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/622975
PROJECT The Lardo Bridge First slide-in bridge in Idaho maintains link to resort town by Brian Byrne, Lochner The Lardo Bridge replacement, in the resort town of McCall, Idaho, is Idaho Transportation Department’s (ITD’s) first implementation of slide-in-bridgeconstruction (SIBC) technology for a permanent superstructure. It also was administered as their first federal aid design-build contract. The new singlespan, 155-ft-long precast concrete girder bridge replaces an existing 80-year-old, five-span bridge carrying State Highway 55 (SH 55) over the North Fork of the Payette River at the outlet of Payette Lake. McCall is a beautiful resort town of about 3000 permanent residents surrounded by the Payette National Forest and is reachable from Boise in just over 2 hours. SH 55 runs north into the busy downtown area of McCall and then cuts westerly along Payette Lake. Much of the lodging, restaurants, tourist attractions, and scenery are located along SH 55 and the Lardo Bridge is the connection between these points of interest. Therefore, detouring throughtraffic during the peak tourist season was not acceptable for the replacement of the bridge. McCall’s tourist season extends from Memorial Day through Labor Day and picks up again from Thanksgiving through New Years for snowmobilers and skiers. With SH 55 as the main route along the lake, ITD wanted to minimize delays on SH 55. Therefore, ITD let this project as a design-build with A + B bidding to encourage the designbuild teams to minimize construction durations and minimize impacts to the peak tourist season. To maintain connectivity along SH 55 between lodging, restaurants, and recreation areas, both lanes on the existing bridge remained open during the summer while the new structure was built to the side. The superstructure and stub abutments were slid in the fall before tourists returned for winter outdoor activities. Superstructure and Belvedere The structure’s out-to-out width is generally 54 ft, which is 16 ft wider than the existing bridge. The clear opening between abutments met the 152-ft requirement for hydraulics, and resulted in a single-span length between centerline of bearings of 155 ft with no skew. The superstructure consists of six, 90-in.-deep, Utah bulb-tee (UBT-90), precast, prestressed concrete girders. The bridge has an asymmetric cross section with a wide cantilevered mid-span viewing platform, which was termed a belvedere, allowing PROFILE THE LARDO BRIDGE / MCCALL, IDAHO BRIDGE DESIGN ENGINEER: Lochner, Meridian, Idaho and East Hartford, Conn. PRIME CONTRACTOR: Ralph L. Wadsworth Construction, Draper, Utah PRECASTER: Forterra Structural Precast (formerly Hanson Structural Precast), Salt Lake City, Utah—a PCI-certified producer