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Procedía - Social and Behavioral Sciences 218 (2016) 104 - 117
11th International Conference of the International Institute for Infrastructure Resilience and
Reconstruction (I3R2) : Complex Disasters and Disaster Risk Management
Investigation of seismic response on girder bridges: the effect of displacement restriction and wing wall types
Desy Setyowulanab*, Toshitaka Yamao a*, Keizo Yamamoto3*, Tomohisa Hamamotoc*
Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555, Japan b
Civil Engineering Department, Universitas Brawijaya, No. 169MT Haryono Street, Malang, East Java, Indonesia
Civil Engineering Department, Gunma National College of Technology, 580, Tribamachi, Maebashi, Gunma 371-8530, Japan
Abstract
In the seismic design specified by Japanese Specifications of Highway Bridges (JSHB), a large gap size between two adjacent girders or the girder and abutment has recommended to be constructed in the concrete girder bridge with multi-spans in order to prevent the collision, when it is subjected to Level 2 ground motion. However, the adoption of large gap into PC bridge will increase the construction and seismic reinforcement costs since relatively large expansion joints have to be used. Also, it causes the girders falling in the presumption of strong earthquake. It has been suggested that allowing the girder collision at the abutment by restricting the girder bridges displacement, the size of expansion joints can be reduced. These conditions are able to reduce the seismic design and seismic reinforcement cost.
Although many studies on the effect of the collision have been published, the effect of displacement restriction of girders is still remains to be elucidated. This present study aims to investigate the seismic response of concrete girder bridges taking into account the effect of displacement restriction of girders allowing the girder collision at the abutment and the wing wall. Two span concrete girder bridge was examined in theoretically by 3D FEM model of ABAQUS with four different approaches at the wing wall abutment model. The dead load and soil pressure were calculated based on JSHB loading conditions and gap between superstructure and parapet wall was chosen to be 10 cm and 20 cm. Level 2 earthquake ground accelerations were applied horizontally at the bottom of pier. The numerical results showed that the parameters such as shear stress, response stress, displacement, and cracking were affected by displacement restriction and different wing wall model. Installing of the wing wall in abutment generally increased the response stress in parapet wall and shear stress around vertical wall of abutment. In contrast, it significantly reduced the horizontal displacement of abutment. © 2016Published byElsevierLtd. This isanopen accessarticle undertheCCBY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of Dept of Transportation Engineering, University of Seoul. Keywords: collision; displacement restriction; gap; impact force; seismic response; wing wall abutment
1. Introduction
A large number of bridges were damaged during unexpectedly severe earthquakes, such as 1995 Hyogo-ken Nanbu earthquake and 2011 Tohoku earthquake. Damage to bridges primarily occurred in reinforced concrete substructures, buckling of steel piers, collapsed span as a result of insufficient support length and bearing damage. During the inspection of the failure, the most common problems observed for collapsed of abutments were caused by high stress on the surface of abutment and collision between adjacent deck and between deck and abutment. Therefore, a new type of abutment is required in order to generate an appropriate abutment model with a better seismic performance. Seismic response investigation of reinforced concrete abutment is very important in term of the ability to survive in severe earthquake. Furthermore, a proper material model of reinforced concrete should be capable in representing the behavior of materials within finite element packages.
♦Corresponding author. Tel.: +62-8123-364-6603
E-mail address: desy_wulan@ub.ac.id (D. Setyowulan), tyamao@kumamoto-u.ac.jp (T. Yamao), keizo.yamamoto1110@gmail.com (K. Yamamoto), hamamoto@cvl.gunma-ct.ac.jp (T. Hamamoto)
1877-0428 © 2016 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of Dept of Transportation Engineering, University of Seoul. doi: 10.1016/j .sbspro. 2016.04.014
Nomenclature
C damping matrix
M mass matrix
K stiffness matrix
a coefficient for mass matrix (sec-1)
ß coefficient for stiffness matrix (sec)
Pea active earth pressurestrength (kN/m2) during an earthquake at depth x (m)
kea coefficient of active earth pressure during an earthquake
kh design horizontal seismic coefficient used for calculation of earth pressure during an earthquake
r unit weight of soil (kN/m3)
q' surcharge on the ground surface during an earthquake (kN/m2)
angle of shear resistance of soil (degree)
a angle formed between the ground surface and horizontal plane (degree)
G angle formed between back surface of a wall and a vertical plane (degree)
5e wall surface friction angle between the back surface of a wall and soil (degree)
e0 tan-1 kh (degree)
In the seismic design specified by Japanese Specifications of Highway Bridges (JSHB), a large gap size between two adjacent girders or the girder and abutment has recommended to be constructed in the concrete girder bridge with multi-spans in order to prevent the collision, when it is subjected to Level 2 ground motion. However, the adoption of large gap into PC bridge will increase the construction and seismic reinforcement costs since relatively large expansion joints have to be used. It has been suggested that allowing the girder collision at the abutment by restricting the girder bridges displacement, the size of expansion joints can be reduced. These conditions are able to reduce the seismic design and seismic reinforcement cost.
Previous researcher [1] investigated the effect of collision between parapet wall and superstructure due to the variation of gap from 10 cm to 50 cm.The effect of earth pressure during earthquake was not taken into account. According to this analysis, it was found that increasing of gap for bridge with and without installation of the wing wall decreased the number of collision. In general, applying the gap of 20 cm and 30 cm had a good effect on reducing the response stress of parapet wall. However, they were varied on different input seismic motions. In addition, installation of the wing wall in parapet had a capability in reducing the maximum response stress of parapet wall, which contributed greatly to the horizontal resistance of abutment against load.
In this study, the seismic response on concrete girder bridges taking into account the effect of displacement restriction and wing wall types was discussed. Four different abutments modeling approaches [2] were installed in two spans concrete girder bridges subjected to Level 2 seismic ground motions. Gap between superstructure and parapet wall was chosen to be 10 cm and 20 cm to analyze the effect of displacement restriction on the behavior of abutments. Effect of earth pressure during earthquake was taken into account.
2. Literature reviews
Collapsed of Higashi Uozaki Bridge which passed over the canal, an example of damaged in abutment due to strong intensity of dynamic excitation from 1995 Hyogo-ken Nanbu earthquake, are shown in Fig. 1 [3]. According tho this figure, it is described that A1 abutment rotated backward and accompanied with large cracks widespread on the front face of the abutment. The shear collapse with widely opening cracks on the front face was also observed at A2 abutment wall. This condition may occurred due to several reasons, such as the liquefaction of the subsoil layer, the earth pressure acting on the back face of the abutment which was pushed outward and the inertial force itself, the lateral movement at the top of abutment was constrained by the deck, and the large tensile force acting at the front face of the abutment.
(a) A1 abutment (b) A2 abutment
Fig. 1. Failure of abutments of Higashi Uozaki Bridge [3]
In the seismic performance of bridge, collision and stress distribution become an important aspect to be evaluated. Before 1995 Kobe earthquake, real bridge structure considered the gap of 10 cm. Thereafter, gap varied from 20 cm to 50 cm has been used. Revision on seismic design in the Japanese Specification on Highway Bridges has been made, especially in the gap section. Necessary gap between the ends of two adjacent girders shall be taken in the design of the superstructure for preventing any loss of the bridge caused by the collision between two adjacent superstructures, a superstructure and an abutment, or a superstructure and the truncated portion of a pier head are determined according to the seismic design by Japanese Specification on Highway Bridges, when it is subjected to Level 2 Earthquake Ground Motion [4]. One such example of damaged to the parapet wall of abutment and movable bearing due to collision is shown in Fig. 2. According to this figure, it can be seen that the main girder end and front face of parapet wall of Imokawa bridge suffered cracks and spalling caused by a collision. The impact force between parapet wall and deck was also large.
(a) Parapet wall cracks
(b) Movable bearing damage
Fig. 2. Damage of parapet wall and movable bearing of Imokawa bridge due to collision
3. Structural system and modeling
3.1. Analytical model of bridge
r 2200
2200 4DDD J
1500 1500
(a) Side view of the bridge
(b) Front view of P1 pier
(c) Cross section of the superstructure (d) Side view of P1 pier
Fig. 3. Dimensions of the concrete girder bridge (unit: mm)
The finite element modeling of two spans concrete girder bridge adopted from previous research [5] was studied, as shown in Fig. 3. Parametric study of bridge taking into account the effect of displacement restriction and wing wall types were investigated. Effect of earth pressure during earthquake was taken into account. In the
modeling technique, the abutment, the reinforcing bars and the box girder superstructure were idealized by C3D8R elements, T3D2 truss elements and S4R element, respectively. Four different abutment modeling approaches; Type 1, Type 2 as the typical model in Japan, Type 3 with full wing wall, and Type 4 as the proposed model of abutment; were used as the main parameter with gaps of 10 cm and 20 cm.
The boundary condition of abutments and pier were fixed (F) at the bottom. In this model, footing was eliminated and the bearing supports were assumed as roller bearing with the friction coefficient of 0.1. Fig. 4(a) through 4(d) displays the 3-D FE models of concrete girder bridge with different type of abutments. In total, the study conducted 48 models to identify the effect of the wing wall and gap on the response of abutments.
(b) Type 2 (typical abutment model in Japan)
(c) Type 3 (full wing wall)
(d) Type 4 (proposed model of abutment) Fig. 4. The 3-D FE models of concrete girder bridges
3.2. Material properties
In this numerical analysis, the damage criterion in reinforced concrete elements was simulated by Concrete Damaged Plasticity method in ABAQUS [6]. Material properties of concrete girder bridge, including of pier, girder and abutment are shown in Table 1.
Table 1. Material properties of the structure
Material Properties Pier Parapet Wall Bridge
Concrete Rebar Concrete Rebar girder
Young's modulus (GPa) 20.60 206.00 25 200 20.6
Poisson's ratio 0.20 0.30 0.167 0.3 0.20
Density (kg/m3) 2450 7850 2400 7850 2450
Compressive Strength(MPa) 29.40 294.00 27.5 375.3 29.40
Tensile Strength (MPa) 2.94 ( Yield Stress ) 2.75 (Yield stress) 2.94
3.3. Ground motion .selection
Level 2 Type 1 and Type 2 earthquake ground accelerations were applied horizontally at the bottom of pier in order to investigate the behavior of abutments under large earthquake, as depicted in Fig. 5. Ground Type 1 was chosen as a representation for the real type of soil.
Time(s)
(a) Type I-I-1 wave
Time (s) (d) Type II-I-1
100 2' Time (s)
(b) Type I-I-2 wave
10 Time(s)
(e) Type II-I-2 wave
Time (s)
(c) Type I-I-3
10 20 Time (s)
(f) Type II-I-3 wave Fig. 5. Input JSHB seismic waves Level II earthquake ground motions
3.4. Loading conditions
The substructures of bridge should be capable in transmitting the loads from superstructures to the supporting ground [7]. Under earthquake condition, the abutment should be designed based on the load combinations of dead load, earth pressure and seismic effects displays in Table 2. Secondary forces due to shrinkage, settlement, temperature, and earth pressure can cause cracks in concrete bridge abutment [8]. In addition, wing-walls can crack due to rotation and contraction of the superstructure [9].
The earth pressure during an earthquake was calculated based on JSHB Seismic Design Part V [4], assumed as a distributed load which was determined in consideration with structural type, soil conditions, level of earthquake ground motion and dynamic behavior of the ground. The strength of an active pressure is calculated by equations (1) through (6).
Based on the previous research [10], y and 8 were determined as 19 kN/m3 and 15o, respectively.
Parameters (¡>,a,0 were determines as </) = 30°, a- 00 and 0 = 00 with kh = 0.16. In this analysis, the
hydrodynamic pressure and ground displacement during an earthquake were not considered herein. In addition, it was assumed that no liquefaction occurred.
Table 2. General load combinations [4]
Design of abutments Load situations
a) Dead loads + live loads + earth pressures Under ordinary condition
b) Dead loads + earth pressure
c) Dead loads + earth pressures + seismic effects Under earthquake condition
- Extreme wind situation
PEA ~ rxKEA + q KEA The coefficient of Kea is calculated by the following equations.
1) Between soil and concrete behind the abutment Sand or gravel
Sandy soil
KEA = 0.21 + 0.90kh KEA = 0.24 + 1.08kh
2) Between soil and soil behind the abutment
Sand or gravel Sandy soil
KEA = 0.26 + 0.97kh
cos 0o cos2 0cos(ß + 0o +SE
sin + SE )sin -a-0o ) cos(0 + &o +SE )cos(0 - a)
KEA = 0.22 + 0.81kh
3.5. Interaction properties and Rayleigh damping
General contact surface algorithm with the friction coefficient of 0.45 and hard contact for pressure-over closure are determined as the interacting surface between superstructure and parapet wall. The friction surface of bearing was 0.1 with the embedded constraint between rebar and concrete in abutment. Nonlinearities, including geometric and material, were needed to be addressed in seismic analysis. In the numerical analysis, a damping model of Rayleigh type which consider first mass-proportional damping and stiffness-proportional damping is used and the damping matrix equation determined by equation (7). The arbitrary proportionality factors a and p are determined by Eq.(8) and Eq.(9), respectively. In this analysis, the constant damping was set to be 0.02.
C - aM + pK (7)
a= 4nfif2 jfh - f2 hi)
fl2 - f22
'ff (9)
3.6. Proposal of the damage assessment
The damage assessment for concrete in abutments were determined by the compressive strength parameter of 29.4 MPa. Damage criteria were divided into four level, minor damage (A) through extensive damage (D), as displayed in Table 3. Effect of gap and modeling approach of the wing wall in abutments were also investigated by some parameters, such as cracking distribution, and shear stress of abutment. An allowable shear stress of concrete was defined as 1.9 Mpa [4].
Table 3. Level of damage for concrete in abutment
Maximum response stress (MPa)_Level of damage_Description
0 < o S 13.75 0 <o S 50% fc A K Minor
13.75 < c S 20.625 50% fc <c S 75% fc B
20.625 < c S 27.5 75% fc <c S fc C
27.5 < c fc <c D \ / Extensive
Moreover, bridge abutments were experience significant displacement during earthquakes. When the deck displacement relative to the abutment in the longitudinal unseating direction was greater than seating length, the girder bridge was assumed to be unseated. In addition, categorization of the degree of damage are specified [11] and shown in Table 4.
Table 4. Categorization of the degree of damage [11]
Rank of 1 2 3 4
damage
Degree of damage slight medium to large severe
Service- Fully operational Operational with No operation temporarily Impossible
ability some restictions w.r.t weight of vehicles and speed limit while doing emergency countermeasure works**
Repair-ability Easy* Possible with minor repair works Possible with major repair works Impossible (reconstruction)
Typical - Shrinkage of spacing - Slumping with - Horizontal movement or - Extensive horizontal
damage of expansion joint back-fill rotation of abutment movement or
contents - Cracks of parapet - Cracks of - Excessive slumping of excessive rotation of
wall structural backfill abutment
members - Collapse of parapet wall - Collapse of structural members
*e.g., within fixing slight cracks
**e.g., operational with some restrictions after constructing temporary bents
4. Dynamic analysis of bridge
Post-earthquake reconnaissance studies have reported that the areas subjected to high stress and collision are the most common problems observed during the inspection of abutment failure subjected to major earthquake. Furthermore, the shear stress distribution and response stress in abutment are the important aspect to be evaluated. Moreover, evaluating of displacement and cracking distribution are useful to control the damage.
4.1. Eigenvalue analysis
An eigenvalue analysis is used to determine the un-damped elastic mode shapes and frequencies of the system. According to Aviram et al. [12], the dynamic characteristics of a bridge structure are explicitly portrayed through modal analysis procedures. The mode shapes assumed by the bridge and the frequencies at which vibrations naturally occur are determined numerically, based on the mass, damping properties and stiffness of the structure. In this study, this analysis was carried out to investigate the effect of different gap and wing wall on the natural periods of the concrete girder bridges. The natural periods and the effective mass ratios of each predominant mode were investigated in order to understand the fundamental dynamic characteristics of the bridge.
Table 5. Results of eigenvalue analysis of girder bridge with abutment Type 1 and Type 2
Order T1-gap 20 cm T2-gap 20 cm
of f T Effective Mass Ratio (%) f T Effective Mass Ratio (%)
Periods (Hz) (sec) X Y Z (Hz) (sec) X Y Z
1 6.72 0.15 98.55 0.00 0.00 5.62 0.18 0.16 0.00 0.12
2 8.09 0.12 0.00 0.53 41.99 5.68 0.18 0.04 0.00 0.61
3 10.78 0.09 0.00 0.00 0.00 5.68 0.18 0.09 0.00 0.40
4 11.12 0.09 1.39 0.00 0.00 5.99 0.17 0.14 0.00 0.45
5 12.39 0.08 0.00 0.28 0.05 6.98 0.14 98.93 0.00 0.00
6 12.39 0.08 0.00 0.00 0.00 8.35 0.12 0.00 0.81 40.64
7 12.72 0.08 0.00 65.35 5.78 12.35 0.08 0.10 0.00 0.00
8 15.27 0.07 0.00 11.12 46.05 12.86 0.08 0.51 0.04 0.00
9 15.87 0.06 0.03 0.00 0.00 13.12 0.08 0.00 76.65 9.03
10 16.03 0.06 0.00 0.00 0.00 15.50 0.06 0.00 17.89 47.82
11 16.03 0.06 0.02 0.00 0.00 15.72 0.06 0.03 0.00 0.00
12 16.53 0.06 0.01 0.00 0.00 16.50 0.06 0.01 0.00 0.00
13 17.93 0.06 0.00 14.38 5.95 17.35 0.06 0.00 0.05 0.15
14 18.53 0.05 0.00 0.00 0.00 17.83 0.06 0.00 0.07 0.10
15 18.81 0.05 0.00 8.34 0.18 18.35 0.05 0.00 4.50 0.67
Table 6. Results of eigenvalue analysis of girder bridge with abutment Type 3 and Type 4
Order T3-gap 20 cm T4-gap 20 cm
of f T Effective Mass Ratio (%) F T Effective Mass Ratio (%)
Periods (Hz) (sec) X Y Z (Hz) (sec) X Y Z
1 5.00 0.20 0.17 0.00 0.54 2.07 0.48 0.01 0.00 0.00
2 5.05 0.20 0.17 0.00 0.03 2.07 0.48 0.00 0.00 0.00
3 5.06 0.20 0.00 0.00 1.97 4.96 0.20 1.09 0.00 1.13
4 5.11 0.20 0.04 0.00 1.49 4.99 0.20 0.23 0.01 0.07
5 7.98 0.13 0.00 0.64 42.41 5.02 0.20 0.11 0.00 4.58
6 8.22 0.12 99.00 0.00 0.00 5.05 0.20 0.09 0.00 2.72
7 10.05 0.10 0.01 0.00 0.12 5.16 0.19 0.00 0.00 0.00
8 10.15 0.10 0.00 0.00 0.22 5.16 0.19 0.00 0.00 0.00
9 10.41 0.10 0.01 0.00 0.09 6.89 0.15 98.46 0.00 0.00
10 10.49 0.10 0.00 0.00 0.21 7.85 0.13 0.00 99.14 90.13
11 12.62 0.08 0.00 84.61 6.56 10.00 0.10 0.00 0.32 0.25
12 12.76 0.08 0.01 0.07 0.01 10.03 0.10 0.00 0.18 0.26
13 13.00 0.08 0.54 0.00 0.00 10.10 0.10 0.00 0.11 0.41
14 14.88 0.07 0.00 14.68 46.36 10.12 0.10 0.00 0.20 0.46
15 15.85 0.06 0.05 0.00 0.00 10.88 0.09 0.00 0.04 0.00
From the numerical results, it is found that different gap of 10 cm and 20 cm do not change the predominant mode position in X, Y and Z directions. Thereafter, the eigenvalue analysis results in Tables 5 through 6 are resulted from bridge with gap of 20 cm. The principal modes of deformation include the longitudinal, vertical and transverse translation of the bridge for bridge with abutment Type 2 and Type 4 are depicted in Figs. 6 through 7, respectively.
(a) X-direction (5111 mode)
(b) Y-direction (9th mode)
(c) Z-direction (10"1 mode) Fig. 6. Principal mode of deformation for bridge with abutment Type 2
As indicated in those results, different type of abutments have a significant effect on its predominant mode. For instance, the bridge with abutment Type 1 is possible to vibrate sympathetically at the 1st mode in longitudinal (X-direction), the 7th mode in in-plane (Y-direction) and the 8th mode in transverse (Z-direction). Installing the abutment Type 2 leads the bridge to vibrate sympathetically at the 5th, 9th and 10th modes in X, Y
and Z-directions, respectively. In addition, bridge with the proposed model of abutment Type 4 is possible to vibrate sympathetically in X-direction at the 9th mode, Y and Z-directions at the 10th mode.
(a) X-direction (9"1 mode)
(b) Y and Z-directions (10th mode) Fig. 7. Principal mode of deformation for bridge with abutment Type 4
4.2. Shear stress of abutments
Shear stress distributions around vertical wall of abutment are shown in Figs. 8(a) through 8(f). As indicated in these figures, it can be seen that installing of the wing wall in abutment generally increases the shear stress around vertical wall of abutment. Existence of the wing wall in abutment Type 2 gives an effect on its distribution, which is first occurred near the intersection between wing wall and parapet wall.
(e) T3 (L2T2G1-2-10) (f) T3 (L2T1H1-1-20) (g) T4 (L2T2G1-1-10) (h) T4 (L2T1G1-1-10)
Fig. 8. Shear stress distribution of abutments
The maximum shear stresses in each type of abutments are depicted in Figs. 9(a) through 9(l). From these results, it can be defined that different types of the input ground motions resulted on different effect on the shear stress of abutments. The shear stresses occurs in all abutments for bridge under L2T2G1-1 seismic motion are larger than the maximum elastic limit of 1.9 MPa, with the maximum stress occurred in bridge with abutment Type 4.
(a) Abutment Al (L2T2G1-1)
T1 T> T3 T4
■ I0<m 1.2« 2.71 1.19 1.31
■ 2Q<m 0 63 5.S4 0.52 1.03
(c) Abutment A1 (L2T2G1-2)
Tl T2 T3 T4
• !0an 0.64 2.14 1.72 1.31
■ 20 cm 0,52 2.70 0.68 1.03
(e) Abutment A1 (L2T2G1-3)
^^^ ^^^ ^^^
1.57 " 1.98 " 1.85 2.29
1.23 1-47 1.36 2-24
(g) Abutment A1 (L2T1G1-1)
3.: _ 3
I I i J 1
Tl T2 T3 T-l
■ ] IJCll 1.47 1.37 1.63 116
■ 20cm 0.63 1.97 0.92 1,19
(i) Abutment Al (L2T1G1-2)
S 3 S -
II T2 T3 T4
■ 10m 1.55 1.29 2.95 1.19
■ ¿bal 1.35 2.19 2.28 2.93
(k) Abutment A1 (L2T1G1-3)
■ lOcra
■ 20cm
J C3 2.12
1.61 1.10
9.11 «26
9 IS 15.17
(b) Abutment.42 (L2T2G1-1)
(d) Abutment.42 (L2T2G1-2)
3 1.5 S 1
Tl T2 T3 T4
■ 10an 1.01 1.24 2.2Ï 1.53
>20tm 1.13 1.90 1.92 1.34
(f) Abutment.42 (L2T2G1-3)
Tl 12 T3 T4
I 10cm 1.52 1.60 1.20 1.68
■ 20cm 1.4S 1.43 1.16 1«
(h) Abutment ^42 (L2T1G1-1)
(j) Abutment.42 (L2T1G1-2)
Tl T2 T3 T4
■ lOffit 1.11 1.59 1.71 5.35
■ 20cm 1.00 1J0 117 4.81
(l) Abutment A2 (L2T1G1-3)
Fig. 9. Maximum shear stress of abutments
Otherwise, input of L2T2G1-2 and L2T2G1-3 seismic motions increase the shear stress in abutment Type 2, larger than the elastic limit. In addition, installation of abutment Type 4 with the input seismic motion of L2T1G1 also increases the shear stress around vertical wall of abutment. Moreover, effect of increasing gap generally reduces its response.
4.3. Response stress
The maximum response stress at the parapet wall for each type of abutments are analyzed and depicted in Figs. 10(a) through 10(f). A1 and A2 denote the position of abutments in the left and right side, respectively. According to these results, it can be seen that the response stress in the proposed model, of abutment Type 4 is larger than Type 2. This condition is possibly due to the effect of soil pressure which is constantly pushed the abutment during earthquake. Moreover, installing of full wing wall in abutment Type 4 contributed greatly to the horizontal displacement resistance of abutment against load, lead the higher response stress at the parapet wall. For bridge with ground motion input of L2T1G1-1, a number of abutments in different types are categorized as medium damage (B), while categorized as minor damage (A) for ground motion input of L2T2G1-2.
: 15 110 ! 5
Tl Tl T3 T4
■ 10 ten Î1J» :ss: 2010 1} 19
19S4 IS ÎÏ iroi M 33
(a) Abutments (L2T1G1-1)
T! T2 T3 T4
■ 10cm 4.99 U.S5 u 9S
■ 20 cm 12.5? 12,59 13.57 14/5!
(c) Abutment 7 (L2T1G1-2)
Tl T2 T3 T4
■ 10am 21,94 9 39 30.S4
■ 20OT1 20.00 23 37 30.07 27.10
(e) Abutment A1 (L2T1G1-3)
a r M M M s | : j-1|
■ lOun 17 J« » I» 17j0i 20 SV
• »am IS 54 1130 17 44 20 06
35 r 30 125
L10 I s
(b) Abutment A2 (L2T1G1-1)
Tl X2 T3 T4
■ lOcni 7.79 7.79 12.3« li .40
■ 20cm 7.66 7.66 12-50 IS 16
(d) Abutment A2 (L2T1G1-2)
Tl T2 T3 T4
■ lflan 11.47 5.12 19.il 8.90
■ 20cm 13.00 4.30 10.53 1248
(f) Abutment A2 (L2T1G1-3)
Fig. 10. Maximum response stress of abutments
4.4. Horizontal displacement of abutments
The effect of abutment types and different gap are demonstrated in Figs. 11(a) through 11 (l) by using ratio between abutment top displacement (A) to abutment height (H) ratios, A/H. In this study, we used two different ratios of 0.009 and 0.025 as a small and large displacement, respectively [13]. Positive and negative values correspond to the left and right direction of displacements, respectively. Unseating of bridge occur when the ratio of A/H is larger than 0.175 and 0.1625 for bridge with the gap of 10 cm and 20 cm, respectively.
Finally, it can be clarified that installing of the wing wall in abutment has a significant effect in reducing the horizontal displacement of abutments due to earthquake load and earth pressure. For instance, constructing abutment Type 4 reduce the horizontal displacement up to 51% when it is compared to abutment Type 2, as shown in Fig. 11(f). In contrast, some decks unseat due to the large movement. At small abutment displacement when the backfill remain within the elastic limits, the external force from earthquake and earth pressure do not
have a significant effect on the magnitude of shear force, as depicted in Fig. 9. However, at larger gap of 20 cm, the maximum displacement increase, generally for abutment with the input seismic ground motion of L2T1G1.
0 120 0 100 0 080 ^ 0 060 0.040 0.020 0.000
♦ Gap 10 cm ■ Gap 20 cm
0.00Î oooo •0.005
I -0.010
-0.015 -0.020 -0.025
Type of abutments (T)
(a) Abutments (L2T2G1-1)
■ ■ ■ ■
1 2 3 4
♦ Gap 10 cm ■ Gap 20 cm ♦
♦ ♦ ♦
Typ* of abutments (T)
(c) Abutment Al (L2T2G1-2)
0.005 0.000 I 0.005 -0.010 -0.015
k à i ■ 4
Gap 10 cm —6
■ Gap 20 cm
Type of abutments (T)
(e) Abutment Al (L2T2G1-3)
ODD 0010 000) 0000 ^ -0005 -0010 -0015 -0020 -0025
OOOO -0.030 4UOO -0.150 -OJOO -0.250
• Gap 10 cm a
■Gap 20 cm
1 2 3 4
■ ♦
« ♦
Type of abutments
(g) Abutment.47 (L2T1G1-1)
1 2 ft 8
♦ Gap 10 cm
■Gap 20 cm
Type of abutments
(i) Abutment Al (L2T1G1-2)
0.250 0.200 0.1SO 0.100 0OÎO 0,000
i ■ *Gsp 10 cm ■ Gap 20 cm
♦ * *
0.020 0.015 § 0.010 0.005 0.000
Tjpe of abutments (T)
(b) Abutments (L2T2G1-1)
♦ Gap 10 cm ■ Gap 20 cm
0 12 3
Type of abutments (T)
(d) Abutments (L2T2G1-2)
0.02J 0.020 0015 § 0.010 0.00Î 0.000 -0.00Î
♦ Gap 10 cm
■ Gap 20 cm ■
1 2 5 4
Type of abutments (T)
(f) Abutment(L2T2G1-3)
01130 0.(125 0.020 ; o at? 0.010 0.005 0000
♦ ♦
■ ■
♦ Gap ÎÛ cm w
■Gap ¿0 cm
Type of abuluièuts
(h) Abutment (L2T1G1-1)
0.120 0100 o.oso
; o .o«G 0.0« 0.020 0.000
* Gap 10 an ■Gap 20 cm
3 Type of abutments ''
(j) Abutment ^42 (L2T1G1-2)
O.ODO -0.020 -0.01S -0.060 _ -0 OS®
^ -o.ioo -0.Ï20 -o.uo -0.160 -0 ISO
♦ Gap 10 cm
■ Gap 20 em
Type of abutmeots
(k) Abutment Al (L2T1G1-3)
0.020 0 013 0.010 0.00 i _ 0 0» ^ -O.OOi -0 010 -0.015 -0.020 -0.0:5
OGap 10 cm ■Gap 20 cm
Type of abutments
(1) Abutment A2 (L2T1G1-3)
Fig. 11. Maximum horizontal displacement at top of abutments
4.5. Cracking distribution of abutments
Figs. 12(a) through 12(d) display the cracking distribution of abutment Type 2 and Type 4 with the input seismic motion of L2T2G1-10, due to tensile stress. In this analysis, we used the contour plot of output variable DamageT, a scalar degradation measure to express the reduced tensile elastic modulus of concrete after it has sustained cracking damage. "Dark blue color" and "red color" region correspond to area of no tension damage or no cracking and maximum cracking, respectively. From these figures, it can be seen that abutments suffer a considerable amount of damage during this earthquake. Cracking occur almost at the entire wall of abutment due to a large pressure from collision. It categorized as an extensive or severe damage (D). Within this limit, collapse of the structural members and extensive horizontal movement occurs with large cracks in abutment. Reconstruction is needed due to the impossibility to repair.
(a) Type 2 (A1) (b) Type 2 (A2) (c) Type 4 (A1) (d) Type 4 (A2)
Fig. 12. Cracking distribution of abutments subjected to L2T2G1-10 cm
5. Conclusions
The seismic response behavior on girder bridges taking into account the effect of displacement restriction and wing wall types were investigated. Level 2 seismic ground motions were simulated and discussed. Effect of earth pressure during earthquake was taken into account. The conclusions of this study are summarized as follows.
1) The results from eigenvalue analysis of concrete girder bridge considering to the earth pressure during an earthquake and input seismic ground motion at the bottom of pier in four different approaches of the wing wall in abutment indicated that the predominant mode of reinforced concrete abutment in X, Y and Z direction was affected by the wing wall structure. In contrast, different gap between superstructure and abutment was not giving any effect on these predominant mode positions.
2) In the damage assessment, abutments were generally categorized as medium damage (B) through extensive or severe damage (D) when an extensive horizontal movement accompanied with large cracks occurred in abutment.
3) The proposed model of abutment Type 4 had a good capacity in resisting the horizontal displacement of abutment due to earthquake and earth pressure. However, reducing the size around vertical wall would increase the shear stress and response stress of abutment. Existence of the wing wall affected on the shear stress distribution, which was occurred in the intersection between wing wall and parapet wall, at the bottom of parapet wall and abutment wall.
4) Further study is necessary in order to investigate the seismic behavior of bridge close to the real condition, subjected to earth pressure and seismic ground motions at the footing of pier and abutments.
Acknowledgements
The first author greatly indebted to "DIKTI" (Directorate General of Higher Education) for providing financial support through this research. Special thanks to the Civil Engineering Department, Universitas Brawijaya for supporting this opportunity.
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