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/439391
STATE SOUTH DAKOTA Focus on durability leads to more concrete bridges being constructed by Keven Goeden, South Dakota Department of Transportation In recent years, the state of South Dakota has focused its attention on designing bridges for longer life and addressing maintenance concerns earlier to alleviate replacement needs. These efforts, along with continued investigation of new concrete mixtures and different types of reinforcement, are aimed at increasing durability throughout the state network. The South Dakota Department of Transportation (SDDOT) owns approximately 1800 structures and local governments own approximately 4000 structures that are included in the National Bridge Inventory. The majority of the bridges in South Dakota consist of relatively short spans, with the average state-owned bridge being about 40 ft wide and 210 ft long. Of the state-owned bridges, concrete superstructures are the most common type, making up approximately 65% of the total. The oldest concrete bridge in the state-owned inventory dates to 1924, while the oldest precast, prestressed concrete-girder bridge was built in 1959. One of the oldest bridges is the scenic Beaver Creek Bridge on SD 87 in Wind Cave National Park, which consists of an open-spandrel concrete arch structure owned by the National Park Service. Built in 1929, it offers a 20-ft-wide roadway with curved approach spans and is a signature example of the durability and flexibility of building with concrete. Over the past 9 years, SDDOT has constructed on average about five new bridges per year on the state-owned highway system and about 10 on the local government-owned system. The bridges built on the state-owned system typically are either cast- in-place continuous concrete slab spans or cast- in-place concrete slabs on prefabricated girders. The supporting girder types are either precast, prestressed concrete I-shaped or steel I-shaped sections. SDDOT has a long and favorable history of performance with cast-in-place continuous concrete slab-span bridges. Jointless bridges that have cast-in-place concrete deck slabs on precast, prestressed concrete girders that are made continuous for live load and have integral abutments have also performed very well, albeit with a shorter history of experience. An example of a typical slab span is the Davis Bridge on U.S. 18 over the Vermillion River, built in 2013. It features four continuous spans, with two interior spans of 47.5 ft and two end spans of 38 ft. The roadway is 40 ft wide. Preservation a Top Priority SDDOT has been in a preservation mode with its highway system in recent years, which has reduced the number of new bridges it has constructed. Bridge preservation has long been a significant portion of SDDOT’s bridge project programming. Its goal has been to extend the lives of existing bridges by addressing maintenance needs early rather than have to replace the bridges later.