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PERFORMANCE OF BUILDINGS DURINGEARTHQUAKES AND LESSON LEARNT

D.K. Paul, Ph.DProfessor

Department of Earthquake EngineeringIndian Institute of Technology, Roorkee, India


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TYPES OF BUILDINGS

Load Bearing wall system

Beam-column Frame system

Dual system

Slab and column frame system


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FRAMED BUILDINGS

.


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Damage to reinforced concrete multi-storeyed

buildings


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Remaining core shaft of a multi-storeyed building


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ONGC Residential Apartments, Ahmedabad


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ONGC Office, Ahmedabad


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Damage to r.c.c. shopping centre, Bachhau


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Damage to short column


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Apartment building with

first storey collapse

First storey collapse of

residential building

Flexural failure at top of

first storey columns

Soft storey collapse


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DAMAGE TO SIDHSHILA APARTMENTS


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Bending of columns and partial collapse of parking structure,

Northridge earthquake


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Soft Middle storey collapse (Bhuj)


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Lack of shear connection between floors and the elevator

shaft


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Identical 4 storeyed R.C. buildings (Amdavad) two out of

four collapsed


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A Building Collapsed in Taiwan 1999 Earthquake


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1.00

0.80

0.60

0.40

0.20

0.000.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1. REALISTIC FORCE LEVEL FOR MAJOR EARTHQUAKE IN HIGH SEISMIC ZONE

2. DESIGN FORCE LEVEL ASSUMING RESPONSE REDUCTION FACTOR R=3

3. REALISTIC FORCE LEVEL FOR LOW-MODERATE

EARTHQUAKE IN HIGH SEISMIC ZONE

4. EARLY (pre-1971)CODE DESIGN FORCES

PERIOD (seconds)

FORCELEVEL

(a

safractionofweightofstructure)

Comparison of Realistic and Design Earthquake Forces


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BUILDINGS WITH SOFT STOREY

Soft storey stiffness is significantly lower thanadjacent floors

Buildings on stilts ( for parking) are most commonexamples of soft-storey

The in-fill wall provide additional stiffness againstlateral loads which is not considered in the

analysis

Floors without infill walls have lower stiffness

Floors with in-fill walls and with out in-fill walls

are treated as same in analysis


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BUILDINGS WITH SOFT STOREY

No consideration is given to soft storey whichexperiences greater drift

Moment demand of column increases due to P- deltaeffect

Many buildings with soft storey collapsed due tofailure of columns at joints in soft storey

The failure occurred due to Lack of strength and stiffness of soft storey

strong beam-weak column behaviour of moment resistingframe

lack of ductility of columns due poor detailing


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WHAT IS A SOFT STOREY ?

A storey having lateral stiffness less

than 70% of the stiffness of thestorey above or less than 80% of theaverage lateral stiffness of the three

storeys above.- IBC 2000, IS 1893


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WHY A SOFT STOREY?

Large open spaces with high ceilingat the ground floor level, for parkingor some other architectural purpose.

Absence of infills and shear-walls,and sometimes, increased length ofcolumns at ground storey reduces thelateral stiffness significantly.


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BUILDING ON STILT

Absence of

masonryinfills atground storeyfor parking

purpose.


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BUILDING WITH DROPPED

COLUMNS/SHEAR WALLS

Columns andshear-walls

are dropped tohave largespaces forcommercial

purposes atground storey.


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DAMAGE TO SOFT GROUND STOYEY

Soft storey attracts

large force

Requires large

ductility

Failure results dueto large P-Delta

shear forces


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LESSONS FROM GUJARAT

Many buildings with soft storey collapsed dueto failure of columns at joints in soft storey

The failure occurred due to Lack of strength & stiffness of soft storey

strong beam-weak column behaviour of momentresisting frame

lack of ductility due to poor detailing


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DESIGN OF SOFT GROUND STOREY

BUILDINGS

Option 1:

Detailed non-linear dynamic analysis to ensurethe deflection of the ground storey columns to

be within safe limits

Option 2:

Increased lateral stiffness of the ground storey to

avoid soft storey effect


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INCREASED BEAM-COLUMN SIZE

The size of theground storey

beams and columnsis increased to havethe stiffness of theground storey

comparable withupper storeys


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SHEAR WALLS AT GROUND STOREY

The ground

storey should beprovided with

shear walls to

increase thestiffness at

ground storey


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REINFORCEMENT DETAILING IN

BUILDINGS HAVING SHEAR WALLS AT

GROUND STOREY

Second storey columns

have stiffness

discontinuity and

should be provided

with special confining

reinforcementthroughout the length


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DAMAGE TO APOLLO APARTMENTS


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15th August Building, Swaminarayan School

(21 students killed)


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DAMAGE TO BUS STATION, BACHHAU


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COLLAPSE OF SHIKHAR APARTMENTS


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RETROFITTING OF EXISTING STILT

BUILDINGS

Increasing the size of ground storey columns

by jacketing

Addition of RC walls at ground floor

Steel bracings at ground storey

Use of energy dissipating devices such as

yielding bracing or viscous dampers


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Damage to short column


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Collapse of 4-storied

apartment at first floorInside view of the apartment

First storey Column collapse

of the above apartmentOpen first storey collapse


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8-storey building with

collapsed 6thstorey8-storey building with

collapsed 4thstorey


collapsed 3rd storey


collapsed 5thstorey


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Damage to apartment in

lower storiesThe other side of apartment

Collapse of first storey of

four storied school buildingSoft storey collapse


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Mid-height collapse of a mixed-use building (built circa

1977) in Nishinomiya. This type of collapse was very

common in this earthquake.


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15th August Building, Swaminarayan School

(21 students killed)


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DAMAGE TO STONE INFILL


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COLLAPSE OF A R.C.C. ELEVATED

WATER TANK

A R.C.C. WATER TANK - FINE CRACKS


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A R.C.C. WATER TANK FINE CRACKS

AT BASE CONSTRUCTION JOINTS

A R.C.C WATER TANK IN BHUJ - NO


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APPARENT DAMAGE


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BEAM, COLUMN, FOOTING AND JOINTREINFORCEMENT DETAIL


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FLEXURAL MEMBERS

In an external joint, both the top andthe bottom bars of the beams shall be

provided with anchorage length in

tension plus 10 times the bar diameter In the internal joint, both face bars of

the beam shall be taken continuouslythrough the column

The longitudinal bars shall be spliced,only if hoops are provided over theentire splice length, at a spacing notexceeding 150 mm

The lap length shall not be less than

the bar development length in tension


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DETAIL OF REINFORCEMENT IN STAGING

BEAMS

A Building collapsed in Taiwan Earthquake 1999


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g p q


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LACK OF TIE BARS


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ROLE OF TIE BARS


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LATERAL TIES PROVIDE CONFINEMENT TO CONCRETE

AND PREVENTS PREMATURE BUCKLING OF

REINFORCEMENT


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FORCES ACTING ON AN INTERIOR


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FORCES ACTING ON AN INTERIOR

BEAM-COLUMN JOINT


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LIQUEFACTION
http://liq.ppt/http://liq.ppt/http://liq.ppt/http://liq.ppt/


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DAMAGE DUE TO LIQUEFACTION

150 m Navigation

tower at Kandla portgot tilted by 30 cm at

the top because of

liquefaction in

foundation soil


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Ground settlement due to liquefaction (Kandla port)


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Los Angeles 1994 earthquake

damage to freewayNatural gas leakage causing

damage due to fire

Los Angeles 1994 earthquake

damage to Anaheim stadiumMountain of books fell during

the earthquake


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The great Hanshin-Awaji

earthquake collapsed highway

The great Hanshin-Awaji

earthquake Fire after

earthquake in Kobe city


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FRAMED BUILDINGS

Dynamic Analysis of Framed Building

Design of Building

Detailing of Reinforcement

Supervision of Construction

Bending of bars

Quality Control

Curing of concrete


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LESSONS LEARNT

Implementation of Building Code/ Land UseRestrictions

Good Construction Practice with Accountability

Active Role of Structural Engineers

Incorporation of Earthquake Engineering Aspectsin Engineering Courses

Rehabilitation & Reconstruction

Communinity Awareness Development of Human Resource in Trained

Manpower ( Structure/Earthquake Engineers)

INDIAN STANDARD CODES OF PRACTICE


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IS : 4326-1993 Code of practice for

earthquake resistant design and constructionof buildings

IS : 13827-1993 Guidelines for improvingearthquake resistance of earthen buildings

IS : 13828-1993 Guidelines for improvingearthquake resistance of low strengthmasonry

IS : 13920-1993 Code of practice for

ductile detailing of reinforced concretestructures subjected to seismic forces

IS : 13935-1993 Guidelines for repair andseismic strengthening of buildings

INDIAN STANDARD CODES OFPRACTICE


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PRACTICE

IS : 1893-2001 Criteria for Earthquake

Resistant Design of Structures Part 1- General Provisions and Buildings

Part 2 - Liquid Retaining Tanks-Elevated

and Ground Supported

Part 3 - Bridges and Retaining Walls

Part 4 - Industrial Structures IncludingStack Like Structure

Part 5 - Dams and Embankments


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