Pittsburgh Bridge Replacement Showcases Accelerated Construction Techniques

📅 5 days ago

The recent replacement of a 75-year-old bridge in Pittsburgh using innovative Slide-In Bridge Construction techniques highlights the benefits and challenges of accelerated construction methods in the U.S. and contrasts with adoption in Canada.

The demolition and subsequent replacement of the 846-foot-long, concrete arch bridge in Pittsburgh, Pennsylvania, is a significant development in the realm of infrastructure, particularly due to the rapid pace at which the new structure was installed. Utilizing the innovative Accelerated Bridge Construction (ABC) technique known as Slide-In Bridge Construction (SIBC), the project achieved completion in an impressive 17 days. This remarkable feat marks it as one of the heaviest slide-in structure projects ever executed in the United States.
The SIBC method is not a new concept; it has been progressively adopted to expedite highway expansions across the country. This technique involves constructing a new bridge superstructure on temporary supports adjacent to an existing bridge, which is then slid transversely into its final position after the old structure has been removed. By employing this method, road closure durations can be significantly reduced, often condensing the disruption into a mere 48 to 72 hours. In stark contrast, traditional cast-in-place construction methods can stretch on for over a year.
However, it is essential to note that SIBC is not universally applicable to all bridge projects. There are specific engineering, spatial, and design challenges that come into play. The process necessitates a considerable amount of stable land adjacent to the existing bridge to set up temporary supports and to build the new deck. As a result, SIBC may not be feasible in densely packed urban areas or on steep terrains.
In this particular project, the joint effort of Mammoet, a Dutch company specializing in engineered heavy lifting, and prime contractor Fay, S&B USA Construction was pivotal. Mammoet provided a sophisticated system of 42 skid “shoes” strategically located across four primary sites—two at the bridge piers and one at each of the abutments. The new 10,000-ton bridge was successfully shifted 102 feet in a single day, showcasing the efficiency of the SIBC technique.
While SIBC has been a game-changer in the U.S., its application has been limited in Ontario, Canada. The more conventional ABC replacement method utilized in the region is the BEBO Bridge Concrete Arch System, which has been around since the 1960s. The BEBO system consists of a combination of cast-in-place concrete footings and modular precast arch elements, suitable for spans ranging from 12 to over 100 feet. Nevertheless, the time required for completion with the BEBO system can vary significantly based on site complexity, as evidenced by the months-long construction timelines for the Highway 17 – Lauzon Creek Bridge and the Highway 630 – Amable du Fond River Bridge.
Most of Ontario’s provincial highway bridges were constructed during the post-war era from 1950 to 1980 using traditional methods. The Ontario Ministry of Transportation (MTO) has since begun to pivot toward a hybrid approach that incorporates precast and prefabricated modular elements. Their “Get In–Get Out” (GiGo) initiative promotes ABC frameworks that enable crews to build prefabricated bridges off-site and then move them into place during brief overnight closures.
Despite the numerous advantages that both the SIBC and BEBO techniques offer, including reduced traffic disruption, enhanced safety in work zones, and lower environmental impacts, these benefits are often overshadowed by cost considerations. The Transportation Association of Canada (TAC) points out that the construction costs for these advanced techniques can be approximately double those of traditional prefabricated bridges, making them justifiable primarily for bridges experiencing exceptionally high traffic volumes.
The adoption of ABC techniques in Ontario trails that of the United States, potentially due to institutional barriers. The procurement model in Ontario tends to favor a traditional design-bid-build approach, which can hinder the implementation of ABC methods. Additionally, the economic implications of time delays versus capital costs remain a contentious issue.
The disparity in ABC adoption could also be attributed to the significant federal support for these techniques in the U.S., which includes a variety of programs designed to incentivize states to adopt innovative construction methods. In Canada, highway construction is primarily managed at the provincial level, with municipalities overseeing most road kilometers. As a result, the federal government’s role is limited to fiscal transfers without imposing engineering or design standards.
As Ontario prepares for major highway projects, such as the Bradford Bypass and the twinning of the Garden City Skyway, industry experts like Mathew Raso of Powell Foundations advocate for the need to reevaluate current practices. Raso emphasizes that traditional methods may no longer suffice, urging for more collaborative and flexible approaches to expedite project timelines and enhance infrastructure development.

Related Posts