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The state Supreme Court has agreed to hear a lawsuit that seeks to ban Sound Transit's light-rail system from using space on Interstate 90. United States Supreme Court - Supreme Court - United States - Sound Transit - Law

Sometimes the comments are pretty interesting after an issue has been identified in an article on light rail- this time by the Seattle P-I (click here):

“Posted by unregistered user at 4/17/09 6:10 p.m.

This sounds like it will involve much more than installing rigid joints. The pontoons, and the anchors and cables holding them in place, would have to be greatly strengthened to prevent even slight motion of the rigid joints and the concrete to which they’re fastened. The amount of strengthening needed to withstand sixty years of storms without any measurable flexure is so far beyond what the bridge and its restraints were designed for that it isn’t just a matter of replacing joints. Even if the joints were made of the strongest material known to man, the pontoons are made of concrete, which has good compression strength but poorer tensile strength. The requirement for rigidity adds the necessity for the materials on both sides of the joint to have higher tensile strength as well, unless the anchors and cables themselves can hold the bridge absolutely still. But as designed they simply can’t do that in a winter storm.“

And again:

“Posted by unregistered user at 4/17/09 9:19 p.m.

Sound Transit did a study where they ran some trucks over the bridge to simulate a train of four 148,000 pound cars (in total a 296 ton train) at 30 mph. They did this in wind conditions of 3 mph and at a static lake level of 20.4 feet. As part of their effort they considered the effects of a 1-year storm, and found their report to be satisfactory after having considered that.

They did note at the end of the study that the lake level can drop as much as 3.8 feet and that this was not part of the study. They did say that under the conditions tested, the anchor cables each exert a 69 ton force.

They didn’t overtly mention that the current expansion joints expand and contract about 4 feet in normal use, but did cheerfully say that a future design effort would be required to come up with a solution to this unaddressed problem.

The Hood Canal Bridge was built 48 years ago and its eastern span sank in a storm. The original Lake Washington (now I-90) floating bridge was built in 1940 and it sank 50 years later in a storm while in poor condition and while being repaired. Don’t you think that this train retrofit should be designed with at least 100-year storms in mind and preferably somewhat more than that?

The report recommended not adding any extra total weight to the bridge. Instead, it proposed that portions of the bridge should be lightened to make up for the heavy additions needed to support the trains. The result could still withstand a 1-year storm, they concluded.

There’s more, but it’s all a recipe for a limited lifespan bridge and another eventual sinking.”