Design and Construction of Looking Back Creek Bridge

摘要

Manitoba Hydro is proposing to develop the Keeyask Generation Project, a 695-megawatt hydroelectric generating station in northern Manitoba, located approximately 725 km northeast of Winnipeg at Gull Rapids on the lower Nelson River. One of the key components of the Keeyask infrastructure project is the design and construction of approximately 25 km of two-lane access all-weather road from the junction of Provincial Route 280 to the proposed Keeyask Generating Station. The road will provide access to the site during construction and during the operational life of the generating station. The construction of the access road will require a clear span bridge crossing at Looking Back Creek. A clear span is preferred at this bridge site to minimize potential environmental impacts and to avoid damaging fish habitat. The bridge is a 30 m clear span structure with a clear roadway width of 13.5 m. The bridge deck is 150 mm thick concrete and acts compositely with the 1200 mm deep partially prestressed concrete box girders. The girders are supported at each end by two integral abutments founded on driven steel 'H' piles. This bridge is required to carry extremely heavy vehicular loads including a 136,365 kg capacity articulating low-bed tractor trailer that will be used to haul large transformers and equipment to the Keeyask Generating Station. The loading equates to about twice the Manitoba Infrastructure and Transportation Provincial Trunk Highway standard design truck weight. The bridge was also required to be designed to accommodate loads from a CAT 740 articulated truck used in hauling rock and aggregate. There are many challenges to the design and construction of this bridge at this remote northern Manitoba site including: design to accommodate heavy vehicular loads, shipping and erecting girders, permafrost protection, and protection of a sensitive environmental site. The construction of the bridge started in March 2012 and was completed and opened to traffic in January 2013.