Above: Replacement Bridge.
|
Key Facts |
| Bridge Name | Facility Carried / Feature Intersected | Location | Structure Type | Construction Date / Builder or Contractor |
| Lincoln Road Bridge | Lincoln Road Over Pine River | Rural: Gratiot County, Michigan | Concrete 90 Foot Plan Curved Chord Through Girder, Stationary | 1922 By: Walter Willets |
|
Technical Facts |
| Structure Length | Roadway Width | Main Spans | Approach Spans |
| 90 Feet (27.7 Meters) | 20 Feet (6 Meters) | 1 | None |
This is perhaps the most severely spalling bridge to appear on this website. Perhaps a bad concrete mix in 1922, coupled with the use of salt on roads today, have combined to bring about the sad fate of this bridge. Oddly though, for all this spalling, the bridge's structure is apparently in fair condition, as no weight limit is posted. The spalling is unimaginable. The shape of the decorative pierced openings on the girders have deformed, nearly the entire top layer of cement on the outmost halves of the girder is gone. The ends of the bridge were patched at some time, and the spalling has continued beneath this patching, and the patch itself has been breaking up. The spalling, which turns solid concrete into a pile of stones and dust have become suitable for grass to begin growing on the girders! Perhaps the only good that has come of this is an opportunity to see inside a reinforced concrete bridge of the 1920s. The main reinforcing rods (apparently acting like the top chord) are quite large, and look somewhat like the decorative twisted steel that uninformed companies call "wrought iron". Smaller, yet similar rods run vertically in the girders, acting like vertical members. Finally, tiny wire-like reinforcing rods are visible in spots as well, for holding smaller portions of concrete together.
This bridge is noteworthy for not only its early 1922 construction date, but also for being a large 90 foot span that also features a notable skew. Most of the 90 foot plan structures are not skewed.
Among Gratiot County's three curved chord through girder bridges, this was the only one to appear on MDOT's website. This is apparently because of its older construction date. Indeed the bridge is significant as one of the first examples of its type to be built, and is one of the oldest remaining today. But it is worth noting that this structure type was only built for about a decade. Even the last girder to be built in Michigan was under ten years newer than this bridge. With perhaps only a few dozen of this structure type remaining, and that number decreasing, all of these bridges are significant, including the others in Gratiot County. Getting Gratiot County to preserve all three of their concrete girder bridges might prove difficult. Perhaps they might agree to preserve one of them however. If this was the case, logic would initially seem to suggest that the Lincoln Road Bridge should be that one, as it was determined to have the most historic significance. However, it may be pertinent, to suggest that the St. Charles Road Bridge might be the way to go. The difference of historic important between a handful or years, versus the structural quality of the actual structure suggest that the St. Charles Road Bridge is more important today. Restoring the St. Charles Road Bridge would be less costly, and because less concrete patching would be needed on its comparatively pristine surface, it would retain a greater degree of historic integrity. It is quite unfortunate, but visually, there is very little left of the Lincoln Road Bridge to preserve. The damage has already been done for the most part. On the other hand, if funding worked more effectively in Michigan, repairs would be less costly that demolition and replacement, and then it would be sensible to restore all three of Gratiot County's girder bridges!
MDOT's explanation for this bridge answers a question some people might have. Usually with a girder bridge, such as a plate girder, one expects to see the floor beams running under the deck between the girders. However, with most of these concrete girder bridges, those girders are cast integrally with the deck itself, rendering them invisible. Only the Griswold Road Bridge actually has these beams visible.
Information and Findings From MDOT
|
Constructed
in 1921-1922 from a MSHD standard design, the structure is comprised of
a pair of 90-foot, arched concrete through girders that rest on angled
concrete brackets cantilevered from the skewed concrete abutments. A
dozen concrete floor beams span between the two girders; these are cast
integrally with the 20-foot-wide concrete deck. The arched girders
feature typical MSHD detailing, with spandrel walls punctuated by five
small arched cutouts aligned over a series of arched recessed panels.
The lack of corbeled bulkheads at the girders’ ends illustrates the
bridge’s early construction. Although the Lincoln Road Bridge suffers
from severe concrete spalling and Armco guardrails have been installed
at the approaches, it retains a relatively high degree of structural
integrity.