Seismic Testing Underway for TallWood Project
The Natural Hazards Engineering Research Infrastructure (NHERI) TallWood project recently announced that testing is underway, with its first table training exercises showing successful results.
The research is anticipated to be the world’s tallest full-scale building ever tested on a shake table.
About NHERI TallWood
According to a news release last month, the team designed the mass timber rocking wall lateral system suitable for regions with high earthquake hazard, aimed at resilient performance. This means the building will have minimal damage from design level earthquakes and be quickly repairable after rare earthquakes.
The project also aims at testing on safety-critical nonstructural components that span floor-to-floor, such as exterior façades, interior walls and stairways, which are subjected to relative movement between stories.
The building reportedly features four exterior façade assemblies, a number of interior walls and a 10-story stair tower.
Testing was anticipated to begin in April at the University of California San Diego outdoor shake table, one of the two largest earthquake simulators in the world. It also holds the largest payload capacity, capable of carrying and shaking structures weighing up to 2,000 metric tons, or 4.5 million pounds.
The team reports that tests will simulate earthquake motions recorded during prior earthquakes covering a range of earthquake magnitudes on the Richter scale, from magnitude 4 to magnitude 8. This will be done by accelerating the table to at least 1g, which could accelerate the top of the building to as much as 3gs.
The project is supported by the National Science Foundation. A consortium of universities are collaborating on the project, including Colorado School of Mines (lead); University of Nevada, Reno; Colorado State University, University of Washington; Washington State University; University of California San Diego; Oregon State University; and Lehigh University.
Latest Shake Table Testing
According to the project’s May newsletter, last month, white noise excitations were applied in each of six directions, including three translational and three rotational, used to determine the natural frequencies of the building in each direction.
Afterwards, the results are used to program the controllers to compensate for the building natural frequencies and to achieve better fidelity when replaying the earthquakes.
“The control algorithms were validated using small earthquake records, and we feel confident in the table’s performance to kick-start the testing of the tallest full-scale building on the shake table, to date,” wrote the research team.
“In the past week, we have finished connecting all sensors to the data acquisition system. With data collected during table training, the site and research team was able to debug and configure the sensor channels so that the data will be recorded appropriately. On Friday, we successfully completed a bidirectional (XY) shake with a record from the Ferndale Earthquake that represents an event with a 225-year return period. There is no noteworthy earthquake-induced damage to the building so far. In addition, several of the nonstructural subassembly joints have already exhibited the type of movement that we are hoping to see.”
The first phase test of the program is anticipated to last about 3 to 4 weeks, starting May 1. Researchers plan to gradually increase the intensity of shaking to document performance at different intensities.
Additionally, with each level, testing will be performed with records representing different earthquake sources such as crustal, interface and intraslab, and earthquakes will also be ran in different directions.
Once Phase 1 is completed, the project team reports that there will be additional testing activities with modified wall configurations and added dampers as part of another NSF-supported payload test.
According to reports, on Tuesday (May 9), the research team simulated the 1994 Northridge quake, a magnitude-6.7 temblor in Los Angeles. Soon after, they ran the magnitude-7.7 Chichi quake that struck Taiwan in 1999.
In both tests, the specimen “performed exactly as we expected,” Shiling Pei, principal investigator, told Engineering News-Record in an email after the tests. Researchers also reportedly found no structural damage after inspection.
The building remained damage free after two major design-level earthquakes back-to-back,” said Pei. "We found a way to build tall wood [structures] that are earthquake-proof for design-level shakes.”