NCREE’s new Tainan Lab is fully equipped to pursue leading-edge experimental and numerical earthquake research.
The Tainan Lab Seismic Simulator is engineered specifically for replicating the high velocities and large displacements of near-fault earthquakes.
The Tainan Lab BATS is used for conducting performance tests and research on full-scale seismic isolation bearings.
Fulfilling the Mission: An Introduction to NCREE’s Tainan LaboratoryLocated on the Pacific Rim, Taiwan is subject to a high level of seismic activity, causing billions of dollars of damage, and in many cases, large numbers of fatalities. To safeguard its citizens from the impact of these earthquake events, the Taiwanese government continues to invest significantly in its National Center for Research on Earthquake Engineering (NCREE). Established at National Taiwan University in 1990, NCREE is one of ten laboratory members of NARL (National Applied Research Laboratories).
NCREE’s mission is to reduce life and property losses resulting from seismic events by enhancing pre-earthquake preparedness, emergency response and post-earthquake recovery. Critical for accomplishing this mission is the experimental and numerical earthquake research conducted at NCREE’s Taipei and Tainan laboratories.
The original Taipei laboratory features a 5 x 5 meter seismic simulator (shake table) for subjecting scale-model structures to real-world earthquake forces and motions, a reaction wall and strong floor testbed for conducting structural experiments, and a Multi-Axial Test System (MATS) for testing scale models of seismic isolation bearings.
On September 21, 1999, a catastrophic 7.3 Ms earthquake occurred in Jiji, Nantou County, killing 2,415 people, injuring 11,305 and causing US$ 10 billion in damage. The second worst in Taiwan’s history, it underscored the pressing need to subject test articles to larger displacements and higher velocities to better simulate near-fault earthquakes, which threaten nearly one third of country’s population. In addition, ongoing earthquake engineering research has revealed that further advancing the science requires the testing of ever-larger scale test structures and bearings. To meet these demands, NCREE established the Tainan Laboratory.
The Tainan lab mirrors its northern counterpart with respect to types of test equipment, but definitely supersedes it in terms of test capabilities and supporting infrastructure. The new lab features a large 6-degree-of-freedom (6DOF) shake table designed specifically for replicating near-fault ground motions, a 6DOF Biaxial dynamic Testing System (BATS) for testing full- scale seismic isolation bearings, a strong wall/strong floor structural testbed and a sophisticated Matrix High-flow System for hydraulic power generation and distribution.
This state-of-the-art test facility is the product of close collaboration among engineers, designers and planners at MTS in the United States and NCREE and Sinodynamics in Taiwan. A truly international endeavor, its construction integrated components from around the world: actuators, pumps, controllers and airbags from the United States; hardline and dampers from Canada; accumulators from Japan. And from Taiwan: enormous volumes of reinforced concrete, massive steel weldments for the BATS reaction frame and shake table, and all the heavy rigging and high-capacity cranes needed to put it all in place.
Foundational to the three-system Tainan lab is its custom Matrix High-flow System for hydraulic power generation and distribution. Comprising six electric hydraulic power units (pumps), an array of high-pressure “blowdown” accumulation and a complex hardline labyrinth, it provides the flexibility needed to accommodate a wide variety of testing scenarios. Each of the three systems can draw continuous flow of 3,500 lpm from any of the assignable pumps. However, for peak flow events each system is assigned a set of dedicated blowdown valves that draw high-pressure flow from the charged accumulator banks. The 8 x 8 shake table is assigned three blowdown valves capable of delivering a peak flow of 26,180 lpm; actuators in the strong wall/strong floor testbed are assigned two valves capable of 11,060 lpm; and the BATS is assigned two valves capable of 18,620 lpm. With this matrix of assignable pumps and completely separate blowdown accumulation, the lab could conduct a very dramatic test on the shake table and it would not affect a test running in the structural area that had been assigned its own pump. Another component of the matrix is a surge tank, which is necessary to capture the high volume of oil that returns from the shake table after peak flow events and then distribute it uniformly back to the six pumps.
The Tainan Lab BATS is used for conducting performance tests and research on full-scale seismic isolation bearings, which are regarded as one of the most effective devices for enhancing the safety and functionality of buildings, infrastructure and equipment. While similar in appearance to the MATS (Multi-Axial Testing system) in the Taipei lab, BATS is engineered for dramatically improved kinematic performance. BATS delivers five times the vertical velocity (0.15 vs 0.03 m/s) of MATS and four times the horizontal velocity (1.0 vs 0.25 m/s); likewise, longitudinal displacement has increased by a factor of six (1.2 vs o.2 meters).
The system comprises a self-reacting frame anchored in a fixed foundation of reinforced concrete that and a massive test platen driven by fifteen servo hydraulic linear actuators. Positioned inline with the test platen, four dynamic actuators combine to provide longitudinal motion (±1.2 m, ±1.0 m/s, ±4.0 MN). Beneath the platen, a large static actuator combines with six dynamic actuators to provide vertical compression (±75 mm, ±0.15 m/s, 60.0 MN); these six dynamic actuators also serve to constrain the platen in the pitch and roll axes. Arrayed on the sides, four static hold-down actuators constrain the platen in the yaw axis and provide vertical tension (8 MN).
Among the largest shake tables in the world, the Tainan Lab Seismic Simulator is engineered specifically for replicating the high velocities and large displacements of the near-fault earthquakes that pose such a threat to much of Taiwan. With an 8 x 8 meter table and 250-ton payload capacity, it can also accommodate larger-scale test articles to yield more realistic simulations and higher fidelity results.
This 6DOF system comprises a large 8 x 8 meter table driven by eight servo hydraulic linear actuators. Four dynamic actuators arrayed in line with the table in a compact V-configuration deliver large motions in the X and Y axes (±1.0 m, ±2.0 m/s for ten seconds, and ±1.4 g for 100-ton specimen). Four dynamic actuators positioned below the table deliver motion in the Z axis (±0.4 m, ±1.0 m/s for twenty seconds, and ±0.8 g for 100-ton specimen). Four static actuators below the table serve to balance the table and specimen on a 4,000-ton floating reaction mass.
The V-configuration of the horizontal actuators is especially noteworthy. Available only from MTS, it features opposing sets of relatively short asymmetric actuators mounted in an angled (v-shaped) arrangement, relative to the sides of the table and reaction mass. This offers several significant advantages. First, shorter, asymmetric actuators are far less susceptible to damaging bowstring effects that occurs when actuators resonate laterally under load. Second, this configuration has proven to exhibit low inherent dynamic cross coupling, which can negatively affect test fidelity. Third, and most importantly, the V-configuration enables longer stroke in more compact space when compared to conventional, orthogonal arrangements. Essentially, the V-configuration delivers superior performance in a smaller space, enabling both greater test fidelity and a far more compact reaction mass.
The resulting low mass ratio of the 4,000-ton reaction mass vs the 250-ton maximum payload (about 16:1) was a significant factor in reducing system cost. Typical orthogonal configurations can exhibit mass ratios well in excess of 30:1. As a result, the reaction mass of the V-configured Tainan Lab shake table required significantly less concrete, construction and curing time. More significant, however, are the savings accrued in reductions to the hardware and systems required for suspending (floating) and damping the far more compact reaction mass.
The NCREE Tainan Lab was officially unveiled to the citizens of Taiwan and the world at a Grand Opening Ceremony on August 9, 2017. It featured inaugural addresses by Taiwan dignitaries, NARL and NCREE leadership, and NCREE suppliers, along with demonstrations of both the newly commissioned 8 x 8 Seismic Simulator and BATS. Additionally, in keeping with another tenet of NCREE’s mission, “promoting educational outreach and consolidation of earthquake knowledge,” the Grand Opening was preceded and followed by technical meetings, drawing seismic researchers from around world to exchange knowledge, share experiences and further the science and technology of earthquake engineering. These included the first-ever MTS Seismic solutions Users Group Meeting, held August 7-8, and a series of expert panel discussions, held August 9-10, envisioning future research for the new lab.
>> NCREE Tainan Lab Grand Opening (local television coverage)
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