May 01, 2014
The Hurricane Deck Bridge carries Missouri State Route 5 over the Lake of the Ozarks in Camden County, Missouri. Built in 1935, the existing 2,281' deck truss bridge was selected for replacement by the Missouri Department of Transportation (MoDOT) in 2010. In order to encourage contractor innovation to meet their project goals, MoDOT elected to employ an Alternate Technical Concept (ATC) procurement approach for the project. Under the rules of the ATC process, contractors were invited to develop alternate design approaches to the project with the intent of reducing their overall bid price. Bids were submitted on either MoDOT's baseline design or the contractors own concept. For those electing to pursue ATC's, a design/build style setting was employed for development. MoDOT's baseline design approach for the project was to construct a long-span steel delta frame structure on temporary foundations adjacent to the existing bridge, to utilize the bridge as a temporary alignment for traffic while the existing structure was demolished and foundations rehabilitated, followed by a slide-over of the delta frame bridge into the permanent alignment. AB elected to pursue a bold ATC involving a total redesign of the baseline concept. Under the AB ATC, a new permanent structure will be constructed on an alignment offset just 37'-7" to the east. AB carefully engineered the proximity of the old and new alignments to minimize environmental and real property impacts while maintaining the ability to construct the new structure and demolish the old. AB will construct a 2,260' long structure comprised of two plate girder units and two precast girder units, founded on a combination of driven piling, drilled shaft and spread footing foundations. The plate girder spans involve span lengths of 265' and use parallel flange plate girders with a 93" web depth. In order to reduce the longitudinal flexural demand of the piers in the deep lake, a unique structural approach was employed whereby the structure was divided into two structural units with an in-span hinge. Longitudinal loads are distributed back to the first land pier location on each side of the lake where it can be more efficiently resolved. The steel units are founded on 8.5' diameter drilled shafts with lengths of up to 120'. Cast-in-place concrete substructure was employed with column diameters of 8'. A standard cast-in-place concrete deck will be constructed using stay-in-place precast pre-stressed concrete panel forming. The plate girder spans are transitioned to the roadway through precast, pre-stressed girder approach units. The north end of the bridge employs two 90' spans of precast girders and the south employs a single span of 70' concrete girders. The precast structural units are supported on a combination of spread footings, driven-piling and drilled-shaft foundations. Upon completion of the new bridge, AB will undertake demolition of the existing 2,281' long deck truss bridge. AB's innovative ATC approach resulted in the low bid for the project, providing a savings over the base bid design. AB's ATC employed less than half of the fabricated structural steel quantity employed by MoDOT's base design. In addition, the ATC approach further supported the project goals by eliminating a seven day total closure of the road required for construction of the baseline MoDOT design. This project is under construction and is anticipated to be complete in May of 2014.