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| Key Facts |
| Bridge Name | Facility Carried / Feature Intersected | Location | Structure Type | Construction Date and Builder/Engineer | |
|---|---|---|---|---|---|
| ! |
Black Bridge
| Railroad (Maine Central) and Bridge Street Over Androscoggin River | Brunswick and Topsham: Cumberland County, Maine | Metal 12 Panel Rivet-Connected Modified Warren (Subdivided) Through Truss, Fixed and Approach Spans: Metal Through Girder, Fixed | 1909 By Builder/Contractor: Pennsylvania Steel Company of Steelton, Pennsylvania |
| Technical Facts |
| Rehabilitation Date | Structure Length | Roadway Width | Main Spans | Approach Spans |
| 1957 | 318 Feet (96.9 Meters) | 12.5 Feet (3.8 Meters) | 2 | 2 |
This double deck bridge is one of the most unusual and unique bridges in Maine due to its suspended highway deck which runs under the truss of this bridge. The truss also has a deck in the "normal" place for railroad traffic. Structurally, the bridge is essentially a rivet-connected railroad through truss bridge with no unusual details aside from its use of a Warren truss that is subdivided in a manner similar to a Baltimore truss. However, there is one detail on the truss superstructure that is unique which is the bottom chord connections also have pins in them. These pins hold eyebars which in turn connect to pins at the floorbeams under the bridge which hold the unique suspended highway deck. The lightweight pin-connected nature of the suspended highway deck is a stark contrast to the riveted connections of the truss superstructure. Double-deck bridges are rare, but what is particularly noteworthy is this use of a pin-connected system for the suspended lower deck, as well as the fact that the lower deck is completely suspended below the truss. More commonly, a double-deck truss bridge either has both decks stacked within the truss superstructure, or it has one deck on top of the truss (like a deck truss) while the lower deck runs along the bottom chord level like a through truss.
This bridge was closed to the one-lane traffic it served in 2011 following a vehicle collision with some of the suspenders and subsequent discovery of deterioration in the floor beams and deck surface. MaineDOT apparantly has little interest in preserving this historic bridge since, without hiring any engineers with experience rehabilitating historic bridges to do a detailed study of alternatives, they put out a press release essentially condemning the suspended deck of the bridge to demolition. The exact quote from MaineDOT was "In order to reopen the bridge to vehicle traffic, the entire vehicle portion of the bridge would need to be replaced." This was following an in-depth inspection. In-depth inspections identify problems, but do not necessarily confirm solutions. For such a unique structure, consultation and study with a firm active in preservation of historic bridges is needed. The truth is likely that the suspended structure does not need to be replaced but could instead be repaired, which would retain the unique deck design, as well as the original, unaltered and historically significant materials such as the eyebar hangers.
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