Steel Shots: Transbay Transit Centerpiece Installed

(Photo: Transbay Transit Center Project’s Facebook page

Installation of the central feature of San Francisco’s new 1.5 million-sq.-ft Transbay Transit Center is complete. The Light Column, which will allow natural daylight from the open air rooftop park into the main public space, the Grand Hall, reaches 150 ft through all five levels of the building. Topped with a 4,000-sq.-ft domed skylight, the structure not only supports the building, but also draws daylight deep into the interior and frames views of the park above.

The Light Column is assembled of tubular steel columns and 56 cast steel nodes with various geometries, supplied by Cast Connex (an AISC Member). Each vertical segment of the structure is topped off with a uniquely designed horizontal ring, made up of roller or induction bent pipe segments, except for the top and bottom rings, with the smallest ring weighing in at approximately 100,000 pounds. As the structure grows taller, the rings become wider and thinner, expanding the capacity for natural light to enter the building.

“Not only is the Light Column one of the signature architectural features of the Center, but it has also been one of the most fascinating sections to construct,” said Dennis Turchon, Transbay Joint Powers Authority senior construction manager.

Due to the Light Column’s sheer size and proximity to Fremont Street, two lanes of traffic were closed in order to install it during the afternoon and evening hours. Despite the unique construction challenges, assembly of the structure was completed in just over a month. Crews are now advancing steel construction toward Fremont Street, which began in September.

A total of more than 24,000 tons of steel will be used to construct the Transit Center, all of which was supplied and fabricated domestically in accordance with the project’s Buy America status. Production facilities in around 20 states have been involved in providing the steel for the project, several of which are AISC Members and AISC Certified facilities. (View a map of the various facilities.)

When finished, the Transit Center will accommodate approximately 100,000 travelers daily. Bus operations are scheduled to begin in late 2017. For more on the project, visit

(Photo at right: Courtesy of Cast Connex)