THE CONCRETE BRIDGE MAGAZINE

WINTER 2018

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/922349

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ASPIRE Winter 2018 | 53 existing utilities. The new bridge was opened to traffic on September 1, 2017. This LPA project was the first use of FIBs in Mississippi. Having used this new feature on a small-scale project, MDOT is now planning to use these beams in multiple projects currently under design. MDOT will begin construction of Mississippi's first state-owned project using FIBs in the spring of 2018. Aesthetic Bridge Solutions With a robust concrete industry, MDOT is able to add aesthetic elements to bridges at a lower cost than would be possible with other construction materials. The U.S. Highway 61/84 Bridge over Liberty Road in Natchez, Miss., is a prime example of such a structure. Liberty Road provides access to the starting p o i n t o f t h e N a t c h e z Tr a c e Pa r k wa y a t milepost 0. The Natchez Trace Parkway is part of the U.S. National Park Service and extends 444 miles from Natchez to Nashville, Tenn. It follows the Old Natchez Trace, a historic trail used by Native Americans, settlers, traders, and soldiers. Also known as the Gateway to the Natchez Trace, the bridge over Liberty Road serves as the entrance to this national landmark. For this reason, its design needed to be signature in nature and invoke the feeling of entering the past. The bridge is a traditional two-span AASHTO Type IV girder bridge with a CIP deck, CIP abutments, and intermediate bents. Aesthetic precast concrete panels and castings were added to the bridge to provide an attractive landmark. The castings and panels were cast by Jackson Precast, Jackson, Miss., a member of PCI Gulf South and a facility specializing in aesthetic panels and castings. Preservation and Accelerated Projects Concrete elements, both precast and CIP concrete, have provided Mississippi with low- cost, sustaina ble bridges constr ucted and maintained to be durable and dependable over the long term. With the flexibility of the federal Moving Ahead for Progress in the 21st Century Act (MAP-21), MDOT spends, on average, $ 1 0 0 m i l l i o n o n b r i d g e r e p l a c e m e n t s , $3 million on preservation, and $20 million on rehabilitation annually. Prior to MAP-21, MDOT was only able to spend funds on replacements, leaving bridges to fall into disrepair. However, because of concrete's ability to withstand decay, MDOT's structures have fared well. MDOT is eliminating joints on CIP decks by the use of link slabs and repairing open joints with modular and preformed joints. In the past 15 years, MDOT has started to experience concrete deck deterioration in portions of north Mississippi bridges. Some of this deterioration has been linked to high chloride concentrations in concrete decks. In response to this problem and as part of the rehabilitation program, MDOT has developed a hydro-demolition and concrete-overlay process to repair these damaged bridge decks. Since 1987, Mississippi's transpor tation funding has remained flat, while construction and maintenance costs have risen by more than 300%. MDOT has recently shifted its primary focus to system preservation, but it is still unable to keep up with infrastructure needs at the current funding level. Accelerated bridge construction projects are becoming commonplace in MDOT's priority and project development. In the past, bridge replacement projects have required either new bridge construction to take place along a new alignment or for temporary detour roads and bridges to be constructed. The right-of-way and utility issues associated with these options make them both costly and time-consuming. Moving forward, MDOT will perform more in-place bridge replacements, which will require road closures. Precast concrete systems allow for fast construction, reduce right-of-way and utility costs, and significantly reduce closure times and the impact on the traveling public. In 2016, MDOT celebrated its centennial year by looking back at the great advancements and investments in the state's transportation network. Looking ahead, in the midst of funding challenges, MDOT will continue finding innovative solutions to sustain Mississippi's t r a n s p o r t a t i o n i n f r a s t r u c t u r e a n d f u t u r e economic growth throughout the state. __________ Justin Walker is the state bridge engineer, Scott Westerfield is the assistant state bridge engineer, and Michael Flood is the public information officer for the Mississippi Department of Transportation in Jackson, Miss. The U.S. Highway 61/84 Bridge over Liberty Road in Natchez, Miss., presents examples of precast concrete aesthetic panels and castings that the Mississippi Department of Transporation is able to add to bridges at a lower cost with a robust concrete industry in Mississippi.

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