Vulnerability Assessment of Kathmandu Valley

and Surrounding Areas

based on Comprehensive Damage Investigation

of the 2015 Gurkha, Nepal Earthquake

Kimiro Meguro, Director/Professor,

International Center for Urban Safety Engineering,

Institute of Industrial Science (IIS), The University of Tokyo (Utokyo)

Ramesh Guragain, Deputy Executive Director,

National Society for Earthquake Technology-Nepal (NSET)

Project team members

Name Affiliation

Dr. Kimiro Meguro (PI) Director/Professor, ICUS, IIS, UTokyo

Dr. Muneyoshi Numada Lecturer, ICUS, IIS, UTokyo

Dr. Hideomi Gokon Asst. Prof., ICUS, IIS, UTokyo

Dr. Osamu Murao Professor, IRIDeS, Tohoku University

Dr. Shunichi Koshimura Professor, IRIDeS, Tohoku University

Dr. Erick Mas Asst. Prof., IRIDeS, Tohoku University

Mr. Kenjiro Yamamoto PhD candidate, Utokyo

Ms. Natsumi Hara Graduate student, Chuo University

Mr. Kazuma Hasekura Graduate student, Chuo University

Name Affiliation

Dr. R. Guragain Deputy Executive Director, NSET

Mr. G. K. Jimee Director, NSET

Mr. H. Shrestha Director, NSET 1

Objective of the Study

� To support the reconstruction activities and retrofitting the

buildings affected by the 2015 Nepal-Gurkha Earthquake,

based on the distribution of building damage, ground

condition and expected distribution of seismic intensity.

2

Study area

� Kathmandu Valley and its surrounding areas.

Framework

• Efficient and effective activities for recovery and reconstruction.

• Identification of the areas and buildings where the retrofitting

should be applied preferentially.

Remote sensing

(UAV, Satellite)

Distribution of

building damage

Developing fragility function by simulation

Distribution of PGA

Propose the appropriate method for retrofitting3

Damage probability of several types of structures

Fragility curve

Expected Outcomes

1. Acquisition of spatial information data of buildings in widespread area

2. Acquisition of extensive building damage data and understanding of actual condition

3. Development of high-precision fragility curve for Nepalese buildings

4. Micro-zoning for efficient recovery and reconstruction of affected areas

5. Clarification of areas and buildings to be strengthened preferentially to reduce thedamage by future earthquakes

6. Proposal of proper seismic retrofit methods for vulnerable buildings in Nepal

4

1. Acquisition of spatial information data

of buildings in widespread area

Open Street Map

Satellite imageBuilding location were

identified using Open Street

Map and visual interpretation

of satellite images, and UAV.

UAV

Aerial photos (UAV :

http://www.dji.com/pr

oduct/phantom)

5

2. Acquisition of building data and identification of the building damage

Field Survey

Visual inspectionDamage

probability

7

Complete damageExtensive damage

Others

3. Development of high-precision

fragility curve for Nepalese buildings

This part is presented by Dr. Guragain.

8

9

Guidance and Utilizing the Facility from Utokyo (ICUS, IIS), Solving the Problem of Nepal

Collaborative Work between

NSET and The University Tokyo

Comparison of Work done before Earthquake

with Findings after Earthquake

In-situ Measurement of Masonry Mortar Joint Shear

Strength: Process Test as per ASTM C1531 – 09

10Start with Understanding Key Parameters

11

Masonry Mortar Joint Shear Strength: Mud Mortar

12

8

14

9

11

6

4

2

0

2

4

6

8

10

12

14

16

<0.02 0.02-0.04 0.04-0.06 0.06-0.08 0.08-0.1 0.1-0.12 >0.14

Nu

mb

er o

f Tes

ts (

Nu

mb

er)

Shear Strength (MPa)

Simulation using AEM

Simulation of Experimental Model

• Simplified

• Roof weight on top layer wooden elements

Experimental Verification

13

(Sakthiparan, 2008)

Result Comparison (Run 37: 20Hz, 0.8g)

14

Result Comparison (Run 45: 5Hz, 0.6g)

15

Analysis of Brick in Cement Buildings with Flexible Floor and Roof

16

BC1BC2

BC3

BC4 BC5

BC6

BC7BC8

•8 Buildings

•3 Mortar types•STRONG, Average, Weak

•5 Time Histories

17

Taplejung Earthquake, Nepal

Chi Chi Earthquake

Koceli Earthquake

Kobe Earthquake

Loma Prieta Earthquake

Strong ground motions used

for developing fragility curves

18

Koceli Earthquake 0.2 g Max Amplitude

(One of the Strongest Case)

0.15g: Slight Damage

0.25g: Moderate Damage

0.6g: Extensive Damage

0.65g: Complete

19

0.25g: Extensive Damage

0.35g: Complete Damage

Average Strength Mortar, Koceli Earthquake

20

N: Negligible; S: Slight Damage; M: Moderate Damage; E: Extensive Damage; C: Complete Damage

Building

Acceleration (g)

0.05 0.10.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

BC1-Strong-Loma N N S M M M M E E E C C C CBC1-Avg-Nep N N S M M E E E C C C C C CBC1-Avg-chi N S M M M E E E C C C C C C

BC1-Avg-Koce N S M M E E E C C C C C C CBC1-Weak-Kobe N M M E E C C C C C C C C C

BC2-Strong-Loma S S M M E E C C C C C C C CBC2-Avg-Nep S M M E E C C C C C C C C CBC2-Avg-Chi S M M E E C C C C C C C C C

BC2-Avg-Koce M M M E C C C C C C C C C CBC2-Weak-Kobe E E C C C C C C C C C C C CBC3-Str-Loma N N N S S M M M E E E E C CBC3-Avg-Nep N S S M M E E E C C C C C CBC3-Avg-chi N S S M M E E C C C C C C C

BC3-Avg-Koce N S S M E E E C C C C C C CBC3-Weak-Kobe S M M E E C C C C C C C C C

BC4-Str-Koce N N S S M M M E E E E C C CBC4-Avg-Nep N S M M E E E C C C C C C CBC4-Avg-Chi N S M M E E E C C C C C C C

BC4-Avg-Koce N S M E E E C C C C C C C CBC4-Weak-Kobe S M M E E C C C C C C C C C

Continue………..

Different level of Damages at Different Acceleration

21

Damage Level

Number of Cases at Different PGA (%g)0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

None 14 2 0 0 0 0 0 0 0 0 0 0 0 0Slight 9 15 5 0 0 0 0 0 0 0 0 0 0 0

Moderate 1 7 17 14 7 0 0 0 0 0 0 0 0 0Extensive 0 0 2 10 16 17 14 9 5 2 0 0 0 0

Complete 0 0 0 0 1 7 10 15 19 22 24 24 24 24

Damage Level

Cumulative Probability of Damage at Different PGA (%g)0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

Slight 0.04 0.29 0.79 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00Moderate 0.00 0.00 0.08 0.42 0.71 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00Extensive 0.00 0.00 0.00 0.00 0.04 0.29 0.42 0.63 0.79 0.92 1.00 1.00 1.00 1.00Complete 0.42 0.92 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

22

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Pro

ba

bil

ity

[d

s/P

GA

]

Peak Groung Acceleration PGA (g)

Case 1: Slight

Case 1: Moderate

Case 1: extensive

Case 1: Complete

Case 2: Slight

Case 2: Moderate

Case 2: Extensive

Case 2: Complete

Fragility Function for Brick in Cement

Buildings in Nepal with Flexible Floor/Roof

23

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Pro

ba

bil

ity

[d

s/P

GA

]

Peak Groung Acceleration PGA (g)

Case 1: Slight

Case 1: Moderate

Case 1: extensive

Case 1: Complete

Case 2: Slight

Case 2: Moderate

Case 2: Extensive

Case 2: Complete

Fragility Functions for Brick in Mud Buildings in Nepal

with Flexible Floor/Roof

Different Models Prepared and Different level of

Damages at Different Acceleration Noted

0.45g, Extensive

0.55g, Complete

0.3g, Extensive

0.4g, Complete

0.2g, Extensive

0.3g, Complete

Damage probability at different level of acceleration

25

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Pro

ba

bil

ity

[d

s/P

GA

]

Peak Groung Acceleration PGA (g)

Case 1: Slight

Case 1: Moderate

Case 1: extensive

Case 1: Complete

Case 2: Slight

Case 2: Moderate

Case 2: Extensive

Case 2: Complete

Stone Masonry Modeling: New Approach

1. Randomly Generated

Triangles2. Clustering certain number of nearby

triangles

Stone properties inside the cluster

Mortar properties in the boundary

Stone properties inside the cluster

Mortar properties in the boundary

3. Assigning stone and mortar properties

26

Fixed in all 3-displacements and 3-Rotations

Z-displacement Free, Other degrees of freedom fixed

Fixed in all 3-displacements and 3-Rotations

Z-displacement Free, Other degrees of freedom fixed

1st Model: 1:4 Scale Stone Masonry Wallet

Experimental ModelNumerical Model

Materials TensileStrength(MPa)

CompressiveStrength(MPa)

Young'sModulus(GPa)

FrictionCoefficient

Mortar 0.078 8 0.4 0.6Stone 100 1000 3 0.6

m

th

s

th

M

th

E

m

E

S

E

M +=

Mth, EM: Thickness and Young’s

Modulus for Masonry

Sth, Es: Thickness and Young’s

Modulus for Stone

mth, Em: Thickness and Young’s

Modulus for Mortar

27

Crack patterns

Crack pattern at 3 mm vertical displacement

from experiment (Sakurai, K., 2011)

Crack pattern at 3 mm vertical

displacement from Numerical Simulation

28

Force Displacement Comparison

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6

Displacement (mm)

For

ce (

KN

)ExperimentNumerical

29

Shaking Table Test Verification

30

(Sakurai, K., 2011)

Crack patterns: (after Run 40, 15Hz, 0.8g)

31

Crack patterns: (after Run 48, 5Hz, 1.0g)

32

Stone Masonry Buildings

33

SM1

SM2

SM3

SM4

SM5

SM6

Damage State at each PGA Noted

34

0.1g, Koceli, Extensive

0.15g, Koceli, Complete

0.25g, Koceli, Extensive

0.35g, Koceli, Complete

Average

Mortar

35

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6

Pro

ba

bil

ity

[d

s/P

GA

]

Peak Groung Acceleration PGA (g)

Case 1: Slight

Case 1: Moderate

Case 1: extensive

Case 1: Complete

Case 2: Slight

Case 2: Moderate

Case 2: Extensive

Case 2: Complete

Fragility Functions for Stone in Mud Buildings in Nepal with Flexible Floor/Roof

36

Comparison of Response Spectra with The Ground Motions Used Earlier with

Gorkha Earthquake

Simulation with Gorkha Earthquake Ground Motion

37

SM1

SM2

SM3

SM4

SM5

SM6

Connecting the Computer at The University of Tokyo from Nepal

38

0.15g, Koceli 0.35g, Koceli

Average

Mortar

0.2g, Gorkha

0.4g, Gorkha

39

Comparison of Fragility FunctionsFive Time Histories and Gorkha Earthquake

40

Simulation of Brick Buildings for Code Implementation

Slight

Damage

Moderate

Damage

Extensive

DamageComplete

Damage

0.1 g 0.15 g 0.25 g 0.35 g

0.4 g 0.6 g 0.8 g1 .0g

With Cement Mortar Single Vertical Bar Enhance Capacity from 0.8g to 1.0 gKoceli

Average

41

Gorkha Earthquake 0.3g Gorkha Earthquake 0.5g

Research for Reconstruction

Model without Earthquake

Resistant ElementsModel with Earthquake

Resistant Elements

Average Mortar

Conclusions

– Numerical Simulation of Some Buildings with

Building Code Implementation conducted and can be

compared with the developed fragility functions

42

• Fragility Functions Developed Earlier are Compared with

Fragility Functions Developed using Gorkha Earthquake Ground

Motions

• Damage by Gorkha Earthquake is Less by about 0.05g in

Average with the Average Damage by 5 Earthquake Ground

Motions Used Earlier

4. Micro-zoning for efficient recovery

and reconstruction of affected areas

43

44

Study Area

1

2

3

4

5

A B C D E F

D E F G H

Study area of evaluation

of damage

Among all seasons, there is snow and the number of houses is very limited.

Out of

study area

Pick up 36 settlements (50 to 1,228 buildings per settlement) in 32 blocks, and evaluate damage levels.

45

Distribution of Settlements and their major type of structures

Micro-zoning for efficient recovery and reconstruction of affected areas

Damage probability of typical structures in each settlement

Kathmandu

Fragility function developed

by Dr. Remesh Guragain

Damage Probability � Peak Ground Acceleration (g)

• BCr : Brick in Cement Buildings with Rigid Floor/Roof

• BCf : Brick in Cement Buildings with Flexible Floor/Roof

• BMf : Brick in Mud Buildings with Flexible Floor/Roof

• SMf : Stone in Mud Buildings with Flexible Floor/Roof

47

Micro-zoning for efficient recovery and reconstruction of affected areas

Distribution of PGA (gal)

A distribution of PGA was estimated by the interpolation of PGA point.48

5. Clarification of areas and buildings

to be strengthened preferentially

against high-risk future earthquakes

49

Clarification of areas and buildings to be strengthened

preferentially against high-risk future earthquakes

Distribution of PGA

Fragility curves

Distribution of damage probability

Clarification of areas and buildings to

be strengthened preferentially

50

• BCr : Brick in Cement Buildings with Rigid Floor/Roof

• BCf : Brick in Cement Buildings with Flexible Floor/Roof

• BMf : Brick in Mud Buildings with Flexible Floor/Roof

• SMf : Stone in Mud Buildings with Flexible Floor/Roof

Damage probability of each type of structureBCr (Brick in Cement with Rigid Floor/Roof)BCf (Brick in Cement with Flexible Floor/Roof)

BMf (Brick in Mud with Flexible Floor/Roof) SMf (Stone in Mud with Flexible Floor/Roof)

)

51

Comparison

BCr

(complete)

SMf

(complete)

Identify the vulnerable zone

52

• According to fragility curve, Brick in Cement Buildings with Rigid Floor/Roof (BCr) is the strongest, and Stone in Mud Buildings with Flexible Floor/Roof (SMf) is the weakest among these structures

• Next step is to compare the damage probability map from several types of structures with BCr.

Subtract Pd(BCr) from Pd(BMf)

53

Pd(BCr)- Pd(BMf)

Brick in Mud

structures with

Flexible Floor/Roof

located in the area

should be retrofitted

Subtract Pd(BCr) from Pd(BMf)

54

Pd(BCr)- Pd(BMf)

Subtract Pd(BCr) from Pd(SMf)

55

Pd(BCr)- Pd(SMf)

Subtract Pd(BCr) from Pd(SMf)

56

Pd(BCr)- Pd(SMf)

Stone in Mud

structures with

Flexible Floor/Roof

located in the area

should be retrofitted

6. Proposal of proper seismic retrofit

method for vulnerable buildings in Nepal

57

1) Unreinforced Masonry Common Residential Buildings:

→ PP-Band Method (PPM)

2) Unreinforced Masonry School Buildings:

→ Splint and Bandage + PP-band Method（SB-PPM)

3) Low or Middle Rise Reinforced Concrete Buildings:

→Modified Reinforced Concrete Masonry Infill

(MRCMI)

58

Retrofitted adobe masonry house (2009)

2-story adobe mud mortar house

(weakest type structure)

Due to lack of power and welders, cross points of PP-bands were not welded. Just weave PP-bands in wave form without connecting at cross points.

Totally collapsed adobe masonry house

Mud mortar adobe house is really vulnerable to earthquake.

Retrofitted adobe house after the quake (2015)

Retrofitted adobe house after the quake (2015)

Spalling of surface finishing

mud mortal. This is an evidence

of the effects of PP-band method.

62

Earthquake Safety School Project by NSET

Before the 2015 Gurkha Earthquake,

NSET has retrofitted about 200 school buildings by Full

Wall Jacketing method (FWJM) and Splint and Bandage

method (SBM). There was no damage to these

retrofitted structures except 4 buildings have fine

cracks. All of these retrofitted school buildings could be

used as shelters for affected people.

While about 300 school buildings were severely

damaged or collapsed. In all affected area by the

Gurkha 2015, about 6,000 school buildings were

severely damaged or collapsed.

63

Un-retrofitted oneRetrofitted ones

Inside of classroom

Inside of retrofitted school. It is used as shelter for affected peopleNo damage to the structure

that NSET retrofitted.

Earthquake Safety School Project by NSET

School buildings after the eq.

64

Splint and Bandage Method

Full Wall Jacketing Method (better but expensive)

Methods that NSET has adopted

65

Recommended Method for School building

2) Splint and Bandage Method（ＳＢＭ）：relatively inexpensive.

Set RC horizontal and vertical bands at critical locations but in case of severe shaking, URM wall may collapse and attack people.

1) Full Wall Jacketing Method（ＦＷＪM）： Efficient but expensive

3) Splint and Bandage + PP-band Method （ＳＢ-ＰＰＭ）：URM wall is retrofitted by PP-band method to prevent collapse of wall and save people. Additional cost is very small.

Model retrofitted by SBM

Model retrofitted by SB+PPM

66

Concrete Beam and Column

MasonryPolystyrene Foam

Mortar PP Band

RCMI

Recommended method for low and middle rise building

(Modified Reinforced Concrete Masonry Infill)

MRCMI

Validation of Numerical Model(AEM)

67

0

20

40

60

80

100

120

140

0 0.002 0.004 0.006 0.008 0.01

Forc

e (

KN

)

Displacement (m)

Force vs Displacement

Experimental AnalyticalAEM Simulation

Failure Behavior

of Frame Structure

68

920

800

75

100

120

50

680

120 1160 20

50

25

2040120

680

Concrete Strength: 20 MPaYoung’s Modulus: 2.49e+10MPa

Masonry:Compressive Strength: 15 MPaInitial Stiffness: 1.35e+10MPa

Engineered FrameNon-Engineered

Frame

Comparison of Engineered and Non-engineered RC frame

69

Collapse analysis of full scale 3D infilled frame

Bare NE_RC Frame

NE_RCMIFrame NE_MRCMI

Frame

NE_MRCMI Frame

with PP-Band

• 2 Storey, S. Width = 3.3 m, S. Height = 4 m

Building 1 Building 2 Building 3 Building 4

70

Building 1

1 2

3 4

Kocaeli earthquake

71

Building 2

1 2

3 4

72

Building 3

1 2

3 4

73

Building 4

1

2

3

Summary

1. Acquisition of spatial information data of buildings in widespread area � O.K

2. Acquisition of extensive building damage data and understanding of actual condition � Could not be obtained all the damage data, therefore we interpolated the building damage data in 36 settlements.

3. Development of high-precision fragility curve for Nepalese buildings � O.K

4. Micro-zoning for efficient recovery and reconstruction of affected areas � O.K

5. Clarification of areas and buildings to be strengthened preferentially against high-risk future earthquakes � O.K

6. Proposal of proper seismic retrofit method for vulnerable buildings in Nepal� O.K

74