3. Earthquake countermeasure for poles on viaduct using stays and overhead wires

Portal structures, with a beam connecting two poles on either side of the railway track, are often used for seismic reinforcement of poles on viaduct.
Although portal structures have been shown to effectively reduce transverse vibration (perpendicular to track direction), the additional mass of the beam can extend the natural period in the track direction and lead to resonance with the viaduct itself.
In the worst-case scenario, the portal structure may collapse. In combination with the stays, we have established that rigid connectors, which are attached to poles to prevent lightning damage to overhead wires, help to reduce the natural period of the poles, in turn suppressing resonance with the viaduct (see Figure 1).

We used full-scale tests to demonstrate the validity of our analysis model (see Figure 2).
We also showed that the stays effectively reduce the natural period of the poles in the track direction, and that the rigid connectors allow for longer intervals between stays without affecting performance (see Figure 3).
The shorter natural period of the poles effectively reduces pole vibration associated with L2 earthquake motion (see Figure 4).

In combination with portal structures that mitigate transverse vibration (perpendicular to train direction), this approach proves to be both faster and cheaper than conventional reinforcement or other solutions such as pole replacement.