eq damage rc
TRANSCRIPT
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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
10-storey building with
collapsed 3rd storey
9-storey building with
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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