Design

One of the most famous buildings of the structural expressionist style, the skyscraper's distinctive X-braced exterior shows that the structure's skin is part of its 'tubular system'. This is one of the engineering techniques which the designers used to achieve a record height (the tubular system is the structure that keeps the building upright during wind and earthquake loads). This X-bracing allows for both higher performance from tall structures and the ability to open up the inside floorplan. Such original features have made the John Hancock Center an architectural icon. It was pioneered by Bangladeshi-American structural civil engineer Fazlur Khan and chief architect Bruce Graham.
The interior was remodeled in 1995, adding to the lobby travertine, black granite, and textured limestone surfaces. The elliptical-shaped plaza outside the building serves as a public oasis with seasonal plantings and a 12-foot (3.7 m) waterfall. A band of white lights at the top of the building is visible all over Chicago at night, and changes colors for different events. For example, at Christmas time the colors are green and red. When a Chicago-area sports team goes far in the playoffs, the colors are changed to match the team's colors.
The building is a member of the World Federation of Great Towers. It has won various awards for its distinctive style, including the Distinguished Architects Twenty-five Year Award from the American Institute of Architects in May 1999.^[29]
The building is only partially protected by a fire sprinkler system,^[30] as the residential floors do not have sprinklers.^[31]