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/485551
PROJECT RIEGO ROAD OVERCROSSING Lessons learned on challenging bridge project north of Sacramento by Sue Hida, California Department of Transportation Sometimes the California Department of Transportation (Caltrans) builds square bridge spans; spans that are as long as they are wide. Such was the case for the Riego Road Overcrossing over Highway 99 just north of Sacramento. New residential areas, high traffic volume to the airport and into the city, and a limited vertical clearance all had to be accommodated in the new bridge design. Design Fourteen lines of 5.5-ft-deep, spliced, wide-flange precast concrete girders were selected for the 156-ft 4-in.-wide, two-span, 295-ft-long overcrossing. The overall 6-ft 5-in.-deep superstructure is supported on seat-type abutments and an integral pier cap. The cap is supported on five 6-ft-diameter columns that are approximately 26 ft in height, fixed at the top, and pinned at the bottom. The columns and abutments rest on precast-concretepile- supported footings. The precast concrete wide-flange girder was developed for its stability during transportation and erection. The shape is so efficient that, had bulbtees been used on this project, the girders would have to have been 6 in. deeper. The top and bottom flanges are 4.1- and 3.8-ft-wide, respectively, and the web is 8 in. wide to accommodate 4-in.- diameter post-tensioning ducts. For the Riego Road Overcrossing, end-blocks for post-tensioning anchorage and 9 ksi concrete are used to satisfy shear requirements. Caltrans requires design for a 15-axle, 200-ton design permit vehicle. Splicing of the girders at the bent was required to keep the superstructure as shallow as possible. Splicing not only provides continuity of the spans, but also stiffens the integral bent cap joints with the column tops. Integral bent caps are used in most Caltrans’ bridges for clean lines and context sensitivity. The detail also ensures desired seismic performance by limiting displacement and forcing damage to occur in the column top, that is, plastic-hinging. Lesson-learned #1 Use AASHTO LRFD Bridge Design Specifications Table 3.5.1-1 expression for concrete unit weight when calculating dead loads; these girders exceed 150 pcf. PROFILE RIEGO ROAD OVERCROSSING / SACRAMENTO, CALIFORNIA BRIDGE DESIGN ENGINEER: California Department of Transportation, Sacramento, Calif. CONSTRUCTION INSPECTION ENGINEER: California Department of Transportation, Sacramento, Calif. GENERAL CONTRACTOR: Teichert Construction, Roseville, Calif. SUB-CONTRACTOR: MCM Construction, North Highlands, Calif. PRECASTER: Kie-Con, Antioch, Calif.—a PCI-certified producer.”