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 composed 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/nominationsNR... or as an HTML document http://22.214.171.124/search?q=cache:8SFM3rbVVN4J:www.kshs.or...
Although the above forms refer to the Asylum Bridge as being a single span, it could be considered to be composed 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.
I drove to the north side of this bridge on Friday, November 11th, 2016 for a field visit. There were two police cars on scene and officers were checking the area. I sheepishly turned around. Sorry, no new photos.
I have also suspected that the piers may pre-date the current superstructure.
As far as continuous vs simple, I really can't speculate. I can see about checking with KSHS though.
I'd agree to the continuous truss description.
It's not cantilevered because the center truss sits on piers, and the end trusses sit on piers and abutments.
The trusses look like they could act as three simple trusses, but they wouldn't need the upward angle to the towers if that was so.
The towers must be more than decorative, and the smaller members from the towers to the upper chords may act to somewhat reduce compressive load in the upper chord of the longer main span.
I guess I should clarify my feelings and what I was hoping for in discussion. My field visit convinced me that it is not a cantilever truss. I did not see any evidence that it functions as a cantilever. What I am looking for is thoughts on whether it is CONTINUOUS (or even an incomplete attempt by engineers to design a truss with continuous function)... continuous being something different than cantilever (the two terms are sometimes used interchangeably, but there are in fact important differences... Gustav Lindenthal's paper on the Sciotoville Bridge reveals these, and the controversy that surrounded each type during that period.
This evening, I reviewed Lindenthal's paper on the Sciotoville Bridge (first "modern" American continuous bridge). Lindenthal claimed his was the first continuous bridge in the American continent since the Lachine Bridge in Montreal. However, that statement might have overlooked "minor" bridges like the Asylum, and it most certainly overlooked hybrid, experimental bridges like the Schell Bridge which is well-documented in its design (cantilever that turns into pure continuous under live loads).
So to summarize, my personal uncertainty with the Asylum bridge is centered upon whether it might be a continuous truss, perhaps a "partial, prototypical, or otherwise experimental" attempt at a continuous truss with questionable success, or whether it is indeed purely decorative and totally designed to function as simple spans. Unlike the Broadway Bridge that Matt noted, which is basically two standard (albeit skewed) thru trusses that only required small adjustments to improve the aesthetic, the Asylum Bridge shows considerable design and fabrication effort to create a bridge with a "pointy tower" shape. This shape by the way was often criticized as displeasing among people of the time.
Another thought is that I think this bridge uses substructure from the previous bridge and sometimes unusual designs arise from such constraints... although again I am not sure how this constraint would result in an unusual bridge like this.
One final thought is that I have been unable to find any documentation of this bridge in engineering periodicals of the time. This suggests that whatever design this bridge is, that engineers of the period did not find it to be noteworthy. This may not mean it was common, but it may suggest it is something unimpressive to engineers of the period (ie decorative towers for simple truss spans, or a badly engineered attempt to create a continuous truss)
Understandable my friend... And who knows if they legitimately found the term in some documentation or simply coined it!
In truth, inverted is probably a better term than reverse. When I first worked on this listing, I simply followed the KSHS terminology.
Kinda what I have thought about this unusual span Robert.
I have never been convinced that it functions as a cantilever truss. I'm more inclined to think that the "Inversion" of the upper chord was more of an attempt to save materials and also help channel the live load and stress reversal into the substructure system. I read an old engineering report one time suggesting that load transferal across a bridge relied on the true abutments to actually "Ground" those forces into a larger base (the surrounding earth embankments if you will), and that the intermediate piers of a multi-span structure would only help to control or lessen it. Sounds somewhat plausible until we look at large multi-span structures built upon Caissons or Lally-columns, then it seems questionable.
Of course 110 years have passed since this beauty was constructed and without documentation it is hard to discern exactly just what the designer was going for... And for the record I still like the term "Inverted Parker"! :-)
So...let us assume for a minute that the towers are strictly cosmetic, or alternatively they exist strictly for the purpose of holding a light standard...
Now, let us assume that the the "Reverse Parker" span distributes the dead weight of loads towards the ends of the span. This weight could then be absorbed by the endposts and pylons. I believe that this is what Dr. Adams was implying by taking everything that we know about the Parker truss and flipping it around.
Given these two assumptions, would the diagonals that run from the top chord of the Reverse Parker to the top of the tower simply act as a way of stabilizing the tower? (ie, the light standard) This would require that the unloaded Reverse Parker distribute a small fraction of its own weight to the towers. Likewise, the diagonals that run from the top chord of the approach spans to the top of the tower would have to function in much the same way. The question then becomes, how would the diagonals function under load? Would the trusses just distribute the extra weight to the pylons, or would the added load push the tower onto the neighboring span?
Of course, this system would be a very expensive and convoluted way of fitting your bridge with light standards. Thus, perhaps the diagonals that run from the top of the towers simply act as stiffening members - ie. somewhat like a stiffening truss in a suspension bridge.
The placement of structural pins might be a clue. Are the diagonal members connected to the top chords and towers with pins, or are they just riveted onto the top chords and towers. Nathan has just added this bridge to his bridge browser, so you can see his photos here:
I am going through his photos to get a better look at these diagonal members.
So, did the Kansas City Bridge Co. come up with a convoluted way of holding up a light standard, or did they simply install a stiffening system to the bridge? This question of course is predicated on the three sections of the bridge not acting as a cantilever.
I'm starting to think that the towers do not contribute at all to the structural functionality of the bridge at all--they may be simply to make the bridge look like a suspension bridge (or a cantilever), and the spans themselves function as three independent, simply-supported spans (much like the Broadway Bridge in St Peter, MN: http://bridgehunter.com/mn/le-sueur/4930/). I think this for a couple of reasons:
1. The members connecting the towers to the rest of the top chords are significantly smaller than the other chords. They are obviously not designed to handle the forces of the much larger chords, and it stands to reason that if they were chords they would be subjected to similar forces. It's almost as if they were placed to soften the appearance of what would look like a very strange bridge if they were not there.
2. The diagonals connecting the small members to the lower chords are the same size as the upper chords, suggesting that they act as the end posts for each span. Picture the bridge without the small members and without the towers, and you have three through trusses, the middle being a Parker with the inverted curved upper chord, as Robert mentioned, and the end trusses being some combination of Parker/Warren/Frankenstein configuration.
This is all speculation and I could be completely out in left field, but it seems to somewhat make sense to me. Feel free to chime in, whether in agreement or rebuttal; I'm definitely curious about this bridge's history.
Well, gee...I was expecting that Nathan would be able to provide a definitive answer within 5 minutes of arriving on scene. Apparently this bridge has done the unthinkable - it has stumped the expert.
I all seriousness, I think we are probably going to have to go old school on this one and look at some company records. The Kansas City Library, KSHS Archives, County records, etc. are all possible places to start.
That being said, I have thoroughly enjoyed all of the engineering discussions on here...
I am attempting to renew discussion of this long-running argument/discussion on the design of the bridge following my field visit to this bridge earlier this year. Thus far, the debate has mostly been whether this was a cantilever truss or not... and agreement was largely reached that this is not a cantilever truss. However, the discussion seems to have assumed that if this is not a cantilever then this trusses spans function as simple trusses. However, does anyone think this might be a continuous truss without cantilever function? Here are larger/newer examples of continuous truss bridges that are shaped like cantilever trusses, but are NOT (post-construction) functioning as cantilever trusses, and instead only function as continuous trusses:
I like Nathan's suggestion. There are numerous historic trusses nationwide that could go into the future fish habitat category. It might become one of the largest categories on here, second only to new fish habitat.
This bridge would be an especially big loss given its unique design. I am amazed that we did not lose it in 2007 when much of the truss was submerged by flood waters.
How about this classification: soon-to-be crumpled up fish habitat... which will eventually be its fate unless someone recognizes the importance of preserving this historic bridge.
Other through truss works well, I think. Having such a category for oddball trusses is probably not a bad idea.
Parker trusses, Pennsylvania trusses, Whipple trusses, and perhaps a few others were all based on the Pratt truss, but none of them are actually Pratt trusses. I think that for this one, the term, "Reverse Parker" is good enough.
I can't log in, but we can remove Pratt truss from the categories. This is definitely not a Pratt.
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.