AISC Staffer Contributes to Complex, Cool Award-Winning Project

Photo: EXP

Before joining AISC’s continuing education team in November 2017, Nathaniel Gonner worked as a structural engineer at Chicago firm EXP. One of his last projects was the city’s Washington/Wabash “L” Station, which opened last August. The station replaced the Madison/Wabash and Randolph/Wabash stations, which both date back to 1896.

Being located in dense, bustling downtown Chicago (aka “the Loop”) elevated the project’s complexity, as did the need for intricate foundation work to avoid impacting existing underground utilities and the foundations of nearby buildings. In addition, space for steel erection—which included replacing four 50-ft spans supporting the trackwork—was limited primarily to the street, while still needing to allow for pedestrian traffic.    

In addition to all of the typical challenges of dense, urban construction, there was one issue that loomed above the rest: the existing steel, produced in the late 1800s,, had to be connected with new, 21st-century steel. “The connection points didn’t necessarily align with the regular building grid that we wanted to establish with the new structure, so designing and constructing connections that transitioned between the two was difficult,” Gonner recalls.

Now completed, the station’s use of AESS creates a dazzling canopy. The white-painted steel beams illuminate the sky via the embedded lighting in the tips of the ribs, each of which consists of a continuous tubular spine supporting closely spaced transverse ribs of varying length and inclination. Due to excellent synergy between architect and engineer—EXP served as both—the shape of the canopy was achieved by varying the slope and length of each successive rib, which produces an undulating effect without the need for curved glass or steel. “The location of the Washington/Wabash Station called for it to be a gateway of sorts to Millenium Park and many other tourist destinations, so for the steel to be fabricated and erected to the standards of AESS was the ideal choice,” Gonner said.

Waukegan Steel, LLC, AISC full member, fabricated the steel canopy and Munster Steel Company, Inc., AISC full member, fabricated the steel for the station’s structure.    

The Washington/Wabash “L” station received an Award of Merit in the Excellence in Structural Engineering Awards Competition at the Structural Engineers Association of Illinois (SEAOI) annual awards banquet last weekend.

View the rest of the award winners here.