The Old Truss Bridge on Crescent Hill Road
When driving on a bridge, do you ever consider its stability and if you will make it safely to the other side? You shouldn’t. The engineers designed it so that these thoughts would not enter your mind.
The bridge on Crescent Hill Road in Miami County, KS was built in 1900 and was in need of replacement. The original thru-truss bridge was a fracture critical bridge, had a low three-ton load posting and was located at a 90 degree bend in the creek. Frequent inspections also revealed scour concerns under the footings. The County did not want anyone worrying about their safety. It needed to be replaced.
Previously, the GBA Stream Team helped the County perform repairs along the creek and it was important to the County that their investment not be wasted. They also wanted a new bridge that would require very little maintenance, provide easy access for rural farming equipment, and for a design from GBA that would generate competitive bids from the contractors.
GBA was hired to provide full engineering services from preliminary through final design including, surveying, hydrology and hydraulics (H&H), road and bridge design. Three different alignments were presented to the County. Also various options for bridge types were discussed, from a multi-span reinforced concrete haunched slab bridge to a single-span bridge. To preserve the work that had already been done in the creek, it was decided that the best option was a new roadway alignment with a haunched slab bridge. This type of bridge provides durable construction and minimal maintenance for the County.
“We looked at multiple options and the haunched slab is a common bridge type throughout Kansas which results in good competitive bids. Miami County got a very durable, low maintenance and cost-effective project” said Jon Karst, GBA Project Manager.
To preserve repairs the GBA Stream Team already did along the creek, the bridge was designed on an offset alignment that crosses the creek at a hydraulically-efficient location. Doing this also minimized the impacts on utilities. One thing the previous bridge was unable to accommodate was wide-load farm equipment. In order to meet this requirement, GBA used a short 27” corral rail that now allows for this equipment to easily pass.
The previous bridge had done its job for over a hundred years and the County is expecting this newly constructed bridge to do the same, if not longer. Farmers, every day commuters, and even a few animals now use the bridge on a daily basis with only their destination in mind.
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Archive: Client Spotlight