Rankin Bridge Rehabilitation

摘要

Using state-of-the-art design methods and employing "lessons learned" from other projects, the $48M rehabilitation of the Rankin Bridge was complicated and complex. A four-lane, twelve-span, 2400' deck truss spanning the Monongahela River in Allegheny County, PA, originally constructed in 1949, the structure offers a notable example of steel bridge technology from that era - riveted construction, deck trusses, and girder-type approach spans. The rehabilitation project began in late 2008 and was substantially completed in December 2010. It contained elements typically associated with repairing and upgrading a 60-year-old bridge; i.e., deck replacement and widening, expansion dam replacement, repair of deteriorated steel and concrete components, and repainting. It also presented design and construction challenges that included the following: 1. Truss Gusset Plates - inspection, load rating, retrofit. 2. Truss Strengthening (49 members) - use of several analytical methods (ASD vs. LFD); design; installation. 3. Dead Load Reduction - modified typical section (lane and sidewalk configurations); use of lightweight concrete. 4. Global Redundancy - addition of supplemental devices at tie-downs of anchor spans and pin/hanger ends of suspended truss span. 5. Truss Rocker Bearing Retrofit - addition of seismic backup devices. 6. Phased (half-width) replacement of a two-girder approach span using a temporary girder. 7. Widening of an abutment and wingwall with tangent caissons to accommodate the wider deck. 8. Stabilizing both abutments and one pier with the installation of passive tie-back anchors.