Steel cable tests: tension guaranteed!

© Matthias Heisler

Steel cables for bridge construction have to withstand enormous forces for many years. Before a bridge is built, the steel cables and their anchorages have to be tested extensively, according to precise test specifications. One of the world’s most powerful cable testing facilities was put into operation at the Vienna University of Technology.

Using a completely new testing technique, it measures within hours what used to take months. The cable is clamped in a device weighing several tonnes and made to vibrate at its own resonance frequency. In this way, it can be loaded up to 30 times per second. In this way, reliable data on the continuous vibration behaviour can be obtained in the course of just one day. The facility is now being operated by the Vienna University of Technology and TÜV Austria TVFA at the Science Center of the university.

Until now, the testing of large steel cables meant subjecting them to extreme forces in servo-hydraulic testing facilities over and over again - about once every one to two seconds, for one or two months. Now, at the Vienna University of Technology, with each individual load cycle, the cable is stretched five millimetres, then it becomes ten millimetres shorter before it returns to its original position. Following the continuous oscillation test, the cable is loaded with an almost unimaginable force of 42 meganewtons to determine the load-bearing capacity of the test specimen - the equivalent of the weight of around 50 railway locomotives or almost a thousand elephants.

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