Creating safe glass facades

Glass facades are attractive, but they also have to be safe. Say if a bomb were to go off nearby, would they withstand the blast? Researchers are using a shock tube to find out, and one of their projects is a new building complex in San Francisco.

Metropolises like San Francisco are in a state of constant flux. Excavators and wrecking balls tear down dilapidated old factories and houses that are beyond renovation, freeing up space for new structures. Entirely in this spirit of dynamism, a huge building complex will soon go up on a site where until recently a train station stood: the Transbay Transit Center, a five-story structure with glass facades, over 20,000 square meters of floor area, and a glass-covered park on the roof.

A second phase will see the construction of an additional high-rise building. The budget is $4 billion.

Though glass facades and glass roofing add greatly to the building's aesthetic appeal, the safety of the huge areas of glass is a major challenge? What happens if a bomb detonates in the vicinity of the complex?

This is precisely what a New York engineering office has commissioned researchers at the Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach Institute (EMI) in Efringen-Kirchen in southwest Germany to investigate. ''We are using the 'Blast-STAR' shock tube to test different glazing structures of glass facades for their resistance to the pressures produced by explosions at various distances,'' says the EMI researcher Oliver Millon.

Testing safety glazing, windows, and doors
This is how the shock tubeworks - the shock tube consists of a high-pressure driver section and a low-pressure driven section, which are separated by a steel diaphragm.