Nakata, Yuki

Ohgi, Kohei

Ohuchi, Hajime

Tsunokake, Hisao

Osaka City University Repository

A Horizontal Loading Test of Viaduct Structure Model Retrofitted by Arc Shaped Damper
Kohei OHGI*, Yuki NAKATA**, Hajime OHUCHI*** and Hisao TSUNOKAKE****
(Received September 30, 2009)
Synopsis
When considering social function of railway viaduct as infrastructure, less damage is expected even against
significant earthquake such as the future Tokai and the Tonankai Ealihquake. Response control technique with
damping device can be one of alternative solutions. In responding, authors have developed the arc shaped
damper retrofit technique. In order to investigate applicability of the proposed damper to rail way viaduct
structures, horizontal loading test for verification were conducted focusing on strengthening and response
control effect. Following results were obtained: the existing structure model provided post yielding shear
failure, while retrofitted structure model assured flexural yielding ductile behavior with high energy absorption.
KEYWORDS: Arc Shaped Damper, Rail Way Viaduct Structure, Response Control
1. Introduction
In the current seismic design standard for rail way viaduct structures, less damage should be required against
the design earthquake action of level I from less recovery aspect, while collapse prevention should be required
against that of level 2 from Iife safety aspect. I) On the other hand, many existing structures designed by
previous specifications are to tend to fail in shear owing to less ductility with less amount of shear
reinforcement. As a seismic retrofit of these structures, jacketing method has been commonly employed.
r----------
r--..,
;-T"'!"_...._ ....._-+-"
I
I
I
I
I
Mil
IvI II A;111
-- After Application - - - - Before Application
(a) Dampers installation (b) Bending Moment Diagram (c) Shearing Force Diagram
Fig.1 Retrofit Strategy of Railway Viaduct by using Arc Shaped Dampers
* Student, Master Course of Department of Civil Engineering
** Researcher, Railway Technical Research Institute, Japan
*** Professor, Dep3liment of Civil Engineering
**** Research Associate. Department of Civil Engineering
- 45-
However, considering their social function of infrastructure, an early recovery and less damage should be also
desired against the level 2 action.
In these backgrounds, as an effective seismic retrofit method, we have developed an arc shaped steel damper
installed at each comers of a portal frame structures as shown in Fig.l, which is to prevent a brittle failure and to
assure damage control Noticeable features of the damper are as follows: First, buckling prevention of itself with
its arc configuration. Second, larger distribution of plastic region for energy absorption Therefore, the following
enhancements are assured, if the dampers are installed as shown in Fig. I(a); First, strengthening of entire
structure. Second, action of shear force decrease from broken lines to solid lines nearby the base of the columns as
shown in Fig.1 (c). Third, shear capacity increase expected due to deep beam action 4ft around the middle portion
of the column also as shown in Fig.l(c) Last, seismic response reduction with a high damping effect. In addition,
the comer an'angement of the damper could draw an open space for usage within the viaduct as shown in Fig.l(a).
An analysis and corresponding experiment for the sole damper has been already conducted. In this paper, the
effectiveness of the damper under cyclic loading is reported from a series of small scaled reinforced concrete
viaduct model test results.
2. Experimental
2.1 Test Specimens
The parameters of all the four model specimens are listed in Table.I. Bearing force ratio herein is defined as a
ratio of shear capacity to horizontal force when bending moments at all column ends reach its flexural capacity,
those values are calculated for the column without retrofit. The first character of the tag as N or R indicates the
specimen without or with the retrofit relevant to the tl'lird column of the table. Another parameter was volumetric
shear reinforcement ratio of the columns varying from 0.05 to 0.25%, which reflects directly on the shear
capacities of the columns,
The scale of the specimens was almost one-fifth of that of an ordinary reinforced concrete railway portal framed
viaduct. A typical specimen we used as shown in Fig.2 were designed based upon STANDARD
SPECIFICATIONS FOR CONCRETE STRUCTUREszl, FUlthermore, the dimensions of the damper of SS400
grade steel are also shown in Fig.3, The dampers were installed to the model with PC steel rod passed through in a
frame.
The reinforcement's an'angement for the specimen of N 15, also identical to R IS, having a shear reinforcement
ratio of O. 15% is shown in Fig.4. Shear reinforcement rebars used in N 15, R 15 and R25 specimens were 04 as a
manufactured deformed steel bar with a nominal diameter of 4mm, while those of R05 were 02, Therefore,
according to the prescribed shear reinforcement ratios in Table 1, the intervals of the bars, so-called hoop-ties
were determined 54mm in R25, and 67mm in R05. Furthermore, the material propelties of the damper, concrete
and rebar are shown in Table 2.
- 46-
Table 1 Parameters of Specimens
Specimens Shear reinforcement ratio(%) Retrofit Bearing force ratio
NI5 0.15 without 1.09
R15 0.15 with 1.09
R05 0.05 with 0.81
R25 0.25 with 1.35
650
Fig.2 Overview of Specimen (unit:mm)
Straight se~tion
: 80 :
R--442
Straight setition
: 80 :
Fig.3 Dimensions of Damper (unit:mm)
- 47-
R--442
t=16
I 185 I 22@50 I 185 I
I
(3)Shear reinforcement rebar D6
l4)She~r reinforcement rebar D6
I I
/ /--# (:1 )Axial rein forcement rebar 016E ~ E . ~ I
---------- - -
'//
l l I h'"i , I o...J/ :3~ l >-~w-cb; 1 ~ ~. Il ! l ~Li-: N
L reinfOrCement~ ----------- --(8)Shear r inforcement rebar D4V
.......
.. ~.
0
~~
-
~. ','
i;I ~
" J§l
p
..
-- - ----- --
y 0~'iE '<~~§ ~ 00......
\ (,
\« ~r' i~ .. : ----- --I II I(6)F.ootink Shear reinforcement rebar D13Front view )Footing Axial rbinforcement rebar D13
I II
I I
I I
145 265 7@150 265 : 145:
I I I~
FigA Reinforcement's Arrangements (unit:mm)
Table 2 Material properties
Materials Properties Values
Elastic Modulus(GPa) 200
damper ss400 Yield Stress(Mpa) 289
Poisson's Ratio 0.3
Compressive Stress(Mpa) 23.4
N15 Elastic Modulus(GPa) 25.4
Poisson's Ratio 0.18
Compressive Stress(Mpa) 25.6
concrete R15 Elastic Modulus(GPa) 27.6
Poisson's Ratio 0.22
Compressive Stress(Mpa) 25.4
R05,R25 Elastic Modulus(GPa) 24.6
Poisson's Ratio 0.18
016 Elastic Modulus(GPa) 177Yield Stress(Mpa) 368
013 Elastic Modulus(GPa) 178Yield Stress(Mpa) 361
rebar Elastic ModulusCGPa) 25404 Yield Stress(Mpa) 441
02 Elastic ModulusCGPa) 163Yield Stress(Mpa) 350
- 48 -
2.2 Test Procedure
The specimen and a testing setup are shown in Fig.5. Loading device consists of a portal reaction frame, two
hydraulic jacks horizontally arranged for loading, H-section steel at bottom for fixing the specimen, load meter for
measurement and spherical washer and Teflon film for adjusting lean.
The program of loading due to an incremental and reversal displacement as a drift angle is shown in Fig.6.
(a) Overall view
Spherical washer
jack
Interfilling steel
(b) Detail view
Fig.5 Specimen and Testing Setup
- 49-
0.08
0.06
<0 0.04
ro
~ 0.02
~ 0
<{
¢: -0.02
;§ -0.04
-0.06
-0.08
time
Fig.6 The program of loading
3. Test Results
3.1 Crack Pattern
The crack pattern ofN 15 specimen is shown in Fig.7. There was a diagonal shear crack in the bottom portion of
the right column. Crack concentration could be also observed at both the columns' ends, while no crack could be
found in middle portion of both the columns. Flowingly, local compressive failure occurred at both the columns'
ends. However, the specimen failed in shear at last.
The crack patterns of three of R series specimens are shown in Figs. 8, 9 and 10. There was a diagonal shear
crack in the middle portion of the column in both of R 15 and R25 specimens. Consequently, a shear failure did not
occurred, because their shear capacities increased owing to a deep beam action in their column middle portions.
R05 specimen, however, failed in shear because of a lack of shear reinforcement amount.
From the above observation, it could be said that the damper installation might make the column failure mode
from in shear to in flexural.
Loading to right
Loading to left
Crush
[I]
[I]
Exfoliation•
Fig.7 Cracking Pattern of N15 Specimen
- 50 -
[III]
,/
1 I
Loading to right
Loading to left
Crush
Exfoliation
Fig.8 Cracking Pattern ofRIS Specimen
~i i.e.. ..-L.. i'-.-r: ,....-
Loading to right
Loading to left
Crush
Exfoliation
[v]
Fig.9 Cracking Pattern ofROS Specimen
- 51 -
Loading to right
Loading to left
~ Crush
• Exfoliation
[VII]
Fig.10 Cracking Pattern ofR25 Specimen
3.2 Load-Drift Angle Relationships
Relations between horizontal load and drift angle of column of N 15 and R 15 specimens are shown in Fig.H.
Both of the rigidity and load carrying capacity of R 15 were superior to those of N15, in which the latter of R 15
was about 1.4 times of that of N15. It was obvious evidence that the damper installation led an enhancement of
load carrying capacity. In addition, the area of R15 loop was also larger than that of N15, which of area is an
impoliant index of energy absorption.
Furthermore, load-drift angle relationships of R05 and R25 specimens are shown in Fig.12. The rigidity and
load carrying capacity of R05 are as same as those of R25 until drift angle attained at 4/1 00. R25 is flexural failure
type, although its load carrying capacity was not impaired when its deformation was so large, because of strain
hardening of damper. R05 is shear failure type, whose load carrying capacity fell clown abruptly. Finally, these
results of all the specimens are summarized in Table 3.
- 52 -
N15 Axial reinforcement rebar yield
R15 Axial reinforcement rebar yield
Damper yield
Shear failure
0.060.040.02
---N15
.....•. R15
•
•
...
•
o
Drift Angle(rad)
-0.02
100
80 - - - - -
60
40
20
o
-20
-40
-60
-80
-100
-0.06 -0.04
z
~
"6
'"o
....J
Fig.ll Load-Drift angle relationship ofNIS and RIS
- - - - - - - - - - --- R05
__________ R25
• Shear failure
__________ L..-~~--:;;~~=c...::.J
100
80
60
40
20
o
-20
-40
-60
-80
-100
-0.06 -0.04 -0.02 o
Drift Angle(rad)
0.02 0.04 0.06
Fig.12 Load-Drift angle relationship ofROS and R2S
Table 3 Test Results
Specimens Yielding State llaximum IOHe Ultimate State Failure TypeDrift Angle Rv(rad Load P,,(kN) Pm",,(kN) Drift Angle RJrad Ductility Factor PlI
NI5 Rv--O.OO8 Pv--40.8 Pm",,-59.8 Ru--O.058 PlI-7.9 "Shear Eaili:irem
R!5 Rv=O.O 13 Pv=66.6 Pllla,=87.7 RlI>O.092 PlI>8.0 Flexural Failure
R05 Rv=O.OI2 Pv=62.! Pllla,=87.1 RlI=O.045 PlI=4.2 Shear FaiLqtei;
R25 R,,=O.O 13 P,,=63.5 Pllla,=87.7 RlI>O.091 PlI>8.1 Flexural Failure
3.3 Hysteretic Damping
Equivalent viscous damping factors of all the specimens are shown in Fig.13, those are calculated when their
drift angle attained to III 00, 21 100, 3/100, 4/100, 5/100 and 6/! 00. The factors of R series specimens were higher
- 53 -
than that ofN series specimen as their drift angle became larger.
0.20
bD 0.18
c
.~ 0.16
~ ~0.14
<h C"
:> '"8 6 012.~ B
> "00.10
+' '"
] 4- 0.08
'"
·S 0.06
C"
w 0.04
0.02
1-----~5>-"'-------____I ~N151--------i
1----#7 '--------____1 -- R15 1 -----i
-k-R05
1------K----7''----------____I -x'- R25 1--------j
1/100 2/100 3/100 4/100
Drift Angle(rad)
5/100 6/100
Fig.13 Equivalent viscous damping factor
4. Concluding Remarks
From the loading tests, followings are concluded.
1) Existing structure can be shifted from shear failure to flexural failure type by the present damper retrofit
technique.
2) Retrofitted series specimens provided 1.4 times loading capacity of existing model specimen.
3) Equivalent viscous damping factor of retrofitted specimen is higher than that of existing model in the large
displacement range.
REFERENCES
1) Railway Technical Research Institute: The Model Code for Design of Concrete Railway Structures (2004) (in
Japanese)
2) Japan Society of Civil Engineers: STANDARD SPECIFICATIONS FOR CONCRETE STRUCTURES -1996,
Seismic Design (1996) (in Japanese)
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A Horizontal Loading Test of Viaduct Structure Model Retrofitted by Arc Shaped Damper

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A Horizontal Loading Test of Viaduct Structure Model Retrofitted by Arc Shaped Damper

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