American Society of Highway Engineers (ASHE) Pittsburgh Section
The Pennsylvania Department of Transportation (PennDOT) District 9-0 and the engineers at ms consultants, inc. knew the state Route 4031 bridge replacement in southwestern Pennsylvania required outside-of-the-box thinking.
The bridge carries state Route 4031 (West High Street) over the Ghost Town Trail (formerly R.J. Corman Railroad) in Cambria County.
The most important considerations and constraints of the project would be: safe and efficient maintenance of pedestrian and vehicular traffic, limited right-of-way, and constructability in tight quarters.
With average daily traffic of more than 12,000 vehicles and numerous driveways and side roads in close proximity, determining the appropriate vehicular and pedestrian traffic control solution was key to the project’s success.
A traffic control alternatives analysis compared full detours, partial detours, half-width construction, and pedestrian access routes. After analyzing the alternatives, it was clear that maintaining two lanes of traffic, one in each direction, would maintain access and mobility in this densely-mixed commercial and residential corridor.
A separate temporary pedestrian bridge was installed to maintain pedestrian use on state Route 4031 during construction, while the recreational and emergency use of the Ghost Town Trail below was maintained at all times (except for removal and placement of beams overhead). In addition, a temporary ‘pedestrian tunnel’ was provided for overhead protection for trail use during construction activities.
The combination of tight quarters and staged construction can make any engineer nervous. During the design process and internal constructability reviews, ms recognized the need for temporary shoring. ms went one step further by determining that something beyond the typical solution would be needed for construction.
Because temporary shoring, which is up to 20 feet high, would need to be installed between the old and new abutments in a gap less than two feet wide, a pilaster was introduced on the back side of the stage one abutment. A pilaster is a rectangular column projecting from a wall, and served as an important piece to construction of the state Route 4031 bridge replacement.
The purpose of the pilaster is difficult to perceive when first reviewing the design plans, however, it soon became evident how important it was during construction.
Without the pilaster, the required temporary shoring would have nothing to bear on but as designed, the shoring was able to rest against the newly constructed abutment. This made construction of the stage two abutment much simpler.
In addition to replacing a structurally-deficient bridge, the project resulted in several improvements to safety of vehicles, pedestrians and trail traffic. Safety improvements for the state Route 4031 bridge replacement included:
The bridge replacement met the needs of PennDOT District 9-0, vehicular traffic, and the local community. The project was completed on schedule and under budget. Traffic was efficiently maintained through the work zone during construction, including recreational traffic along the Ghost Town Trail. Disruption to local businesses was minimized due to the staged construction and detour avoidance.
Every project has its own set of challenges. There were a number of factors addressed during both the design and construction of the state Route 4031 bridge replacement. The solution ensured the bridge was replaced with as little impact to the traveling public and local businesses as possible. With a little ingenuity, the state Route 4031 bridge replacement project was a success.