Although one of the smallest projects that I have worked on in terms of dollars, the North Bank Pedestrian Bridge has been one of the most geometrically challenging. This 700-foot long structure snakes its way through a maze of existing infrastructure and in the process, exhibits some bizarre and interesting geometry. Horizontally, the basic shape is a simple reverse curve while vertically, approach tangents are connected by a single parabolic curve but this is where the “ordinary” ends. While the “deck” chords of the supporting pipe trusses follow the basic geometry, the “outer” chords undulate above and below the deck in a sinusoidal fashion resulting in trusses that appear to most nearly resemble warped strands of DNA.

Working for both the general contractor (Barletta Heavy Division) and the fabricator (Newport Industrial Fabrication), I have been involved in nearly every “geometric aspect” of the project from survey control on the ground to the intricate details of pipe bending and fish-mouthing.  Perhaps the biggest challenge of all was the control of the structure’s geometry in the shop.  Working with Newport Industrial personnel, I developed coordinate transformation procedures and shop survey methods that allowed millimeter-level control of the structure’s very complex geometry as it went through various stages of fabrication.

With erection of the superstructure now complete (Fall 2011), this has been a challenging but very satisfying project for all parties.