At the 253-metre-long network arch bridge across the Ohio River, the damping of the 64 hanger cables was verified by means of snap-back tests.
The 253-metre-long network arch bridge with suspended deck was built as a new connection between Brilliant, Ohio, and Wellsburg, West Virginia, across the Ohio River. To ensure the safety and functionality of the 64 hanger cables with free lengths of up to 48 metres, Structural Technologies LLC commissioned measurements of the cable damping. The hanger cables are equipped with friction dampers to reduce undesirable vibrations and to guarantee the required minimum damping of 4.0 % (logarithmic decrement).
For this purpose, snap-back tests were performed: the cables were specifically excited to oscillate in their 1st or 2nd eigenfrequency respectively, the decay process was precisely recorded by means of 3D acceleration sensors and subsequently evaluated using a specially developed curve-fitting algorithm.
Hanger cables carry the entire load of a bridge deck. Only by measuring their damping can we tell whether the cables are sufficiently protected against harmful vibrations.
