Structural steel enables a 15-story tower to overhang a train tunnel.
CANTILEVERING THE CORNER of a 15-story high-rise over an Amtrak train tunnel, which offers no possibility of bringing a direct load path to bedrock, isn’t a job for just any structural material. in this sort of condition, engineers know that structural steel
is the only material with the strength-to-weight ratio capable of handling the dynamic forces at play.
The team of architects and engineers who de- signed the recent expansion of the John Jay college of criminal Justice faced this very challenge when devising a structural system for a new tower sited on 11th avenue between 58th and 59th streets.
The tower design, envisioned by architecture firm soM as a vertical campus—essentially a stacked academic program that seeks to offer the same opportunities of random encounter and collabora- tion common to more traditional campuses—itself added more challenges. The design called for double- height spaces and 50-foot clear spans through
the center of the building. in the words of Jason Stone, associate at structural engineering firm Leslie e. robertson associates (lera), “steel was the obvious choice because it’s lighter than reinforced concrete and keeps the loads down. it was also the only option for the project’s long span areas.”