There have been some interesting discussions on this page concerning the design of the Asylum Bridge. The bridge generally appears to be of a Cantilevered design, but also features a Parker truss, with inverted top chords as the main span. This main span is comprised of eight panels. The two middle panels contain counters in addition to the diagonal members. The inverted top chords seem to be the only features that distinguish the main span (ignoring the "towers") of the Asylum Bridge from a standard Parker truss.
A standard Cantilever truss would generally feature alternating diagonal members, often of heavy or "built up" steel. These alternating diagonal members can be seen very well on the Murray Baker Bridge in Illinois. http://www.bridgehunter.com/il/peoria/illinois-74/ and on the much smaller Neosho River Bridge in Lyon County, Kansas http://www.bridgehunter.com/ks/lyon/560350/ Similar alternating diagonal members are not found on the Asylum Bridge, which was buit in 1905, well before the Cantilever truss became a popular design.
Thus, the Asylum Bridge is neither a Parker truss, nor a standard Cantilever span. The suspension of a separate truss within a Cantilever truss is unusual, but can also be seen on the Lansing Bridge in Iowa/Wisconsin, which contains a Pennsylvania truss that is supported by the main cantilever structure. http://www.bridgehunter.com/ia/allamakee/black-hawk/ Notice that the suspended span on the Lansing bridge is not connected directly to the substructure.
Unlike the Lansing Bridge, the main span of the Asylum Bridge (the "Reverse Parker" span) is supported directly by the same stone piers that support the "towers" which give the bridge a Cantilever appearance.
I have been able to locate some further information concerning this bridge. The Kansas State Historical Society completed a National Register nomination for for the Asylum Bridge. That form is now online and can be viewed either as a PDF
http://www.kshs.org/resource/national_register/nominationsNRDB/Miami_AsylumBridgeNR.pdf or as an HTML document http://184.108.40.206/search?q=cache:8SFM3rbVVN4J:www.kshs.org/resource/national_register/nominationsNRDB/Miami_AsylumBridgeNR.pdf+asylum+bridge&cd=15&hl=en&ct=clnk&gl=us
Although the above forms refer to the Asylum Bridge as being a single span, it could be considered to be comprised of three spans. These would include the main span and the two approach spans which rest on the aforementioned stone piers. All three of these spans appear to be suspended by the "towers".
Regardless of how one would classify the Asylum Bridge, it remains as one of the most unique truss bridges in the United States.
FYI - One of the names on the steel plaque over the bridge is "R. Hampson". Richard Hampson was a Miami County Commissioner at the time the bridge opened. He died 1909, at 71 yrs old. The Hampson family was, and still is, very prominent in Miami County, as well as the Kansas City area.
In answer to a question, the Asylum Bridge got its name from its location. It spans the Marais des Cygnes River in Osawatomie, KS, and it connects the city of Osawatomie to the Osawatomie State Mental Hospital, which was the first mental hospital west of the Mississippi. The bridge is maybe 200 yards from the grounds of the hospital. In those days, mental hospitals were often referred to as "insane asylums". The hospital is still in operation. The road and bridge has been abandoned for many years. Just to the north of the bridge, the grounds of the hospital were once a beautiful park, outlined with field-stone walls and iron gates. There are old photos showing elaborate flower gardens, fountains and picnic areas, which are all gone now. The hospital itself is at a higher grade above the river, with one of the main buildings still referred to as "The Hill". Only a couple of the original buildings still stand. Before the hospital was built, the "hill" was used as a lookout point for Civil War soldiers and John Brown's Underground Railroad... helping slaves escape from the south into Kansas. The entire area around the bridge and the hospital grounds are very prominent in Kansas history, and it's a shame that these areas haven't been restored and protected.
Here are two more peculiar bridges to mull over:
I do like this discussion!
The Milton-Madison Bridge is quite a peculiar design with its odd arrangement of simple spans and split cantilever/suspended spans. I've never seen one quite like it. Since I read Mr. Holth's post, I've been staring at those pictures and I'm going to have to post a comment on it now! http://bridgehunter.com/in/jefferson/madison/
And thank you, Mr. Baughn, for pointing out the Pruitt bridge. From the standpoint of its appearance versus its actual design, it may be the closest thing there exists to being a relative to the Asylum Bridge. It's a simple Pennsylvania truss (essentially a Parker with stiffening sub-members) that attaches to a descending outer span on each end in such a way that the main span almost appears to be anchored by them.
Despite the hazards to my mental health, I've continued staring at this bridge even more, and I've developed even more doubts that this could be a cantilever bridge: The lower chord of the main span looks awful thin, even for the time it was built, for it to be a cantilever span; and the diagonals in the outer spans appear to be built for tension rather than compression and would likely bend if those spans were anchor arms.
Here's another bridge that looks like a cantilever at first glance, but is actually a simple truss:
Inverted Parker sounds good. The bridge appears to function like one of the spans on the Milton Madison Bridge on the Ohio River, specifically the second main span from the south side. On this span, the endposts of what is essentially a simple truss span rest on the pier. In addition however, the top chord receives additional support from being connected to a tower and anchor arm span. This Asylum Bridge appears to function in this way, albeit with the unusual inverted top chord.
I have not had a chance to search the county records, if they even exist. I have posted a couple links below to the KSHS pages. There are some discussions on the internet concerning this bridge, but I have not had any luck locating original plans.
I myself have wondered if maybe this bridge would be better labeled as an "Inverted Parker" truss. When I think of the term "reverse" in relation to bridge trusses, my thought would be to turn the members around (not upside down). In the case of this bridge (or a Pratt truss in general), the verticals would remain constant while the diagonals would be flipped around 180 degrees. The result would be something similar to a multiple kingpost truss.
The first time I saw pictures of the Asylum Bridge, my initial thought was that it looked like some experiment based off of an inverted bowstring.
but it is definitely more complex than the latter. I would assume that the reduced height of the top chord in the center would stiffen (and thus strengthen) it. With stress reversal becoming a factor at mid-span, this might play into the reasoning behind an inverted top chord.
On the other side of the coin, when I look at the V shaped members off of each pier I immediately think of the fulcrum arms of a cantilever.
I would love to know if any records of this span still exist, then we could decide this once and for all! Not that I don't enjoy all the discussion.....
Reply to D.W. Adams:
Thank you for your discussion of this bridge. That was one of the most informative posts I have read on this website. I was particularly interested in the idea that the main span would remain standing if the outer spans were to be removed. This further convinces me that this bridge is not a cantilever at all.
I've been staring at these pictures long enough to make nearly anyone else crazy, and I believe I can tell you several things about the true nature of this bridge and some of the conjectures that have been made about it.
First of all, I do not believe that this is in any way a cantilever bridge although its profile appears to be modelled after one. Each arm of a cantilever span is supported only by the pier from which it extends, hence the name cantilever. A cantilever span can be cut completely in two in the middle (or have its suspended span removed, if there is one) and still stand on its own. It may drift slightly, but it won't collapse. This bridge doesn't appear to have this capacity.
In fact, this bridge appears to be right the opposite. I do believe, based on the arrangement of the truss members, that the center span would continue to stand if both of the outer two spans were removed, something which would make a cantilever span fail in the middle.
"Reverse Parker" seems likea fittlng name for the main span since with it's dipping top chord, it does right the opposite of everything Parker set out to do with his design. The Parker truss is an improvement of the Pratt truss that aims to remove dead weight from the ends of the span and concentrate strength toward the middle. The Asylum design appears to add dead weight to the ends and reduce strength at the middle, but otherwise has the same arrangement as a typical Pratt truss.
Finally, I've run the virtual modelling in my head, and it seems to me that the only way to build a strong and efficient cantilever truss bridge of the Pratt/Parker family is to take everything you know about the Pratt and flip it around, making it somewhat like a Howe truss, where the vericals are under tension and the diagonals, which would point up away from the piers, are under compression, but the top chord would be mostly in tension while the lower chord would be mostly under compression. I can't find a bridge like that.
You know, perhaps it was just someone who was trying to copy something they had seen and this was as close as they got. While we think of all the engineering marvels. Perhaps this time it was just luck that it worked as opposed to something else. trying to put a name on might be just like calling tripping on the red carpet "a grand entrance".
I am not certain when the technology for this style originated initially. This particular bridge was built in 1905 however. I agree, it is a very interesting, and rare style of bridge. Thankfully it has been listed on the National Register of Historic Places. I would like to see it restored however. Most of the bridge, including much of the truss was submerged in a major flood in 2007. Thankfully, it survived.
The Plaque looks like it says "1805", rather than 1905. Is that possible? Did they even have this technology in 1805?
I would vote this bridge the one of the most interesting bridges on this web site. Definitely in the top 5. I sure hope somebody jumps on this beautiful example and preserves it.
It's funny you mention this, because on more than one occasion my wife has threatened to have me committed. I have a unique ability to turn just about any trip into a bridge hunt.......drives her crazy! HUH
LOL J.R Manning. I guess with our hobby, any bridge could be the Asylum Bridge. The State of Kansas has a mental health facility near the north end of the bridge. When the bridge was open, it could be used to access the site.
I love this, if for no other reason than all the names for the bridge, the location and the waterway! Anyone know why it's called the Asylum Bridge? (Besides the fact that most of us bridge hunters are headed there?)
The center span of this bridge is actually a Parker Truss with the top chords inverted so they "dip" towards the center of the span, hence the term Reverse Parker. This is easier seen in a side view of the bridge. This bridge is believed to be the only Reverse Parker Truss in existence.
Looks like a small cantilever bridge to me, ie a continuous through truss. Stylistically similar to the Thamesville Bridge in Ontario. I am not familiar with the term "reverse parker" unless this was an early term to describe cantilever technology.
This is a Reverse Parker through truss. This may possibly be the only example of Reverse Parker in existance.