Two more important upgrades

I hope everybody is enjoying the holidays! During my Christmas vacation, I've been spending some quality time adding new features to the website.

Photo license tracking

To help prevent copyright violations and to keep the lawyers at bay, I've added a field to the database to keep track of the copyright license (if any) attached to each photo.

For photos that you've taken, you can decide what license to offer them under. This could be a standard "All rights reserved" position in which you grant permission for visitors to see your photos, but that's about it. You can also choose "Public domain" (renouncing your copyright and allowing anybody to use the photo in any way) or one of the "Creative Commons" licenses (which give various levels of permission for re-using the photo). If in doubt, just use the default "All rights reserved."

For photos that you've obtained from elsewhere, you must specify how they were obtained. If you have permission from the photographer/copyright holder, select "Have permission." If you found the photo on Flickr, Wikipedia, or another website with a Creative Commons license, then choose the applicable C.C. license version -- but be sure to follow their rules carefully, especially about providing attribution. For photos that are out of copyright or were produced by a Federal agency or program (such as HABS/HAER), then you can select "public domain." In some limited cases, you may be able to use a photo under "fair use", but first make sure you understand what that means before using this exception.

This isn't as bad as it sounds. When uploading or importing photos, you can choose the license for each photo from a drop-down menu. To make things easier, you can select the license (and credit line) for the first photo, and apply that to all of the other photos by clicking the little red arrows on the right. For photos that you've taken, it's safe to keep "All rights reserved" and not worry about this.

Expanded design types

I've always been puzzled why the various kinds of Pratt trusses (Parker, Camelback, Pennsylvania, Baltimore, Whipple, etc.) have their own distinctive names, but Warren trusses are just called Warren trusses regardless of variation. To better keep track of Warren truss bridges, especially the more exotic designs, I've expanded the list of available design types:

  • Warren through truss
    • Warren through truss with no verticals
    • Warren through truss with all verticals
    • Warren through truss with alternating verticals
    • Warren through truss with sub-panels
  • Polygonal Warren through truss
    • Polygonal Warren through truss with no verticals
    • Polygonal Warren through truss with all verticals
    • Polygonal Warren through truss with alternating verticals
    • Polygonal Warren through truss with sub-panels
  • Lattice through truss
    • Triple-intersection lattice through truss
    • Quadrangular lattice through truss
    • Quintangular lattice through truss
    • Town lattice through truss

(I've added similar subtypes for pony and deck trusses as appropriate.)

These should be fairly self-explanatory. The Warren with no verticals is the most elegant, featuring the "W" diagonals of a Warren without any vertical members in between:

The Warren with all verticals features a vertical member at all possible panel points:

A Warren with alternating verticals sounds complicated, but this just means that the truss has two diagonals in between vertical members. This is a common arrangement for pony trusses:

The Warren with sub-panels is a hybrid between a Warren truss and a Pennsylvania truss, where the panels have intermediate verticals and struts to help support the floorbeams. In the past I've called this a "Subdivided Warren", but that term is somewhat ambiguous.

I've also expanded the various Lattice truss types (which are, in essence, a bunch of Warren trusses superimposed on each other). The Quadrangular (also called Quadrilateral or Quadruple-intersection) is the most common lattice truss for metal bridges, enjoying brief popularity for railroad spans. The members intersect other members four times (photo by Steve Conro):

The elusive Triple-intersection lattice follows the same principle, but the members only intersect three times. These are mostly found in Kansas:

Pennsylvania includes one known Quintangular lattice in which the members intersect five times. This must be one of the more complicated truss ever built (photo from HAER):

I've also included the Town Lattice truss used for covered bridges. The number of intersections in a Town lattice truss can vary, but I've never seen any covered bridge guide try to make a distinction.

BONUS: To accommodate some other exotic bridge designs that have been spotted lately, I've created categories for these types:

  • Scissors deck truss (one known extant example in California)
  • Canticrete deck truss (a weird kind of arch-truss embedded in concrete, invented by John B. Leonard and seen in California)
  • Hammond through truss (a Pratt truss where the diagonal counters cross two panels, kind of like a Whipple truss, name coined by

Comments  (9)

Two more important upgrades
Posted January 5, 2012, by Nathan Holth (form3 [at] historicbridges [dot] org)

The Erie Canal lift bridges (like Middleport) do have end posts that extend below the bottom chord, where they function as a rack for a rack and pinion system. For this reason I guess an argument could be made to call them a bedstead truss. However, they do not fall into the mainstream of bedstead design, since the legs are a design to facilitate the lifting process. The typical "bedstead truss" we are all familiar with was a utilitarian design developed to reduce the cost of a bridge by reducing the size of the required abutment.

Two more important upgrades
Posted January 5, 2012, by Robert Elder (robertelder1 [at] gmail [dot] com)

I suspect that it is just a Warren without verticals.

Not all trusses with vertical endposts are bedsteads. In order for a truss to be classified as a bedstead, the enposts must extend doward through the floor where they also serve as supports.

Here is a genuine bedstead truss:

Here is a non-bedstead truss in which each of the five spans have vertical endposts that do not extend below the deck:

Two more important upgrades
Posted January 4, 2012, by Frank Hicks

Just a question from a neophyte: would the Middleport Bridge pictured above be better classified a Warren with no verticals or a bedstead Warren?

Two more important upgrades
Posted December 30, 2011, by Nathan Holth (form3 [at] historicbridges [dot] org)

Another thought/comment. The term "Warren with sub-panels" is accurate and descriptive, however I would argue that subdivided Warren is equally accurate and I do not see where that term is ambiguous... the definition of a subdivided truss is one that has had additional panels created by the addition of members to a basic truss.

Two more important upgrades
Posted December 28, 2011, by Robert Elder (robertelder1 [at] gmail [dot] com)

I know of a couple more Quadruple-intersectionals over the Bad River near Pierre, S.Dak. I don't think they are on here, so I need to remember to post them soon.

Two more important upgrades
Posted December 28, 2011, by Robert Elder (robertelder1 [at] gmail [dot] com)

I also like the expanded categories. For reference, the old category of Double-Intersectional Warren through truss is available.

Of course this raises the philosophical question, when does a Warren truss become a Lattice truss?

I am in agreement with Nathan on his terminology below.

Two more important upgrades
Posted December 28, 2011, by Robert Elder (robertelder1 [at] gmail [dot] com)

I am very glad to see this update. Several months ago, I actually found one of my photographs from this site on another site without attribution. I left them a comment and reported it to google, and the site has since disappeared from Google search results.

Of course, if they had just asked permission and agreed to give credit I would have been happy to let them use it...

Two more important upgrades
Posted December 27, 2011, by Nathan Holth

I know we all (myself included) have used the term "quadrangular" truss. However after reviewing some good literature: as well as some historical literature, I now am thinking it is better to use the naming scheme of intersections rather than angles... ie Quadruple Intersection Warren Truss, following from Triple Intersection, Double Intersection, etc. Quadruple Warren for short. Quadruple maintains consistency and is clearer in what it refers to (intersection of panels).

Feel free to discuss, disagree, etc.

Two more important upgrades
Posted December 27, 2011, by Nathan Holth (form3 [at] historicbridges [dot] org)

Smart move on the copyright feature, something essential to the operation of any large photo-based website in my opinion.