Hillhouse Avenue Pedestrian Bridges, Yale University+ expand detail
New Haven, Connecticut, USA
Hillhouse Avenue is one of New Haven’s best preserved historic districts, home to mansions by Henry Austin and Alexander Jackson Davis. As part of the replacement of a vehicular bridge there, Yale University commissioned two pedestrian bridges, designed in collaboration with structural engineer Guy Nordenson and Associates, to align with the existing Hillhouse sidewalks. Spanning 18 meters (60 feet) over the Farmington Canal Greenway, the two bridges leave unobstructed views of the tree-lined street that, according to legend, both Charles Dickens and Mark Twain called the most beautiful in America.
With their diamond-shaped perforations, the new bridges recall a lattice truss, a bridge type once widely used throughout New England. Patented in 1820 by New Haven architect Ithiel Town, the lattice truss uses a diagonal arrangement of thin bars, rather than perforated steel plate. The primary structure and handrails (the main load-carrying members) are two 117-centimeter-deep (46-inch) steel-plate girders with 6-millimeter (quarter-inch) corrugated perforated webs. The decks are Greenheart, a sustainably harvested tropical hardwood.
Like the lattice truss, the Hillhouse bridges are an advance in bridge design. These cutouts lighten the structure and allow sunlight to reach the walking and cycling trail below. The wave patterns of these girders vary in amplitude across the bridge spans according to structural demands, creating an efficient design. Web sections with the greatest amplitudes are located at the bridge ends and at mid-span, allowing for thinner web plates and eliminating the need for stiffeners.