earthquake resistant design & construction · 2020. 8. 25. · concept of earthquake resistant...
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by
ProfessorAPPLIED MECHANICS DEPARTMENT
L D COLLEGE of ENGINEERINGAhmedabad
Earthquake Resistant Design & Construction
(Gujarat Institute of Disaster Management)
(28-07-2020)
.
Earthquake Engineering Practice
Concept of Earthquake Resistant Design of RC
structures
Actual Construction Practice
Construction practice - Beam, column, foundation,
walls and roofs
Geotechnical considerations
– Earthquakes do not kill,
unsafe buildings do
– Earthquake is a manmade disaster
– Solution lies in “buildings” & not in
“earthquakes”
Challenge : Understanding
2005 NPEEE Earthquake Design Concept : Lecture 1: Impact of Earthquakes
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Destruction of Human life.
Structural Design
• Life of Structures
• Loads acting on civil engineering structures
Design Loads• Dead Load• Live Load• Wind Load• Earthquake Load• Many other types of loads
Structural Design
• Design for Gravity Loads : (DL+LL)
1. Permanent load
2. Factor of Safety
3. No damage
• Design for Lateral Load: (Wind + EQ)
Lateral forces create discomfort to structures
1. Wind Force – frequent - No damage
2. EQ Force - ??? (Max effective time 2 minutes)
Dead Load + Live Load +Wind or EQ Load DL + LL + WL or EQ
Earthquake ForceF = mass x acceleration
= ma
Wind ForceF = Intensity of wind x Area of Obstruction
Cyclone Resistant Design• No damage condition
Earthquake Resistant Design - ???????
Design Philosophy for Earthquake
Which design philosophy should we follow?
Earthquake Proof Design
OR
Earthquake Resistant Design
Philosophy of earthquake resistant structure
During an earthquake, lighter the building and the
roof, the better is the performance of the house.
Lighter roof would not induce as much load on the
walls, and the walls would be able to transfer the
loads easily during an earthquake.
On the other hand, during a cyclone, heavier the
roof, the better is the performance of the house. It
would resist strong loads due to the wind pressure,
hold itself and the house in place.
Cyclone Resistant Design• No damage allowed
Earthquake Resistant Design• Damages allowed but no collapse• We heavily rely on ductility
IS 13920 – 2016 – Ductile Design & Detailingof RC Structures subjected to Seismic Forces– Code of Practice
Ductility is defined as
the ability of a
structure to undergo
inelastic deformations
beyond the initial yield
deformation without
decrease in strength &
stiffness
Elastic Response Vs Inelastic Response
Advantages of Ductility1. Absorbs lots of energy, therefore good performance
during
• load reversals,
• Impact
• secondary stresses due to differential settlementof foundation.
2. Enough warning by showing large deformationbefore failure - loss of life is minimized
3. Yielding of steel reinforcement - assumptions in thedesign of reinforced concrete structures by limitstate method.
WHY IS DUCTILTY REQUIRED?
TO PREVENT BRITTLE FAILURES.
• SHEAR FAILURE
• BOND FAILURE
• COMPRESSION FAILURES (OVER REINFORCED
SECTIONS)
VARIOUS CONVETIONAL LATERAL LOAD RESISTING SYSTEMS
• COLUMNS
• SHEAR WALLS
• BRACING SYSTEMS
• MOMENT RESISTING FRAME
• TUBES
2005 NPEEE Earthquake Design Concept : Lecture 9: Overview of EQ resistant Structural Systems
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2005 NPEEE Earthquake Design Concept : Lecture 9: Overview of EQ resistant Structural Systems
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2005 NPEEE Earthquake Design Concept : Lecture 9: Overview of EQ resistant Structural Systems
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Learning from failures
DEFICIENCIES IN BUILDINGS
• LOCAL DEFICIENCIES
• GLOBAL DEFICIENCIES
LOCAL DEFICIENCIES IN BUILDINGS
Failures of Flexural Members
2005 NPEEE Earthquake Design Concept : Lecture 14: Ductility of MRFs
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2005 NPEEE Earthquake Design Concept : Lecture 14: Ductility of MRFs
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Confinement & Anchorage
Confinement to increase strength
Continuity & Anchorage for integral action
Confinement to increase strength
Continuity & Anchorage for integral action
Anchorage for integral action
135 degree bend
LOCAL DEFICIENCIES IN BUILDINGS
Failures of MEMBERS SUBJECTED TO
BENDING & AXIAL LOAD
Hinges
FAILURES DUE
TO INADEQUATE
LINKS
FAILURES DUE TO
INADEQUATE LINKS
When a column terminates into a footing or mat
2005 NPEEE Earthquake Design Concept : Lecture 14: Ductility of MRFs
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Thanks to well detailed
confining reinforcement
(Taiwan 1999)
IS 13920 -2016
• Design of Beam Column Joint
• Design of shear wall
MITIGATING GEOLOGICAL HAZARDS
• Ground collapse
• Liquefaction
• Differential compaction
• Landslide
• Earthquake-induced flood
ASSESS THE POTENTIAL FOR SOIL LIQUEFACTION
The building sank evenly
about 1 m due to soil
liquefaction. The
displaced soil caused a
bulge in the road.
This inclined building sank unevenly and leans against a neighbouring building
The solid building tilted as a rigid body and the raft foundation rises above the ground. The building itself suffered only relatively
minor damage.
This tank is also
tilted due to the
liquefaction of
the sandy
artificial landfill.
Mitigating Liquefaction
• Foundation on bed rock
• Vibro-floatation
• Soil with stabilizing materials
• Provision of drainage to release pore pressure
Factors for Good Seismic Performance
• Architectural configuration• Simple and regular configuration
• Structural design• Adequate lateral strength
• Adequate stiffness
• Adequate ductility
• Integral Action
• Non-structural elements
• Quality of construction
CONCLUSION
For safety in future earthquakes, all provisions
of the codes should be followed in design &
construction. This should be a mandatory
provision in the Building Bylaws.
Wish U
All the Best
Courtesy: Dr S K JainDr C V R M Murthy