AJX Bridge over South Fork and Powder River facts for kids
Quick facts for kids |
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AJX Bridge over South Fork and Powder River
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AJX Bridge
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 Location in Wyoming
Location in the United States
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| Nearest city | Kaycee, Wyoming |
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| Area | less than one acre |
| Built | 1931 |
| Built by | Omaha Steel Works |
| Architectural style | Pratt deck truss |
| MPS | Vehicular Truss and Arch Bridges in Wyoming TR |
| NRHP reference No. | 85000426 |
| Added to NRHP | February 22, 1985 |
The AJX Bridge is a special old bridge in southwestern Johnson County, Wyoming. It was built in 1931. This bridge crosses the South Fork of the Powder River near Kaycee, Wyoming.
The AJX Bridge was built so people could cross the river easily on U.S. Route 87. It is a type of bridge called a Pratt truss bridge. In 1985, it was added to the National Register of Historic Places. This means it is an important historical site that should be protected.
Contents
What is a Pratt Truss Bridge?
A Pratt truss bridge is a type of bridge design. It was created in 1844 by Thomas and Caleb Pratt. Imagine a bridge made of triangles. A Pratt truss has vertical bars and diagonal bars. The diagonal bars slant downwards towards the middle of the bridge.
In this design, some parts of the bridge are pulled tight (under tension). Other parts are pushed together (under compression). Pratt truss bridges were very popular for medium-sized bridges in the late 1800s and early 1900s.
Roadway on Top: Deck Truss
A truss bridge can carry the road in different places. The road can be on top, in the middle, or underneath the truss structure. When the road is on top of the truss, it's called a deck truss. The AJX Bridge is a deck truss bridge because its roadway sits right on top of the truss.
Unique Cantilever Design
The AJX Bridge is also a cantilever bridge. A cantilever is a structure that sticks out horizontally, supported only at one end. Think of a diving board! Steel truss cantilever bridges were a big step forward in engineering. They could span very long distances, over 1,500 feet (457 meters). The AJX Bridge is the only surviving cantilevered deck truss bridge in Wyoming. This makes it quite special!
Building the AJX Bridge
The AJX Bridge was built between 1931 and 1932. The company that built it was Omaha Steel Works from Omaha, Nebraska. They worked under a contract with the Wyoming Highway Department.
The steel part of the bridge is 306 feet (93 meters) long. It has three main sections, called spans. The bridge piers, which are the supports in the water, are made of solid concrete. The road on the bridge is 20 feet (6 meters) wide.
Where is the Bridge Now?
The AJX Bridge was first built on U.S. Route 87. Today, that road has been changed to a service road for Interstate 25. The bridge is located a few miles south of Interstate 25 exit 249. It is about 7 miles (11 kilometers) south of Kaycee, Wyoming.
The future of this historic bridge is decided by an agreement. This agreement is between the Federal Highway Administration and several Wyoming state agencies. The AJX Bridge is currently rated as "structurally deficient." This means it needs repairs and is being watched closely to make sure it stays safe.
Photo gallery
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HAER photo of AJX Bridge
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A close-up view of the AJX Bridge trusses
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The AJX Bridge marker on the southern pier
