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SEISMIC PERFORMANCE EVALUATION OF A BASE-ISOLATED BUILDING

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 1, January 2019, pp.285–296, Article ID: IJCIET_10_01_027
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
©IAEME Publication
Scopus Indexed
SEISMIC PERFORMANCE EVALUATION OF A
BASE-ISOLATED BUILDING
U. Wijaya
Department of Civil Engineering, Universitas Tarumanagara, Jakarta, Indonesia
R. Soegiarso
Department of Civil Engineering, Universitas Tarumanagara, Jakarta, Indonesia
Tavio
Department of Civil Engineering, Institut Teknologi Sepuluh Nopember (ITS),
Surabaya, Indonesia
ABSTRACT
The Lombok and Palu Earthquakes that have recently occurred in Indonesia caused
significant damage. Earthquakes are closely related to damage, landslide, and the loss
of life and economy. However, the causes of these things are not solely due to the
earthquake itself. The cause loss of life and economy caused solely due to the collapse
of buildings that built by humans during an earthquake. To reduce impact loss of life and
economy, Performance Based Seismic Design (PBSD) using based isolator can be one
of the solution. By using PBSD economic considerations the cost of repair after an
earthquake can be predicted. In this study, modeling 12-storey reinforced concrete
buildings located in Yogyakarta Indonesia stands on soft soil using base isolator High
Damping Rubber type (HDR HH090X4S, thickness 20 cm product of Bridgestone). The
average of non-linear dynamic time history analysis of seven ground motion respectively
Denali earthquake 2002, Imperial Valley 1940, Kobe 1995, Loma Prieta 1989,
Northridge 1994, San Fernando 1971, Superstition Hills 1987 was conducted. Seismic
response modification coefficient R was taken respectively 2.5, 3.5, 5.5, and 8. From
these coefficients, the performance of the building is obtained with R 2.5 and R 3.5
performance building in the category of immediate occupancy, R 5.5 and R 8 Category
damage control. Thus the building with R 2.5 and R 3.5 according to FEMA 273 will
produce a building with a repair cost of 25% and repair time only 1 day, so that after
the earthquake the building can resume normal operation.
Keywords: earthquake, PBSD, time history analysis, base isolator.
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Cite this Article: U. Wijaya, R. Soegiarso and Tavio, Seismic Performance Evaluation
of A Base-Isolated Building, International Journal of Civil Engineering and Technology
(IJCIET), 10 (1), 2019, pp. 285–296.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=1
1. INTRODUCTION
Indonesia is located at the subduction zone of tectonic plates, the Eurasian Plate, the IndoAustralian Plate and the Pacific Plate. In the most recent earthquake in Indonesia, the
earthquake in Lombok and Palu caused significant damage. Earthquakes are closely related to
damage, landslide, and the of loss of life and economy. However, the causes of these things are
not solely due to the earthquake itself. The cause loss of life and economy caused solely due to
the collapse of buildings that built by humans during an earthquake. To reduce impact loss of
life and economy, Performance Based Seismic Design (PBSD) using based isolator can be one
of the solution. By using PBSD economic considerations the cost of repair after an earthquake
can be predicted.
Rubber Base Isolator is the most effective tools to reduce earthquake force that is
transmitted to the building. Separating structures from the effects of earthquakes is the main
goal in using this device [1-2]. In principle, rubber base isolator can extend the fundamental
period of the structure far beyond the period of the high energy period of an earthquake when
it was deformed. For low-rise buildings under fifth floors can use the type hyperelastic low
damping rubber where it obtained from recycled rubber material, but for buildings higher than
fifth floors can use the type of hyperelastic high damping rubber combined with steel plate
material to get certain rigidity [3].
In this study modeling 12-storey reinforced concrete buildings located in Yogyakarta
Indonesia stands on soft soil using a High Damping Rubber type isolator (HDR HH090X4S
thickness 20 cm product of Bridgestone were used) [4].
Average of non-linear dynamic time history analysis of seven ground motion respectively
Denali earthquake 2002, Imperial Valley 1940, Kobe 1995, Loma Prieta 1989, Northridge
1994, San Fernando 1971, Superstition Hills 1987. According to ASCE 7-16, Seismic response
modification coefficient for the design of earthquake resistant buildings using a base isolator
was taken to respond the elastic conditions (R 2.5). Basically, base isolators can extend the
fundamental period of a building structure. Since the fundamental period of the building
extended, the acceleration response will be reduced and it will minimize building damage [57]. However, from the regulations of ASCE 7-16 limiting the coefficient of seismic response
modification is only R 2.5 so that in the economic value with the base isolator the economic
value of building prices will increase, but building performance will also increase [8]. Therefore
in this paper It will study buildings using base isolators designed in elastic responses (R 2.5),
R3.5, R5.5 and inelastic response (R 8.0) regarding the performance due to damage and building
repair costs after the earthquake according to FEMA 273.
2. BASE ISOLATOR DESIGN
2.1. Seismic Elastic Response
According to ASCE 7-16 the base isolators design considered is based on seismic elastic
response. Maximum consideration earthquake is 2500 years return period. For base isolator
design, there is no seismic response coefficient reduction. Regarding PBSD in this paper tried
to study the seismic response coefficient until reach inelastic condition (reduce factor up to 8).
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2.2. Bearing Stiffness
The horizontal rubber bearing stiffness can be shown in equation (1) and (2) as follows [9]:
=
(1)
Where: G = shear modulus of elastomer (MPa).
A = section area (mm).
tr = total thickness of rubber (mm).
D = maximum horizontal displacement (mm).
γ = maximum shear strain.
=
(2)
The vertical rubber bearing stiffness can be described in equation (3) as follows [6]:
=
(3)
Where: Ec = compression modulus of composite rubber-steel plate (MPa)
2.3. Design Displacement
Design displacement of base isolator can be illustrated in equation (4) and (5) as follows [10]:
=
Where: DD
g
TD
CVD
BD
(4)
= design displacement at the center of rigidity at the DBE (mm)
= gravity acceleration.
= isolated period (sec).
= seismic coefficient.
= damping coefficient for DBE.
=
Where: DM
g
TM
CVM
BM
(5)
= design displacement at the center of rigidity at the MCE (mm)
= gravity acceleration.
= isolated period (sec).
= seismic coefficient.
= damping coefficient for MCE
2.4. Composite Damping Coefficient
Composite damping coefficient of base isolator can be illustrated in equation (6) as follows
[11]:
=
∑
(6)
"
Where: β = base isolator damping ratio
KD = effective stiffness of isolation system
DD = design displacement at the center of rigidity at the DBE (mm)
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ED = effective linear properties from cyclic load
2.5. Base Shear Isolator
Base shear of base isolator can be illustrated in equation (7) as follows [7]:
Vb = KDmax DD
(7)
Table 1 Isolator Properties
HH070X4S
Outer Diameter (mm)
Weight (kN)
Mass (tonf)
Compressive Stiffness (103 kN/m) Kv
Initial Stiffness (103 kN/m) Ki
Post yield Stiffness (103 kN/m)
Characteristic Strength (kN)
Equivalent shear Stiffness (103 kN/m)
Equivalent Damping Ratio
700
7.90
0.80
2290
4.42
0.44
61.50
0.75
0.24
Figure 1 High Damping Rubber Bearing (Product catalogue Bridgestone)
2.6. Response Spectrum
In this research study the seismic area was located at Yogyakarta Indonesia and the
response spectrum can be illustrated in Figure 3. Site class categorized as soft soil based on soil
investigation data as illustrated in Table 2.
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Acceleraion (g)
Response Spectrum D.I. Yogyakarta
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
1
2
3
4
Period (s)
Figure 2 D.I.Yogyakarta Response Spectrum – Soft Soil [12]
Table 2 Site Class [12]
Sites Class
A-Hard Rock
B-Rock
C-Very dense soil and soft rock
D-Stiff soil
E- Soft soil
Vs (m/sec)
>1500
750 to 1500
350 to 750
175 to 350
< 175
N
N/A
N/A
>50
15 to 50
< 15
Su (kPa)
N/A
N/A
> 100
15 to 100
< 50
2.7. Ground Motion Selected
Seven ground motion records list in Table 3 and illustrated in Figures 4(a) to (n) [13].
Table 3 Selected Earthquake the Ground Motions
Earthquake
Year
Magnitude
Distance (Km)
Vs 30 (m/s)
Imperial Valley
1940
6.95
2.66
223.03
Denali
San Fernando
2002
1971
7.9
6.61
270.25
11.34
212.48
256
Superstition Hills
Kobe
1987
1995
6.84
6.9
5.02
38
1070.34
349.6
Loma Prieta
Northridge
1989
1994
6.93
6.69
1.81
5.61
2016.13
362.38
(a)
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(b)
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(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
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(k)
(l)
(m)
(n)
Figure 3 Selected Ground Motion
2.8. Scaling Procedure
According to ASCE 7-16, the target ordinate response spectrum for structures using a base
isolator is in the range of 0.5 TD to 1.25 TM. Each of graph should be composite with Indonesia
earthquake code (SNI 1726:2012) as shown in Table 4 and Figures 5(a) to (d). The pseudoacceleration target for site class was taken as the median of the damping 5% pseudoacceleration spectrum response that corresponds to the average horizontal component of the
record that is not scaled can be illustrated in equation (8) as follows [14]:
# = ∑.&/ $%& ' ()*. %& ,-
(8)
Where A i and Ai are the target spectral acceleration and record's (unscaled) spectral
acceleration, respectively. The legend ith is spectral period, and n is the number of periods from
0.5TD up to 1.25TM. The purpose is to determine Scale Factor (SF) that decrease the erratum
using equation (9) as follows [14]:
)*
0∑.&/ %& %& 1/(∑.&/ %& %& ,
(9)
From Equation (9), it produces an optimal scale factor to ensure a scale spectrum that matches
the target spectrum from 0.2TI up to 1.5TI. The ground motion record scale factor according to
Equation (9) is shown in Table 4 [14].
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Table 4 Scaling Factor of Ground Motion
Earthquake
Year
Denali
2002
Imperial Valley
Kobe
1940
1995
Loma Prieta
1989
Northridge
1994
San Fernando
1971
Superstition Hills
1987
Station
Direction
Magnitude
TAPS Pump Station
#10
El Centro Array #9
Amagasaki
Los Gatos Lexington Dam
Anaverde Valley City R
Pacoima
Superstition Mtn
Camera
X
Y
7.9
12.974
12.424
6.95
6.9
1.339
0.977
1.683
0.832
6.93
0.708
0.743
6.69
8.955
8.955
6.61
0.474
0.509
6.84
0.998
0.634
(a)
(b)
(c)
(d)
Figure 4 Selected Ground Motion
3. ANALYSIS PROCEDURE
A mathematical model of the structure is determined to get seismic response using base
isolator. Computer program that will be used is ETABS non-linear v16.2.1. Analytical
procedure is determined as follows [9]:
1. Determined Risk Category.
2. Determined Importance factor (Ie).
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3. Site specific ground motion procedure.
4. Determined Site soil class (SA-SF).
5. Determined Site coefficient short and long period (Fa, Fv).
6. Design spectral acceleration parameter (SDS, SD1).
7. Determined Seismic Design Category (A-F).
8. Determined Seismic response modification coefficient.
9. Determined base isolator properties.
10. 3D dynamic non-linear time history analysis.
11. Base isolator PBSD method.
3.1. Building Data
In this study, the building data as follows:
1. Building function
: Apartment.
2. Building height
: 43 m.
3. First floor level
: 4.5 m.
nd
th
4. Floor level 2 – 12
: 3.5 m.
5. Floor numbers
: 12 storey (43 m).
6. Location
: Yogyakarta.
7. Material
: Reinforced concrete.
8. Concrete grade (f’c)
: 35 MPa.
9. Reinforcement grade (fy)
: 420 MPa.
10. Thickness of floor
: 12 cm.
11. Thickness of roof
: 12 cm.
12. Column (K1)
: 60 x 60 cm.
13. Primary beam (B1) x-x
: 40 × 60 cm.
14. Primary beam (B2) y-y
: 50 × 70 cm.
15. Secondary beam (B3)
: 25 × 35 cm.
16. Thickness of Shear wall
: 35 cm.
17. Base isolator (BI)
: HDR HH090X4S (Bridgestone product).
18. Thickness of BI
: 20 cm.
19. Ground Motion
: Denali Earthquake 2002, Imperial Valley 1940,
Kobe 1995, Loma Prieta 1989, San Fernando
1971, Superstition Hills 1987.
20. Soil type
: Soft Soil.
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Figure 5 Plan view twelve storey building
4. RESULTS AND DISCUSSION
From non-linear time history analysis, it obtained that twelve stories building with
height 43 m, sitting at soft soil, isolated with HDR HH070X4S product of Bridgestone Japan
at each column support. Analysis of seismic modification coefficient of R 2.5; R3.5; R 5,5 and
R 8.0 were calculated and illustrated in Figures 6(a), (b), 7(a), and (b).
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0.025
Drift
0.015
0.01
0
Displacement (m)
0.02
R = 2.5
R = 3.5
R = 5.5
R=8
12
11
10
9
8
7
6
5
4
3
2
1
0
180
160
140
120
100
80
60
40
Storey
R=
2.5
R=
3.5
20
(b)
Story Drift (x-x)
0.005
12
11
10
9
8
7
6
5
4
3
2
1
0
0
Storey
Displacement (x-x) (a)
Figure 6 Displacement and drift elastic - inelastic X direction
(a)
10
9
8
7
7
5
6
5
0
160
140
0
120
1
0
100
2
1
80
3
2
60
3
40
4
20
4
Displacement (m)
Drift
0.02
6
0.015
Storey
8
0
Storey
9
11
0.01
10
R = 2.5
R = 3.5
R = 5.5
R=8
12
R = 2.5
R = 3.5
R = 5.5
R=8
11
0.005
12
(b)
Story Drift (y-y)
0.025
Displacement (y-y)
Figure 7 Displacement and drift elastic - inelastic Y direction
Figures 6(a), (b), 7(a), and (b) explain the building deformation occurred when using
seismic response modification coefficient, R, i.e. 2.5 and 3.5 It obtained performance level
Immediate Occupancy (IO) with repair costing 25% and repair time only one day, otherwise
for seismic response modification coefficient R 5.5 and R 8, it can be obtained the performance
level damage control with repair costing 50% and repair time is between 7 days to 30 days as
shown in Figure 8. All of the coefficient fulfills the minimum requirement for PBSD for base
isolator.
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Figure 8 Illustration of PBSD [15]
5. CONCLUSION
This paper obtained the result of performance based seismic design for building that is use base
isolator. According to that illustrated, the following below is the conclusion of this study:
1. PBSD using base isolator for seismic response modification coefficient R 2.5 (elastic
condition) got the best performance IO and only need one day repair and 25% of repair
costing during the earthquake, after that the building can be use and operate.
2. PBSD using base isolator for seismic response modification coefficient R 8 (inelastic
condition) got the performance damage control and need 7-30 days repair and 50% of repair
costing during the earthquake, after that the building can be use and operate.
3. Seismic response modification coefficient R 8 is the maximum level that is allowed for
PBSD using base isolator, but using this method, investment for base isolator will be useless
because level of damage is 50% and need to repair more than 30 days.
ACKNOWLEDGEMENTS
The authors would like to gratefully acknowledge for all the facilities and the supports received
to make this research possible.
REFERENCES
[1]
Habieb, A. B.; Milani, G.; and Tavio, “Two-Step Advanced Numerical Approach for the
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[2]
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Seismic Performance Evaluation of A Base-Isolated Building
[3]
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