INVESTIGATIONS ON LONG CABLE-STAYED BRIDGE ROPES
Filigree cable-stayed bridges are often used to cross large spans. The full locked ropes used are subject to a complex load spectrum of tension-tension-stress, vibration and aggressive environmental influences. In order to guarantee the important operational safety of these ropes, various special methods of non-destructive testing can be used.
ROTEC GmbH currently uses three default testing methods: Magnetic Rope Testing, visual rope inspection and high sensible vibration measurement to determine the preload force.
In order to save testing time and to combine the results, magnetic and visual testing are carried out simultaneously with a special combined device. The drive takes place via a self-propelled rope robot, the visual inspection via four clocked line scan colour cameras.
By using Fast Fourier Transformation (FFT) and suitable filters, the preload of the individual ropes can be determined from the measured natural frequency and conclusions can be drawn about possible damage in the anchorage area.
This allows the analysis of the condition of the ropes over a wide range.
Author(s): M. Wehr and S. Winter