What is a Marsh Rainbow Arch bridge? It is a very specific type of arch bridge. First, consider some of the more general bridge types in this realm. Rainbow arch bridges are a commonplace name for a type of bridge that is technically described as a concrete through arch, or they have alternatively been described as concrete bowstring arch bridges. Rainbow arch bridges have some sort of metal reinforcing within, the exact type of which may vary, from reinforcing rods (re-bar) to very complex and sturdy built-up beams and plate that are so sturdy even in their own right that they could be thought of as a steel arch bridge encased in concrete. Bridge builder James Marsh who owned the Marsh Engineering Company was one of the people responsible for designing a rainbow arch bridge with a complex design of built-up beams to act as reinforcing for the concrete, which he filed a patent for in 1912. His particular use of built-up beams as the reinforcing differed from other more common methods of reinforcing concrete such as modern reinforcing rods (rebar) or the patented Melan system that was common during Marsh's period. By creating this unique "Marsh" form of reinforcing, James Marsh was able to avoid having to pay to use the other patented forms of reinforcing available at the time. As a result, rainbow arch bridges built under the specifications of the James Marsh patent are termed "Marsh Rainbow Arch" bridges. Finally, it is worth noting that the term "marsh arch" is sometimes used more generically to describe any arch form where there is a steel arch encased in concrete, whether or not they directly follow the Marsh patent.
Rainbow arch bridges of any type built within the appropriate period (1900-1940) are rare and should be considered historically and technologically significant. Further, they tend to be among the more beautiful of historic bridge types, with their graceful arches that can be appreciated even when simply driving over the bridge, since the arches are always in the "through" rather than "deck" format. However, true Marsh Rainbow Arch bridges are even more rare and historically significant. Their additional significance is derived from their association with a creative, prolific, and noteworthy engineer and bridge builder, and also as physical examples of an unusual, patented bridge technology. The accurate identification of true Marsh Rainbow Arch bridges can be difficult if information is lacking. Recognition of style can aid in identification, but often documentation (plaque, plans, county minutes etc) or physical inspection of damaged and spalling concrete that may reveal the reinforcing below may be required for positive identification. Also, geographic location can be a guiding aid, since the majority of Marsh Rainbow Arch Bridges were built in Iowa and Kansas.
Located on a county line, Kossuth and Emmet Counties have a shared ownership of this rare Marsh Rainbow Arch Bridge which with a 100 foot span is among the longest spans of this bridge type remaining in Iowa today. As such, it enjoys a high level of significance.
Sadly, this bridge has been covered in offensive graffiti. While this does not affect the structural or historic integrity of the bridge, it is extremely detrimental to the aesthetic qualities of the bridge.
This bridge is in need of preservation. Most noteworthy, the condition of the railings on the bridge is unusually serious, since whole sections of railing have fallen away or broken off. Recommended preservation work would include constructing replica railing to replace the missing railing. It is also recommended that the bridge be coated with a graffiti-resistant paint due to the unusually large amount of graffiti on this bridge. Structurally, the overall bridge is in decent condition, but there do appear to be areas that could benefit from repair, such as a vertical member that has had the concrete fall away to reveal the edge of part of the reinforcing.. Currently deterioration on the bridge is in a condition that it can easily be fixed. As such, the time to preserve this historic bridge is now.
Historic American Engineering Record created a large and very informative historical overview and context for Iowa's bridges, and it is offered here by HistoricBridges.org in convenient PDF format for easy printing or offline viewing. The HAER source for the documents composing the PDF is here.View Marsh Rainbow Arch Bridges in Iowa (44mb PDF)
James C. Hippen has composed a concise yet detailed overview of Iowa's beautiful historic Marsh Rainbow arch bridges. It has been made available for free by Iowa Department of Transportation.View The First Marsh Arch Patent (PDF)
James Marsh first patented a concrete through arch patent in 1912, and later filed a second patent in 1921. This is the first patent, and is the patent which applies to the 580th Avenue Bridge.View The Second Marsh Arch Patent (PDF)
James Marsh first patented a concrete through arch patent in 1912, and later filed a second patent in 1921. This is the second patent. Since it was filed after the construction of the 580th Avenue Bridge, this patent does not apply to the history of the 580th Avenue Bridge, but it has been included here for general reference and research convenience.View Adapted HAER Drawings Showing Typical Marsh Arch Construction Details (PDF).
Historic American Engineering Record never prepared measured drawings for the 100th Street Bridge. However, they did create drawings for other March Arch bridges. HistoricBridges.org has taken one of these drawings and adapted it to make it generic and applicable to all true Marsh arch bridges. This document shows the typical design of a Marsh Arch bridge, including exterior as well as the interior reinforcing. The drawing includes labels. An alternative to the PDF version listed above is a large size PNG version.
Information and Findings From Iowa's Historic Bridge Inventory
Discussion of Bridge
Kossuth County, like virtually all of Iowa's counties, adopted the state highway commission's standard designs for its concrete bridges in the 1910s. Most of the county's structures during these years were small-scale slabs or girders, but in 1916 the board of supervisors deviated from this trend on one important span--this concrete arch over the East Fork of the Des Moines River, in the northwestern part of Kossuth County on the Kossuth/Emmet County line. For the Des Moines River Bridge, the county purchased a design from Des Moines Engineer James B. Marsh. Marsh had received a patent for his innovative medium-span arch in 1912. Comprised of two tapered concrete arches that carried the roadway deck between them from hangers, his invention soon became known as the rainbow arch for its distinctive profile. Marsh's design represented the hybridization of continuous concrete and segmental steel arch designs.
The Des Moines River Bridge features a 100-foot
span, divided evenly between nine panels. In February 1916 the county
contracted with the Marsh Engineering Company to build the single-span
arch for $7150.00, of which each county would pay half. Like virtually
all of Marsh's bridges, the Des Moines River Bridge used a standardized
construction sequence. The abutments and piers were poured first,
followed by the arch ribs, hangers and floor beams. Then the
intermediate ties, floor slab, wall copings and rails were concreted.
Once the formwork for the floor was removed, the intermediate hangers
were coated. Because the hangers had to be under full dead load when
they were concreted, the forms were struck no less than 10 days or more
than 21 days after the slab was poured. Pouring the guardrails later in
1916 completed the bridge. It has functioned in place since that time,
Bridge Considered Historic By Survey: Yes
This bridge is tagged with the following special condition(s): Marsh
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