April 25, 2015 Nepal Earthquake and Aftershocks · Failure of foundation (mostly isolated footings on ... Several buildings damaged severely due to pounding . ... 2015 Nepal Earthquake

EERI LFE Briefing for the April 25, 2015 Nepal Earthquake and Aftershocks

April 25, 2015 Nepal Earthquake and Aftershocks Building Performance Part I: Building Type Overview, RC Frame with

Masonry Infill, and Wood Frame

Hemant B Kaushik Associate Professor

Department of Civil Engineering Indian Institute of Technology Guwahati

EERI / Hemant Kaushik EERI / Hemant Kaushik EERI / Hemant Kaushik


EERI Briefing Series of Videos ● Introduction: Objectives, methodology, unique features, team – Bret Lizundia ● Nepal Earthquake: Geography, demographics, and general damage – Surya Shrestha ● Seismology and Ground Motion – Kishor Jaiswal ● Building Performance Part I: Building type overview, RC frame with masonry infill, and

wood frame – Hemant B Kaushik ● Building Performance Part II: URM bearing wall, postearthquake safety evaluation,

barricades/shoring, school retrofits – Bret Lizundia ● Health Facility Performance – Judy Mitrani-Reiser and Hari Kumar ● Social, Psychological and Cultural Factors – Courtney Welton-Mitchell ● Geosciences – Jan Kupec ● Emergency Response – Ganesh Kumar Jimee ● Performance of Cultural Heritage Structures – Suraj Shrestha ● Building Codes – John Bevington ● Lifelines – Rachel Davidson ● Resilience and Community Case Studies – Chris Poland ● Summary of Findings – Bret Lizundia


Common Building Types in Damaged Areas ● RC Frame with Masonry Infill

● Unreinforced Masonry

(URM) Bearing Wall

● Wood frame Buildings

RC Frame with Brick Infill: Chautara

EERI / Hemant Kaushik

URM: Dhulikhel

EERI / Bret Lizundia

EERI / John Bevington

Wood Frame: Dolakha District


RC Frame with Masonry Infill

• Concentrated in urban areas and district headquarters • Found in low-rise, medium-rise, and high-rise • Most private buildings are non-engineered • Observed issues include: Poor geometric configuration Non-seismic detailing Improper workmanship No geotechnical investigation Inappropriate foundation on slopes

• Minor, moderate, and severe damage (even collapse) depending on location and details


RC Frame with Masonry Infill Low/Medium/High-rise: All suffered damage

Chautara: 3-story

Balaju: 6-story

Dhapasi: 17-story

More damage to buildings on ridge tops - likely ridge top shatter/amplification effects

Less damage to infill walls in tilted buildings - walls completely intact in many cases





RC Frame with Masonry Infill Poor Geometric Configuration

Sankhu Dhulikhel

Large Overhangs: Progressive increase in floor area in upper stories by extending beams/walls beyond column grid lines - Discontinuity in load transfer path




RC Frame with Infill Poor Geometric Configuration

Balaju: Trapezoidal Plan. At one end: • Ground floor practically only a column • Upper floors 1.5 m wide

Chautara: Floating Columns: • Columns without foundation • Discontinuity in load transfer path

Lokanthali: Soft Stories: • Drastic reduction in lateral stiffness





RC Frame with Masonry Infill Non-seismic Detailing

Irkhu: Collapse of a 4-story building due to poor design and detailing





RC Frame with Masonry Infill Non-seismic Detailing

Chautara: Collapse of 3-story buildings due to poor design and detailing





RC Frame with Masonry Infill Improper Workmanship

Dolalghat

Irkhu




EERI / Hemant Kaushik EERI / Hemant Kaushik


RC Frame with Masonry Infill Inappropriate Foundation on Slopes

Chautara

Irkhu

Failure of foundation (mostly isolated footings on slopes) resulted in collapse or tilting of large number of buildings.




Lokanthali

Chautara Street Survey: 150 buildings surveyed • 49% buildings on up slope/flat ground and 60% buildings on down slope damaged more details in Buildings Part II presentation by Bret Lizundia


RC Frame with Masonry Infill

Type of Damage/Failure • Pancake type collapse • Beam-column joint failure • Shear failure of columns near door/window openings

o Short column effects • Rupture of column reinforcement

o General Practice: 4 bars of 12-16 mm dia as long. steel, 6 mm dia @ 200 mm c/c as shear steel

o Shear reinforcement not provided as per the mandatory rules of thumb (NBC 201 and NBC 205) discussed later

• Ground cracks • Pounding of buildings • In-plane and out-of-plane failure of masonry infills


RC Frame with Masonry Infill Pancake-type Collapses

• Non-seismic design and detailing • Poor geometric configuration extremely weak columns

Balaju: 6-story building Balaju: 3-story building

Chautara: 3-story building





RC Frame with Masonry Infill Beam-Column Joint Failure

• Poor connection detailing • Insufficient anchorage • Insufficient support to lintels

Chautara: 3-story school building

Dhapasi: connection failure at lintel in a 17-story Park View Horizon Apartments Sankhu: 4-story school building






RC Frame with Masonry Infill Short Column Effect

Columns adjacent to door/window openings

Sankhu: 4-story school building




300mm

8mm @ 200mm c/c

6-16mm

230mm


RC Frame with Masonry Infill Buckling/Rupture of Column Steel

General Practice: 230×230 column 4 bars of 12-16 mm dia as long. steel, 6 mm dia @ 200 mm c/c as shear steel 90° hooks

Sankhu: Reinforcement detailing in a 5-story building under construction

Chautara: Rupture of column rebar in a 3-story building

Balaju: Buckling of column rebar in a 4-story building




230mm

6mm @ 200mm c/c

4-16mm

230mm


Nepal National Building Code (NBC) Mandatory Rules of Thumb

General Practice: - 230×230 column - 4 bars of 12-16 mm dia as long. steel, - 6 mm dia @ 200 mm c/c as shear steel with 90° hooks NBC 201 (1994): Mandatory Rules of Thumb for RC Frames with Masonry Infills NBC 205 (1994): Mandatory Rules of Thumb for RC Frames without Masonry Infills ○ Allow such column dimensions and longitudinal reinforcement ○ Shear steel requirement in critical regions of columns (end 450-600 mm):

• 8 mm dia @ 75-100 mm c/c with 135° hooks

o Clearly, the mandatory rules of thumb are not being followed Shear failure of columns and buckling of longitudinal reinforcement observed in many buildings

o More details in Building Codes presentation by John Bevington

230mm

6mm @ 200mm c/c

4-16mm

230mm


RC Frame with Masonry Infill Ground Cracks

Lokanthali (Arniko Highway): - buildings along the ground cracks tilted - Foundation failure observed

A

B

A B B

EERI / Hemant Kaushik EERI / Hemant Kaushik





RC Frame with Masonry Infill Pounding of Buildings

Balaju

Chautara: Several buildings damaged severely due to pounding





RC Frame with Masonry Infill In-plane and Out-of-plane Failure of Masonry Infills

Sankhu: Severe damage to infill walls due to diagonal and shear sliding crack at mid-height of walls in a school building

Dhapasi: Severe damage to masonry infill walls (in-plane as well as out-of-plane) throughout the Park View Horizon apartments




Wood Frame Buildings

● Post and Beam Frame up to 3 story ● Timber flooring and GI sheets as roof ● Infill Walls: Wooden planks/CGI sheets/Bamboo

with mud

All images: Dolakha District


EERI / Kishor Jaiswal

EERI / Kishor Jaiswal


Wood Frame Buildings Damage due to:

slope failure and large ground movements cracking and collapse of the brick veneer on

the building exterior failure of foundation posts and roof struts

All images: Dolakha District EERI / Kishor Jaiswal EERI / Kishor Jaiswal



Summary

• Poor performance of non-engineered buildings • Foundations on slopes performed extremely poorly • Severe geometric irregularities in buildings make them

seismically vulnerable • Poor material and poor quality control resulted in more damage. • Seismic codes not followed • Non-ductile detailing observed in most buildings. • Unplanned development resulted in haphazard construction,

which is more vulnerable to pounding • Mandatory Rules of Thumb (NBC 201 and NBC 205) are not

followed poor detailing of members • Wood frame buildings damaged mostly due to slope failure and

large ground movements, and cracking and collapse of the brick veneer on the building exterior


More Information: Reports, Data & Photos

● Visit EERI’s Virtual Clearinghouse Website for: ○ Geolocated Data Map ○ Photo Gallery ○ Team Report (available in late

summer 2015)

○ Reports from other teams & organizations

○ Curated Topic Posts

● Thanks to my Virtual Team Collaborator, Sabina Surana, who uploaded my photos to the EERI map

http://www.eqclearinghouse.org/2015-04-25-nepal/


Acknowledgements

● I would like to thank the following individuals and organizations who supported my reconnaissance effort: ○ EERI’s Learning from Earthquakes Program for travel and logistic support ○ NSET for coordination, logistics, and linkages to local individuals and

organizations in Nepal ○ EERI LFE Team Members for the discussion and intellectual stimulation

during the visit that enhanced my thinking and findings ○ Prof. Prem Nath Maskey, Tribhuvan University, Kathmandu, Nepal and

Prof. Sudarshan Raj Tiwari, Tribhuvan University, Kathmandu, Nepal for helpful discussion on building typologies in Nepal

○ IIT Guwahati for allowing me to undertake the work ○ Bonisha Borah, a doctoral student at IIT Guwahati, for assisting with this

presentation ○ Kishor Jaiswal, USGS, for assisting with the wood frame slides ○ Bret Lizundia, Rutherford + Chekene, San Francisco, for reviewing the

presentation and providing helpful comments

Documents

April 25, 2015 Nepal Earthquake and Aftershocks · Failure of foundation (mostly isolated footings on ... Several buildings damaged severely due to pounding . ... 2015 Nepal Earthquake