TWISTED PRETZEL

2017 Footbridge conference submission

Berlin, Germany. 2017

description

The best urban bridges excel at reconciling civic purpose with utility (connecting one side to the other). These bridges are simultaneously iconic emblematic moments in a city’s fabric, and are yet functional.  One need only ponder the likes of bridges in Venice or London to consider the impact of these spans. On this site in Berlin, linking an existing south bank green-way to a new north side urban park with a dynamic footbridge, expands the charge to simply replace a forgotten span. It’s an opportunity not just for improved pedestrian connectivity, but to participate in meaningful place-making at this significant river bend.

strategy

Large single-block institutional buildings, wide boulevards, and elevated rail infrastructure characterize the north bank of the Spree.  At four and a half meters above the river, the edge is impersonal, desolate, and disengaged.  It’s a barren landscape compared with the richness of the heterogeneous urban edge and river-level park to the south.

The old unstable north-side bridge abutment is replaced by a new river-level promenade. Ideal for sunbathing, steps adjacent to a new abutment provide distant views both up and down river. Extended eastward, the promenade links to an existing boat landing and garden kiosk. A wide slope up to Littenstrasse extends broad river views deeper into the street-scape while suggesting an opportunity as an informal performance space.

A neighboring park and barren roadway are repurposed as a community center, offering futsal or basketball courts and a new year-round infinity edge swimming pool.  Access to a more recent existing office building is maintained by refurbishing abandoned roadway alongside and beneath the raised railway.  New street trees shade reconfigured displaced parking.

Along the south bank (on axis with the Markisches Museum tower),  the bridge is linked to the existing promenade below with new sloping paths from the curbside bridge entrance.

structure

Inspired by the work of Eero Saarinen, the bridge is conceived as simple extruded equilateral triangle, yet like a pretzel, is twisted, then bent to follow walkway slope requirements.  It’s a rigid stress skin shell reinforced by three warping triangular structural tubes. Where arcing walkway clearances (represented by the orange bar) intersect the twisted structure, the skin is subtracted. The results are reminiscent of traditional Weidling and Langschiff boat forms.