (due to the BEJ presence) was greater than Alignment 1. Figure 18: Power spectral density (for each axle, average value of the four tests with the 20 g accelerometer). In fact, the rotation of the carriageway along the transition curve has its torsion axis (inner roadside) very close to Alignment 1. Figure 19 also reports the DLC mean value for both front and rear axles calculated considering all three alignments. A major dispersion (referred to the DLC mean value) was found for the rear axle, probably caused by the mechanical parameters considered. The results obtained from the DLC analysis, in analogy to what was found through in situ acceleration measurements, highlighted that the rear axle is the most critical one in terms of the dynamic load transmitted to the pavement and to the bridge structure. DLC values were also calculated for the first 100 m of the examined road branch, where no BEJs are present, to better underline the effects caused by BEJ1. Figure 20 shows that the DLC of the first 100 m-long road has values significantly lower than those calculated in the area surrounding BEJ1. Finally, the stress distribution on heavy vehicle mechanical components due to the transit on BEJ1 was investigated by means of a 3D model. The obtained results are depicted in Figure 21: since the  
Figure 19: Front and rear axles dynamic load coefficient (DLC) values at different speeds. Figure 20: Dynamic load coefficient (DLC) values at different speeds before the bridge expansion joint and across it (Alignment 3). maximum depth of the measured elevation is about 2.5 cm, the stress magnitude is not particularly burdensome for vehicle components. Figure 21: Heavy vehicle stress (MPa) at 90 km/h: (**a**) full vehicle, (**b**) magnification of medium and rear axles and (**c**) magnification of front axles. Thus, the location of a BEJ in a transition curve does not provide a significant increase in the mechanical components of road vehicles, while it meaningfully affects traffic safety (due to the loss of tire/pavement contact) and dynamic load increment (i.e., higher forces transmitted to the road pavement and bridge structure). For these reasons, the road agency planned:  
* the reconstruction of the joint to permit a more regular and continuous variation of the planimetric geometry of the road platform;
* measures for the reduction of the driving speed (i.e., speed cameras and speed enforcement) to ensure a better circulation. The adopted strategies ensure that under ordinary conditions, the circulation is regular, and the accident risk for road users is reduced; moreover, the reduced number and frequency of the required maintenance works increase the traffic safety.