Project Overview
The Metropolitan Transportation Authority needed a bridge that not only served pedestrians but also encouraged bicycle use, with the goal of reducing vehicular traffic. This project involved constructing a pedestrian bridge connected to an existing highway bridge. The site was tightly constrained by surrounding barriers, including a river, two highways, and an expressway.
To overcome these challenges, precast concrete elements were chosen for the bridge structure, significantly accelerating the project timeline and reducing environmental impact. The bridge's precast concrete components, including haunches, retaining wall panel, ramp panels, and deck panels, were fabricated by The Fort Miller Company.
A switchback ramp was designed to meet the grade changes, allowing for wheelchair and bicycle access. The restricted site footprint and complex geometry demanded a construction solution that minimized on-site labor and disruption while maximizing safety and durability.
Precast Solution
Precast concrete was the key to achieving both the architectural vision and the accelerated construction schedule for this pedestrian bridge. The benefits of using precast concrete solutions were multifaceted, encompassing safety, durability, aesthetic appeal, and long-term sustainability.
Precast haunches were attached to the sides of the existing cast-in-place highway bridge piers using ultra-high-performance concrete (UHPC) connections, eliminating the need for elaborate scaffolding and formwork 50 feet in the air.
UHPC was also used in the connection between precast elements to achieve superior durability and structural integrity. The use of color-matched UHPC, reinforced with stainless fibers, allowed the joints to blend seamlessly into the design, enhancing both the strength and aesthetic of the structure. The use of UHPC also eliminated the potential for water leakage, a common cause of maintenance issues in traditional structures, thus extending the service life of the bridge.
At the end of the pedestrian and bicycle bridge, a 180-degree U-turn switchback provided the final section of access to the grade. The ramp from the U-turn to ground level was constructed with precast architectural retaining wall panels, which were backfilled and topped with precast ramp panels, all connected with color-matching UHPC field cast connections for a seamless, durable finish.
The bridge's aesthetic design was carefully considered to blend into the surrounding environment. The precast deck panels, haunches, and retaining walls were manufactured to match the existing bridge's architecture, creating a cohesive visual profile. This level of attention to detail maintained the architectural integrity of the project while supporting the structure's longevity.
Precast concrete accelerated the construction process because many of the new bridge elements were fabricated off-site, reducing time spent on-site and minimizing disruption to the surrounding communities. The entire precast erection process was completed in just three months, saving an estimated three additional months compared to traditional cast-in-place methods.
The pedestrian bridge was designed to encourage non-vehicular traffic, directly contributing to the reduction of carbon emissions by decreasing car usage. The use of precast concrete, combined with UHPC, provided a resilient and low-maintenance solution, ensuring that the bridge will serve the community with minimal upkeep.
This pedestrian/cycle bridge exemplifies how innovative precast concrete solutions can provide long-lasting infrastructure with significant environmental, aesthetic, and practical benefits. The bridge not only enhances safety and accessibility for the community but also supports a more sustainable transportation system.
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