1 2WCEE空州02823

APPLICATION OF THE POWERFUL TMD AS A MEASURE FOR SEISMICRETROFIT OF OLD BRIDGESTakeyasu SUZUKIl, Isao KANEK02 And Touta KATSUKAWA3SUMMARYAuthors have developed a seismic control device which can counter excessive defamation inbridges due to large‑scale earthquakes, called the Power丘II TMD. It provides higher damplng thana conventional TMD by utilizlng the pnnciple of lever. Originally, lt Was developed to be applied
to newly designed bridges. But it is possible to apply the device to an old bridge f♭r increaslng

apparent damplng Ofthe bridge as a measure for seismic retrofit. In this paper, authors conducted
non‑linear ea仙quake response analyses of two existlng bridges to examine an application of thedevice to old bhdges which requlre Seismic retrofitting.Asa result, it was proved that the device
could be available as a measure for the seismic retrofit ofold bridges.

INTRODUCTION
The Power凡ll TMD is a seismic control device which was developed in order to improve the damplng Capabilityof a conventional TMD considerably. The device is attached to a bridgegirder and is compulsorily shaken by
the reaction force from a bridge abutment or a bridge plerwithout any external energy. Tt was developed to beapplied to newly designed bridges･ Fo‑ulation or equation of motion, optimum tunlng and numericalsimulations were conducted rigorously fわr a 2‑DOF system lKaneko et al･, 1994]･ Shaking table tests using aslmPle bridge model were also carried out to verify the validity of formulation and the seismic control effect for
the Powerful TMD lKaneko et a1., 1995].

After the Hyogoken‑Nanbu earthquake of 1995, major measures for seismic retrofit ofold bridges include use ofhigh damplng rubber beanngs and reinforcement of bridge plerS With steel jackets. When high damplng rubber
beanngs are applied to an old bridge constructed on so氏ground whose natural frequency lS more than 0.6
seconds, Type lH ground condition 【Japan Road Association, 1996], the bridge is in danger orresonance. In thiscase, the Powerful TMD performs better･ On the other hand, when seismic retrofit work of an old bridge pler
constructed in the water is carried out, temporary coffering work should be conducted flrSt before strengthening
piers･ In general, the cost needed for coffering is much more expensive than that fわr strengtheming work itself.
The Powerful TMD is preferable in this case as well, because it does not need temporary coffe血g work. Thus,

it has become urgently necessary to examine if the Powerful TMDmight replace the seismic retrofit of oldbridges.

In response to such necesslty, authors examined an application of the device to old bridges which requlre Seismic
retro紬ing･ Numerical analyses were conducted and methods to attach the device to old girders were examined,

selectlng eXistlng bridges as subject. In this paper, the outline and design method of the device are describedfirst･ Then, two examples of seismic retrofit design fTor two different types of existlng Old bridges uslng thePowerful TMD are presented.

I Technical Research & Development lnstEEute･ KILmagaL'GumL'Co･,エtd･ 1043 0nigaklLbo･ TsILkuba‑ski, Lbaraki 3()0‑2651, JapanI Technical Research & Development lnstitule･ Kumagai GumL･ Co･･ LEd･ 1043 0nigakubo. TsLLklLba‑shL･, ]baraki 300‑2651. Japan3TechnL･cal Research & Development lnsIL･tute･ Kumagai GILmi Co･･ Ltd･ Il)43 0nL･gakubo･ Tsukuba‑shi･ lbaraki 300‑265I, Japanln response to such necessity, authors examined an application of the device to old bridges which require

seismic retrofitting. Numerical analyses were conducted and methods to attach the device to old girders wereexamined, selectmg existing bridges as subject. h this paper, the outline and design method of the device aredescribed first. Then, two examples of seismic retrofit design for two differenttypes of existing old bridges
uslng the Powerful TMD are presented･2. OUTLINE AND DESIGN METHOD OF THE POWERFUL TMD
2.1 OUTLINE OF THE POWERFUL TMD
Figure I illustrates a schematic diagram to representthe function of the Powerful TMDI The device should beplaced at a bridge girder which is close to an abutment or a p上er, pOSSeSlng movable bearlngS･ Although theconcept of the device is based on conventional passive TMD, a TMD system is not simply rlXed at a bridge
deck directly but is fixed at a steel frame which is able to slide freely on a bridge deckinthe longitudinal
direction. The steel frame is connected to an abutment through a lever.
Jlridge Girder

LeyerTMDrLiJ 剪T儡teel Fmme

剪ｔ鋳∫AbtmerLt 裕｢.̲IlLui.)̲pp 僮l′tJ'I rip ripド劔劔白窒■■‑I‑I(rL‑I)P(rL‑I

FigtJre 1: A schematic diagram to represent the function of the Powerful TMD◆一一二一一uG

Figure 2: A schematic diagram to represent the dynamic model for the Powerful TMD
If the arm ratio of the lever is rL and the relative displacement between a bridge deck and a abutment due toearthquake excitation is us as shown in the figure,the TMD is compulsorily shakenwith an amplitude of rLuS,
which is rL times larger than that ofa bridge deck. When the control force, P is applied by the TMD excitation,フ

it is transmitted to the bridge deck after beingamplified by rL times･ Therefore, we can obtain a seismic
control force rL times largerthan that obtained by a conventional TMDwithout any external energy adoption･
The dynamic model for the Powerful TMD is illustrated in Figure 2･

2.2 DESIGN METHOD OF THE POWERFUL TMJ)
The design of the Powerful TMD is based on the optimum tuning for harmonic excitation lDen Hartog, 1956]･
The optimum frequency v.,( is calculated using Eq･(1)･ And the optimum damping h.,( is calculated usingEq.(2).

(1)

(2)

where, p is the ratio of mass ofa TMD to that ofa bridge structure. An increment of apparent damplng Of abridge structure due to the device is evaluated by the effective damplng ratio heff･ This is denned as follows:

7hl rL2 IW
hen = Ch(3)

(V2 ‑1)2 +(2中)2where, ch is the parameter which depends on the irregularity of earthquakes (=0.7), v is the ratio of natural&equency ofa TMD to that ofa bridge structure,and hT is the damplng ratio of the TMD. Figure 3 shows thevariations of effective damplng ratio of the optimized devicewith respect to mass ratio LL fわr six different

values of the arm ratio rL.

0.や6u!guec)瓜^!p卦 30 25 20 1 5 1 0
rL 白 I 6圭r r r 氾ﾒ ﾇ ﾇ 5 4 ●3rL 偃X,brL 偃V｢0.05

0.00

56789

2340.01

56789
0.1

Mass Ratio, IFigtJre 3: Variations of effective damplng ratio of the optimized device

with respect to mass ratio p3

3. EXAMPLES OF THE SEISMIC RETROFIT DESIGN
3.I EXAMPLE‑I ( BRIDGE‑I)

The outline of Bridgel1 is showninTable 1,and Figure 1 is its elevation･ The seismic retrofit design for thisbridge has been conducted based on uReference for Applying the Guide Specifications for Reconstruction andRepalr Of Highway Bridges which Suffered Damage in the Hyogoken Nanbu Earthquake, to New Highway
Bridges and Seismic Strengthening" lJapan RoadAssociation, 1995]･ At first, reinforcing the bridge pierswith
RC jackets was adopted as a measure for seismic retrofit･ But temporary coffering work had to be conductedfirst before strengthening of piers because plerS With fixed bearlngS had been constructed in the water･ The

cost needed for coffering work is much more expensive thanthat for strengthening work itself･ And then,applying the seismic control device to the bridge was examined as a substitute to the first measure of seismic
retrofit. Parameters for the device are showninTable 2.

Table 1: OtJtline of Bridge‑I
Typeofsuperstructure 牌W&&W"ﾗGLength鼎W7FVVﾇﾒｳcWidthGv

Typeofpiers

6FVv

FW&'&芳vR

6Cﾒ

ﾒﾓ

ﾒｵ6芳Wv

Weightofsuperstructure
fTypeoffbundation

ﾆﾒｳC

#ﾃ綏ﾒｴ

ﾇ6VG

FVVﾂ

免Rﾈ

Typeofsoil 膝認T粕殆&Yearofconstruction

ﾆｳ$

跏V7FVBV襷6妨"ﾄc

V没④｣

ﾖﾕ

ﾓSB

繝Vﾒ
ﾒ

襷友柳

都"

二二二二重二二二二二±諾.二二二二=三ホ二二:Figtlre 4: Jlridge‑1 elevation

Table 2: Parameters for the device for Bridgell (Total)

Lever
Armratioofthelever

磐77&F鑓網B
ｸｲ

Natural斤equencyratiovoot

5.00.阜oo

認ﾗﾆ誣&F柳sB

The devices were installed on two abutmentswith movable bearings (Al, A2) as shown in Figure 4･ From theresults of the non‑linear earthquake responseanalyses uslng earthquakeinputs for TypelII ground conditionlJapan RoadAssociation, 1996], it was confirmed that the bridgewith the device was safe during a Level 2
Earthquake input 【Japan Road Association, 1996】.

The load‑displacement diagram for pier Pl is shown in Figure 51 The allowable ductility factor p of this pier iscalculated at the time when the concrete cover of this pler cones Off, Since it has been assumed that fixing of
the hoops of this pler Was not enough. Figure 6 shows one of the results of the numerical analyses. As shownin this figure, the maximum displacement ･ when the control device is used, is almost the yield displacement 8,,4

5

Figure7: Struc a)drwlngOfthesimcontr devicdesigndforBidge･1690(Type｣,TypeIt groundcondit on,No,2)

Figure6:Comparisnoftheim storiefhdisptacemnofthebridwthaniouthedvic

Time(sec)
30tJ

lC)

tJ

Displacement (cm)FigtJre5: Load･isplacemntdiagrmforpierPtofBridge･lDisptacement8(cm)u⊂)t^⊂〉ち H tJ ヽ一〇 ( tJ ■‑ 0 旦⊂〉⊂〉‑▲⊂)utJ<…

(≡⊂)⊂)トJLoad P (tf)contrldevisgforBde･lishwnFgur7･disptacem n of h struc ewi h d v ce s lo t Z rO･A las ,the ruc ald w ngOfthes i m Calthoug thaIwithou 〜 ingthecontr l devic soverth al ow bledisplacem ntp8,･Andther 〜 idual

3.2 EXAMPLE‑2 ( BRIDGE‑2)
Bridge‑2 has been built over the canal dividingthe plant site into two areas･ It is important to resume

operations early after a large earthquake･ So the seismic retrofit design for this bridge has been conductedbased on "Design SpecirlCations of Highway Bridges ‑ Part V Seismic Design" lJapan RoadAssociation,1996].

The outline of Bridgel2 is shown in Table 3, and Figure 8 shows its elevation･ The structure of pier P2 isdouble‑layer RC rigid‑frame･ At first, the ultimate horizontal strength duringanearlhquake of this pler Was
checked by conducting static non‑linear analysIS･ Figure 9 shows the analytical modeL From the study, it wasconfirmed that the pler is safe if shearlng Strength of two piers Of the first layer is reinforced･ The load‑

displacement diagram for pier P2 is showninFigure 10･Table 3: Outline of Bridge‑2
Typeofsuperstructure 彦

Length田VW7

蹤也VW77FVVﾆ&綰ﾒｳ

ﾒｳc

WidthGv
Weightofsuperstructure
Typeofpier

認V&ﾆRﾓTypeofsoil

膝v

FW&'&芳vR綰ﾒﾒｴ

妨%$7&没蓬自]Typeoffbundation 杷ﾖW

妨"ﾄV没④｣

繝Vﾒ

F匁r

XuFw&Yearofconstruction

ﾒﾓ#V襷6

襷友柳

田R

Figure 8: Bridge‑2 elevation

Furthermorethe non‑linear earthquake responseanalysIS using earthquake inputs for Type I ground condition

was conducted, since this bridge is important andanunlque StruCture･ It was found thatthe maximum
displacements depended on the characteristics of the phase of those Inputs,and in one case,that the value wasoverthe allowable displacement. So the seismic control device instaHed on the bridge was examined･
Parameters for the device are shown in Table 4. From the results of the nonllineaT earthquake response

analyses, it was confirmed thatthe bridge with the device was safe, thoughthe mass ratio (p=0.003) was
smaller thangeneral mass ratio (p=0.01). For example, the comparison of time histories of displacement of

the bridge girder with andwithout the device is shown in Figure ll. At last, the structural drawlng Ofthe

seismic control device designed for Bridge‑2 is shown in Figure 12.

6Plside.8000P3side町←p2p. ▼■■■一ケ■一一二■■■■ー■■■ 劔tJl

Non‑linear rocking
spnng element

DKLH‑ Rigid area
Linear beam elementrヽl√ーOヽ"

trlll〇､cI,Gi⊂⊃ くつヽ α) ﾓﾒ ⊂⊃⊂)一 ̀ NB'Fく=)汎韮rーrヽ

t′1

劔

綿ﾈｲ

くつヽ⊂hAEl

VyWm/Figure 9: Analytical model for pier P2 ofJ}ridge‑2 for static non‑Iinearanalysjs′hU42iiiil00 00 00P≡p由12.5

粕､TUﾅｲ劔A‑O))u+l』pt!01
J■̀……ro=383.3≡1■■■■■■

qH

0.00て寸 ;qt=〉｢⊂⊃ ̲JLh̲.̲̲."̲̲ >■■ く′○
lー0.05

1■‑>ヽ

免ﾂ

0. 10

披

辻ｲｲｲ簫ｺ3ｲ

Yeild Ultimate

5"

0. 15

0.20

0.25

0.30

0.35

0.40

Displacement 81 (m)Figure 10: Load‑displacement diagram for pier P2 ofBridge12

Table 4: Parameters for the device for Bridge‑2

Lever
Armratioofthelever 磐 77&

疋ﾔBF薮
Naturalfrequencyratiov.0. 認

5.02

ﾗ0.924ﾆ誣&F柳c日.1'..一一 I I 剿ﾆﾂ粐r粐 ;.'1.1'l:‑I..ll.:li.'甘ii 窒粭# 粐粐苴｣｢貲GB粤I̲:̲I.:..1'.Jヽ.'t..㌔.T(u3) Uau93t2tds!Q
ヽ 一.:1...Tt.I..' 劍甁r粐I ∫ 汎T停rﾔ免ﾂﾔ貞ｧB‑..I 稗簓"篦■ ●F耳而Br示ﾂ｢罎tJt:I.'日.. 宥'BﾕEB穩ﾒﾒ

ﾃ簫簫ﾒ粤｢r粐

I..1.‑I,‑一‑tr‑〟.‑白爾‑■■■

51015202530

Time (sec)Figure ll.' Comparison of the time histories of displacement of the bride girderwith and without thedevice (Type‑I, Type I ground condition, No･1)

7B

Figure 12: Structural drawing Ofthe seismic control device designed for Bridge‑2

4. CONCLUSIONS

Tn this paper, a measure for seismic retrofit of existing old bridges uslng the seismic control device isintroducedwith some examples of seismic retrofit design. The measure makes use of the effectiveness ofdamping Ofthe device, So that it reduced not only the acceleration of bridge girder but displacementalso. That
is why this measure is a good application to existing old bridges, Since it restricts the displacement within theallowable limit of the girder. Especially, since the displacements of bridges constructed on Type Ill groundcondition are large, the measure is expected as a substitute for seismic isolation.

REFERENCES

Hartog, JP. Den (1 956), Mechanical Vibrations, 4th edn., McGraw‑Hill, New York.
Kaneko ISAO et al., (1994), "A seismic control device based on TMD with the simple mechanism f♭r control

force amplification", PT･OC. 9(hJEES, 1861‑1866. (in Japanese), Kaneko tSAO et al., (1995), "Shaking table

test of the Powerful TMD", Proc.23rdJSCE Earthq. Eng.Symp., 525‑52i. (inJapanese).

Japan RoadAssociation JRA ( 1 995), Reference for ApplyL'ng the GuL'de SpecLjicationsfor Reconstruction andRepair ofHighw町Bridges wh L‑ch SuHeredDamage in the Hyogoken Nanbu Earthquake, to New Highwqy BridgesandSeL.SmL'C Strengthe17L.ng, JRA, Tokyo, Japan RoadAssoc iation JRA ( I 996), Design Spectjications ofHL'ghwqy
Bridges ‑ Part VSet'smic Design, JRA, Tokyo.

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