FGIA Annual Conference Participants Tour Seismic Shake Table Test Site
More than 40 Fenestration and Glazing Industry Alliance (FGIA) members had the opportunity to tour a seismic shake table test site as part of the FGIA 2023 Annual Conference. The Natural Hazards Engineering Research Infrastructure (NHERI) TallWood Project shake table test will take place in the San Diego area. Those on the tour were able to see outside, inside, and beneath the structure built on top of the shake table. At 10 stories tall, this is the largest test of its kind, and its construction is nearly complete.
About the test site
Two FGIA members, Winco Window Company and Innotech Windows + Doors, donated windows to the project, which began in 2016. The shake table facility completed a multi-year upgrade last spring, to extend the shaking capabilities from one direction to three-axis translation and rotation. The construction of the building itself started in July.
The research team anticipates the building can go through large earthquakes with very little damage. The exterior façade is made up of four sub-assemblies at the base of the building, all of which are attached to the main wood frame structure. The first three sub-assemblies feature cold-formed steel framing with exterior aluminum composite finish and windows, while the fourth is a curtain wall. All are detailed for drift compatibility, by providing horizontal and vertical joints.
• CFS 1: This sub-assembly is platform framed with horizontal drift joints at the top of the wall. Slip is intended to occur between the two tracks. The corner uses special joints that expand and the joint is on two of the three stories. The third story without the joints serves as a reference, so the researchers can compare the performance with and without joints.
• CFS 2: This sub-assembly is bypass framed with drift clips that allow the studs to slip relative to its diaphragm. At the corner, it’s expected that up to 10 inches of drift will be accommodated.
• CFS 3: Featuring spandrel units with ribbon windows, this sub-assembly also has slip joints at the top of the windows, between the window and the spandrels, while the spandrel framing is fixed to the diaphragm. The first and third stories use Winco and Innotech windows that wrap around the corner. On the second story, a drift joint was used at the corner, similar to CFS 1.
• CFS 4: This final sub-assembly is a finished, fire-rated glass curtain wall assembly whose glass rotates within its frame. It has steel mullions and 1 1/16 inches of thick fire-rated glass and was framed on-site.
Beneath the building sits the shake table itself. Actuators drive the shake table platform in all directions. The table moves a maximum of 35 inches in the East-West direction, 15 inches in the North-South direction, and 5 inches up and down, according to Site Manager Koorosh Loftizadeh. At a payload capacity of 1100 kips, about twice that of the timber building, the peak acceleration capacity is 1.6g, 1.2g, and 0.6g (“g” referring to the acceleration of gravity at the Earth’s surface) in East-West, North-South and vertical directions, respectively. To be ready for testing, more than 700 sensors and approximately 60 video cameras need to be installed in the building.
Testing to begin in March
During the Seismic and Wind-Induced Inter-Story Drift Review Task Group (AAMA 501.4 and 501.7) meeting held at the FGIA Annual Conference, Dr. Keri Ryan with the University of Nevada, Reno, who is a co-investigator of the project, provided an update on how testing will go. “We will impose a range of intensities over a four-week period, starting with a low level of shaking and building up to larger earthquakes through design level shaking to maximum considered earthquake (MCE),” she says. “We plan to scale up from low-level drifts up to 2 percent inter-story drift. Some of the input motions will have peak acceleration over 1g.”
The group hopes to begin testing at the end of March. Multi-camera streaming of the construction site can be seen online and will be available to view this spring when the four-week test begins. “It will be great to see it in action on that live feed,” said Tanya Dolby, chair of the FGIA task group.