Photo: Tom Lohman, Horner & Shifrin Inc. and Landon Streit, Jensen Construction

“Precast allowed the construction schedule to move along very quickly, and it maintained a lot of the same character.”

Nancy Daubenberger

 

Rehabilitated Bridges

Route 76 Bridge Over Lake Taneycomo

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Rehabilitating the Route 76 Bridge, one of the oldest open-spandrel-arch designs in the country, required a number of precast concrete elements to retain the original appearance and minimize disruptions to traffic along this heavily traveled route.

The 1087 ft (331 m) long bridge consists of five 195 ft (59 m) arch spans over the lake with concrete deck-girder approach spans. It carries about 20,000 vehicles daily and provides a vital connection between Branson, Mo., and Hollister, Mo. The existing deck and spandrel beams needed structural repair quickly, and a value-engineering study determined the best course.
The upgrade features precast concrete spandrel beams and partial-depth deck panels. The beams were placed on the existing spandrel columns and connected to existing spandrel-column steel using a grouted connection. Then specially designed partial-depth precast, prestressed concrete deck panels were placed to span the 10 ft (3 m) distance between the spandrel columns.
The panels also were used as stay-in-place formwork for the cast-in-place portion of the slab. The two 52 ft  (16 m) long approach spans were replaced with precast concrete I-girders and partial-depth deck panels.

“We liked the use of precast concrete in the partial-depth deck panels and for the spandrel beams to preserve this 1930s historic arch,” says Nancy Daubenberger, a member of the transportation awards jury. “Precast allowed the construction schedule to move along very quickly, and it maintained a lot of the same character.”

The spandrel beams had pockets cast into them to allow the existing column steel to be reused in the connection detail. The beams were set on epoxy, which acted both as a leveling pad and joint sealant around the exterior of the reinforced connections. This approach saved months in the construction schedule. Casting time was saved by using only three form types to cast 95 beams.
A special design was needed for the partial-depth deck panels because the design required that the main reinforcement run parallel to traffic on the spandrel arch spans, not transverse to traffic as is more typical. The standard panels’ shapes and materials were retained, allowing existing forms to be used.

In addition, the bridge was constructed with a flared entry on one end to add a storage lane for a new roundabout intersection. This involved creating variable-girder spacing and complicated geometry, but standard precast concrete I-girders were used along with the standard partial-depth precast concrete deck panels.

“Precast concrete provided the most cost-effective way to rehabilitate this 1930s arch bridge,” says Myint Lwin, a member of the transportation awards jury. “I definitely expect to see more of this application, as it has been proven very effective.”

Location: Route 76 over Lake Taneycomo, Branson, Mo., and Hollister, Mo.
Owner: Missouri Department of Transportation, Springfield, Mo.
Engineer: Horner & Shifrin Inc., St. Louis
Contractor: Jensen Construction Co., Des Moines, Iowa
Precaster: Coreslab Structures (Missouri) Inc., Marshall, Mo.
Bridge length: 1087 ft (331 m)
Project cost: $4.45 million