earthquake resistant design & construction · 2020. 8. 25. · concept of earthquake resistant...

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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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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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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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