Cedar Canyon Bridge and Corduroy Creek Bridge
Ron Foluch

CEE321 Structural Analysis & Design Extra Credit Paper

 

The Bethlehem Steel Company fabricated the original Cedar Canyon Bridge and Corduroy Creek Bridge, two identical steel arch bridges, in 1937. Both bridges needed to be brought up to current design and geometric standards. The solution was to replace the Corduroy Creek Bridge with a new AASHTO I-girder bridge, then reuse the Corduroy arch to double the width of the Cedar Canyon Bridge located 5 miles south. The arch bridge at Corduroy Canyon was located on US 60 about 12 miles south of Show Low, Arizona (Photo 1).

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Photo 1

The original width of both arches was a narrow 24 feet. The concrete decks, floor beams and bridge rails were all substandard.

Arizona Department of Transportation (ADOT) oversaw the project and designed the new Cedar Canyon Bridge. Reusing the arch from Corduroy Creek allowed ADOT to preserve both of these old historical steel arch bridges. Making this task easier were the facts revealed in a 1989 inspection of both bridges. The arched ribs, arched cross bracing, columns, and column cross bracing all met current design standards. Both bridges were in excellent shape. Replacement of the pins was recommended, as a safety precaution.

The Corduroy Creek Bridge, spanning a U-shaped stream, had the same narrow 24-foot roadway width as the Cedar Canyon Bridge. The bridges differed only in the approach span configuration. The location of the Corduroy Creek Bridge made removal a relatively simple task because it was easily accessible from ground level. The original plan was to disassemble the arch into 5 pieces. Instead, the arch was tensioned in place with inch steel cables to hold its original shape and moved in its entirety. Calculating the horizontal component of the vector at the pin predetermined the amount of tension to place on the arch. The cables used were similar to ones used on the post-tension bridges commonly constructed in the Phoenix area (Photo 2).

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Photo 2

The general contractor, Sletten Construction, removed the deck, rails and vertical posts prior to loading the arch onto the transport vehicle, leaving only the main portion of the arch. Steel plates were welded onto the arch above the pin connections to lift the arch out of the creek (Photo 3).

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Photo 3

To do this, the anchor bolts were cut below the bearing shoes and the arch was lifted from the bearing pad. The bearing shoes for one side of the arch were then taken to the new structure site and bolted in place (Photo 4). The other shoes (see Photo 10) remained attached to the arch.

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Photo 4

The arch was then loaded onto a transport vehicle with a tractor at one end and a dolly at the other (Photo 5).

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Photo 5

This next photo shows the underside of the existing arch at Cedar Canyon. The transported arch was placed to the right of the existing structure (Photo 6).

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Photo 6

Placing the arch to the left would have made the task of matching the existing roadway alignment easier, however, the canyon was too wide and would not accommodate the bearing foundation. The canyon wall was scaled back in a stair-step fashion to prepare for the  arch foundation (Photo 7).

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Photo 7

This stair-step method helped lock the foundation into the canyon wall. There were some rock fractures discovered, so in addition to the reinforcing steel, anchors were epoxied into the canyon walls (Photo 8).

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Photo 8

In order for the contractor to lower the arch into the canyon, a temporary pad was constructed on each end of the canyon to accommodate the cranes. Once the arch was in place, this false work was removed (Photo 9).

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Photo 9

These next photos (Photo 10 and 11) show the arch being lowered into it new location. This was a slow process because the tensioned arch had to remain level as it was lowered.

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Photo 10

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Photo 11

One of the bearing foundations was poured around the bearing shoes once the arch was in place. The other end of the arch had the bearing shoes already bolted to the foundation, and the pin connection was just lowered onto its final resting-place (Photo 12). Also shown in this photo as part of the bearing pad foundation are the tower supports.

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Photo 12

Once the arch was secured, the arch columns were attached at a spacing of 17.3 feet. These columns supported the new bridge deck. The existing bridge deck is shown in the background (Photo 13).

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Photo 13

This next photo (Photo 14) was taken during bridge deck construction. It shows one of the vertical towers extending from the bearing tower to the approach slab. A deeper girder section was used for the approach due to the approximate 50-foot span.

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Photo 14

Both Cedar Canyon and Corduroy Bridges were listed in the National Register of Historic Bridges. These two-hinged, ribbed arch bridges each have a span of 180’ and rise of 31’ 6". The project was completed in 1994. It incorporated some of the features of the old structure to preserve the historic nature of the original bridges. Original steel barrier pattern was incorporated into the face of the new concrete barriers and the original tower fascia was reused. The project was a success. It was an innovative cost effective method of widening and preserving two of Arizona’s Historic Bridges.

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Photo 15

The photographs in this presentation have been provided by Tina Sisley, Senior Bridge Engineer, ADOT.