| On January 20, 1993, the Evergreen Point Floating Bridge incurred structural damage at two mooring cables and at various other locations during a storm event of approximately the 20-year return period magnitude. The two mooring cables damaged were the shorter and stiffer cables located at the ends of the bridge and were likely damaged due to load attraction issues. Following the 1993 storm, special replacement cables were installed near the areas where cable distress was noted to improve the performance of the floating bridge during storms.; Measurements of cable forces were made during the winter season of 2001–2002 to evaluate the effectiveness of the replacement mooring cables. From the experimental measurements, it was found that the special replacement mooring cables have slightly reduced the load attraction at the shorter end cables with respect to cable tension values reported for the pre-retrofit analysis. However, the measurements indicate that the replacement cables continue to attract loads between 65% and 80% higher than those measured at the longer and more flexible cables located near the midspan of the floating bridge during storm events of approximately the 1-year return period magnitude.; A technique was developed for the analysis of the mooring cables retrofitted with the elastomers and a parametric study was performed to investigate the possibility of further improving the performance of the floating bridge. The cable analysis showed that the retrofitted cables are more flexible than the former cables, up to pontoon displacements approximately equal to 12 in. to the north. Beyond this displacement, the analysis showed that the retrofitted cables are stiffer and higher tension loads are expected for the larger magnitude storm loading. The parametric study showed that a true uniform distribution of wind and wave loading to the mooring cables may not be possible. However, some further improvements to the performance of the bridge may be obtained by adjusting cable pretension values at various mooring cable pairs. |
