Galloping Gertie bridge is the same root cause as
those Chrysler radio antennas wiggling before they wrapped the stiffening wire coil around the vertical rod.

“Vortex Shedding”

Same root cause as those stop signs that waggle back and forth in hurricane winds,
and why a tall tree sways in the wind.

Those far end of airplane wing add-ons vanes are to control a vortex