Homestead Grays Bridge Rehabilitation and Widening

摘要

The widening and rehabilitation of the Homestead Grays Bridge required a number of unique design solutions and create several innovative construction techniques. The 3,102 foot-long, four lane deck bridge comprised of 17 spans and two intersecting Ramp, spans the Monongahela River, railroad tracks, two streets, and The Waterfront, a 260-acre mixed-use development located beneath the bridge. The structure is the first and one of the few bridges in the world constructed with Wichert Trusses. One of the major challenges was that all construction took place while maintaining two lanes of traffic on the main bridge. Some of the other issues were replacement of through girders, floorbeams and seismic vulnerable bearings while maintaining traffic which required innovative temporary support and jacking system, retrofitting of the existing foundation using lightweight flowable backfill, reinforcing of existing failing retaining without removing the exsiting wall and reuse of the existing 70-year-old concrete filled grid deck and pedestrian railing. This paper will present the unique design solutions and innovative construction techniques required to widen and rehabilitate this 3100 foot-long Wichert Truss bridge with two intersecting ramps. While maintaining two lanes of traffic at all time through girders, floorbeams, expansion dams and bearings were replaced. The reuse of the existing 70-year-old concrete filled grid deck and pedestrian railing will also be discussed.