Citation:Saadun, M. A., S. Nakai (2021), Fragility evaluation of typical RC government quarters
buildings designed by BS 8110 in Sabah, Malaysia, Synopsis of IISEE-GRIPS Master’s Thesis.

FRAGILITY EVALUATION OF TYPICAL RC
GOVERNMENT QUARTERS BUILDINGS DESIGNEDBY BS 8110 IN SABAH, MALAYSIA
Mohd Assyarul Bin Saadun1,2

Supervisor: Shoichi NAKAI3
ABSTRACT

A study to evaluate the performance of the existing building by the development of fragility curves wasintroduced in this paper. A typical five-story residential government RC building becomes the target
building, designed based on BS 8110 without incorporating any seismic action. It consists of plan andelevation irregularities. The target building was analyzed by performing Incremental Dynamic Analysis(IDA) and excited by several ground motion records through equally scaling from 0.1 g to 0.8 g withevery 0.1 g increment. Nonlinear time-history analysis was executed using STERA 3D software andrecorded the structural response in terms of maximum inter-story drift ratio (IDRmax). This study initiatedtwo different methods of developing fragility curves: (1) using a limit state of five levels of performancebased seismic designs, and (2) the conditional probability of IDRmax exceeded the specified limit state of
IDR with the aid of static pushover analysis. Both X- and Y-directions were examined to investigate theirregularity effect of the target building. Findings indicated that X-direction is weaker than Y-direction
for both methods to reach or exceed specific performance levels and for the conditional probabilities ofexceeding the targeted limit state at a given peak ground acceleration (PGA).
Keywords: Fragility curve, performance levels, limit state, incremental dynamic analysis.
1. INTRODUCTION
Malaysia is categorized as the low-seismicity zone and tectonically located within a region that is
relatively stable Sundaland (Saruddin & Nazri, 2015). Unfortunately, Sabah state, which is situated at
Kalimantan Island, is categorized as a moderate-seismicity zone. The Ranau Earthquake on June 5th,2015, changed the Earthquake Engineering landscape in Malaysia, which seismic action should beincorporated in the building design. Government buildings constructed before 2017 are mainly designed
based on the conventional BS 8110 reinforced concrete (RC) building code without integrating seismicaction. Additionally, most buildings in Malaysia, particularly apartments and office buildings, had anirregularity in plan and elevation, which tend to cause seismic hazards. Hence, there is a need to evaluate
the performance of existing Government buildings which fragility evaluation is one of the bestapproaches, thus initiating this research topic.
Therefore, this study intended to develop and evaluate fragility curves for five-story RCGovernment quarters buildings with typical plan and elevation irregularities. Furthermore, this study
aims to assess the seismic performance of the target RC structure designed by BS 8110 code and identify
the size of an earthquake the building can withstand.

1Public Works Department (PWD), Malaysia.
IISEE-GRIPS Master’s course student.
3
Professor Emeritus, Chiba Univ., and Visiting Research Fellow, Building Research Institute.
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2. DATAThe structural model was a five-story frame categorized as a typical mid-rise building for a residential
government building in Malaysia. This structural model frame was classified as an RC moment-resisting
frame designed by BS 8110 without incorporating seismic action. Additionally, it possessed irregularity
in plan and elevation, which tend to have various columns and beams. The height of each floor of thetarget building is 3.3 m, with an overall dimension is 30.6 m (longitudinal) by 25.8 m (transverse).
Characteristics of material strength are: 1) concrete compression strength, fC is 35 N/mm2, 2)
characteristic yield strength, fyk for main bars is 460 N/mm2, and 3) fyk for shear links is 260 N/mm2.
There was no shear wall for the target building.
Table 1. Examples of detailing for structural elements for beam and column.
Parameters
Beam name: B11
Beam name: B17Column
Size (mm)250  475
250  375
250  350
Top: 3T16
Top: 3T16
Reinforcement
4T25
Bottom: 3T16
Bottom: 2T16
Shear link
R10-200
R10-200
R10-200
2.5

Sa (g)

2.0
1.5
1.0
0.5
0.0
0.01

0.1

1

10Period (sec.)

Figure 1. Analytical model of the target building
performed by STERA 3D software.

Figure 2. Ground motions records scaled at
PGA of 0.4 g.

The target area, Sabah state, was used as a reference for selecting ground motion records.
The Sabah state area was mainly affected by distance earthquakes, and the choice of far-field record sets
was essential for collapse assessment by nonlinear dynamic analysis. Criteria selection of ground motion
records set referred to FEMA P695. Totally 40 ground motion records consisting of horizontal
components were selected with the distance of sites 10 km or greater than that from the fault rupturethat was considered. These characteristics of ground motion records selection were used to develop
fragility curves corresponding to the limit state of building failure.
The 40 ground motion data were obtained from the Pacific Earthquake Engineering
Research Center (PEER). Selection criteria of source magnitude based on large magnitude events cancause building collapse even for new structures. Ground motions with a moment magnitude range
between 6.5 to 6.9 were selected for this study, as detailed in FEMA P695. Most of the site conditions
were in site class D (stiff soil). Figure 2 shows 40 sets of motion records scaled at peak groundacceleration (PGA) of 0.4 g.
Furthermore, for developing fragility curves by using a limit state of five levels ofperformance-based seismic designs, it required seven or more time-history analyses to record thestructural response. Then, selected seven sets of ground motion records (Table 2) will limit the state ofperformance level in developing the fragility curves for this study.

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Table 2. Selective ground motion records for IDA.
No. Name Record
12
34
567

GMC 1400
GMC 0001
GMC 0901
GMC 2700
GMC 0902
GMC 0002
GMC 0003

EventStation Name

YearImperial Valley-06

El Centro Array #12
El Centro Imp. Co. Cent
Westmorland Fire StationSunnyvale - Colton Ave.
Lake Hughes #1
Fukushima
Kobe University

1979
1987
1987
1989
1994
1995
1995

Superstition Hills-02
Loma Prieta
Northridge-01
Kobe, Japan

Earthquake
Magnitude (MW)
6.53
6.54
6.54
6.93
6.69
6.90
6.90

3. METHODOLOGY
3.1. Incremental dynamic analysis (IDA)
A method or technique to identify the structural limit state in the series of the amplified intensity ofground motion has been discovered by the IDA to determine the level of shaking that will cause astructure to exceed a specified limit state, thus failing a given performance objective (Vamvatsikos &Allin Cornell, 2002). IDA was developed by performing a series of nonlinear time-history analyses
under a suite of ground motion records by equally scaling each record to several intensity levels andrecording the structural responses. Ground motions records can be from real earthquakes or generatedartificially.
This research used two different methods: by limit state of performance levels andconditional probability under static pushover analysis (SPOA) approach. Both ways were conductedusing seven and 40 ground motion records for limit state by performance levels and conditionalprobability, respectively. The IDA was carried out by nonlinear time-history analysis that was performed
by STERA 3D (Saito, 2020) software. The seismic intensity was amplified from 0.1 g to 0.8 g for every
0.1 g increment.
3.2. The limit state of a structural model
The FEMA 356 and a research study from Xue et al. (2008) stated the limit state in performance level
conditions. Table 3 shows IO and LS having similar performance levels between FEMA 356 andsuggested values by Xue et al. (2008). Damage Control (DC) lies in between Immediate Occupancy(IO) and Life Safety (LS), while an Operational (OP) is at the beginning of performance level.
Additionally, the Collapse Prevention (CP) value suggested by Xue et al. (2008) is more conservative
compared to FEMA 356 (Ibrahim & El-Shami, 2011).
Nonlinear static pushover analysis (SPOA) was carried out to evaluate the lateral
deformation of the building in determining the conditional limit state for the second method of fragility
curves development. In SPOA, the lateral force will be statically applied to the building, whichever inX or Y direction. An applied force will gradually increase until the sequenced failure mode occurred.
These failure modes will start from flexural until shear failure occurs. Hinges between the connectionof the structural members will develop from the formation of the elastic state, followed by the yield
point until plastic hinges occur. In addition to this, the ductility of the structural members can be obtained,
and the load at which the failure modes occur is recorded. The incremental load will push the building
until it reaches global collapse or a predefined drift limit.
Additionally, output data from SPOA such as capacity curve and drift-shear relation curve
will be used in these studies to determine the limit state of the building. The estimation of the limit stateof the structural model in the weaker direction and the weakest floor regarding the failure mode wascalculated in terms of the IDRmax.

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Table 3. The IDRmax for different phases of performance level between FEMA 356 and Xue et al.
(2008) proposed values.
FEMA 356
Xue et al. (2008)(elements: concrete frames)(suggested values)
Maximum inter-story drift
Limit state parameterMaximum inter-story drift ratioratio
IOLSCPOPIO
DCLSCPPerformance level(1.0%)(2.0%)(4.0%)(0.5%) (1.0%) (1.5%) (2.0%) (2.5%)
Where: OP – Operational, IO – Immediate occupancy, DC – Damage control, LS – Life safety, and CP –Collapse prevention.
Description

3.3. Statistical analysis for fragility curves development
The conditional probability of a structure to reach or exceed a specific damage state corresponding to
the PGA is expressed in Eq. (1) as below:
𝑃 𝐷 𝑃𝐺𝐴𝛷𝑙𝑛 𝑃𝐺𝐴𝜎𝜇(1)where 𝛷 is the standard normal cumulative distribution function, 𝜇 is the mean value, and 𝜎 is thestandard deviation of the natural logarithm of PGA at which the structural model reaches the limit stateof performance levels. Furthermore, the mean and standard deviation log-normal functions were suitedfor different performance levels: OP, IO, DC, LS, and CP related to the structural model.
Differing from the method of defining the conditional probability that maximum inter-story
drift (IDRmax) exceeds the specific limit state of IDR at a given PGA, the equation is expressed as Eq.
(2) below:𝐼𝐷𝑅𝑃 𝐼𝐷𝑅
1where 𝐼𝐷𝑅
Eq. (3) below:%𝛷

1𝑙𝑛 𝐼𝐷𝑅𝑃 𝐼𝐷𝑅𝑙𝑛 𝐼𝐷𝑅𝛿is equal to mean value (), while𝛿ln 𝐼𝐷𝑅%𝐼𝐷𝑅%(2)
𝛿ln 𝐼𝐷𝑅is standard deviation and expressed as%2(3)where 𝛿 can be represented as the equivalent dispersion of the 16th and 84th percentile data of IDRmax
in the normal distribution of statistical data for specified ground motion intensities.
The probability of exceedance is indicated in the fragility curve by means is the damage
parameters representing by IDRmax, lateral drift, and base shear of the structural model under predefined
limiting value at a given intensity measure (IM) of ground motion. In other words, if a predetermined
PGA value of 0.5 g is occurring, it will provide a percentage of damage measure at which the line wascrossing the fragility line.
4. RESULTS AND DISCUSSION
Through the development of fragility curves, the seismic performance of the target building can beevaluated. Both fragility curves of the X- and Y-directions will be obtained to assess the performanceof the building in terms of plan and elevation irregularities effect. In addition, from observation of Figure
3, under weak ground motions, which is 0.2 g, the probability of the target building will be experiencing
the OP and IO levels in the X-direction that is 83% and 32%, respectively. However, the likelihood of4

reaching LS and CP levels is 0%. Meanwhile, in the Y-direction for 0.2 g, the probability of getting theOP and IO levels is 72% and 17%, respectively.
Furthermore, when exposed to the strong ground motions with PGA equal to 0.5 g, thetarget building will experience approximately the probability of 67% for LS and 44% of CP in the Xdirection. The probability of reaching or exceeding the IO level is around 97% and 94% in X- and Ydirections, respectively. In addition, the probability of reaching OP levels is 100% for both X- and Ydirections. Meanwhile, in the Y-direction, the probability of achieving or exceeding LS and CP levels
is approximately 45% and 21%, respectively. Undoubtedly, the irregularities of the target building
affected the behavior of the structure, which was illustrated in fragility curves. The effect of irregularities
on the building was clearly shown at OP, IO, LS, and CP performance levels. The X-direction was seen
as a weaker direction than the Y-direction.
Meanwhile, the fragility curve development by conditional probability limit state showsthat the probability of damage increases as the level of intensities becomes large. Figure 6 (b) represents
the different pattern of fragility curves between X- and Y-directions, which indicates the Y-direction of
the target building performs better in seismic response than the X-direction for the conditional
probabilities of exceeding 1/125 rad at a given PGA.
GMC 1400
GMC 0002
GMC 0902
GMC 2700

0.6

GMC 0001
GMC 0003
GMC 0901
Mean

GMC 1400
GMC 0002
GMC 0902
GMC 2700

0.8
PGA (g)PGA (g)

0.8

0.4
0.2
0.0

0.6

GMC 0001
GMC 0003
GMC 0901
Mean

0.4
0.2
0.0

0.0

0.5
OP

1.0
IO

1.5
DC

2.0
LS

2.5
3.0
CP
DRIFT (%)

0.00.5
OP

1.0
IO

1.5
DC

2.0
LS

2.5
3.0
CP
DRIFT (%)

1.0

1.0

0.8

0.8
0.5% (OP)0.6

1.0% (IO)

0.4

1.5% (DC)2.0% (LS)0.2

Probability

Probability(a)(b)
Figure 3. The IDA curves for: (a) target building in X-direction and (b) the target buildingin Y-direction.

0.6

0.5% (OP)1.0% (IO)

0.4

1.5% (DC)2.0% (LS)

0.2

2.5% (CP)0.0

2.5% (CP)

0.0
0.0

0.2

0.4

0.6

0.8
PGA (g)

0.0

0.2

0.4

0.6

0.8
PGA (g)

0.40

0.40

0.30

0.30

0.20

Target Drift 1/200
Target Drift 1/100
Target Drift 1/50
Column Flexural Failure

0.10
0.00
0.000

Qi/ W

Qi/ W(a)(b)
Figure 4. Fragility curves of the target building in (a) X – direction and (b) Y – direction.

0.010

0.020

Column Flexural Failure
Target Drift 1/200
Target Drift 1/100
Target Drift 1/50

0.20
0.10
0.00
0.000

0.030
Drift, Ri

0.010

0.020

0.030

Drift, Ri(a)(b)
Figure 5. Drift-shear relation of the target building in the (a) X-direction and (b) Y-direction.

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1.0
0.8
0.7

0.8

16th - X-Dir.
50th - X-Dir
84th - X-Dir
16th - Y-Dir.
50th - Y-Dir.
84th - Y-Dir.

0.5
0.4
0.3
0.2
0.10.000

Probability

PGA (g)

0.6

0.005

0.010

0.015

(a)

0.020

0.025

0.030

0.6
0.4

X - Direction
Y - Direction

0.2
0.00.035

IDRmax (rad)

0.0

0.1

0.2

0.3

0.4

(b)

0.5

0.6

0.7

0.8

PGA (g)Figure 6. (a) The IDA curves for 40 sets of ground motion records equally scaled at every
0.1 g from 0.1 g to 0.8 g to record the structural response. (b) The fragility curves ofconditional probabilities of exceeding damage measure at the first flexural failure of acolumn at 1/125 rad in X-direction and Y-direction.
5. CONCLUSIONS
Through the observation of OP, IO, LS, and CP performance levels, X-direction exhibits a weakerdirection than Y-direction from the assessment percentage of probability of collapse. Furthermore, thefragility curves developed by the limit state method using specific IDR also show similar results, which
is X-direction is weaker than Y-direction. An evaluation of the appropriate shape of the building underintensity measures in both X- and Y-directions can be obtained from this study. The performance of thebuilding in a similar category can be evaluated by developing a single fragility curve.
Further research is recommended to determine or evaluate the structural vulnerability ofdifferent categories of the existing building at high seismicity zones. On the other hand, the retrofitting
method of the existing building is also essential to enhance performance capacity and withstand theseismic load.
ACKNOWLEDGEMENTS
This research was conducted as the individual study of the training course “Seismology, Earthquake
Engineering and Tsunami Disaster Mitigation” by IISEE/BRI, JICA, and GRIPS. I would like to express
my sincere gratitude to my supervisor, Dr. Shoichi Nakai, and my advisor, Dr. Hiroto Nakagawa, forsupervising and giving me beneficial advice, guidance, assistance, continuous support, and suggestions
during my individual study.
REFERENCES
Aisyah, S., Vafaei, M., Alih, S.C., and Aljwim, K., 2019, The Open Civil Eng. Journal, 13(1), 140–146.
ASCE., 2000, American Society of Civil Engineers, FEMA 356.
Ibrahim, Y.E., and El-Shami, M.M., 2011, IES Journal Part A: Civil and Struct. Eng., 4(4), 213–223.
Nagae, T., Suita, K., and Nakashima, M., 2006, Annuals of DPRI, Kyoto Univ. No. 49 C, 189-196.
PEER Ground Motion Database, Pacific Earthq. Eng. Research Center, https://ngawest2.berkeley.edu/.
Q. Xue, C.-W. Wu, C.-C. Chen, K.-C. Chen., Engineering Structures, 2008. 30(6), 1535-1547.
Saito T., 2020, STERA 3D Technical Manual Ver. 6.4.
Saruddin, S. N. A., and Nazri, F. M., 2015, Procedia Engineering, 125, 873–878.
Vamvatsikos, D., and Allin Cornell, C., 2002, Earthq. Eng. Struct. Dyn., 31(3), 491–514.

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