Our 155th Mystery Bridge takes us to Vulcan, in Missouri and this unusual bridge. The bridge was built by Missouri Pacific Railroad in 1949 and spans not only Highway BB but also a small stream running alongside it. The bridge was built using concrete and features a rather unusual style that is similar to a rare truss design, the Vierendeel.
Arthur Vierendeel patented the design and it consists of trusses where only the vertical beam supports the upper and lower chords of the truss. Normally, truss bridges use triangular beams, consisting of a combination of vertical and diagonal beams needed to support the span. Because of the lack of diagonal members, Vierendeel trusses employ moment joints to resist substantial bending forces.. Vierendeel trusses are more common in Europe, with most of the trusses being located in Belgium. This includes the first truss built in 1902 at Avelgem, Belgium. Most of the spans can be found in and around the metropolitan areas of Brussels and Antwerp. While Vierendeels are seldom to be found in the United States, the city of Glendale, California has three Vierendeel truss bridges: the Geneva Street, Kenilworth Avenue, and Glenoaks Boulevard bridges, all two-lane bridges spanning 95 feet. They were built in 1937 as part of the Verdugo Flood Control Project, the first project of the United States Army Corps of Engineers after passage of the Flood Control Act of 1936.
While steel Vierendeels were common for bridge construction, it was not unusual to find them made of concrete, which takes us back to this bridge in Vulcan. One can see clearly that the spans are Vierendeel using heel supports to ensure that the bridge maintains its stability. Originally the bridge was built as part of the project to introduce fast moving trains between Missouri and Texas. The structure is still being used by Union Pacific Railroad to this day. The question is who was behind the design of this bridge and what were his/her motives for using the Vierendeel?
This is one for the historians and pontists to find out. 😉 Happy Bridgehunting, folks.