Synopses of Master Papers

Bulletin of IISEE, 47, 49-54, 2013

VERIFICATION OF PHILIPPINE BRIDGE DESIGNSEISMIC PERFORMANCE BASED ON JAPANESE
SPECIFICATIONS FOR HIGHWAY BRIDGES
Ruel M. Nazareno ∗MEE11609

Supervisor:

Jun-ichi HOSHIKUMA∗∗

ABSTRACTThe author gives importance to a lifeline structure like bridges. Verification of Philippine bridge
design seismic performance based on the Japanese Specifications for Highway Bridges is the key
factor. Serviceability of a bridge is very important especially after a disaster like earthquake.
Serviceability of a bridge must be maintained to give way for an effective rescue operation andbringing of relief goods to the affected area. Maintaining the effectiveness of the bridge after a big
earthquake is not only economical and advantageous to the government but also reduces the possibilityof human casualties.
Using the January 1995 Kobe Earthquake Ground Motion (Type II-near-fault type
earthquake) and March 2011 Tohoku Earthquake Ground Motion (Type I-subduction type earthquake)standard values of the design horizontal seismic coefficient for the level 2 Earthquake Ground Motionin the verifications of the Model bridge in accordance with the Japanese Specifications for HighwayBridges is more appropriate to the model bridge which is located near to an active fault, just like Kobeearthquake.
In this study, the importance of residual displacement is deemed necessary and very
important in the serviceability of the bridge. Philippine bridge design is so ductile that even after avery large displacement of the column after input of Kobe and Tohoku earthquake ground motion thebridge is still on safe condition. On the other side bridges with high ductility performance, usually
endure residual displacement.
Keywords: Residual Displacement.

1. INTRODUCTION
As a country located in the Pacific Ring of Fire Philippines obviously is vulnerable to disasters likeearthquakes. With a booming construction industry which includes the construction of bridges, Bridge
design seismic specification is very important. Bridges play a very important role in the developmentof the country. Although the Philippines are not totally like Japan where an earthquake is frequent, thePhilippines also have a history of big earthquakes that resulted in some bridges collapsed.
Since the unpredictability of an earthquake is a key factor the author is motivated tointroduce the importance of verification of the seismic performance of existing bridges in our region.
One great example of this unpredictability of a big earthquake is the March 2011 Great East JapanEarthquake, which shocked not only Japan but the whole world. It was concluded that we cannot
totally rely on predictions of earthquake occurrences at all times. The 2011 disaster was beyond theprediction of Japanese seismologist even in the modern era. The earthquake with a magnitude 9.0 isthe strongest earthquake in the history of Japan.
∗Department of Public Works and Highways-CARAGA, Philippines
Public Works Research Institute (PWRI), Japan∗∗Philippines are a country of many active faults throughout the Regions. So there is a bigpossibility that a Kobe like earthquake will hit the Philippines someday. And because of this it justadvantageous and helpful not only to the government but as well to the commuting public that alifeline structure like a bridge is serviceable and useful even a big earthquake like the Kobe earthquake
happened in the future.

2. DATAA circular reinforced concrete column, designed in accordance with the AASHTO Standard
Specifications for Highway Bridges 16th Edition 1996 and DPWH Design Criteria and Standards for
Highway Bridges and Airports 2004 Edition, is considered in this study see Figure 1.

33.0 m33.0 mFigure 1. Maglambing Bridge Plan (Model Bridge)
The bridge is a two-(2)-span pre-stressed Girder Bridge with a total length of 66.0 linear
meters, with its support fixed at both ends. It is a two-(2) way bridge with a total width of 9.34 meters
including the two concrete shoulders. The bridge is supported by two (2) circular columns, which areconfined columns, on the footing on piles foundation. The column diameter, D, is 1.60 m., and itsheight from the bottom of the column to the gravity center of the superstructure, h, is 14.68 m. The
total weight, W, supported by the columns is 9258 kN. The conventionally designed column isreinforced longitudinally with 56 pcs. - 36 mm diameter deformed bars with 16-mm diameter spirals
reinforcement used to confine the concrete core, spaced at a 100 mm at 1800mm from the top of thefooting and at the top with 1800 mm from the bottom of the coping with75 mm at the center portion ofthe pier respectively.
In the computations of Superstructure and Sub-structure weight we consider the concrete
weight ratio (γc) equal to 24 kN/m³. 34.5 MPa is used for Girder Concrete Compressive Strength and21 MPa for the Compressive Strength of the Concrete (f’c) of Cast in Place Concrete, Ec=4730√(f’c)
for the Modulus of Elasticity of the Concrete, 414 MPa for Steel Tensile Strength (fy) and Es=200000
for Modulus of Elasticity of Steel.
Model bridge properties are used as a reference for the assessment of its seismic performanceusing the Japan Road Association Specifications for Highway Bridges, Part V, Seismic design, Japan,
2002. Please be noted that the model structure considered in this study is only one type of bridge
structure in the Philippines.
It should be noted that the deck end condition of the model in this research is not consideredin the analysis. Although this condition affects the behavior of the bridge significantly, the bridge issimplified to the model.

3. THEORY AND METHODOLOGY
3.1. Computation of Moment of Inertia
Comparison of bridge design seismic performances between Japan and Philippine bridge specification

gives us an idea how JapaneseArea Inertia specifications give importance to theeffect of the residual displacement(A)(I)
comparedtothePhilippine(fc)Mpa (Ec)Mpa (Ec)kN/m2 (m2) (m4)specification. Computations of theBridge Moment of Inertia are needed inGIRDER
2121675.58 2.17E+07 4.16 1.67
the computation and estimating theCOPPING
2121675.58 2.17E+07 15.58 4.69
Flexural Stiffness of Columns. The
PIER 12121675.58 2.17E+07 2.01 0.32
stiffness of the Columns dominates thecomputed
performance of the bridge
PIER 22121675.58 2.17E+07 2.01 0.32
subjected to earthquake ground motions.
FOOTING
2121675.58 2.17E+07
60
125
In linear analysis, the stiffness controls
the predictions of the period of the structure, distribution of loads within the structure and deformation
demands. It also controls the yield displacement which affects the displacement ductility demand ofthe structure in the nonlinear analysis.
Computation of Moment of Inertia differs by its shape. For Coping and Footing which arerectangular in shape, the computation of I is expressed in Eq. (1). Where a is the width of the surface
and b is the depth of the surface.

Table 1. Moment of Inertia
Concrete Modulus of Modulus ofMembers Strength Elasticity Elasticity

𝑎𝑏 3(1)
𝐼=12
Computation of I for Circular column is expressed by the following Eq. (2).Where D
corresponds to the diameter of the column.
π𝐷 4𝐼=(2)64

3.2 Creation of Analysis Model.

Appropriate model is needed and it should be established according to the purpose of the analysis andthe level of design earthquake ground motion. Modeling is very important in any analysis, of StaticAnalysis or Dynamic Analysis. A model should provide us the correct number of nodes and thenumber of elements for theTable 2. Eigenvalue results
subject structure that can be used% of each vibrationin the analysis. Results from thisLongitude verticalmodecontributes
model bridge totaled nineteen(19) nodes and the total number
to the response
frequency period effective effective
strainmode
sechz
damping of elements is eighteen (18).
mass

mass

Longitude

verticalratio-X

ratio-Y stimulating stimulating

3.3 Computation of Eigenvalue.

%%

factor-X

factor-Y%

10.5223

1.91

82

0

33.04

0

5.734

2

2.294

0.44

82

00.375

0

3.004

3

3.53

0.28

81

57

026.26

3.118

4

9.07

0.11

82

57

0.68

03.021

5

10.74

0.09

82

63

0

8.5

3.632611.57

0.09

86

63

7.74

0

6.351

7

18.13

0.06

86

88

0

17.64

5.379

8

18.9

0.05

86

88

0039

19.27

0.05

86

88

0.39

0

3.01

10

23.89

0.04

86

96

0

9.67

4.681

Eigenvalue computation needs
parameters as material properties
andsectionproperties.
Eigenvalues computation is used
to obtain frequency value inevery mode to be used in thecomputation of the natural periodof the bridge structure. With thegiven parameters of the structure,
Eigenvalue computation can becalculated see Table 2 fortabulated results.

4. RESULTS AND DISCUSSION
4.1. First Verification Method
The author used two types of Earthquake Ground Motion in the verification of the model bridge
design seismic performance, the 2011 Tohoku earthquake (Type I) and the 1995 Kobe earthquake(Type II). Demand force (𝑘ℎ𝑐 W) must be equal to or less than the lateral strength (Pa) of reinforced
concrete column as shown in Eq. (3).
𝑘ℎ𝑐 W ≤ Pa

(3)𝑘ℎ𝑐 = Cs Cz 𝑘ℎ𝑐0

(4)

W = Wu + CpWp

(5)

Pa = Mu/h(6)Design horizontal seismic coefficient for level 2 earthquake ground motion(𝑘ℎ𝑐 ),equivalent weight(W),lateral strength(Pa) can be obtained by Eq. (4), (5) and (6) respectively where (Cs) is the force
reduction factor, (Cz) zone modification factor equal to 1.0 for Kobe area, (Wu) weight of superstructure, (Cp) equivalent weight coefficient, (Wp) weight of pier, (h) height of super structural inertia
force and (Mu) ultimate bending moment.

Force reduction factor (Cs), standard value of the design horizontal seismic coefficient for level 2
earthquake ground motion (𝑘ℎ𝑐0 ) and ductility capacity of the reinforced concrete column (𝜇𝑎 ) can beobtained as shown in Eq. (7), (8) and (9) respectively where (T) is the natural period of the bridge,
𝛿𝑢 is ultimate displacement of the reinforced concrete column, 𝛿𝑦 is the yield displacement of pierand α is a safety factor for reinforced concrete columns resulting to flexural failure.
𝐶𝑠 =1(7)�𝜇𝑎 −1𝑘ℎ𝑐0 = 1.24 T^ (-4/3)
𝛿𝑢 −𝛿𝑦𝜇𝑎 = 1 + 𝛼𝛿

𝑦(8)
(9)

Where the yield displacement of the pier (𝛿𝑦 ) and 𝛿𝑢 is ultimate displacement of the reinforced
concrete column can be obtained in Eq. (8) and (9) respectively.is the product of the horizontal
displacement at the time of yielding of axial tensile reinforcing bars at the outermost edge of thecolumns bottom section. (𝛿𝑦0 ) and the result from dividing the ultimate bending moment at column
bottom section (Mu), with the bending moment at the time of yielding of axial tensile reinforcing bars
at the outermost edge of the column’s bottom section (My0) as shown in Eq. (10). For the ultimate
displacement of reinforce concrete column (𝛿𝑢 ) computation can be as shown in Eq. (11), where 𝜑𝑢is the ultimate curvature at the column’s bottom section, 𝜑𝑦 is the yield curvature at the column’sbottom section and 𝐿𝑝 is the plastic hinge length and h is the height of the super structural inertia
force from the bottom of the column.
𝛿𝑦 =𝑀𝑢𝛿𝑀𝑦0 𝑦0𝛿𝑢 = 𝛿𝑦 + (∅u-∅y) Lp (h-(Lp/2))

(10)
(11)

Table 3-a.First Verification Method Results (using Kobe Earthquake)

Resultsforthefirst
verification
methodusingPaKhcW
Khc
Khc0CsμaδuδyW
the two types of Earthquake
2164kN 3890kN 0.38021 0.52143 0.72916 1.44043 0.39011 0.23492 10230kN
Ground Motion (Type I andType II) are shown in Table
Table 3-b.First Verification Method Results (using Tohoku Earthquake)4-aandTable
4-brespectively. For the Kobe
Pa
KhcW
Khc
Khc0
Cs
μaδu
δyW
earthquake
resultsof2164kN 4818kN 0.47094 0.64587 0.72916 1.44043 0.39011 0.23492 10230kN
3,890.0 kN for ( 𝑘ℎ𝑐 W)
which is greater than the value of lateral strength of the reinforced concrete column (Pa) of 2,164.0 kN.
So much with the Tohoku earthquake results which value of (𝑘ℎ𝑐 W) is much bigger of 4,818 kN.
4.2 Second Verification Method

Residual displacement is the amount of retained displacement from a large ground motion shaking
after an earthquake. Large residual displacement can cause difficulty in the repair process. To address
this problem, residual displacement must be verified so as to be safe. Residual displacement of thecolumn (𝛿𝑅 ) must be equal to or less than the allowable residual displacement (𝛿𝑅𝑅 ) of the column asshown in Eq. (12).
𝛿𝑅 ≤ 𝛿𝑅𝑅(12)𝛿𝑅 = 𝑐𝑅 (𝜇𝑟 − 1)(1 − 𝑟)𝛿𝑦

(13)

Residual displacement can be obtained as shown in Eq. (13), where CR is the modification
factor on residual displacement valued 0.60 for a reinforced concrete column, 𝜇𝑟 is the maximum
response ductility ratio of piers, r is the ratio of the secondary post-yielding stiffness to the yielding
stiffness of a pier and the ratio value of 0 shall be taken for reinforced concrete column. Residualdisplacement can be obtained as shown in Eq. (14).

12𝐶 𝑘2𝜇𝑟 = � 𝑧𝑃ℎ𝑐0 � + 1𝑎(14)For the computation of the allowable residual displacement, (𝛿𝑅𝑅 ) is provided as shown in Eq. (15).
Where h is the height of the super structural inertia force from the bottom of the column.
𝛿𝑅𝑅 =

ℎ100

(15)

Zone modification factor (Cz),standard value of the design horizontal
μr
khc0PaδyδR
δ Raseismic coefficient for level 2
0.4282m.
0.1468m.
4.0381
0.52142164kN
0.2349m.
earthquake ground motion (𝑘ℎ𝑐0 ) andthe lateral strength of the reinforced
Table 4-b. Second Verification Method Results (using Tohoku Earthquake) concrete column (Pa) values are thesame value for the first modification
μrkhc0Pa
δyδR
δ Ra
method. See Table 5-a and Table 5-b0.657m.
0.1468m.
5.066120.52142164kN
0.2349m.
for tabulated results.
.

Table 4-a. Second Verification Method Results (using Kobe Earthquake)

4.7 Analysis Computation Results
Dynamic response analysis results described the behavior of the column after application of the Kobe

Table 5. Dynamic Analysis Response Resultsδ ( Dynamic Analysis Response ) (m)0.324δy ( Yield Displacement ) (m)0.235δa ( Allowable Displacement ) (m)δu ( Ultimate Displacement ) (m)

0.338
0.39

earthquake ground motion. Tabulated results are
as shown in Table 5. The graph in Figure 2
explains that the bridge column displacement
behaves inside the allowable displacement of thecolumn which tells us that the bridge column issafe

5. CONCLUSIONS
Bridges are a lifeline structures, quick response todisaster and quick recovery of the area depends on
the serviceability of concerned bridges.
Verification of bridge design seismic performanceis very important especially for existing and oldbridges. For a third world country it is very
advantageous to the government to preserved oldbridges serviceability rather than constructing a
new one. After the comparison of specificationsand verification using two different earthquakes
conclusions are concluded as follows:

ii.
iii.
iv.

i.
Based on the dynamic response analysis
the model bridge can withstand the Kobe likeearthquake input ground motion. Actual
displacement less than allowable displacement.
Model Bridge is so ductile that even after a very large displacement at column after input of
Kobe and Tohoku earthquake ground motion the Model Bridge will not collapsed.
Bridges with high ductility performance, usually endure residual displacement.
Based on Japanese verifications on bridge seismic performance, Model Bridge failed in bothdemand force verification and displacement verification. One interesting factor is theverification of residual displacement which is not included in our bridge seismic performance
specification.

ACKNOWLEDGEMENT
I would like to express my heartiest gratitude to Mr. Sato Takashi, staff Structural Engineering
Division-Earthquake Engineering and Wind Engineering of CHODAI Co., LTD, Japan for (doingdynamic analysis), and giving valuable data’s, suggestions and ideas and guidance during my study.

REFERENCES
AASTHO Guide Specification for LRFD Seismic Bridge Design, 2nd Edition 2011
CHODAI CO., LTD., Consulting Engineers & Planners, Japan, use of software TDAP III (TAISEI CO.
& ARK INFORMATION SYSTEMS) for Dynamic Analysis
Department of Public Works and Highways D.O. No.75, series of 1992, issued on July 17, 1992,
Department of Public Works and Highways Regional Office XIII, Materials Quality Control andHydrology Division (MQCHD), Soil Exploration Results, Maglambing Bridge
Department of Public Works and Highways Regional Office XIII, Planning and Design DivisionJAPAN ROAD ASSOCIATION March 2002, Specification for Highway Bridges, PART V SEISMICDESIGN 1-230