Experimental Response and Analysis of the Evergreen Point Floating Bridge

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 a 20-year return period magnitude. The two mooring cables damaged were the shorter and stiffer cables located at the ends of the bridge. Following the 1993 storm, larger mooring cables with Sealink elastomeric devices were installed at the areas where cable distress was noted to resist higher cable loads and to provide energy absorption and reduced cable stiffness. In this study, cable forces were measured 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 reduced the load attraction at the shorter end cables when compared to cable tension values reported for the pre-retrofit analysis. However, the measurements indicate that the replacement cables continue to attract loads between 64% and 79% higher than those measured at the longer and more flexible cables located near the midspan of the floating bridge during storm events of a 1-year return period magnitude.

Publication Date: 
Saturday, March 1, 2003
Publication Number: 
WA-RD 558.1
Last modified: 
10/12/2016 - 15:41
Authors: 
David I. McLean, Scott T. Peterson.
Originator: 
Washington State Transportation Center (TRAC)
Number of Pages: 
82
Subject: 
Elastomers, Energy absorption, Floating structures, Loss and damage, Measurement, Mooring cables, Performance, Pontoon bridges, Retrofitting, Stiffness, Storms.