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Weave Bridge Philadelphia

The Weave Bridge at the University of Pennsylvania creates a pedestrian passage over the Amtrak train tracks that currently separate the main campus from athletic fields along the Schuylkill River. The Weave Bridge is a 145 ft (44 m) bridge at The University of Pennsylvania, USA which was conceptualized by Cecil Balmond and engineered by Ammann & Whitney. It was commissioned by the University of Pennsylvania in 2007, and opened in June 2009.

Weave-Bridge-Philadelphia-By-Cecil-Balmond-02-Alex-Fradkin-759x597 Weave Bridge Philadelphia / Cecil Balmond

© Alex Fradkin

The bridge was designed by the Arup engineer Cecil Balmond. TEUFFEL ENGINEERING CONSULTANTS worked on the design as a partner of the Advanced Geometry Unit (AGU) at the Arup offices in London. Two contrary spirals form a structure with extraordinary spatial qualities. The 44 m long footbridge for pedestrians and cyclists consists of a geometrical-structural fabric made of six different straps which unfold in the surrounding landscape.

The Weave Bridge will connect Penn Park with the existing Recreation and Athletic Facilities south of Hollenback Center. The bridge will allow pedestrians to cross the Amtrak rail lines to reach the Hollenback Center and the fields to the south, both during the reconstruction phase of the South Street Bridge and beyond.

Weave-Bridge-Philadelphia-By-Cecil-Balmond-32-University-of-Pennsylvania-759x482 Weave Bridge Philadelphia / Cecil Balmond

© University of Pennsylvania

The bridge creates a pedestrian passage over the Amtrak train tracks that currently separate the main campus from athletic fields along the Schuylkill River. The design features a “braided rope” structure consisting of six steel strands. It marks the first milestone in the University’s plan to transform a former postal depot into a 24-acre (97,000 m2) complex, called Penn Park. The design uses a “never before used bridge structure” It is in keeping with Balmond’s purusal of a “non-linear world, and his principle that “structure as conceptual rigour is architecture.” His dynamic and organizational approach to structure is informed by the sciences of complexity, non-linear organization and emergence.

The design obviates the use of conventional longitudinal supporting beams. According to Esquire magazine:”The span is a poetic solution to a pedestrian problem.” Balmond founded and runs the University of Pennsylvania’s Non-Linear Systems Organization, a research group he set up to explore ways in which architecture can demonstrate, test and apply insights from mathematics and sciences. He currently holds the Paul Philippe Cret chair as Professor of Architecture at PennDesign. Cecil Balmond realized the design through Arup’s AGU, an experimental research and design unit he founded in 2000. Balmond joined Arup in 1968 and is Deputy Chairman.

Weave-Bridge-Philadelphia-By-Cecil-Balmond-07-Cecil-Balmond-836x1200 Weave Bridge Philadelphia / Cecil Balmond

© Cecil Balmond

Design features:

  • The project is key to the university’s vision for urban design which revolves around enlivening a strong network of pedestrian pathways, in particular those located near the Eastern half of the campus, which is currently being extended.
  • In elevation this 42m coil looks like a conventional bridge – a warren truss with diagonally crossed bracing lines. However, its true geometry is comprised of two interweaving steel spirals.
  • Weave-Bridge-Philadelphia-By-Cecil-Balmond-21-flickr-roofdoorwall-896x1200 Weave Bridge Philadelphia / Cecil Balmond

    © flickr-roofdoorwall

    The design has no need for longitudinal beams, as conventionally used. The winding narrows at mid-span over the tracks to intensify and reinforce the structural action. It then flares out at the supports. Psychologically, it’s been suggested that the feeling of enclosure at this point is also reassuring for the pedestrian.

  • The unusual design is the result of a larger narrative, created by Arup AGU, which develops a combined approach to landscape and tectonic form in one unfolding master plan. The bridge is the first phase of the plan completed which was designed to provide immediate access to the sporting grounds.
  • The 45-ton Weave Bridge is narrowest at the center of the span, flaring gradually toward the openings to increase visibility. Its sleek lightness of figure makes the adjacent rail bridges look cartoonishly massive–and makes the trek to the ballfields a lot more exciting.
Weave-Bridge-Philadelphia-By-Cecil-Balmond-19-flickr-Christophr-Hiestr-759x505 Weave Bridge Philadelphia / Cecil Balmond

© flickr-Christophr Hiestr

“The project is not about engineering a new type of bridge structure per se. It is about treating the bridge as architectural space: a space of passage in a master plan that is not unlike a major corridor or link in a large building complex,” explains Cecil Balmond, founder of Arup’s Advanced Geometry Unit (AGU).

Weave-Bridge-Philadelphia-By-Cecil-Balmond-28-Alex-Fradkin-759x380 Weave Bridge Philadelphia / Cecil Balmond

© Alex Fradkin

Penn Connects:

Penn Connects is a land use and urban design campus plan that will advance Penn as a premier urban research university. The buildings highlighted in red below are proposed renovations or new construction projects.  The Plan recommends:

  • Creating civic and open space
  • Identifying land use and development zones
  • Improving physical connections for pedestrians, automobiles, and bicycles

Cecil Balmond

The Weave Bridge is part of PennConnects – A strategy for The University of Pennsylvania’s campus to better link itself to the city of Philadelphia.

As a result, Balmond’s design solution for The Weave Bridge proposed a combined approach to the landscape and tectonic form in one unfolding strategy. Four lines start at the end of the sports fields farthest from the railway and wind their way, gathering energy as they approach the railway lines. They turn in a tight spiral, and in a burst of energy, spin across the railway, before unfolding rapidly down into the urban space on the opposite side of the tracks. The double helix woven by the strands also creates the load-bearing structure of the bridge.

Weave-Bridge-Philadelphia-By-Cecil-Balmond-29-flickr-Shumon-Huque-759x504 Weave Bridge Philadelphia / Cecil Balmond

© flickr-Shumon Huque

Woven into this concept of lines are walkways and landscaping elements which are part of a wider masterplan for the campus. The bridge signals a new way of thinking about passage, about bridges not just as structures but as architectural space.

Geometric principles of weaving and braiding are used in this project to break the conventional truss model which characterizes the vast majority of footbridges across Amtrak to create a new spatial language capable of unwinding, rooting and connecting disjointed parts of the UPenn campus.

Weave-Bridge-Philadelphia-By-Cecil-Balmond-31-flickr-Shumon-Huque-759x504 Weave Bridge Philadelphia / Cecil Balmond

© flickr-Shumon Huque

Project Data:

Project name: Weave Bridge
Location: Philadelphia, Pennsylvania, United States
Coordinates: 39.948635,-75.186996
Type: Street / Road / Highways / Bridges
Project Scale: 145 ft (44 m)
Project Year: 2006 – 2009
Status: Completed
Cost: $2,000,000
Completion Year: September, 2009

The people:

Client / Owner / Developer: University of Pennsylvania

Project Architect: Cecil Balmond
Structural Engineer: Arup Advanced Geometry Unit
Engineer Consultant:Teuffel Engineering Consultants – Kriegsbergstr. 34, D-70174 Stuttgart, Germany
Project Manager: Brenda Loewen
Text Description: © Courtesy of University of Pennsylvania, constructionweekonline
Images: © Cecil Balmond, Greg Benson, Alex Fradkin, Ammann & Whitney, flickr-Albert Yee, flickr-Christophr Hiestr, flickr-roofdoorwall, flickr-Shana McDanold, flickr-Shumon Huque, Jeffrey Totaro, Arup Advanced Geometry Unit, University of Pennsylvania, Teuffel Engineering Consultants

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Weave Bridge Philadelphia / Cecil Balmond
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