BASE ISOLATION TECHNOLOGIES

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International Association of Museum Facilities Administrators (IAMFA)

The 2003 IAMFA Annual Conference in San Francisco, California

September 21-24, 2003

BASE ISOLATION TECHNOLOGIES FOR SEISMIC

PROTECTION OF MUSEUM ARTIFACTS

Bujar Myslimaj, Scott Gamble, Darron Chin-Quee and Anton Davies

Rowan Williams Davies & Irvin Inc., Consulting Engineers

650 Woodlawn Road West, Guelph, Ontario, Canada, N1K 1B8

Brian Breukelman

Motioneering Inc.

650 Woodlawn Road West, Guelph, Ontario, Canada, N1K 1B8

INTRODUCTION

Base isolation technologies have been used traditionally to improve the seismic

performance of buildings and other large structures such as bridges, etc.. In recent years the

application of base isolation has been gradually extended to smaller structures - private

housing, computer servers storing valuable data as well as in the seismic protection of

museum artifacts. Installation of base isolation systems beneath showcases or sculptures

displayed inside or outside museums provides effective protection of important and

irreplaceable cultural properties and works of art (Fig. 1). Display cases or sculptures are

often rigidly connected to the floor (Fig. 2) thus being prone to intensive shaking and damageto contents or internal structures during seismic events.

Fig. 1 Conceptual representation of a base isolation system installed beneath a pod.



Fig. 2 Current practice in museum displays.

Current seismic design codes consider showcases, preservation racks and shelves as non-

structural elements or components. Their seismic design is covered by code provisions fornon-structural elements, which focus mainly on the design of the connection of the non-

structural elements to the main structural system. Ensuring the seismic integrity of the

connection between the building structure and shelves, showcases, etc. does not guarantee the

safety of the showcase or shelf contents. Significant motion of artifacts supported on or

housed within display cases can occur, leading to damage. To improve the seismic

performance of non-structural components and avoid the permanent loss or breakage of

irreplaceable or expensive assets (Fig. 3), application of effective technologies that can

control the seismic response of non-structural components is needed.

Fig. 3 Avoiding the permanent loss or breakage of irreplaceable or expensive assets during a

seismic event should be the top priority.



RECENT DEVELOPMENTS AND APPLICATIONS

Recently developed compact base isolation systems for small-scale structures are based on

sliding, rolling and rubber bearing techniques [1,2]. The rolling type design has proved to be

very effective in improving the seismic performance of non-structural components. In Japan, a

rolling type base isolation system called Tuned Configuration Rail (TCR) has been

successfully applied during recent years in seismic base isolation of private housing, computer

servers and more widely in museum showcases [3-6]. This system consists of eight wheelsand eight tuned configuration rails installed between two parallel platforms. These platforms

can move freely against each other in one orthogonal direction only (Fig. 4), which provides

for movement in any direction in the horizontal plane. By adjusting the curvature of the rails,

the system can be tuned so that its motion in the presence of a seismic event offsets the

motion of the supporting structure. It is a simple and compact base isolation system that can

be easily installed underneath existing (Fig. 5a) or new showcases (Fig. 5b).

Fig. 4 A TCR isolator designed for small size artifacts (courtesy of AS Inc., Japan).

Fig. 5 Base isolation systems installed under existing (a) or new (b) showcases (courtesy of

AS Inc., Japan).

a b



Since the force that brings the system back to its initial/original position and the damping

force generated as a result of the friction between wheels and rails are both proportional to the

weight, the system can be easily adjusted for a wide range of museum applications. It reduces

the seismic response acceleration up to one tenth of the input excitation as shown in Fig. 6,

where the input motion (i.e. motion of the non-isolated platform) and the seismic response of

the base isolated platform in terms of acceleration are plotted for comparison. Results shown

in Fig. 6 are taken from a recent 3-dimensional seismic performance shaking table test. The

shaking table can simulate the earthquake ground motion. In the example, the inputacceleration wave corresponds to the North-South direction of ground motion recorded during

the Kobe earthquake of January 17, 1995 with peak acceleration of 818gal

(1gal=1cm/s2=0.001g, where g is gravity acceleration). Peak response acceleration of the

system is 72gal, or approximately 1/12 of the magnitude of the input motion.

Fig. 6 Shaking table test results for a TCR isolator.

Table 1 illustrates the significance of the input earthquake ground motion levels and the

output or the base-isolated motion levels shown in Fig. 6.

Depending on the showcase or display location inside the museum, the TCR design can beeasily adapted to meet the aesthetic and seismic performance requirements (Fig. 7). For the

existing showcases enclosed directly against a wall, the base isolation system can be designed

in the form of an integrated set of isolated platforms that can be installed within the

showcases, offering thus a cost and time effective solution. Applications are also not limited

to indoor locales as a TCR can be installed outdoor where valuable art works (sculptures,

statues) are often displayed (Fig. 8). For these applications the TCR’s can be readily designed

to meet stringent aesthetic and performance requirements.

INPUT ACCERALATION N/S

-1000-800-600-400

-2000

2004006008001000

0 5 10 15 20 25 30 35TIME(sec)

A C C ( g a l

OUTPUT ACCERALATION N/S

-1000-800-600-400

-2000

2004006008001000

0 5 10 15 20 25 30 35TIME(sec)

A C C ( g a l



Table 1 Overview of earthquake ground motion levels in relation to human perception and

damage potential [7]

EarthquakeIntensity

IMM Description

Approximate peak

ground horizontal

acceleration (gal)I Detected with sensitive instrumentation

II Felt by few persons on upper levels; suspendedobjects may swing

<3

III Felt noticeably indoors, but not alwaysrecognized as an earthquake; parked cars rock

slightly

3-7

IV Felt indoors by many, some people awaken;

parked cars rock noticeably7-15

V Felt by most people; cracked plaster in a few

places; disturbances of trees, poles, and othertall objects sometimes noticed

15-30

VI Felt by all; many are frightened; a few

instances of fallen plaster; slight damage 30-70San Francisco

1957VII Everybody runs outdoor; damage to buildings

varies, depending on the quality of the

construction

70-150

Taft, 1952 VIII Panel walls thrown out of frames; walls,

monuments, chimneys fall; drivers disturbed150-300

El Centro1940

IX Buildings shifted off foundations, cracked,thrown off plumb, ground cracked;

underground pipes broken

300-700

Northridge, 1994

Kobe, 1995

X Landslides; rails bent; most masonry and

framed structures destroyed; ground cracked700-1500

XI Bridges destroyed; broad fissures in ground;

earth slumps and land slips in soft ground1500-3000

XII Total destruction 3000-7000

Fig. 7 Works of art on base isolated display platforms (courtesy of AS Inc., Japan).



Fig. 8 A base isolated statue in display outside the museum (courtesy of AS Inc., Japan).

OTHER IMPORTANT CONSIDERATIONS

The evaluation of seismic performance of the base isolation systems for museum artifacts

requires detailed information on the system’s fundamental dynamic response properties (i.e.,factors affecting its characteristic motion and response to a disturbing force). In addition, a

reliable prediction of input motion characteristics (i.e., ground motion during an earthquake)

is required at the site where the museum is located. This would normally lead to additional

analyses to generate site-specific ground motions [8] or seismic design spectrum compatible

input ground motions needed for performance evaluation [9].

Besides the use of analytical methods for seismic performance evaluation, shaking table

testing has been also used to verify the seismic performance of the isolation systems. This

approach has been used in addition to the analytical one, and has proven to be very important,

particularly at the early stage of the design.

CONCLUDING REMARKS

Rolling type base isolation systems have been proven to be very effective in improving

the seismic performance of operational and functional components attached to the main

structural system. Recently, a rolling type base isolation system called Tuned Configuration

Rail (TCR) has been successfully applied during the last few years in seismic base isolation of

private housing, computer servers and more widely in museum showcases. It is a compact

isolator that significantly reduces the acceleration response and can be easily installed

underneath new or existing showcases, preservation racks, shelves and statues.

REFERENCES

1. Iiba, M., Midorikawa, M., Yamanouchi, H. and Myslimaj, B. (1999), “Three dimensional

shaking table tests on seismic behavior of isolators for houses”, Proceedings of the 30-th Joint Meeting of U.S.-Japan Panel on Wind and Seismic Effects, UJNR, May 1999,

Tsukuba, Japan.

2. Myslimaj, B., Iiba, M. and Midorikawa, M. (1999), “3-dimensional shaking table tests on

base-isolation systems for houses”, International Workshop on Seismic Isolation, Energy

Dissipation and Control of Structures, 6-8 May 1999, Guangzhou, China.

3. Yamada, C., Iiba, M., Myslimaj, B., Inoue, K., Seki, M., Hasegawa, O., Yatsuhashi, M.,

Yasui, Y. and Akimoto, M. (1999), “Three dimensional shaking table tests on seismic

behavior of isolators for houses - Part 2: Effect of bi-directional and vertical earthquake

TTHHEE NNAATTIIOONNAALL MMUUSSEEUUMM OOFF WWEESSTTEERRNN AARRTT

2 SETS OF TCR SEISMIC ISOLATORS



motions on characteristics of isolators”, Summaries of Technical Papers of Annual

Meeting of Architectural Institute of Japan, Vol. B-2, pp. 743∼744 (in Japanese).4. Inoue, K., Iiba, M., Myslimaj, B., Yamada, C., Seki, M., Hasegawa, O., Yatsuhashi, M.

and Yasui, Y. (1999), “Three dimensional shaking table tests on seismic behavior of

isolators for houses - Part 3: Effect of unbalanced weight on characteristics of isolators”,

Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan,

Vol. B-2, pp. 745∼746 (in Japanese).

5. Enomoto, T., Omori, Y., Iiba, M. and Myslimaj, B. (1999), “Three dimensional shakingtable tests on seismic behavior of isolators for houses - Part 6: Effect of base isolation on

the response of superstructure”, Summaries of Technical Papers of Annual Meeting of

Architectural Institute of Japan, Vol. B-2, pp. 751∼752 (in Japanese).

6. Egmond J.V. and Myslimaj, B. (2002), “Seismic damage control technologies for

protection of national assets and treasures”, Presentation at Public Works and

Government Services Canada, August 2002, Ottawa, Canada.

7. Richter, C.R. (1958), “Elementary Seismology” , W.H. Freeman, San Francisco.

8. Myslimaj, B. and Matsushima, Y. (1997), “Stochastically based estimation of site-

specific ground motion parameters: - A design oriented approach -”, Proceedings of the

Seventh International Conference on Computing in Civil and Building Engineering

(ICCCBE-VII), 19-21 August 1997, Seoul, Korea, VOLUME 2, pp. 1265∼1270.

9. Myslimaj, B. and Matsushima, Y. (1997), “Inelastic earthquake response of structures

accounting for local soil conditions” , Journal of Structural and Construction

Engineering, Transactions of AIJ , No. 497, pp. 47∼55.

BASE ISOLATION TECHNOLOGIES

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