This article describes the design and construction of the Old 99 (Riverside) Bridge, an 850-ft-long (260 m), 72-ft-wide (22 rn), five-span, post-tensioned, spliced-girder bridge spanning over the Skagit River in Washington State. In 2004, this bridge won a PCI Design Award. The bridge’s superstructure consists of recently developed Washington State Department of Transportation W95PTG “supergirder�? sections. These precast concrete girder sections were transported to a staging area close to the site, where they were spliced into single pieces that produced maximum spans of 180 ft (55 m). After delivery to the site, the post-tensioned girders were erected on top of the piers with no intermediate temporary supports. High-performance concrete (HPC), with design strengths of 7.5 ksi (52 MPa) and 10 ksi (69 MPa), was specified for the cast-in-place splices and precast supergirder segments, respectively. The use of HPC allowed a high initial post-tensioning force to be applied to the precast concrete girders. Special attention was paid to the lateral stability during erection and time-dependent camber of the assembled girders.
