The impressive structure you see in these photographs is the Old OK 18 bridge across the Arkansas River. This bridge was built in 1927, and is an excellent example of a larger state-standard bridge of its time using all-riveted joints. Many big multiple-Parker spans like this one were built in the 1920's throughout Oklahoma, and sadly, not many survive. The photo below is of the Pawnee County end. The bridge is at an angle and runs NW to SE, the Pawnee end being the SE end.
As you will see from the following photos, the bridge consists of five 210-foot riveted Parker through spans and an 80-foot Pratt pony span. A long concrete trestle makes up the approach on the Osage Co. end of the bridge.
Above, the old bridge shimmers like gold in the evening sun.
Below, a view looking from the Osage end. The approach trestle is trimmed out with the standard concrete "fence" style guards, and are, very remarkably, undamaged in any way.
Below, a long view of the whole bridge from the Osage end. The curved portal knee-braces stand out in this view. These were a common feature in better built bridges up until 1930, and in Parker spans, gently add to the aesthetic value of the bridge.
Above, the first portal form the Osage end. The steelwork in the overhead systems are in very good condition, and are unmolested.
Below, the Pawnee end.
Above, typical meeting of two spans.
Below, a bridge this long can lead to tunnel vision, as in this view looking towards the Pawnee end.
Above, a side view of the trestle spans. These are really just a long series of short steel stringer spans erected over concrete pile bents. The concrete piles are pre-cast and then driven to the required depth.
Below, view of the upper laterals and sway bracing
Above, the portal sway bracing, composed entirely of angles and plate.
Below, portal back view. The upper laterals attach entirely to the flanges of the endposts and upper chords.
Above, midspan view. Notice how slender the vertical members are that are braced by the horizontal strut running through the middle of the X's. These are "H" shaped in section, and built up by riveting four angles to a plate.
Below, another telescopic view from the approach, from deck level.
Above, another similar view form the Pawnee end. This is an excellent bridge, and in an attractive location too. If only it had a paint job.....
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