Ellison Avenue Bridge Replacement Project
Background:
The Ellison Avenue Bridge is located in the Village of Westbury over the Mainline of the Long Island Rail Road (LIRR) which had 2 tracks at the time of reconstruction. This project involved the complete replacement of an existing three-span steel bridge, which consisted of two (2) short approach spans (bridge abutments to support piers), and one longer main span (pier to pier) over the two tracks.
The bridge was originally built in 1896 as an overpass; rebuilt in 1941 as a two-lane roadway bridge with pedestrian walkways on both sides; and rehabilitated in 1982. The bridge was in a severe state of bad repair for over 2 decades and as such, necessitated a posted load weight restriction limit of 3 tons before construction. Over 75% of the existing bridge deck was covered with steel plates due to thru holes in the concrete deck and nets were set up below to catch debris from falling onto the tracks. The structure was regarded as one of the most deteriorated and dangerous bridges on Long Island.
Normally undergrade bridges, meaning the LIRR tracks are below the structure, are owned and maintained by the municipality where it is located, i.e. state, county or local municipality. Due to legislation in the early 2000’s, railroads where tasked with maintaining the portions of the bridge which are only accessible from the track level. This is in large part due to the extreme safety hazards of working on an active railroad, and the stringent safety requirements that the Federal Railroad Authority (FRA) enacted in the 1990’s regarding Railway Worker Safety. Due to the extremely poor condition of this structure, LIRR added it to their construction program and awarded the contract to the Design-Build team of Posillico Inc. of Farmingdale as the contractor and Greenman-Pedersen, Inc. (GPI) of Babylon as the engineer of record.
Project Objectives
There were two major improvements required for the new bridge. First the vertical clearance had to be raised by 2’ from the existing 17’-9” to 19’-6”, to allow for future freight accessibility. The other major improvement was to allow for the future construction of a third mainline track for the LIRR. This project then effectively became one of the firsts steps towards the LIRR Mainline Third Track Program.
Innovative Design Methods
In order to allow for the installation of the third track, the existing three span bridge was reconstructed as a single span bridge which eliminated the two piers adjacent to the existing tracks. This typically requires an increase in the bridge beam depth, which would reduce vertical clearance. In order to minimize the beam depth, prestressed concrete solid slab units, 63’ long, were used. These beams were designed to incorporate the vertical curve of the roadway resulting in a smoother riding surface. The prestressed concrete solid slab units were designed with the wearing surface being incorporated into the top of the units. Each unit was fabricated with a variable depth thickness, ranging from 20 to 24 ½ inches, specifically to accommodate the roadway profile and cross slope.
Another major constraint was minimizing track outages during construction. In order to do this, the Design-Build team incorporated use of ultra-high performance concrete (UHPC) to connect the precast units in the field. By using UHPC, the contractor was able to reduce onsite construction time by not having to post-tension the units together, thus minimizing the disruption to LIRR operations and the Village of Westbury. UHPC is a steel fiber-reinforced, portland cement-based product which exceeds the performance of conventional concrete, exceeding 20,000 psi when fully cured in only 24 hours. The properties of UHPC make it an ideal candidate for use in developing solutions to pressing concerns about deterioration, repair and replacement. Field cast UHPC connections are simpler to construct and perform better than conventional methods of connecting prefabricated elements.
Another challenge to the project was the raising of the approach roadways without impacting the private properties that where adjacent to the existing concrete crib walls. There were numerous planning and constructability review meetings between the Design-Build team regarding construction sequencing and equipment types to ensure that all the work could be performed from the roadway without overstressing or undermining the existing crib walls.
The raising of the approach roadway was achieved by installing helical piles inside the crib wall sections. These helical piles were designed to support the sidewalk, TL-2 impact vehicle loading and additional soil loads. The use of the helical piles allowed for the roadway profile to be raised and provide a zero net force on the existing crib walls.
At the beginning of the project, the LIRR scheduled two (2) weekend track outages for the construction of the bridge. The first was utilized for the demolition of the existing bridge. The second was utilized for the installation of the new prestressed concrete slab units, and placement of the UHPC joints as previously mentioned. These dates were established by the LIRR and the Design-Build team was committed to meeting them. Therefore, all of the design, fabrication and other construction activities were scheduled around these allotted weekend outages. Based on this aggressive schedule, it was necessary to accelerate the design of the prestressed concrete solid slab units and the review of the subsequent shop drawings so that the fabrication would be completed prior to the scheduled weekend track outage.
Summary:
Throughout the project, the contractor, designer, and construction management team worked together to flesh out potential problems that could be encountered during construction, which met all schedule milestones for the project. On April 15, 2016, hundreds of residents, local and state elected leaders and LIRR officials gathered to attend a ribbon-cutting ceremony at the bridge. The new bridge has improved site distance and smoother riding surface resulting in a safer bridge for vehicular traffic as well as rail operations beneath. This project was completed on time and within budget while meeting the following project goals:
- Replacing an aging and obsolete structure that was vital to the Village of Westbury and its residents.
- Providing a new bridge that was harmonious and consistent with the character of the surrounding Community and nearby structures.
- Replacing an important truck route in the Village of Westbury.
- Increasing the vertical clearance under the bridge to accommodate future use of freight cars on the LIRR main line.
- Providing additional horizontal clearance for LIRR future main line track capacity improvements.
Total Project Cost: $7,130,000 Completion Date: July 2016
Submitted by GPI staff: Kevin Padden, PE Principal Engineer (former LIRR)
Jason Stern, PE, Director of Structures
Mike Salatti, PE, Director of Engineering, RMLI member