Workshop on Design for School...

Workshop on Design for School Buildings

Chandani Chandra Neupane

Post-earthquake School Reconstruction Project

Lesson learnt from GorkhaEarthquake

Day : 1Session: 2

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Gorkha Earthquake 2015

Gorkha Earthquake 2015

is followed by 465 numbers of aftershocks

with local magnitude ≥4

until 07 July 2016

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Gorkha Earthquake 2015 (April 25)

Response spectra of ground motion

• Higher acceleration between 4 to 6 second• Unusual response spectrum as compared with

design spectrums.• More damaging effect to tall buildings (long period

structure)

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7 8 9 10

SA,g

Natural Period,sec

Comparison of Elastic Spectrum (ξ = 5%)

90 360 NBC 105-1994 IS 1893-2002 UBC 97

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Gorkha Earthquake 2015 (May 12- Aftershock)

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7 8 9 10

SA,g

Natural Period,sec

Comparison of Elastic Spectrum (ξ = 5%)

90 360 Aftershock(Mw 7.3) NBC 105-1994 IS 1893-2002 UBC 97

Response spectra of ground motion

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An aerial view of the village of Barpak, near the epicentre of the earthquake

David Ramos/Getty Images

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Affected Area (31 districts)

D. Gautam & H. Chaulagain (2016)

14 districts

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Loss: Gorkha Earthquake 2015

Deaths

8,686

Injured 16,808

Government Houses

• Fully Destroyed: 978

• Partial Destroyed: 3,021

Public Houses

• Fully Destroyed: 500,223

• Partial Destroyed: 269,156

5,000 schools

estimateddestroyed

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Is damages/causalities less ?

• Both earthquakes occurred on a non-school day.

• Time of Earthquake (Mid day) : 11:56 am (NST) , 12:50 pm (NST)

• Less no of tall buildings

• Less population density in epicenter and severely hit region.

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Earthquake Effects

• Four basic causes of earthquake-induced damage

Ground Shaking

Ground Failure

Fire

Tsunami

Secondary Disasters

Main Cause

Gorkha Earthquake (2015)

Gorkha Earthquake (2015)

Kobe Earthquake (1995)

Tohoku Earthquake (2011)

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Ground shaking

People struggle for balance as the ground flails beneath themhttps://youtu.be/AJc5J2iDcRM

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Ground failure

Vertical movement of ground which resulted in severe damages to road

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Ground failure

Landslide on road to Kathmandu

Performance of Load bearing masonry

1515Complete collapse of a brick + mud mortar building

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Damage in brick + mud mortar building and RCC buildings got no damage

(buildings in back)

RC Building performed better than masonry

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Out of plane failure of gable wall

RC Building performed better than masonry

Out of plane failure

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Heavy floor on weak

brick masonry wall

Corner crack, separation of wall

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Serious damage in cultural heritage structures

Performance of RC Structure

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Pancake collapse (Poor reinforcement detailing, poor quality of

construction material, faulty construction practices)

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Soft and weak story Collapse (Poor reinforcement detailing, poor

quality of construction material, faulty construction practices)

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17 story Park horizon apartment, Kathmandu

Significant damages in infill wall (non-

structural components)

Some minor damage to RC frame members

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17 story Park horizon apartment, Kathmandu

Significant damages in infill wall (non-

structural components)

Some minor damage to RC frame members

Should tall building be designed for long-

period ground motion?

Should the seismic performance of non

structural components be considered in the

seismic design of tall building?

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Out of plane failure of wall (Lack of bands) Large displacement in foundation led

tilting of building constructed in river bank

26Pounding Effect on nearby building

27Short column Effect

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ACI Survey

30 High Rise (>7 storey)Engineered

146 Low Rise (<7 storey)Non-engineered

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30

31

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Poor construction practices

Poor geometric configuration

Long cantilever extension Floating columns

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Poor construction practices

All the rebar are spliced at the same location in the column as marked in the diagram

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Gongabu

Swayambhu

Sitapaila

Sankhu

Bhaktapur

Severely damaged buildings were concentrate on some areas in Kathmandu valley

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Gongabu

Swayambhu

Sitapaila

Sankhu

Bhaktapur

Severely damaged buildings were concentrate on some areas in Kathmandu valley

Stronger ground shaking might be caused by site effect, basin effect, or topographic effect.

‘Seismic Microzonation Study’ should be properly carried out.

Building should be made more seismic resistant.

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Lesson learnt

• Local site seismicity, geology and subsoil properties

More damage in the buildings on right side than on the left side of the road in Kathmandu, in Balaju area

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• Construction and structural deficiencies

Wall failure(binding materials)

Column failure(Insufficient rebar and poor detailing)

Lesson learnt

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• Attention to earthquake resistant features

• Proper maintenance

Infill wall failure(no bands )

Rusting(lack of maintenance)

Wall failure(no seismic features )

Lesson learnt

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Lesson learnt

• Regulations, building by laws and seismic codes- revision and implementation

• Active interaction between earthquake engineers, structural engineers, seismologist, architects and government authorities

• Education of field engineers and construction practices

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Lesson learnt

• Partial damaged structures should be replaced or retrofitted

• Transfer of Technology from Theory/Research to Practice

• Disaster Response

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References

• http://www.seismonepal.gov.np/

• USGS

• http://www.nset.org.np/eq2015/

• http://www.dpnet.org.np/

• Gorkha (Nepal) Earthquake 2015, performance of masonry structures by D.C. Rai ,V. Singhal , S.L. Sagar, B.R. S, The masonry society.

• Learning from the Nepal 2015 Earthquake, S. Pujol, ACI Survey

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References

• Lessons learned from the 25 April 2015 Gorkha Earthquake in Nepal, Prof. Pennung Warnitchai, AIT, 2015

• Common structural and construction deficiencies of Nepalese buildings, Gautam, D., Rodrigues, H., Bhetwal, K.K. et al., Innov. Infrastruct. Solut. (2016)

• Observation of building damage patterns in Kathmandu due to Earthquake, K. Acharya (2015)

• Lessons learned from the Nepal Earthquake 2015, T. Pokharel & H.M. Goldsworthy (2016)

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Any Questions

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