That's the answer to the problem of how to get funding for the Sellwood Bridge: propose making it a covered bridge, with an ecoroof.

How big an earthquake would it take to collapse the Sellwood Bridge?

The answer is inversely proportionate to the size of the lawsuits filed by the families of those who were on the bridge when it collapsed.

If a (Richter) 4.0 moves it one-tenth of a foot, (about an inch), then a 5.0 moves it 1 foot, a 6.0 moves it 10 feet, a 7.0 moves it 100 feet. Etc. Go figure.

[Achtung!: N.S.F.W. ] Shake that thing like we in the city of sin, and
no fakin i know you see me shakin
and the way i break it down i got the whole world quakin
Off the Richter,
off the Richter,
off the Richter,
off the Richter,
off the Richter,
off the Richter steady are you ready ...

"The answer is inversely proportionate to the size of the lawsuits"

I think that County Councilwoman Cruz was the one showing sense when she recommended closing it traffic. It's going to be a horrible tragedy to find out she was right.

Cruz has zero sense at all. Her cavalear suggestion to close the bridge to traffic was hard core stupid and irresponsible.

If she had any sense or responsibility she would be "leading" as an elected official and find the means to take care of this vital infrastructure prior to any new spending on Milwaukie light rail or any other lame project.

The documents for a the bridge state that the seismic vulnerability for the bridge is for any event greater than magnitude 0.2g would cause major damage.

The bridge is stated to lack the ability to withstand lateral seismic loads.

I've googled it, but I can't find a conversation that will tell me what a "0.2g" magnitude earthquake is on the more media-friendly Richter scale. Any help?

I think the Loma Prieta quake was about 7 on the scale, and the Northridge quake was between 6 and 7, if memory serves, and both quakes brought the bridges and highways down.

I found my answer! A 0.2g seismic event is comparable to a Mercalli Scale VII or VIII (which is listed as being from 0.1g to 0.3g). Since we're in the middle of that on the "g" scale, we're looking at between those numbers.

Converting from Mercalli Scale VII gives us Richter scale 6. Converting from Mercalli Scale VII gives us Richter scale 6.5. So, going from the middle of those numbers, the documents suggest that the Sellwood bridge would suffer major damage from a quake larger than about 6.25 (based on the conversions above).

Now, the interesting thing I know about earthquakes is that there are more than one kind of earthquake. You have up and down motion and side-to-side motion. The side-to-side stuff is MUCH more dangerous, because structures aren't accustomed to lateral loading while they are used to vertical loading (think gravity). (And, thank you Smash Lab on Discovery Channel) I'd be willing to wager that the 0.2g (6.25 Richter) rating for the bridge is for an up-and-down quake since the rest of the seismic section warns about the bridge's weakness to lateral stresses.

If you held a meeting on the Sellwood Bridge with all the stakeholders, the city, county, metro and other kabitzers, the bridge would collapse before the opening invocation criticizing George Bush was completed.

That bridge will collapse before it is replaced ( or least they will ban all traffic and then start to get serious).

Why rush, none of those government types have to commute over that bridge.