Citation:
Nwet Nwet Yi, T. Azuhata (2020), Seismic evaluation and retrofitting of existing reinforced
concrete buildings in Myanmar, Synopsis of IISEE-individual study report.

SEISMIC EVALUATION AND RETROFITTING OF
EXISTING REINFORCED CONCRETE BUILDINGS IN
MYANMAR
Nwet Nwet Yi1Supervisor:

Tatsuya AZUHATA2

ABSTRACT
Myanmar is an earthquake-prone country. Although earthquakes do not kill people, the subsequentcollapse of building, for example, can cause human death and economic losses. In this study, hazard
maps were initially used to implement an earthquake disaster mitigation strategy. Two cities, inparticular, Mandalay and Yangon, were selected to investigate the hazard risk of buildings in the highand low seismic zones. A three-story reinforced concrete (RC) building with brick walls was evaluatedby the Japan Building Disaster Prevention Association (JBDPA) standard and the Capacity Spectrum
Method (CSM). After evaluating the target building with the JBDPA standard and the CSM, it was
cleared that the target building did not meet requirements. Two simple retrofitting methods, RC column
jacketing and RC shear wall, were applied in order to retrofit the target building. These two methods are
not expensive and they only require the application of a simple technology. After construction of a small
number of RC shear walls or increasing the size of selected columns on the 1st story, the building could
be designated safe, even in a very high seismic zone. The results showed that we could obtain asatisfactory earthquake-resistant building.
Keywords: Seismic evaluation, Retrofit, Capacity Spectrum Method.

1. INTRODUCTION
Earthquakes are frequent events in Myanmar. The buildings should be resistant to earthquakes to avoid
the collapse of the buildings. Myanmar National Building Code (MNBC) was published in 2016. Before
2016, buildings were designed by the international building code like ACI. Although these buildings are
more robust than non-engineered structures, the seismic performance of these buildings is uncertain.
According to the recent hazard maps, which harmonize with the seismic design forces of MNBC, many
cities are in a zone with high seismic activity. When the earthquake struck in high seismic zones, thebuildings in those areas can suffer severe damage. It is needed to check the seismic capacity of thebuildings before potential future earthquakes happen. In this study, the low-rise building's seismic
performance was evaluated by the JBDPA Standard and the CSM method to investigate the hazard riskof buildings in high and low seismic zones. If the seismic performance of the building is deficient, retrofit
methods will be proposed.

1

2

Department of Meteorology and Hydrology, Myanmar.
International Institute of Seismology and Earthquake Engineering, Building Research Institute.

12. METEOROLOGY AND TARGET BUILDING
2.1. Meteorology applied in this study
The targeted building was evaluated by two methods: the seismic diagnosis method of the Japan Building
Disaster Prevention Association (JBDPA) and the capacity spectrum method (CSM). For the CSM, theauthor uses the STERA3D program (Saito).

SpectralResponseAccelerati
on,Sa(g)2.2. Design response spectrum by MNBC
1.5
1

Mandalay
0.5

Yangon

0
0

1

2

3

4

5

6

7

8

9

10

Period, T(sec)Fig.1. Comparison of design response spectrum of two cities.

In this study, the author produced twocities' design acceleration response
spectrum (2% probability ofexceedance in 50 years), referring to
the MNBC. The soil condition was
assumed to be soil type D, whichmeans stiff soil. Figure 1 shows acomparison of the two cities' design
response spectrum. The peak spectral
response accelerations Sa(g) of
Mandalay and Yangon were 1.34 g
and 0.6 g, respectively.

2.3. Outline of the structure targeted in this study
A three-story reinforced concrete building with brick walls was used as a case study in this study. The
strength of the brick walls was not considered in seismic evaluation because they were designed as nonstructural elements. The yield strength of the steel reinforcement was 275.79 N/mm2, and the design
compressive strength of the concrete was assumed to be 17.24 N/mm2, which is the minimum
requirement of MNBC, in this calculation. The areas of the 1st story, 2nd story, and 3rd story were 140
m2, 152 m2, and 80 m2, respectively. The heights of the 1st story, 2nd story, and 3rd story were 3.81 m, 3.5m, and 3.5 m.

Fig.3. Front Elevation.

Fig.2. Ground floor plan.

23. SEISMIC DIAGNOSIS BY JBDPA SECREENING METHOD
3.1. The results of the second level screening method

Story

In the application process of the JBDPA method, it was found out that all columns in the X-direction
and some columns in the Y-direction have a low ductility index F(F=1), although the failure mode ofthem was flexural. The reasons for these results were that the tensile reinforcing ratio Pt of all columns
was higher than 1%, and the axial force acting on those columns was high. Due to the higher P t ratio,bond splitting failure can occur in the columns. Thus,
Comparison of Is and Iso
the author investigated the possibility of this failure(Second Level Screening)4
Isotype by a more accurate method. AIJ structural design
3
guidelines for reinforced concrete buildings (1994)
Is (Xwere used to check the column's bond splitting failure.
direction)
2
Results obtained from the AIJ guidelines showed that
Is (Ydirection)bond splitting failure might not occur in all columns.
1
Therefore, Pt values were neglected in the JBDPA
0
seismic evaluation, and the Is value of the target
00.5Is and Iso 1
1.5
building was calculated again in both directions.
Figure 4 shows the comparison of IS and ISO in secondFig.4. The comparison of IS and ISO.
level screening. Only the 1st story required a retrofit.

4. SEISMIC PERFORMANCE EVALUATION BY CAPACITY SPECTRUM METHOD
4.1. The results of the capacity spectrum method
The seismic response can be predicted as the performance point by the CSM method, as shown in Figures
5 and 6. From the performance points of the structure, demand story drifts for each city were obtained.
The limit story drifts of the structure were compared with the demand story drifts for two cities, as shownin Table 1. It was observed that the limit drift on the 1st story was lower than the corresponding demand
story drift. Therefore, the target building was unsafe in both high and low seismic zones.
Table 1. Comparison of limit and demand story drifts of the structure.
Mandalay
YangonLimit story
2% Probability 10% Probability 2% Probability 10% Probability
drifts of thestructure
demand story drifts(cm)demand story drifts(cm)- (NG)
3.98 (NG)3.45 (NG)
2.81 (NG)1.52- (NG)
3.35
2.97
2.4
7.01
- (NG)
4.25
3.72
3.04
7.01

Story
1
2
3

Performance Point for Mandalay City

1400

Performance point for Mandalay City

1000
800

1000

µ=1

800

Sa(cm/s^2)

Sa(cm/s^2)1200

h=0.05600
400

h=0.05600

400

Performance
Point

200

200
0

0

4

8

12

16

20

24

µ=1
µ=2
µ=3

Capacity Curve

0

28

0

Sd(cm)

2

4

6

8

10

Sd(cm)

12

14

16

18

Fig.5. The building's performance point for Fig 6. The building's performance point for Yangon
Mandalay city using the demand spectrum (2% city using the demand spectrum (2% probability).
probability).

3

5. RETROFITTING
5.1. Basic concept for retrofitting
The author judged the original building needs a retrofit based on the results shown in the previous chapter.
The retrofitting technique is an effective way to minimize the damage caused by earthquakes. Figure 7
shows the retrofit model by installing RC shear walls, and Figure 8 shows the retrofit model by RC
column jacketing. The main purpose of seismic retrofitting shown in figure 7 is to upgrade the strength,
and that of the other retrofitting shown in figure 8 is to upgrade the ductility of a building to meet theseismic performance demands.

Increased column size

Shear wallFig.7. The retrofit model by installing
RC shear walls on the 1st story.

Fig.8. The retrofit model by RC column jacketing on the 1ststory.

5.2. Seismic rehabilitation of the structure using RC shear walls

Story

The author suggested installing three RC shear walls in the X-direction, and four RC shear walls in the
Y-direction on the 1st story. The thickness of each wall is 200 mm. The compressive strength of concreteand the yield strength of shear
Comparison of Is and Iso
reinforcement in the RC shear walls were
(Second Level Screening)4
Fc=18 N/mm2 and σwy=294 N/mm2. PostIso
installed anchors were placed along withIs (X-direction- RC
boundary columns and beams of the3
Shear Walls)
existing structures to transfer shear forces
Is (Y-direction, RC
Shear
Walls)
between the existing structure and infilled2
shear walls. The 1st story's seismic
capacity was upgraded after constructing
1
RC shear walls. Figure 9 shows that theseismic capacity of all stories evaluated by0
the second level screening of the JBDPA
00.5 Is and Iso 1
1.5
was enough in the longitudinal andtransverse directions.
Fig.9. Comparison of IS and ISO (X and Y direction).

45.3. Seismic rehabilitation of the structure using RC column jacketing
Comparison of Is and Iso(Second Level Screening)

Story

4
3

Iso

2

Is (X-direction,
RC Column
JacketingIs(Y-direction, RC
Column Jacketing)10
0.5 Is and Iso 1

0

1.5

Fig.10. Comparison of IS and ISO (X and Y direction).

In the 1st story, the existing eight columns
were jacketed with reinforced concrete at a
thickness of 100 mm. The concrete's
compressive strength and the yield strength oftensile reinforcement in the jacketing part ofthe column were Fc=25 N/mm2 and σy=400
N/mm2. The seismic capacity of the 1st story
was increased using RC jacketing. All stories
were determined safe in the second levelscreening of the JBDPA, as shown in Figure
10.

5.4. Seismic evaluation of the structure by the CSM method (after retrofitting)After retrofitting the 1st story with RC shear walls and RC column jacketing, the building was evaluatedby the CSM method. Figures 11 and 12 show the performance point for the retrofit model with RC shear
walls in Mandalay and Yangon cities. It was found out that the seismic capacity of the structure washigher than the requirement, as shown in Table 2. Therefore, the target building was determined to besafe in both high and low seismic zones.
Performance point for Mandalay City
1400µ=1 µ=2

700

µ=3

1200

Sa(cm/s^2)

Performance Point

2
Capacity

500

800
600

µ=1 µ=

600

µ=4

1000

Sa(cm/s^2)

Performance Point for Yangon City

h=0.05

Capacity Curve

Curve
Performance Point

400
300

400

200

200

100

h=0.05

0

0
0

4

8

12

16

20

24

28

32

36

40

0

4

8

12

16

20

24

Sd(cm)

Sd(cm)

Fig. 11. The building's performance point for Fig. 12. The building's performance point for
Mandalay city using the 2% probability demand Yangon city using the 2% probability demand
spectrum (after retrofitting with RC shear wall).
spectrum (after retrofitting with RC shear wall).
Table 2. Comparison of limit and demand story drifts (after retrofitting with RC Shear Walls).
Mandalay
YangonLimitedstory drifts
2% Probability
10% Probability 2% Probability 10% Probability
Storyof thestructure
demand story drifts(cm)demand story drifts(cm)
1

0.66

0.47

0.37

0.28

1.52

2

5.31

3.07

2.48

2.08

7.01

3

6.99

3.84

3.10

2.59

7.01

5

Table 3. Comparison of limit and demand story drifts (after retrofitting with RC Column Jacketing).
Mandalay
YangonLimit story
10% Probability
2% Probability
10% Probability drifts of the
Story 2% Probability
structure
demand story drifts(cm)demand story drifts(cm)
1
1.10
0.77
0.77
0.28
1.52
2
5.54
2.86
2.86
2.08
7.01
3
7.72 (NG)
3.64
3.64
2.59
7.01
Table 3 shows the evaluation results of the retrofitted model with the RC column jacketing.
Even after retrofitting the 1st story with RC column jacketing, the 3rd story did not meet the requirementfor Mandalay. We should increase the column size of the 3rd story. However, the demand story drift isalmost equal to limit story drift. The 3rd story can obtain enough seismic capacity by increasing the sizeof a small number of columns.

6. CONCLUSION
The results of this study were summarized as follow:
 According to the seismic evaluation results by the JBDPA Standard and the CSM, the 1st storyof the target building did not have enough seismic capacity for both of Mandalay and Yangon.
Retrofitting is needed to increase the seismic performance of this story.
 Two types of the retrofit method were suggested. One is installing RC shear walls, and the otheris the RC column jacketing.
 After installing a small number of RC shear walls and increasing the size of selected columnson the 1st story, the building's seismic capacity was increased. The building was considered safe,
even in a very high seismic zone. The results showed that we could obtain a satisfactory
earthquake-resistant structure.

ACKNOWLEDGEMENTS
This research was conducted during the individual study period of the training course “Seismology,
Earthquake Engineering and Tsunami Disaster Mitigation” by the Building Research Institute, JICA. I
would like to express my sincere gratitude to Dr. Tatsuya Azuhata for his supervision, guidance, support,
encouragement, discussion, and suggestions during my individual study. Moreover, I am thankful to all
the professors and lecturers for teaching us and for providing valuable knowledge. I am extremely
thankful to Dr. Kyaw Moe Oo, the Director General of my department, for giving me the chance to join
this program and supporting me with valuable advice. I would also like to thank Mr. Kyaw Lwin Oo,
the Director of my department, for his guidance, support, and encouragement.
REFERENCES
The Japan Building Disaster Prevention Association (JBDPA) “Standard for Seismic Evaluation of
Existing Reinforced Concrete Building (1st English Version 2001)”.
The Japan Building Disaster Prevention Association (JBDPA) “Guideline for Seismic Evaluation of
Existing Reinforced Concrete Building (1st English Version 2001)”.
Saito: STERA_3D Ver. 6.3 Technical Manual, Building Research Institute, Japan
https://iisee.kenken.go.jp/net/saito/stera3d/index.html.
Y.Wang and S.Pujol, The Capacity Spectrum Method: Evaluation Against The Measured Response ofa Nine –Story Structure, 2014.
Dr. Jagadish. G. Kori, Seismic Response Spectrum
http://www.sginstitute.in/activities/Civil/Day_6_1.pdf.

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