Frances Appleton Pedestrian Bridge

The Frances Appleton Pedestrian Bridge project achieves visual transparency and lightness through a carefully selected structural steel system as it connects Boston’s Beacon Hill neighborhood to the Charles River Esplanade.

Designers had to balance the slenderness of the bridge against creating a structure that would potentially have issues with pedestrian-induced vibrations. During the design process, multiple iterations of the structural system were evaluated to achieve the maximum comfort range for pedestrians while eliminating the need for future supplemental measures, such as installing tuned mass dampers. The final design includes the creative use of a lightweight concrete deck with foam-filled, stay-in-place forms and appropriate foundation details.

The 750-ft-long multiuse walkway, adjacent to the historic landmark Longfellow Bridge, consists of a contemporary tubular steel arch with a span of approximately 226 ft over a parkway. The steel superstructure, approximately 550 ft in length, is continuous, without any joints, and its shape in plan follows a curvilinear alignment in two directions. The arch and approach spans employ a distinct architectural theme of slender steel piers and struts for visual consistency and aesthetic appeal.

The new crossing replaced an existing bridge that was too narrow and had inadequate access stairs; conflicts between pedestrians and bicyclists were common. The placement and overall geometry of the new bridge were carefully selected to comply with the ADA maximum slope requirements and avoid impacting large trees in the parkland as much as possible—and its width of 14 ft doubles that of the original bridge. Several entry points and connections to the existing network of walkways along the Esplanade are integrated into the design of the new bridge.

The major challenge of this unique bridge was the fabrication of the steel structure and its overall constructability. Its design included complex curves and welded connections. The elegant steel superstructure consists of steel girders branching into two curved staircases and a scenic overlook plaza near the river. The bridge’s steel fit-up required careful planning during the final design phase, as construction over a busy arterial road necessitated a detailed erection plan and sequencing. Stresses were evaluated in all structural members during both fabrication and erection.

The main steel arch has a unique shape, being wider at the crown and narrower at the abutments, which helped minimize the size of the anchoring abutments at the park level. The arch also includes a series of inclined struts, creating a unique aesthetic truss effect. It is the longest bridge span over Storrow Drive, connecting the city to the riverfront. The crossing is also higher than any other existing bridge along the highway corridor, opening views and incorporating appropriate vertical clearances.

The arch was brought to the site in pieces and assembled during overnight hours to reduce traffic impacts, and it was welded in place in order to avoid using visible bolted connections. The bridge approaches include Y-shaped piers, which visually match the main architectural theme creating a visually unified structural system. Aesthetic lighting is also included to increase the sense of safety and appeal at night. The sinuous crossing is perfectly integrated into the landscape thanks to its transparency and lightness.

The new signature pedestrian bridge has quickly become a source of pride for the community due to its technical ingenuity, elegant detailing, and context-sensitive design, which perfectly integrates into Boston’s landscape and historic riverfront.

For more on the Frances Appleton Pedestrian Bridge, see “Take Me to the River” in the April 2019 issue of Modern Steel Construction.

Project Team

• Steel team:

  • Fabricator and detailer: Newport Industrial Fabrication, Newport, Maine *AISC MEMBER* *AISC CERTIFIED*

  • Castings: Cast ConneX Corporation, Toronto *AISC MEMBER*

  • Bender-roller: Kottler Metal Products, Willoughby, Ohio *AISC MEMBER*

  • Erector: Saugus Construction Corp., Georgetown, Mass. *AISC MEMBER* *AISC CERTIFIED*

• Engineer: STV, Boston

• Designer: Rosales + Partners, Boston

• General contractor: White/Skanska/Consigli, JV, Framingham, Mass. 

• Owner: Massachusetts Department of Conservation and Recreation, Boston