The Jeremiah Morrow Bridge I-71
- Sep 11, 2014
When the Ohio Department of Transportation decided to replace the existing Jeremiah Morrow Bridge with a new concrete structure, they specified the use of epoxy-coated reinforcement to help achieve the desired service life of 75 to 100 years. Epoxy-coated reinforcement is used in all the bridge components including the drilled shafts, mass concrete footings, piers, and superstructure.
The Jeremiah Morrow Bridge, named after an Ohio governor, is located northeast of Cincinnati, Ohio and carries I-71 over the Little Miami River. The existing bridge was built in the 1960s and consists of two parallel steel deck truss structures similar to the I-35 bridge in Minnesota that collapsed in 2007. The decision to replace the bridge was based on existing structural deficiencies, maintenance of traffic during repairs, and future capacity requirements.
The replacement bridge consists of twin, six-span, cast-in-place concrete, segmental box girders with a variable depth. The total bridge length is approximately 2200 ft with span lengths ranging from 229 to 440 ft. Each box girder will carry two 12-ft wide lanes of traffic initially but is wide enough for additional lanes when I-71 is widened in the future.
The cross section of each structure consists of single cell box girder with depths ranging from 12 ft at midspan and abutments to 25 ft at the piers. The top flange width is 55 ft and the thickness varies from about 9 in. at the centerline and end of the flanges to about 2 ft 4 in. over the webs. The typical web thickness is 18 in. The bottom flange varies in width from 25 ft 9 in. at midspan to 20 ft 0 in. at the pier table and in thickness from 9½ in. at midspan to 3 ft 8 in. at the pier table. Specified concrete compressive strengths for the superstructure were 6.0 ksi for design and 3.5 ksi for post-tensioning.
The Little Miami River is designated a State and National Scenic River for recreation. The bridge is approximately 240 ft above the river valley, which has steep sides and limited access. For these reasons, the balanced cantilever method of construction was selected for the bridge. To reduce the environmental impact, none of the piers are located in the waterway.
The cast-in-place concrete piers consist of hollow boxes for about 135 ft above the water level. Above that, the boxes split into two walls. This provides flexibility to accommodate thermal movements, elastic shortening, and creep and shrinkage of the concrete. Sliding bearings are only provided at the abutments and at a short pier.
The new bridge will be built in two phases. The new southbound structure will be built between the existing northbound and southbound structures. When complete, this structure will initially carry the northbound traffic while the existing northbound bridge is demolished and a new northbound bridge is constructed. The traffic will then be switched to its final configuration and the existing southbound bridge demolished. Throughout construction, two lanes of traffic are being maintained except for some night time lane closures. The estimated quantities for the project are 58,000 yd3 of concrete and 4987 tons of epoxy-coated reinforcement.
When completed in 2015, the new Jeremiah Morrow Bridge will provide the Ohio Department of Transportation with a new crossing over the Little Miami River. The new bridge will be more aesthetically pleasing than the existing bridge, will require less maintenance, will be safer, and will have a longer service life due to the use of epoxy-coated reinforcement.