Fatigue Tests of Galvanized Parallel-Wire Stay Cables

The Bandra Worli Sea Link Bridge consists of multiple 50-m approach spans and two 250-m-long cable stayed main spans. Approximately 208 stay cables are used for the bridge, with lengths varying from 80 to 275 m. Public access to the top of the bridge's tower via exterior elevators is expected to make the structure a unique tourist destination. Shanghai Pujiang Cable Company, Ltd., were required to subject their stay cables to fatigue and static ultimate tests, as specified by the Post-Tensioning Institute's (PTI) Recommendations for Stay Cable Design, Testing, and Installation," 1993.

SPCC contracted with CTLGroup to test three different stay cable specimens, with 85, 109, and 127 7-mm-diameter wires, respectively. Each bond-socket-anchorage, stay cable specimen was subjected to 2,000,000 cycles of fatigue loading between 33.43% and 45% of the guaranteed ultimate tensile strength (GUTS) of the specimens, providing a stress range of 193 MPa. This was followed by a static ultimate test to determine the ultimate tensile strength of the specimens. To detect changes in elastic properties of the cable, periodic static tests were performed after every 500,000 load cycles during the fatigue test.

PTI criteria allow fracture of no more than 2% of the total wires during a stay cable fatigue test. Accelerometers combined with an automated electronic data acquisition system monitored wire breaks, providing data on the date and the time of each trigger.

One of CTLGroup's two custom-designed stay cable testing fixtures was used for these tests. This stay cable test setup has a peak dynamic load capacity of 4.8 million lbs and a nominal static load capacity of 9.6 million lbs at 8000 psi oil pressure.