SEWC (Structural Engineers World Congress) Seoul October 2023

E-Isolation—Design of Japan’s First Full-Scale Seismic
Isolation Testing Facility.
*Takahiro Nakajima1), Masayoshi Takazawa1), Yozo Shinozaki1)
Yoshikazu Takahashi2), Toru Takeuchi3), Shoichi Kishiki4), Masako Yoneda3)and Akira Wada5)1) TAISEI Corporation,1-25-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-0606, Japan2) Kyoto University, Nishikyo-ku, Kyoto, Japan, 615-8540
3) Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo, Japan, 152-8550
4) Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa,Japan, 226-8503
5) Tokyo Institute of Technology1)

t-nkjm@arch.taisei.co.jp

ABSTRACTIn Japan, the seismic isolations and damping materials used are diversifying
and increasing in size due to the application to various civil engineering andbuilding structures. However, the mechanical properties of these members havenot been sufficiently experimentally verified. Many engineers understood thatdynamic tests using full-scale members were necessary to verify andunderstand the dynamic characteristics of seismic isolation bearing members
under vertical loads. Since there was no "testing facility", verification byexperiment was difficult. However, in 2023, Japan's first "full-scale seismic
isolation testing facility" was completed and started operation. In this paper, wewould like to describe the mechanism and features of this testing facility calledas E-isolation.
1. INTRODUCTION
The "full-scale seismic isolation testing facility" designed this time is the firsttesting facility in Japan that can excite the high-speed and large deformationthat occurs during an actual earthquake while applying a vertical load of up to36,000kN. And this testing facility was built adjacent to the full-scale threedimensional seismic destruction test facility "E-Defense" in Miki City, Hyogo
Prefecture. The building's large shaking table and full-fledged seismic isolation
testing machine are installed in one place, and it is expected to become a basefor seismic structure research around the world.

Fig. 1 Facility Appearance

Fig. 2 Facility Interior

2. DEVICE OVERVIEW
E-Isolation's full-scale testing machine has a vertical load capacity of 36,000kN(static), 30,000 kN(dynamic), stroke limit of 250mm and velocity capacity of70 mm/sec. In the horizontal direction, dynamic single directional loading
capacity is 6,500 kN(static), 5,100 kN(dynamic) with ±1,300 mm stroke limit andthe max velocity is 800 mm/sec.
The specimen is placed in a sandwich between 24 vertical dynamic jacks
placed side by side on the bottom plate against the vertical direction and thecenter of the upper reaction beam span, as shown in the Fig 3.
Compressive axial forces are applied
to this specimen. The reaction beams
and bottom plate are held incompression by a total of 48 unbonded
PC steel strands inserted into thesidewalls of the concrete dock andsubjected to a constant prestressing
force of 50,000kN. On the other hand,horizontal loads are applied
dynamically by means of horizontal
dynamic jacks to the upper moving
plate, which is placed on bearings
arranged on the lower moving plate in
the Fig 3. The reaction beam is
supported horizontally by V-shaped
reaction measurement links androtational constraint reaction force
measurement links, and is elastically
fixed to the dock RC frame in thehorizontal plane via "12 units of natural
rubber laminated rubber with noholes”.

Fig 3 Overview of Measuring Equipment

3. DEVICE CONCEPTThe new E-Isolation full-scale testing machine, as shown in Fig 4, consists of
12 natural rubber laminated bearings mounted on a rigid RC bearing wall, withthe test specimen mounted on the center underside of the wall. 4 reaction force
measurement links are horizontally connected between the reaction beam andthe rigid RC reaction wall. Majority of the horizontal reaction force is measured
in real-time through these force-measurement links, and since the reaction
beam moves minimally, almost no inertia force is generated. Furthermore, bysupporting the reaction beam with elastomeric bearings, less than 1% horizontal
force is transmitted through the support layer. To keep the bearings undercompression, pre-tensioned PC strands are provided, while the horizontal
stiffness with their P-Δ effects can also accurately be captured because theirtension forces are unchanged.

Fig 4. Comparison between the conventional system and the proposed
measurement system
The parallelogram hysteresis loop
shown in green is the load history fromthe horizontal dynamic jack, and the black
loop with almost no hysteresis ismeasured with four load measurement
links. Until now, in the measurements
conducted in Japan, the results ofhorizontal jacking have been corrected
and judged based on the frictional forceof the bearings and the results ofexperiments using reduced-size test
specimens. With E-Isolation, we canobserve the behavior of full-scale seismic
isolation members and check theirperformance in real time without
modifying them.

Fig 5 Verification test results using
laminated rubber

4. REACTION STEEL BEAM AND RC WALL
The RC reaction wall has been designed to withstand future extension to50,000 kN vertical loading capacity with a two-dimensional horizontal excitingplan. The reaction beam has 11 m clear span, the thickness of the reaction
walls is 3.50 m, and the foundation thickness is 4.5 m. Prestressing is
implemented in the foundation and walls, for preventing cracks in these
concrete walls.To allow the expected horizontal movement of the reaction
beam, PC strands have been placed in sheath tubes with 190.7 mm diameter.
The 11.52 m tall sheath tubes are precisely installed into the RC reaction walls
within 1/650 error margin, using template frameworks.

Fig 6 Plan and cross section of the full-scale seismic isolation tester

Fig 7 Pictures of PC Strand during construction and after completion
5. CONCLUSION
Unlike existing facilities in the world, E-Isolation is a high-performanceexperimental facility that can obtain experimental results in real time. By using
this facility, it has become possible to conduct various new experiments, suchas hybrid simulations that connect experimental results and analysis in virtual
space in real time.
REFERENCES
Yoshikazu Takahashi et al (2023), “E-Isolation--High-performance Dynamic
Testing Installation for Seismic Isolation Bearings and Damping Devices”
International Journal of High-Rise Buildings March 2023, vol12, No1, 1-13