Mike Goff

Washington has a few of these simple span "continuous" bridges. They are exactly what Nathan described. They are simple spans that appear continuous, but have a break in the truss at the piers.

The Vernita Bridge is of similar design. (SEE PHOTOS 10 & 11)

http://bridgehunter.com/wa/benton/7619A0000000/

WSDOT spokesman stated they are very confident the collapse is the result of an oversized vehicle hit. There are also reports of "No Fatalities". Hopefully this holds true.

This certainly is an interesting find Craig, Good Work!

Per the 2011 inspection report the deck does get soggy and sticky during Oregon's rainy season from September to July. So make a visit in August and hope all the modern day hermits are fully dressed.

Plus, it only makes since that the hermits must be licensed in Lane County (Eugene), Oregon since they make such an effort to make them comfortable.

On that note, I guess I'm off to Eugene to inspect the fine bridges of Lane County. There is nothing like dancing with cars on the Beltline Highway to liven up ones Tuesday.

James,

You give me a reason to look forward to April 1st each year. This one is classic, well played.

MG

The truss arrangement for the Coyote Creek Bridge is the same as the 1929 - Standard 60-foot Howe Truss from the Oregon Highway Department. However, the member designs are different and no cast iron connection blocks are used on the Coyote Creek structure.

The main difference between a Howe and a multiple king post from what I understand is that the tension members at the panel points in a multiple king post are timber, while the Howe has iron/steel members. This may be an over simplification, but that is the main point I have noticed.

I believe Will is by far the most knowledgeable on this subject since he actually spends a great deal of time rehabilitating and constructing the magnificent structures.

I have to agree with Mr./Ms. Anonymous. I believe the center pier was cast in place just like the fixed span columns.

How about a way to "vote" unworthy structures off the island. Similar to the 5 star rating, but a simple does it belong or not and if there is lets say a super majority of "not" they away it goes. At least this way it's a vote of bridge peers and not just a single opinion. However, it is James' site so he would ultimately have the final say.

Anonymous,

If you do not want the street view there is a way of turning it off. If you have an editors account just adjust the setting to reduce the street view to a link as oppose to the full picture.

Once you are logged in click the "my settings" link under your name on the homepage.

In "my settings" scroll down and check hide under the "Show the Street View widget if available?"

I hope this helps with one of your requests.

MG

The old Goff Bridge was a steel through truss while the new bridge is tied arch. It’s not exactly a model for the new bridge, but the new arch bridge is defiantly a nicer structure than a pre-stressed girder bridge.

I was able to find a photo on ITD's Flickr site of the old bridge during the construction of the new.

http://www.flickr.com/photos/itd_digitization/8117477248/in/set-72157631838875085

However, it is not a Chevy. It is simply a 54 year old interstate era Ugly Eyesore Steel Bridge (UESB). Nothing historically exciting about this one, just a simple freeway overpass like mentioned before. We have thousands just like it around the country.

I agree with both of you on this subject. The value of original is huge in a historical context and the value of the separate entries is important in the current inventory category.

Did I miss a discussion about whether this should be done or not? It seems this discussion point just sort of appeared out to the blue.

Nathan is absolutely correct.

That’s why when you look at the drawing from the "generic" swing bridge I posted yesterday you will notice the entire end of the truss is highlighted meaning all of those are tension members.

If you have studied engineering you will know that you can not have every member in tension like that at one time. The reason all of them are highlighted is due to the reversal of forces. When the bridge is closed and under traffic the bridge acts as a continuous truss supported at both ends and in the center. Under these conditions the bottom chord will take tension loading for a set distance. When the bridge is open it acts like a continuous truss that is cantilevered from the center without end support. Under these conditions the bottom chord will take no tension loading and only compression.

All of these movable bridges are pretty amazing machines. The ability to balance such a tremendous amount of weight and have it glide in and out of place is pretty remarkable, especially considering the technology in which these structures were designed and built with.

This is a very common truss arrangement for a center pivot swing bridge. The forces in the members are as described by Fmiser. Since it is continuous over the center pier one must remember the forces essentially act in reverse over the pier, with tension in the top chord and compression in the bottom chord.

I attached a photo of a “generic” swing bridge (without any particular name) showing the general forces. The solid black members are the ones that are generally in tension.

So as Fmiser stated the truss acts more like a Pratt than anything else, though I do not necessarily agree with calling it a Pratt. Swing bridges are sort of a unique beast since they not only carry static loads (traffic, self-weight ect.) but also dynamic loading when opened.

I'm really not sure what is going on here. This appears to be a case of the old farmer saying "I'll take that there bridge." It has sat there for over five years now; maybe the county is trying to find it a home.

I also think Siskiyou County is still trying to find a home for the Ash Creek Bridge if there is an interested party out there. http://www.bridgehunter.com/ca/siskiyou/2C0041/