|
Key Facts |
Bridge Name | Type | Road | Location | City | Crossing |
| 7 Mile Road Bridge | Truss | 7 Mile Road | Preble County, OH | Rural | 7 Mile Creek |
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Technical Facts |
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Construction Date |
Structure Length | Roadway Width | Builder |
| 1906 | 154.9 Feet | 15.75 Feet | Indiana Bridge Company of Muncie, IN |
Quietly tucked away in Ohio's Historic Bridge Inventory, as outlined on www.oldohiobridges.com,is this visually appealing and historically significant bridge that in my opinion has national significance for an unusual truss type. The inventory listed the truss type as a "Pegram Through Truss" This is a truss configuration that I am unfamiliar with, and so I am unsure of what the exact configuration is, other than what I see on this bridge. I observed a few characteristics on this bridge that likely describe this unusual truss configuration. First, the bridge has a polygonal top chord, producing that wonderful arch shape. Second, is the organization of the diagonals, which in general take on a Warren truss appearance. However some of the diagonals are larger than others. The larger members point to the upper center, much like a Howe configuration. Finally, all vertical members are very small. The diagonal members seem to be doing the most work on the bridge, rather than the verticals.
This is the only bridge I have encountered with this truss configuration. As such, even if I have missed a handful of bridges that might also use this configuration, I would consider this bridge nationally significant as an example of an unusual truss type. It is likely that this was an experimental truss type that didn't work out as well as expected and never found common use. The 1906 date that this bridge was constructed seems past the period where truss configuration experimentation was going on. I am unsure why this unusual configuration was used here.
Cambria stamps were found on the steel for the bridge. The bridge features pinned connections and is composed of six panels. The deck is wooden with an asphalt wearing surface. Original lattice railings remain on the bridge. The bridge is extensively v-laced. Some of the members are unusual box members that feature v-lacing on all four sides, reminding me of the Blue Rock Road Bridge. A very lazy and unimpressive paintjob was done on this bridge: only the floor beams and the bottom of the members near the bottom chord were painted with Preble county's signature sky blue paint. No one bothered to get the ladder out and paint the trusses! Preble County apparently is oblivious to the importance of this bridge, and this worries me. The thought that this bridge might face demolition in the future is unthinkable. Instead, a full restoration is in order for this bridge in my opinion.
