World’s Tallest Earthquake Simulator Tests Limits of Fenestration, Glazing

The relationship between earthquakes and man-made structures has been one-sided for as long as humans have been capable of building. That relationship is being tested at the University of California San Diego thanks to the Natural Hazards Engineering Research Infrastructure Tallwood project.

The project aims to investigate the resilience of tall buildings by simulating a series of large earthquakes on a full-scale, 10-story mass timber building. The Tallwood structure is the tallest full-scale building ever to be constructed and tested on an earthquake simulator. The seismic shake table tests not only the structure’s resiliency but also a multitude of
elements, including the integrity of glass and the resiliency of window seals.

Among the many professionals who traveled to La Jolla, Calif., is Lothar Erkens, an engineer at Winco Window Company. The Saint Louis-based custom aluminum window manufacturer provided windows for the project. Erkens says the tests afford the fenestration industry a perfect opportunity to validate testing on smaller shake tables and test whether window installation clearances are designed to handle actual earthquakes.

The Tallwood shake table boasts the world’s largest payload capacity, carrying and shaking structures weighing up to 2,000 metric tons (4.5 million pounds). Recently, the table underwent an upgrade courtesy of funding from the National Science Foundation. It now has the capability to accurately replicate the complete three-dimensional ground motions
experienced during earthquakes, encompassing all six degrees of freedom: longitudinal, lateral, vertical, roll, pitch and yaw.

Tests simulate earthquake motions recorded during prior earthquakes covering a range of earthquake magnitudes on the Richter scale, from magnitude four to magnitude eight. This is done by accelerating the table to at least 1g, which could accelerate the top of the building to as much as 3gs.

The testing began officially in early May, says Erkens. The process involves shaking one level before walking the structure to check for damage. The process is then rinsed and repeated at differing levels.

The first three levels of the building feature non-structural elements, such as a curtainwall provided by Technical Glass Products and windows provided by Innotech and Winco.

Erkens says the test came about after the Kobe, Japan, earthquake in 1995 that killed more than 6,000 people and the Auckland, New Zealand, earthquake several years ago. Those earthquakes showed that windows, doors and other non-structural components might not initially exhibit any failures. However, “two to three weeks later, the first heavy rainstorm
comes, and suddenly there are major water intrusions into the building,” says Erkens.

Glass failures are evident to everybody, he adds. Glass cracks and breaks. If only the seal fails, it’s not noticeable unless you know what to look for. Those failures don’t appear until you have excess air filtration during winter or excess water filtration during the first heavy rainfall.

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