Study of the influence of track and wagon defects on the safety of railway bridge structures

Train load variability has been a big concern of the railway administrators, since they affect directly the durability of bridge structures. With the objective of ensuring railway bridge durability and stablishing parameters to control the regularity of track geometry and wagons, a Brazilian railway concessionary has demanded a structural assessment of two non-ballasted bridges simultaneously with wagon axle monitoring. For this purpose, a train composed with sixteen GDU and GDT gondola wagons was used, and two wagons of this train were instrumented. Each group of four wagons of the train were used to simulate a different condition, listed as follows: variation of axle loads, wheel defects and springs with low elastic reserve. Furthermore, in one of the bridges, dynamic tests were accomplished with different track geometry irregularities, one of them with track quality TQI of 5.3 and other of 3. Dynamic and quasi-static tests were accomplished. Regarding the importance of each defect, springs with low elastic reserve were the main responsible for the increase of axle load, almost half of the equivalent impact, followed by wheel defects, variations of loads and lastly the track defects. Comparing measured impact factors with values specified by current standardization for railway bridges, it is verified that measured impact is higher than the NBR7189 and AREMA values. Therefore, the simultaneous existence of simulated defects must be avoided.