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Spanning Ingenuity with Practicality

SR 4031 Bridge Replacement Project: Spanning Ingenuity with Practicality

ms consultants, inc.

January 19, 2018

The Pennsylvania Department of Transportation (PennDOT) District 9-0 and the engineers at ms consultants, inc., worked together to design and construct the SR 4031 bridge replacement in southwestern Pennsylvania. The bridge carries SR 4031 (West High Street) over the Ghost Town Trail (formerly R.J. Corman Railroad) in Cambria County. Prior to finalizing the technical scope, the most important considerations of the project would be safe and efficient maintenance of pedestrian and vehicular traffic, limited right-of-way and constructability in tight quarters.

Maintaining Normal Operations

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 examining these options, it was clear that maintaining two lanes of traffic, one in each direction, would allow access and mobility in this densely mixed commercial and residential corridor. A separate temporary bridge was installed to enable use by pedestrians on SR 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 as overhead protection for trail use during construction activities.

Designing for Complex Conditions

While the proposed typical section consisted of two 11-foot travel lanes, a 12-foot left turn lane, two-foot, eight-inch curb gutters and two five- foot sidewalks, the staged construction maintained only two 10-foot travel lanes. To minimize the width of each bridge stage even further, the proposed raised sidewalk was not constructed in the first stage. The sidewalk was constructed in the final stage, allowing vehicular traffic to use the future “sidewalk area” during early construction stages. Pedestrians were able to use the separate, temporary pedestrian bridge. This approach allowed the bridge to be built on alignment, and at a minimal width, to minimize impacts to existing right-of-way and reduce impacts to surrounding properties and businesses.

 

The combination of tight quarters and staged construction always poses a challenge. During the design process and internal constructability reviews, ms consultants, inc., recognized the need for temporary shoring. The company then 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. The pilaster—a rectangular column projecting from a wall—served as an important component for construction of the SR 4031 bridge replacement. Without the pilaster, the required temporary shoring would have nothing to bear on, but with this design, the shoring was able to rest against the newly constructed abutment. This simplified construction of the stage two abutment.

Safety Improvements

In addition to replacing a structurally deficient bridge, the project resulted in several improvements for the safety of vehicles, pedestrians and trail traffic. One improvement included a left turn lane for westbound SR 4031 vehicles turning onto SR 0160. This reduces the likelihood of rear-end collisions between through-moving vehicles with vehicles stopped in the travel lane waiting to turn left onto SR 0160. It also helps to prevent through-moving vehicles from driving around stopped vehicles and onto the shoulder.

 

The project also included the construction of sidewalks on both sides of SR 4031 to provide safe access for pedestrians throughout the project. The project was coordinated with Ebensburg Borough’s sidewalk improvement project to ensure community aesthetics and continuity. In addition, trail traffic was maintained under the bridge throughout the majority of construction—with the use of the temporary pedestrian tunnel. It provided safe passage of trail traffic for the majority of the construction duration, except during short-term bridge beam demolition and beam installation when the trail was closed for pedestrian safety. The pedestrian tunnel was also made large enough to accommodate emergency medical services traffic on the trail.

Project Completion

With its completion, the SR 4031 bridge replacement met the needs of PennDOT District 9-0, vehicular traffic and the local community.

 

The project was finished on schedule and under budget. Traffic was 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 avoidance of a detour.

 

Originally published by ASHE ScannerOriginal article can be found here.