2.2 Curved track
Periodic damage can occur in curved track, where it is superposed on the damage that would usually be seen in a curve. The most obvious result is periodically high gauge face wear and GCC on the high rail, and plastic flow on the low rail, which appears as a periodic vertical irregularity. This is illustrated by the measurements below.
Damage of this severity is rare and usually results from excitation of a lateral resonance of the vehicle. This dynamic behaviour is usually “triggered” by variations in lateral track geometry e.g. poorly finished welds or joints. Sometimes a feature as simple as a walkway across the track or a level crossing is a sufficient “trigger”.
GCC sometimes appears periodically in so-called “clusters” as a result of a similar mechanism. “Clusters” of GCC are a feature primarily of large radius curves, but occur also in straights. In tighter curves GCC is usually either continuous or absent.
The best way to avoid periodic damage of this type is to maintain good lateral geometry, thereby eliminating the “triggers” for dynamic excitation. Because vehicles respond differently to lateral irregularities, problems may exist on one railway with one set of rolling stock that does not exist on an almost identical railway with different rolling stock.