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What is a Warren Truss?

A. Leverkuhn
A. Leverkuhn

A Warren truss is a type of structure used in different kinds of construction for supporting a load. Trusses are items that architects and engineers use in both residential and public works design. The Warren truss is often part of the structure professional designers use in bridge construction.

Some experts define a Warren truss as a truss having a set of diagonals in a “W” design relative to a horizontal structure. Others include trusses with both diagonals and verticals in the definition of a Warren-style truss. The common version has a distinctive look, where a series of triangles hooks up to a long span. Bridges utilizing the Warren truss are blocky, rigid designs, rather than arched ones.

Man with hands on his hips
Man with hands on his hips

Many engineers working with these types of trusses will reference a top and bottom chord, which are the horizontal parts that the individual diagonals attach to. These steel diagonals are sometimes called web diagonals. Warren trusses also commonly include interior railing attached to the web diagonals to prevent pedestrians or others from falling from a bridge.

Warren trusses have a long history of providing the basis for continuous bridges in many parts of the world. This truss style was patented in 1848 by a James Warren, and quickly became a common type of construction. Historians show it as an element in British and European bridges, that later spread to become a common landmark in the American scenery. In America, the Warren truss was often the type of engineering workers used for constructing the traditional railway bridges that were part of the rail infrastructure that paved the way for easy cross-country travel and shipping in the nineteenth century.

Now that some of the older bridges across the country are in need of some structural examinations, public officials in many states are looking at bridge design to see if modern engineering can add safety to some of the traditional installations that are still in use across America. Engineers might look at whether an older Warren truss bridge includes verticals, or how to limit the stress from either live load or dead load on the bridge. Live load is defined as some load factor that will change with time, such as snow or ice. Dead load is a load that is constant. All of these factors contribute to stress, which engineers study to make sure that a bridge can withstand the demands that are placed on it.

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Discussion Comments


I am a passerby on this thread, but it happens that reading about the Warren truss made my day today. I have always wondered about the blocky, rigid design that defines such bridges, and to me, they are the classics.


@kylee07drg – They probably were. I know that some department stores use Warren trusses in their ceilings.

I believe they use steel trusses instead of wooden ones, though. They have a lot more weight to support than trusses in houses because of the larger surface area.

If you are in a big department store with a tall ceiling, look up and see the trusses. I've seen them in several different buildings, mostly the ones that are like giant warehouses.


Has anyone ever seen a wood truss like this in a ceiling? I've seen some fancy beams in houses with very tall ceilings before, but I can't remember if they were Warren trusses or not.


@Kristee – If I were building a bridge, I'd want a solid wall across the guard trusses. I wouldn't take any chances of falling through!

I think of this rickety old bridge in my hometown when I think of the Warren truss design. It is all rusted out, and the boards just don't look too sturdy anymore.

It's for pedestrians, cyclists, and horseback riders only, though. So, it doesn't have to support several tons. Still, I am scared to walk across it.


Bridges with this type of truss design look pretty sturdy to me. I also love the fact that the rails often have the same design as below.

The W shape makes me feel safer than just a couple of rails. It is really hard to fall through something that has both horizontal and diagonal bars across it.


Thanks. This actually helped me with my project!

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