E-ISOLATION : DYNAMIC TESTING FACILITY
WITH HIGH-PERFORMANCE FORCE MEASUREMENT SYSTEM
Y. Takahashi1, T. Takeuchi2, S. Kishiki2, Y. Shinozaki3, M. Yoneda2, K. Kajiwara4 & A. Wada2

1

Kyoto University, Kyoto, Japan, takahashi.yoshikazu.4v@kyoto-u.ac.jp
2

Tokyo Institute of Technology, Tokyo, Japan
3

4

Taisei Corporation, Tokyo, Japan

National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan

Abstract: The dynamic characteristics of seismically isolated bearings are highly dependent on the size effectand rate-of-loading, especially under extreme loading conditions. Therefore, confirming the actual properties
and performance of these bearings with full-scale specimens under prescribed dynamic loading protocols isessential. The number of large dynamic testing facilities is still limited and even though the existing falicities in
the US, China, Taiwan, Italy, etc. are conducting these tests, the acquired reaction force at their dynamic
loading tests are contaminated by friction generated by the large vertical loads and inertial force of the heavy
moving platen. To solve this problem, the authors have proposed a high-performance reaction force
measurement system that can eliminate the effects of friction and inertia forces even under large vertical loadand high-speeds, and a seismic isolation testing facility with the proposed system (E-Isolation) has been
completed on March 2023 in Japan. This test facility is designed to conduct not only dynamic loading tests ofseismic isolation bearings and dampers but also to perform hybrid simulations of seismically isolated structures.
In this paper, design details and the realization of this system into an actual dynamic testing facility arepresented and the outcomes are discussed.

1 Background
Since around 1970, seismic isolation and vibration-controlled structures have been developed and widely
implemented to minimize or eliminate damage to the main structural frame during earthquakes. These
innovative methods do not dissipate energy during an earthquake by plasticizing structural members, such ascolumns and beams, but instead by using seismic isolators and energy-dissipating dampers. Seismic isolatorsand dampers are essential components that determine the seismic response of a structure. Test methods forevaluating the performance of seismic isolation bearings are outlined in both ISO and JIS standards.
Specifically, horizontal performance evaluation tests necessitate that the seismic isolation rubber bearing isrepeatedly forced to deform to a specified shear strain while under constant vertical pressure. While it ispreferable to test seismic isolation bearings at their full-scale and actual velocities, reduced models and static
loading are often employed due to the limitation of the capacity of testing equipment. However, static tests
using scaled-down specimens can produce results different from full-scale dynamic tests. Among the standard
rubber laminates used for seismic isolation bearings, natural rubber bearings (NRB) exhibit a relatively linear
load-displacement relationship. In contrast, lead-plugged laminated rubber bearings (LRB) and high-damping
rubber bearings (HDRB) with enhanced damping capabilities exhibit more complex behaviors. Additionally,

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the size of the specimen notably influences the performance of these bearings. Ensuring the stableperformance of larger rubber bearings, especially those with diameters exceeding 1 meter, is more challenging
than their reduced-size ones. This is primarily because, during the manufacturing process of seismic isolation
laminated rubber, achieving a flawless bond over the entire surface of a full-size rubber bearing is more
intricate. Additionally, it is recognized that the energy dissipation capacity of seismic isolation bearings can bereadily impacted by the heat generated from the lead-plug or high-damping rubber. Therefore, it is crucial toverify the behavior of seismic isolation bearings using a dynamic testing machine with a full-scale specimen.
Seismic isolation bearings, utilized in large structures such as high-rise buildings and long-span bridges,
sometimes support vertical loads exceeding 3,000 tons in a single unit. As these seismic isolation structures
increase in size, Extrapolating full-scale dynamic results from reduced or static test results reduces reliability.
Thus, there has been an increasing demand to verify the performance of seismic isolation bearings via fullscale dynamic testing. Figure 1 shows the typical components of dynamic testing machine, including the
Seismic Response Modification Device (SRMD) testing facility (Benzoni et al. 1998) at The University ofCalifornia, San Diego. The moving platen, which induces a shear force on the test specimen, is dynamically
moved in the horizontal direction while subjected to large vertical loads. However, the inertial force of themoving platen and the frictional force due to the large vertical loads are mixed into the measured reaction force
from the load cell of the horizontal dynamic jacks. It is not easy to extract accurate reaction force of test
specimens in real time because the friction forces in the measured force vary depending on the pressure,velocity, and temperature.
To solve these problems, the authors proposed a high-performance reaction force measurement system thatcan eliminate the effects of friction and inertia forces, and a seismic isolation test facility (E-isolation) equippedwith the proposed system was completed in Japan in March 2023. The purpose of this test facility is not only
to perform dynamic loading tests of seismic isolation bearings and dampers but also to perform hybrid
simulations of seismic isolation structures. This paper presents the design details of this system and its
realization in an actual dynamic test facility and discusses the results.
The reaction beam is rigidly fixedSpecimen

Reactionbeam

Controlled byhorizontal displacement
Horizontal dynamic jackMovingplatenVertical dynamic jack(Apply pressure
to specimen)

Load cell

Fixed

Lubricated bearing

Figure 1. Typical components and conventional force measurement system in dynamic testing machine.

2 Technical issues in dynamic testing machines under large vertical loads
Most seismic isolators utilized in civil and architectural structures are designed to support extremely large
vertical loads. While there is a desire to conduct dynamic loading tests with large deformations at high speeds
under these conditions, conventional techniques often have problems, especially with accurate measurements.
To achieve horizontal deformation of a specimen under a vertical load, several external forces (Figure 2) must
be applied. Consequently, the moving platen, on which the test specimen is mounted, is subjected to thefollowing forces (Figure 2):•

Vertical loads applied by vertical jacks (in the vertical direction)•

Self-weight of the moving platen itself (in the vertical direction)•

Friction force between the moving platen and the vertical jacks (in the horizontal direction)•

Inertia force from the moving platen during high-speed horizontal vibrations (in the horizontal direction)
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•

Shear force due to the deformation of the specimen (in the horizontal direction)*This is the primary measurement target.

•

Bending moment at the base of the specimen

Specifically, the friction force, influenced by velocity and vertical loads, acts horizontally. It is challenging to
remove this force from the measured horizontal reaction force. In large dynamic testing facilities, the friction
force is measured by tests in the absence of a test specimen, and remove the effect of the friction force fromthe measured reaction force after the tests. However, the detailed methodology for modeling these frictional
characteristics has not been disclosed to the public. Furthermore, in full-scale tests, the size of the moving
platen needs to be increased, leading to a correspondingly greater inertia force. Consequently, load cells of
the horizontal dynamic jacks that drive the moving platen are unable to measure the shear force of thespecimen in real-time, presenting a considerable technical issue.

M

Reactionbeam

P : Vertical forceFP

F : Shear force(measurement target)F
MovingPlatenM : Bending moment

Combined horizontal force
acting on shake table

Load cell
Complex frictional forces
due to vertical loads

High-speed
horizontal displacement(inertia force generated)

Figure 2. Force acting on moving platen by horizontally deformed seismic isolation bearing.

3 Proposed reaction force measurement system under large vertical loads
This paper proposed a new horizontal reaction force measurement system. In the proposed system, the loadcell of the horizontal dynamic jacks is used solely to control the moving platen. The horizontal reaction forceof the specimen is measured by a new force measurement system (V-shaped measurement link) attached tothe strong reaction beam on the side opposite the moving platen, as illustrated in Figure 3 (right). This systemenables the direct measurement of horizontal reaction force of the specimen, excluding inertial and frictional
forces. While similar measurement mechanisms have been employed in past experiments with non-significant
large vertical loads (Kasai et al. (2005)), the primary objective of our development is to realize this horizontal
reaction force measurement system under immense vertical loads exceeding 10,000 tons.
In this study, a new reaction beam support was proposed (Figure 3, left). This support incorporates laminatedrubber bearings, which exhibits high linearity even under small deformation, positioned between the reaction
beam and a rigid concrete structure and tightened by PC strands. Approximately 99% of the specimen's shear
force can be measured directly by the load cells of the V-shaped measurement link, while the remaining 1%
was intended to be supported by the reaction beam support. The load carried by this support can be calculated
by measuring the horizontal displacement of the laminated rubber bearings. The system's accuracy wasvalidated through pilot tests using small-scaled system at Tokyo Institute of Technology (Takeuchi et al. (2023)).
Following this, a testing machine capable of bearing a vertical load of 3,000 tons was constructed with theproposed reaction beam support mechanism integrated into it.

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Reaction
beam
Verticalforce

Rubberbearing withhigh linearity
even in small
displacement
PC strand(inserted in asteel pipe witha large enoughinner diameterto avoid lateral
restraints)

Joint between rigid beam and strong reaction concrete
structure ((fixed vertically, but capable of small
displacement in the horizontally without resistance))

Detail｛Load cellfor reaction force

Reactionbeam

Rigid measurement link
Fixed

SpecimenMovingplatenLubricated bearing(complex frictional forces
due to vertical loads)

Strong concrete reaction structure

Horizontal dynamic jack
Fixed
Load cell forcontrolling moving platen
High-speed
horizontal displacement(inertia force generated)

Figure 3. Reaction force measurement system (measurement link and reaction beam support).

4 E-Isolation
E-isolation (Figure 4) is capable of uniaxial dynamic excitation with a maximum vertical load of 3,000 tons
(dynamic), a maximum horizontal displacement of ±1.2 m, and a velocity of up to 0.8 m/s. One of its mostdistinguishing features is the integration of a high-performance force measurement system (Figure 5), which
was developed in this study. This system employs a V-shaped measurement link mounted on the reaction
beam to directly measure the specimen's reaction force in real-time, unaffected by frictional or inertial forces
generated on the moving platen.
To validate the high-performance force measurement system, a test specimen was subjected to a load of up
to 100 tons. The measured values from the load cell directly attached to the specimen were then comparedwith those from the V-shaped measurement link. The results indicated that the two measurements were in
extremely close agreement. Furthermore, it was confirmed that at the 100-ton loading level, the force exerted
on the reaction beam support was minimal, rendering it almost negligible (Takahashi et al. (2023)).
Moreover, to evaluate the system's performance under the maximum vertical load (dynamic) of 3,000 tons, afull-sized laminated rubber bearing with a shear modulus of 0.29 MPa and 1200 mm in diameter was installed.
The dynamic cyclic loading tests were then conducted in the horizontal direction. Figure 6 shows an exampleof these results. This figure reveals that the force measured by a load cell of the horizontal dynamic jacks,
similar to those in conventional testing machines, exhibited a bilinear hysteresis loop due to frictional effects.
In addition, this hysteresis loop oscillated because of the inertial forces by the moving platen. However, ournewly developed high-performance force measurement system effectively removed the contaminations offriction and inertia, and accurately measured forces on the specimen.
The proposed high-performance force measurement system can effectively remove frictional and inertial
forces, even in tests involving extremely large vertical loads. Being able to determine the accurate horizontal
force of a specimen in real-time means that accurate results can be immediately available right after tests.
When testing machine is employed for product inspections, products can be dispatched right after tests with
precise data. This process not only shortens the construction period but also offers societal benefits andsignificant advantages in industrial applications. Furthermore, E-Isolation can conduct real-time hybrid
simulations where force testing and numerical analysis are concurrently integrated. The subsequent chapter
provides an example of such a real-time hybrid simulation utilizing E-Isolation.

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4

Rigid measu

Horizontal
dynamic jack

R ig

Reaction beam

rem ent link

id

me

a

re
su

me

nt

lin k

Upper
movingplatenLower
movingplaten

Ho

dyn

am

ic ja

ck

Figure 5. High-performance force measurement
system in E-Isolation.

Figure 4. Configuration of E-Isolation.

1000 Horizontal Load[kN]

1000 Horizontal Load
[kN]

600

600

400

400

800

800

Conventional
Measurement(Load cell ofhorizonta jack)200
0-500 -400 -300 -200 -100 0-200

Φ1200mm
Seismic Isolator

riz

al
ont

Horizontal
DIspl.[mm]100 200 300 400 500

200
0-500 -400 -300 -200 -100 0
-200

-400

-400

-600

-600

-800

-800

-1000

-1000

Horizontal
DIspl.[mm]100 200 300 400 500
New Measurement Link

Figure 6. Force – displacement hysteresis loops of seismic isolator (vertical load 16929kN, 2.5Hz sine loading).

5 Hybrid simulation
The hybrid simulation (Hakuno et al., 1969, Nakashima et al., 2020) was proposed in Japan and is now widelyused in the world to simulate the seismic response of large-scale structures. It is an experimental method thatis used to deform a structural specimen as if it were responding to an earthquake ground motion using an
online computer-controlled simulation of dynamic response. In hybrid simulation, one member or part of astructural system is built experimentally while the remaining parts are modeled using a computational modeland the equation of motion for the structural system is solved by time integration schemes. The restoring force
characteristics of the experimental part are obtained by data acquisition from the force sensor of the physicaltest run in parallel to the analysis. Since E-Isolation has the high-performance force measurement systemeliminating the effects of friction and inertia forces, the precision of hybrid simulation can be substantially
improved. The servo-controller in this facility has a hybrid simulation mode to communicate with computational
kernels (ex. OpenSees) in real-time by OpenFresco (Takahashi et al., (2006), Schellenberg et al. (2009)),
which provides a high-speed, low latency data communication between the servo-controller and the analyticalcomputer by reflective memory (GE Intelligent Platforms 5565PIORC product family).

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Pseudo-dynamic simulations and real-time hybrid simulations were conducted. For the pseudo-dynamic hybrid
simulation, results were compared between the cases: one using measurements from the load cell on the
dynamic jack and the other using measurements from a high-performance force measurement system. The
test specimen used in the pseudo-dynamic simulation was an 800 mm-diameter laminated natural rubber
bearing. The test specimen for the real-time hybrid simulation was a 1200 mm-diameter laminated natural
rubber bearing. An actual two-story seismically isolated building, as shown in Figure 7, was assumed as themodel building for the hybrid simulations. The numerical model employed was a shear spring model with threemasses, also illustrated in Figure 7; its parameters can be found in the same figure. The building was supported
by 20 bearings of 800 mm-diameter, or by 10 bearings of 1200 mm-diameter. In the hybrid simulations, only
one bearing was tested at E-Isolation, and the number of bearings was multiplied against the measured
reaction force for the simulation. Since the hysteresis of the bearings are almost linear, hybrid simulations andpure numerical analysis can be compared with high accuracy.
The results of the pseudo-dynamic simulation are shown in Figure 8. Figure 8 reveals that the results using
the load cell of the horizontal dynamic jacks differ significantly from the pure numerical analysis results due tothe frictional forces mixed into the measured reaction forces. Conversely, the results using the highperformance force measurement system align closely with the results of the analysis. The real-time hybrid
simulation also calculated the accurate response of the building (Figure 9).
Therefore, the high-performance force measurement system of E-isolation allows for real-time accurate
measurements of forces on the test specimen. This capability facilitates the evaluation of the entire structure's
dynamic response through hybrid simulation.

Seismic isolation
layer (experimental part)

Figure 7. The objective 2-story building and numerical model.

Lateral force [kN]

40
20
0

Results using the highperformance force
measurement system25
500

E-Isolation

Results using the load cellof the dynamic jack

0

-25
-500

-20

Linear analysis results

-50
-1000

-40
-60

One bearing

50 tested by
1000

0

10

20

30

40

50

60

-75
-1500
-60
-60 -40-40 -20

70

00

20
20

40
40 60
60

Lateral displacement [mm]Time [s]Figure 8. Results of the pseudo-dynamic simulation using 800mm-diameter seismic isolator.
150

60
60
40
40

Lateral force [kN]

Lateral displacement [mm]Displacement(mm)Lateral displacement [mm]

1500
75

60

20
20

00
-20
-20
-40
-40
-60
-60

0

0

10

10

20

20

30

40

30Time [s]40
Time(s)

50

50

60

60

70

70

75
50

One bearing
tested by
E-Isolation

Results using the highperformance force
measurement system
Linear analysis results

0
-50
-75

-150
-60

-40

-20

0

20

40

60

Lateral displacement [mm]Figure 9. Results of the real-time hybrid simulation using 1200mm-diameter seismic isolator.

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6 Conclusions
Full operation of E-Isolation began in June 2023, marking the beginning of the accumulation of high-quality
data on the dynamic behavior of full-scale seismic isolation bearings and energy-dissipating dampers. With
this development, Japan is now on par with nations like the United States, China, and Taiwan, which havepioneered the development of full-scale seismic isolation testing machines. Furthermore, we believe thatJapan has been able to stay one step ahead of other countries through innovations in measurement technology.
E-isolation, serving as a third-party organization, will certify the performance of commercial seismic isolationsand vibration control components. The certification is expected to assist Japan in not only preserving but alsoenhancing its position in the field of seismic isolation and vibration control technologies. In addition, if theworld's largest three-dimensional shaking table, E-Defense, were paired with E-Isolation (to be locatedadjacent to E-Defense) and complemented by a supercomputer, such a comprehensive setup would be
expected to bolster forefront role in earthquake engineering education and research in the world.

7 Acknowledgments
This work was partially supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial
Strategic Innovation Promotion Program (SIP), Enhancement of National Resilience against Natural Disasters(Funding agency: National Institute for Earth Science and Disaster Resilience) and JSPS KAKENHI Grant-inAid for Scientific Research(A) Grant Number JP21H04574. The authors would like to express their deepest
gratitude to all those who contributed to this research project.

8 References
Takahashi Y., Takeuchi T., Kishiki S., Yoneda M., Wada A. (2023) E-Isolation–High-performance dynamic
testing installation for seismic isolation bearings and damping devices, International Journal of High-risebuildings, 12(1), 1-13.
Takeuchi T, Takahashi Y., Umemura Y., Terazawa Y., Uemura K., Ueda T. (2023): Scaled dynamic loading
tests on seismic isolation bearing excluding the contamination of friction and inertia forces, Engineering
Structures, (296), 116844.
Benzoni, G., Seible, F. (1998). Design of the Caltrans seismic response modification device (SRMD) test
facility, Research co-ordination meeting of the IAEA's co-ordinated research programme onintercomparison of analysis methods for seismically isolated nuclear structures, pp. 101-115.
Kasai, K., Sakata, H., Komehana, S., Miyashita, Y. (2004). Experimental study on dynamic behavior of timber
frame with viscoelastic damper (in Japanese), Journal of Structural Engineering (AIJ), 50B, pp. 349-360.
Hakuno, M., Shidawara, M., Hara, T. (1969). Dynamic destructive test of a cantilever beam controlled by ananalog computer (in Japanese). Journal of JSCE, No.171, pp.1-9.
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Takahashi, Y., and Fenves, G.L. (2006). Software framework for distributed experimental-computational
simulation of structural systems, Earthquake Engineering and Structural Dynamics, Vol. 35, pp. 267-291.
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