STUDY ON APPLICATION OF ENERGY-DISSIPATING SACRIFICIAL DEVICE (EDSD) FOR ENHANCING SEISMIC PERFORMANCE OF GIRDER BRIDGES

Abstract

A new Energy-Dissipating Sacrificial Device (EDSD) is developed for steel plate girders, which can effectively dissipate the energy stored in the structures during seismic actions. A simplified bridge analysis method is utilized first to see the effectiveness of the EDSD, and then using a commercial FEM program, the seismic performance of the device is examined on the whole bridge system. To verify the performance of the EDSD, various seismic responses of a sample bridge with the EDSD are analyzed in terms of energy, member forces and deformation. The full scale model tests are conducted to certify the performance of the EDSD when it is applied on existing bridges. The results show that the proposed EDSD under seismic excitations can significantly decrease the energy stored in the bridge structures and reduce the relative displacements of each superstructure to the ground. The EDSD is also found to function as a structural fuse under strong ground motions, sacrificing itself to absorb the excessive energy. Consequently, economical enhancement of the seismic performance of bridges can be achieved by employing the newly developed energy-dissipating sacrificial device.

Full text

4th International Conference on Earthquake Engineering
Taipei, Taiwan
October 12-13, 2006
Paper No. 087
STUDY ON APPLICATION OF ENERGY-DISSIPATING SACRIFICIAL
DEVICE (EDSD) FOR ENHANCING SEISMIC PERFORMANCE OF
GIRDER BRIDGES
Sang-Hyo Kim1, Ho-Seong Mha2, Kwang-Il Cho3, Jeong-Hun Won4 and Jin-Hee Ahn5
ABSTRACT
A new Energy-Dissipating Sacrificial Device (EDSD) is developed for steel plate girders, which can
effectively dissipate the energy stored in the structures during seismic actions. A simplified bridge
analysis method is utilized first to see the effectiveness of the EDSD, and then using a commercial
FEM program, the seismic performance of the device is examined on the whole bridge system. To
verify the performance of the EDSD, various seismic responses of a sample bridge with the EDSD
are analyzed in terms of energy, member forces and deformation. The full scale model tests are
conducted to certify the performance of the EDSD when it is applied on existing bridges. The results
show that the proposed EDSD under seismic excitations can significantly decrease the energy stored
in the bridge structures and reduce the relative displacements of each superstructure to the ground.
The EDSD is also found to function as a structural fuse under strong ground motions, sacrificing
itself to absorb the excessive energy. Consequently, economical enhancement of the seismic
performance of bridges can be achieved by employing the newly developed energy-dissipating
sacrificial device.
Keywords: EDSD, retrofit, energy-dissipating device, seismic loads
INTRODUCTION
Various new innovative devices based on ductile design concept have been developed as solutions to
enhance seismic performances of new or existing bridges (ATC, 1983; Buckle et al. 1986; SED, 1993;
Shirole and Malik, 1993). They can be categorized into three broad areas such as the base isolation,
active control and passive energy dissipation systems. The base isolation and active control systems
are highly effective means for enhancing structural functionality and safety, but the high cost of
installations and maintenances considering Life Cycle Cost (LCC) might be an economical burden in
weak and moderate seismic regions.
On the contrary, passive energy dissipation systems are relatively low-cost, and can be used both for
seismic damage mitigation and for rehabilitation of aging or deficient structures (Soong and Spencer,
2002). These systems dissipate energy thorough simple structural behaviors, such as frictional sliding,
metal yielding, and phase transformation in metals without any expensive control systems or sensors.
This gives economical advantages for moderate seismic regions and it means that passive energy
1 Professor, Yonsei University, Seoul, Korea, sanghyo@yonsei.ac.kr
2 Associate professor, Hoseo University, Cheonahn, Korea, mhah@office.hoseo.ac.kr
3 Doctor’s course student, Yonsei University, Seoul, Korea, cky222@yonsei.ac.kr
4 Doctor’s course student, Yonsei University, Seoul, Korea, wjh0611@yonsei.ac.kr
5 Doctor’s course student, Yonsei University, Seoul, Korea, palanorange@yonsei.ac.kr

dissipation systems might be relatively proper method for the region where the possibility of seismic
occurrence is not quite high.
Eccentrically Braced Frames (EBF), Shear Panel Systems (SPS), and Triangular-plate Added
Damping and Stiffness Devices (TADAS) are examples of the most recent passive energy dissipation
systems which are using ductile end-diaphragms for seismic retrofit of steel girder bridges. The ductile
end-diaphragms are designed to show plastic behaviors before pier structures are damaged under
seismic excitation. However, each of these devices works only in transversal direction of a bridge and
has no capacity to dissipate energy in longitudinal direction of a bridge (Zharai and Bruneau, 1999;
Bruneau et al. 2002).
In this study, a new Energy-Dissipating Sacrificial Device (EDSD) is proposed, which can effectively
dissipate the energy stored in the major members, such as piers in bridges, due to the longitudinal
seismic excitations. Also, the mathematical bridge model is developed to analyze seismic performance
of a bridge with the EDSD. The seismic performance enhancement due to the application of EDSD is
examined by comparing hysteretic energy of piers on relative energy theory.
The EDSD is composed of restraining devices and sacrificial members, which are selected among the
secondary members, such as the end sway bracing. To make EDSD as an effective method for
enhancement of seismic performance, the following characteristics are required. 1) EDSD prevents
severe damage of major members such as girders or piers by dissipating excessively stored energy
through repeated plastic behavior of sacrificial members. 2) The EDSD has simple installation
procedure and can be easily replaced after damage. 3) The EDSD should not require the expensive
cost for installation and maintenance during a bridge service life.
COMPONENTS AND BEHAVIOR OF EDSD
In this study, the EDSD is developed firstly for steel plate girder bridges widely used on a middle-size
river in Korea. Fig. 1 shows one example of EDSD applied at a steel plate girder bridge. As shown in
Fig. 1, the EDSD is composed of a ductile vertical bracing (sacrificial member) and a displacement
restrainer (restraining device) for both longitudinal and transverse direction. A vertical end bracing of
a bridge is designed to have a role of an energy-dissipating device by repeated nonlinear flexural
behavior. A restraining device has relatively large stiffness and it is fixed on the top of a pier or an
abutment. Also, a restraining device will not cause any plastic behavior of a vertical bracing for the
small deformation due to the temperature change because of the designed initial gap distance between
a restrainer and a bracing. This initial gap distance makes EDSD to activate only when the relative
distance between a main girder and an adjacent substructure is larger than initial gap distance. This
behavior can be simplified as a fixed-end supported beam with initial gap distance shown as Fig. 2,
and can be represented by a simplified model, which has nonlinear spring elements with initial gap
distance in both directions as shown in Fig. 3.
Pier or Abutment
A
A
EDSD
R/C Slab
Initial Gap
Displacement
Restrainer Bracing
Restraining Device (A-A)
Figure 1. EDSD Applied at a steel plate girder bridge.

-P/2 P/2
Relative Distance
between Deck and Pier,
E,I
-P/2 P/2
r
lbr
dgap
k
dgap
gap
d
Figure 2. Simplified behavior of a sacrificial member. Figure 3. Mathematical model of EDSD.
The bi-linear hysteretic model with initial gap distance (dgap) and stiffness (k) in both directions is
shown in Fig. 4, and can be described as follows.
⎪
⎩
⎪
⎨
⎧
≤−
>−−
=)0|(|0
)0|(|)(
gapr
gaprgapr
d
ddk
P
δ
δδ
(1)
F
dgap gap
d
yt
Fy
f
-F
y
f
-
Stiffness ,k
r
Stiffness ,k
1
2
Figure 4. Hysteretic model of a sacrificial member.
PRELIMINARY ANALYSIS BY USING THE SIMPLIFIED BRIDGE MODEL
This study analyzes firstly the energy-dissipating capacity of EDSD and its effects on seismic
responses of a simple structure by using the simplified bridge analysis model. Energy responses and
displacement responses are examined to certify enhancement of seismic performance. Energy
responses are total input energy, hysteretic energy of EDSD and piers, and damping energy.
Displacement responses are relative displacement against ground motions. Total input energy (Ei’) of a
bridge structure due to the seismic excitations can be expressed as follows (Bruneau and Wang, 1996).
hskaki EEEEEEEE +++=++=
ξξ
''' (2)
where Ek’, E
ζ’ and Ea are the relative kinetic energy, damping energy, and energy absorbed in the
structure, respectively. Ea is composed of recoverable elastic strain energy, Es and irrecoverable
hysteretic energy, Eh.
A Sample Bridge and Corresponding Simplified Mathematical Model
Fig. 5 shows the configuration of the considered sample bridge, which is designed according to the
Korean Design Codes for Highway Bridges (2005) as a purpose of simulation only and each
component has minimal safety factor. The corresponding simplified mathematical model is

represented in Fig. 6, and this model can consider the effects of the friction force at a movable support,
the nonlinear behavior of piers, and the translational and rotational motions of foundations (Kim et al.,
1999).
300 16.000 300
7@2.000=14.000
1.300 1.300
250
10.0002.000
2.000
6.000
14.000
80
1.000
650
2.000
1.000
50
1.700
(a) Plan view (b) Cross section (unit: mm)
Figure 5. Configuration of a considering bridge.
S
m
m
h
m
h
u
S
u
h
u
h
u
g
u
g
m
C
m
C
K
h
h
C
K
h
C
h
r
m
r
m
K
r
C
rr
r
C
K
u
rr
u
K
C
C
C
C
L
C
K
C
L
CC
F
K
u
C
u
C
S
m
m
h
m
h
u
S
u
h
u
h
u
g
u
g
m
C
m
C
K
h
h
C
K
h
C
h
r
m
r
m
K
r
C
rr
r
C
K
u
rr
u
K
C
C
C
C
L
C
K
C
L
CC
F
K
d
K
d
G
u
C
u
C
EDSD
(a) Without EDSD (b) With EDSD
Figure 6. Simplified mathematical model with multi degrees of freedom.
Energy and Displacement Response of the Sample Bridge
Using SIMQKE code (Vanmarcke and Gasparini, 1976), 10 artificial ground motions are generated for
each PGA from 0.1g to 0.5g, which are compatible to the design spectrum of Korean Design Codes for
Highway Bridges (2000) for the seismic analysis of this section. The properties of a sacrificial member
and initial gap distance of the EDSD are designed as minimum dimensions provided with Korean
Design Codes for Highway Bridges (2000). A sacrificial member is selected as a 75mm×75mm
rectangular shape member with 10mm thickness, and the initial gap distance is set as 4cm.
Without EDSD, most of input energy is dissipated by hysteretic energy of piers as shown in Fig. 7(a).
With EDSD, large portions of input energy (about 40% of hysteretic energy of piers) are dissipated as
shown in Fig. 7(b). The little difference of total input energy is because it is changed according to the
stiffness of structure under the relative energy equilibrium equation (Uang and Bertero, 1990; Bruneau
and Wang, 1996).
Table 1 shows the mean values of the ratio of hysteretic energy to total input energy. The EDSD
reduces the hysteretic energy of pier up to 44% (PGA=0.3g) and is relatively more effective at the
range of PGA 0.2g~0.4g than other PGA ranges. It is because the response under PGA 0.1g is not
large enough to activate the EDSD frequently, and because the failure of a sacrificial member occurs
during energy dissipation process under PGA 0.5g (Fig. 8).
M F M F
F M MF
P1 P2
35m

0 5 10 15 20 25
Time [Sec]
0.0E+000
1.0E+006
2.0E+006
3.0E+006
4.0E+006
5.0E+006
E
nergy
[
k
gf
.
c
m ]
Hyst eretic E
dissipated
in Pier
Damping E
Total Input Energy
Total
Hyster etic
Energy
in Pier
0 5 10 15 20 25
Time [Sec]
0.0E+000
1.0E+006
2.0E+006
3.0E+006
4.0E+006
5.0E+006
E
nergy
[
k
gf
.
c
m]
Hyster esis E
dissipated
in Pier
Hyst eresis E
dissipated
in Device
Damping E
Total Input Energy
Total
Hyster etic
Energy
in Pier
(a) Without EDSD (b) With EDSD
Figure 7. Total input energy history with and without EDSD (PGA=0.3g).
Table 1. Hysteretic energy ratio to total input energy with EDSD
PGA 0.1g 0.2g 0.3g 0.4g 0.5g
Without EDSD 0.83 0.83 0.86 0.90 0.92
With EDSD 0.66 0.51 0.48 0.52 0.65
Decreasing Ratio 21.0% 38.6% 44.2% 42.2% 29.3%
0 5 10 15 20 25
Time (sec)
-4.0E+004
-2.0E+004
0.0E+000
2.0E+004
4.0E+004
T
o
t
al D
e
v
i
c
e
For
c
e
(
k
g
f
)
lsw
Figure 8. Force of EDSD (PGA=0.5g).
Fig. 9 shows the time histories of relative displacement between ground and P1 pier under PGA 0.2g
and 0.3g. The EDSD restrains the displacement of each vibration unit, and results in decrease of
relative response displacement. In case of PGA 0.2g, the maximum relative displacement is reduced
from 9.4cm to 8.3cm. In case of PGA 0.3g, it is reduced from 14.6cm to 11.9cm. These results can be
explained by not only the restrains effect but also the force-redistribution effect of the EDSD. The
EDSD effectively redistributes inertia force of super-structure to the adjacent P2 pier and reduce the
force of P1 pier.
0 5 10 15 20 25
Time (sec)
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
Rela
t
i
v
e D
i
spla
c
emen
t
(
c
m)
w/o sacrificial device
w/ sacrificial device
lsw
9.4cm
8.3cm
0 5 10 15 20 25
T
i
m
e
(
s
e
c
)
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
Re
l
at
i
v
e D
i
sp
l
a
c
ement (
c
m)
w/o sacrificial device
w/ sacrificial device
lsw
11.9cm
-14.6cm
(a) PGA=0.2g (b) PGA=0.3g
Figure 9. Time histories of relative displacement between ground and P1 pier with EDSD.

The mean values of the maximum relative displacements between ground and P1 pier are listed in
Table 2, as results of simulations with 10 ground motions for each PGA. Large decreasing of
maximum relative displacements is obtained by application of the EDSD, and this decreasing rate
becomes larger with increasing PGA. On the contrary, this decreasing rate is dropped when PGA is
lager than 0.5g, and it is because failure of a sacrificial member. Although the sacrificial member
reaches at failure state, before failure it still has significant role of dissipating large energy that is
generated at early stage of seismic excitation.
Table 2. Maximum relative displacement between ground and P1 pier with and without EDSD
PGA 0.1g 0.2g 0.3g 0.4g 0.5g
Without EDSD 4.96 10.03 15.66 23.88 35.65
With EDSD 4.39 8.44 13.05 18.14 28.76
Decreasing Ratio 11.5% 15.9% 16.7% 24.0% 19.3%
FULL SCALE PSEUDO-DYNAMIC TESTS FOR SEISMIC PERFORMANCE OF EDSD
KISTC (Korea Infrastructure Safety and Technology Corporation) strongly recommends that the
energy-dissipating device, such as EDSD, developed for enhancing seismic performances of bridges
should be tested to verify its performance and safety before practical application (2004). In this study,
therefore, the EDSD tested to evaluate its energy-dissipating performance and estimate the safety of
connection between the sacrificial device and the girder of the bridge. A simple modeling and analysis
process need to be developed, moreover, to design the EDSD easily for application of itself to any
structures.
The full scale models composed of EDSD and partial bridge referred just in front of this section are
prepared. Corresponding pseudo dynamic tests are conducted to investigate the ductile behavior of
sacrificial members and stress level of plates connecting a sacrificial member and a girder of bridge.
The specimen, that is end part of the steel plate girder bridge, is fixed to bases, and then load increased
gradually is applied by the actuator machine the restraining device is attached to, as shown in Fig. 10.
Restraining
device
Attached to
actuator machine
Sacrificial
member
End part of
Steel plate girder
Base
Load
Load
Restraining
device
Attached to
actuator machine
Sacrificial
member
End part of
Steel plate girder
Base
Load
Load
sacrificial member
restraining device
(a) Full scale specimen of the bridge with EDSD (b) Specimen of EDSD
Figure 10. Schematics of the test for EDSD
Fig. 11 shows hysteretic curve of sacrificial members obtained from the experimental data with and
without the gap between the restrainer and the bracing. According to the result, the actual stiffness of
sacrificial members is slightly larger than the stiffness calculated through the theory. It is because the
cross section of the sacrificial member is increased by welding process and attached stiffeners. In
order to apply more practical hysteretic model of the sacrificial member in the following seismic
analysis, the stiffness and the hysteretic curves of the sacrificial member are corrected based on the
test results. Fig. 12 shows the hysteretic curves of sacrificial devices obtained by the mathematical
analysis using corrected hysteretic model, which will be used in the numerical simulations.

-8 -4 0 4 8
Displacement [cm]
-60000
-40000
-20000
0
20000
40000
60000
F
or
c
e
[
kgf]
-8-4048
Displacement [cm]
-60000
-40000
-20000
0
20000
40000
60000
For
c
e
[
kg
f
]
(a) without gap (b) with gap
Figure 11. Hysteretic curves obtained by test.
-8-4048
Displacement [cm]
-60000
-40000
-20000
0
20000
40000
60000
For
c
e
[
kg
f
]
-8-4048
Displacement [cm]
-60000
-40000
-20000
0
20000
40000
60000
F
or
c
e
[
kg
f
]
(a) without gap (b) with gap
Figure 12. Hysteretic curves obtained by analysis.
The maximum stress of plates connecting a sacrificial device and a girder of bridge appears as
1124kgf/cm2 that is less than the allowable stress of 1400kgf/cm2. It means connecting parts are safe
during the EDSD dissipates the seismic energy of the structure.
SEISMIC RESPONSE OF THE PSC GIRDER BRIDGE WITH APPLICATION OF EDSD
Seismic responses of a whole bridge system are examined using a commercial FEM analysis program
(SAP2000) so that engineers are able to utilize EDSD in practical bridge design. Through 3-
dimensional analysis of a bridge with various values of number, applied locations and stiffness of
EDSD, the optimum design of EDSD may be possible with consideration of some limitation occurring
in setting up the EDSD.
A PSC girder bridge actually designed to be in service which needs seismic retrofit is chosen and
shown in Fig. 13. The modeling and analysis method using SAP2000 have been verified in the
preliminary study by comparing results with those from numerical method and it shows good
agreement. The second segment of the bridge from pier P2 to P5 was selected for seismic analysis and
EDSD are applied between every neighboring girder on P2, P4 and P5 longitudinally movable bearing
installed at, as shown in Fig. 14. To find the optimum stiffness of sacrificial members of each EDSD,
the variation of hysteretic energy of each EDSD with various stiffness values of sacrificial members is
generated as shown Fig. 15. Stiffness of sacrificial members of EDSD1, EDSD2 and EDSD3 are
determined so that the amount of seismic energy dissipation would be maximized. The initial gap
distances are set as 2cm for EDSD1 and EDSD 2 and 3cm for EDSD3.

P3
P1 P6 P9
F
MF
MM
MM
FM
F
M
P3
o1,500 L=VAR
현장타설 말뚝
o1,500 L=VAR
현장타설 말뚝
(a) Plan view (unit: mm) (b) Cross section (unit: mm)
Figure 13. Configuration of a considering bridge.
Figure 14. 3-D Bridge model with EDSD for seismic analysis.
0 200000 400000 600000 800000 100000
0
EDSD Stiffn ess [ kgf
/
cm ]
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
2000000
Hysteresys Energy [ kgf . cm ]
Energy dissipated by the
EDSD1
PGA 0.154g
PGA 0.2g
PGA 0.3g
0 200000 400000 600000 800000 1000000
EDSD Stiffness [ kgf
/
cm ]
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
2000000
Hysteresis Energy [ kgf . cm ]
Energy diss ipated by the
EDSD2
PGA 0.154g
PGA 0. 2g
PGA 0. 3g
0 200000 400000 600000 800000 100000
0
EDSD Sti
f
f
ness [ kg
f
/
cm ]
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
2000000
Hysteresis Energy [ kgf . cm ]
Energy dissi pated by t he
EDSD3
PGA 0.154g
PGA 0.2g
PGA 0.3g
(a) EDSD1 (b) EDSD2 (c) EDSD3
Figure 15. Variation of hysteretic energy of each EDSD
Table 3 shows the mean values of the maximum relative displacement between superstructure and P2,
P4 and P5 respectively under PGA 0.154g, 0.2g and 0.3g. Overall, the maximum relative displacement
decreased by more than 60% under not only 0.154g, that is design ground acceleration of this bridge,
but also 0.2g and 0.3g.
Table 4 shows the mean values of the maximum shear force of piers under PGA 0.154g, 0.2g and 0.3g.
Overall, the maximum shear force of P3 longitudinally fixed bearings are installed at is decreased and
that of P2, P3 or P5 is increased. This result reveals the force-redistribution effect of the EDSD clearly.
Especially, the providing capacity of P3 evaluated from the process represented in “Guide for
Evaluation and Improvement of Seismic Performance of Existing Bridges (KISTC, 2004)” is 475tonf;
it is smaller than the required capacity of 511tonf before application of the EDSD. However, after
application of EDSD, the required capacity of P3 is reduced to 222tonf, and it means P3 pier becomes
safe under the design earthquake.

Table 3. Maximum relative displacement between superstructure and piers with and without EDSD
(unit : cm)
Without EDSD With EDSD Decreasing Ratio
PGA S-P2 S-P4 S-P5 S-P2 S-P4 S-P5 S-P2 S-P4 S-P5
0.154g 6.75 6.90 6.73 2.29 2.40 2.43 66% 65% 64%
0.2g 8.73 9.86 8.91 3.20 3.19 3.44 63% 68% 61%
0.3g 13.10 14.79 13.36 4.69 5.00 4.97 64% 66% 63%
Table 4. Maximum lateral force of piers (unit : tonf)
Without EDSD With EDSD Decreasing Ratio
PGA P2 P3 P4 P5 P2 P3 P4 P5 P2 P3 P4 P5
0.154g 56 511 124 59 97 222 121 83 -73% 57% 3% -42%
0.2g 78 654 151 75 119 305 162 118 -52% 53% -7% -57%
0.3g 117 982 227 113 153 450 192 151 -30% 54% 15% -34%
CONCLUSIONS
An energy-Dissipating Sacrificial Device (EDSD) is proposed as a solution for enhancement of
seismic performance of a bridge, which is designed to dissipate excessive energy stored in piers. A
simplified mathematical bridge model with EDSD is developed and various ground motions are
applied to analyze energy dissipating capacity and enhancement of bridge seismic performance.
Analysis of energy responses and displacement responses are performed for more quantitative
evaluations. With full size specimen, pseudo dynamic tests are conducted to see the dissipation
capacity of the EDSD, and also to obtain the more practical stiffness and the hysteresis curves for the
further numerical simulations. The seismic responses of a whole bridge system with the EDSD are
also evaluated to determine the optimal design of EDSD by examining various ways of application of
the EDSD. The proposed EDSD under seismic excitations can significantly decrease the hysteretic
energy of the piers and reduce the relative motions in bridges. In addition, the EDSD is found to
function as a structural fuse under strong ground motions, sacrificing itself to absorb the excessive
energy with application to the bridge in service. Employment of EDSD can be a possible solution for
economical enhancement of seismic performance.
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