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| Key Facts |
| Bridge Name | Facility Carried / Feature Intersected | Location | Structure Type | Construction Date and Builder/Engineer | |
|---|---|---|---|---|---|
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Henry Bridge
Iowa Bridge Number 348910 | Scenic River Road Over Upper Iowa River | Rural: Winneshiek County, Iowa | Metal 8 Panel Pin-Connected Pratt Through Truss, Fixed | 1911 By Builder/Contractor: Unknown |
| Technical Facts |
| Main Span Length | Structure Length | Roadway Width | Main Spans | NBI Number |
| 120 Feet (36.6 Meters) | 121 Feet (36.9 Meters) | 15.4 Feet (4.7 Meters) | 1 | 348910 |
This eight panel bridge is a traditionally composed example of a bridge type that was in its time the most common type of bridge built, but is today becoming rare at a rapid rate due to demolition. The 1911 bridge is noteworthy because it is what the mainstream of bridge design at the end of the pin-connected truss era. With no usual or distinctive details it provides a clear example of what an "average" bridge of this period would have looked like. In our efforts to single out rare and unusual historic bridges, it is important to also preserve some of these more "normal" historic bridges, in order to retain a clear physical record of bridge construction in that period of history.
This bridge retains fair historic integrity. The bridge has been altered by the addition of cables, however original bridge material does not appear to have been removed or harmed, with the exception of holes created to feed the cables through.
The bridge includes a detail that appears on a number of pin-connected truss bridges, but is still worthy of mention, which is a segmented hip vertical, with the top three quarters being an eye bar, and the bottom quarter being a built-up beam, and an intermediate pin connection to connect these two parts. Hip verticals are the black sheep in a Pratt truss, since they tend to be in tension rather than in compression like the rest of the vertical members, so often eye bars were used at the hip vertical instead of the built up beams usually used on the other vertical members. This however presented a problem for bridge builders, since with an eyebar hip vertical and the inherent slim profile of an eyebar, it was difficult to attach the railing at the hip vertical. On a traditional built-up beam vertical with back-to-back channels connected by lacing or lattice, the railing would simply be bolted or riveted on. However, this was not possible to do with an eyebar. Solutions for attaching railings to these troublesome hip verticals varied, but one solution was to run a built-up beam on the hip vertical up from the bottom chord just far enough to provide a railing attachment, and then run the eyebar for the rest of the distance to the top chord. The Henry bridge is an example of this solution.
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