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EARTHQUAKE AND ITS EFFECTS

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Earthquakes and its effects on buildings,earthquake zones in India, Architectural

design considerations and construction

detailing for earthquake resistance.

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CONTENTS1 .What is Earthquake

1.1 The earth and its interior

1.2 Plate tectonics

1.3 The circulation

1.4 What causes Earthquake?

1.5 How ground shake

1.6 The Focus and Epicenter of an Earthquake

2 .Seismic waves

2.1 What are seismic waves

2.2 Types of seismic waves

2.3 The seismic effect on structures

2.4 Seismic zones in India

2.5Effect on structure

3 .Architectural features

3.1 Why building twist

3.2 How buildings twist

3.3 Why building twists

3.4 Effect of earthquake on different elements

3.5 Behavior of different parts of structure during earthquake

3.6Design consideration

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FIGURES LIST

1 .ERTHAUAKE1.1 INSIDE THE EARTH

1.2 LOCAL CONVECTIVE CURRENTS IN THE MANTLE

1.3 MAJOR TECTONIC PLATES ON THE EARTH S SURFACE

1.4 TYPE OF INTER PLATE BOUNDARIES

1.5 ARRIVAL OF SESMIC WAVES AT A SITE

1.6 THE FOCUS AND EPICENTER OF AN EARTHQUKE .

1.7 BASIC TERMINOLOGY OF FOCUS AND EPICENTER OF AN ERTHQUAKE

1.8 BASIC TERMINOLOGY OF FOCUS AND EPICENTER

1.9 GEOGRAFICAL LAYOUT AND TECHTONIC PLATE BOUNDARIS AT INDIA1.10 SOME PART ERTHQAKES

2 .SESMIC ZONE2.1 BODY WAVE P & S WAVES

2.2SURFACE WAVE R AND S

2.3 INDIAN SESMIC ZONE MAP OF 1970

2.4 INDIAN SESMIC ZONE MAP AS PER IS 1893-2002

2.5EFFECT OF INERTIA IN A BUILDING WHEN SHAKEN AT ITS BARE2.6 INERTIA FORCE AND RELATIVE MOTION WITHIN A BUILDING

2.7 PRINCIPAL DIRECTIONS OF A BUILDING

2.8 FLO OF SESMIC INERTIA FORCES THROUGH ALL STRUCTURAL COMPONENTS

2.9 PARTIAL COLLAPSE OF STON MOSNAORY WALLS DURING 1991 UTTARKASHI (INDIA)

2.10 EARTHQUAKE

2.11 COLLAPSE OF RENFORCED CONCRETE COLLOPSE (AND BUILDING)

2.12 DURING 2001 BHUJ (INDIA)ERTHQUAKE.

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What are Earthquakes?

The shaking or trembling caused by the sudden

release of energy

Usually associated with faulting or breaking of rocks

Continuing adjustment of position results in

aftershocks

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Inner Core (radius ~1290km),

the Outer Core (thickness

~2200km),

the Mantle (thickness ~2900km)

and the Crust (thickness ~5 to

40km).

Convection currents develop in the

viscous Mantle, because of

prevailing high temperature and

pressure gradients between theCrust and the Core, like the

convective flow of water when

heated in a beaker (Figure 1.2).

Structure of earth:

fFig:1.1

Fig:1.2

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The convective flows of Mantlematerial cause the Crust and some

portion of the Mantle, to slide on the

hot molten outer core. This sliding ofEarths mass takes place in pieces

called Tectonic Plates.

Three types of inter-plate

interactions are the convergent,

divergent and transform

boundaries (Figure 4), respectively.

Fig:1.4

Fig:1.3

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:

How ground shakes:

Large strain energy released during an earthquake travels asseismic waves in all directions through the Earths layers,

reflecting and refracting at each interface.

three types of inter-plateinteractions are the

convergent, divergent and

transform

boundaries (Figure 4),respectively

Fig:1.5

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ORIGIN OF EARTHQUAKE-

The point within Earth where

faulting begins is the focus, or

hypocenter

Fig:1.1

The point directly above the focus

on the surface is the epicenter

Connect the focus/hypocenter tocentre of earth & extend the line

to the surface of earth i.e.

epicenter is located

The Focus and Epicenter of

an Earthquake:

Fig:1.7

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What are Seismic Waves?

Response of material to the

arrival of energy fronts released

by rupture

Two types: Body waves

P and S

Surface waves

R and L

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Body Waves: P and S waves

Body waves

P or primary waves

These waves are generated due tolongitudinal vibrations within the earth &its velocity is approx 8KN/sec

fastest waves

travel through solids, liquids, or gases

compression wave, material movement isin the same direction as wave movement

S or secondary waves

These are transmitted due to transversevibrations causing shaking of the earthsurface. The velocity is 45KN/sec.

slower than P waves travel through solids only

shear waves - move materialperpendicular to wave movement

Fig:1.10

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Surface Waves: R and L waves

Surface Waves

Generated due to reflection, refraction & severe vibrations due to which

several minute waves are generated at epicenter & these waves travelalong the ground surfaces in all direction.

Travel just below or along the grounds surface

Slower than body waves; rolling and side-to-side movement

Especially damaging to buildings

Fig:1.11

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Seismic zones in

India :

Fig:2.2

Fig:2.1

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Inertia Forces in StructuresEarthquake causes shaking of the

ground. So a building resting on it will

experience motion at its base. From

Newtons First Law of Motion, even

though the base of the building moves

with the ground, the roof has a

tendency to stay in its original position.

But since the walls and columns are

connected to it, they

drag the roof along with them.

The seismic effect on

structures:

Effect of Deformations in Structures

The inertia force experienced by the roof is

transferred to the ground via the columns,

causing

forces in columns

Fig:2.3

Fig:2.4

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Forces acting on Structures:

Three forces in X, Y and Z directions.

Usually vertical is managed by the

downward forces.

X and Y direction of forces are of

more concern.

Flow of Inertia Forces to Foundations

Inertial forces

Floor slab

Beams

Columns

`

`

FoundationHence Joints are critical and need to be

designed cautiously

Fig:2.5

Fig:2.5.1

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The convective flows of Mantle

material cause the Crust and some

portion of the Mantle, to slide on

thehot molten outer core. This sliding

of Earths mass takes place in

pieces called Tectonic Plates.

three types of inter-plateinteractions are the convergent,

divergent and transform

boundaries (Figure2.6),

respectively.Fig:2.6

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Why a Building Twists

Fig:2.11

Fig:2.13

Fig:2.12

H B ildi T i t

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How Building Twists

Due to Twist i.e. Torsional Forces

Fig:

1.1

Fig:2.14

Fig:2.15

Fig:2.16

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The Earthquake Problem

Fig:2.17

Fig:2.18 Fig:2.19

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EFFECT OF EARTHQUAKE ON DIFFERENT ELEMENTS

Surface & subsoil- Many a times buildings are damaged or

collapsed due to failure of soil over which they are erected.a) Surface fault & rupture- sometimes fault line with wide gap or

rupture or sudden change in level may appear.

b) Land slide- seismic forces may trigger massive land slide or

avalanche during earthquake damaging building.

c) Shaking or back or forth movement of surface- building without

strong bond between different elements may not withstand

severe vibrations & shaking

d) Horizontal waves along the surface

e) Liquefaction- due to continuous vibrations & shaking differentelements in soil may lose cohesion & particles may disintegrate.

Soil behaves as liquid.

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Behavior of brick masonry walls :

Fig:2.20 Fig:2.21

Ho to Impro e Beha ior of

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How to Improve Behavior of

Masonry Walls

Fig:1.1

Box Action in Masonry

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Box Action in Masonry

Buildings

Influence of Openings

Fig:2.25

Fig:2.24

B A i i M B ildi

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Box Action in Masonry Buildings

Fig:2.25

Fig:1.1

Role of Horizontal Bands

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Role of Horizontal Bands

Fig:1.1

Fig:1.1

Design of Lintel Bands

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Design of Lintel Bands

Fig:1.1Fig:1.1

Response of Masonry Walls

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Response of Masonry Walls

Fig:1.1

Fig:1.1

How Vertical Reinforcement

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How Vertical Reinforcement

Helps

Fig:1.1Fig:1.1

Behavior during Past India

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Behavior during Past India

Earthquakes

Fig:1.1

Fig:1.1

Stone Wall Construction

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Stone Wall Construction

Fig:1.1

Fig:1.1

Fig:1.1

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Reinforced Concrete Building

Fig:1.1

Fig:1.1

Fig:1.1

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Reinforced Concrete Building

Fig:1.1 Fig:1.1

Reinforcement and Seismic

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Reinforcement and Seismic

damage

Fig:1.1

Fig:1.1

Reinforcement and Seismic

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Reinforcement and Seismic

damage

Fig:1.1

Fig:1.1

Fig:1.1

Fig:1.1

Possible Earthquake Damage

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Possible Earthquake Damage

Fig:1.1

Fig:1.1

Fig:1.1

Possible Earthquake Damage

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Possible Earthquake Damage

Fig:1.1

Fig:1.1

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H t R d E th k

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How to Reduce Earthquake

Effects on Buildings?

Fig:1.1

Fig:1.1

Wh B C l J i t

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Why BeamColumn Joints are

special

Fig:1.1

Fig:1.1

Fig:1.1

Why BeamColumn Joints are

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y

special

Fig:1.1

Fig:1.1

Fig:1.1

Why are Open-Ground StoreyWhy are Open-Ground Storey

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y p y

Buildings Vulnerable in

Earthquakes?

y p y

Buildings Vulnerable in

Earthquakes?

Fig:1.1

Fig:1.1

Why are Open-Ground Storey

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y p y

Buildings Vulnerable in

Earthquakes?

Fig:1.1

Fig:1.1 Fig:1.1

Why are Short Columns more

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Why are Short Columns more

Damaged During Earthquakes?

Fig:1.1

Fig:1.1

Fig:1.1

Why are Short Columns more

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y

Damaged During Earthquakes?

Fig:1.1Fig:1.1

H t R d E th k

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How to Reduce Earthquake

Effects on Buildings?

Two basic technologies are used to

protect from damaging earthquake

effect. These are Base isolation

devices and seismic dampers. The idea

behind base isolation is to detached

(isolate) the building from the groundin such a way that earthquake motions

are not transmitted up through the

building or at least greatly reduced.

Seismic dampers are special devicesintroduced in the building to absorb

the energy provided by the ground

motion to the building .

Fig:1.1

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Questions

1.Explain the various planning aspects and construction

systems /techniques which can be integrate as part of buildings

design to improve the ability of buildings to withstand the effects

of earthquake.

2.Give a brief explanatory note on earthquake zones in india .

3. What are the earthquakes and how do they influence building ?Draw net sketches

of various precaution that should be incorporate in the design of buildings tomake them earthquake-safe.

4.During earthquake, what factors lead to server damages to the building ?Explain the

systems / techniques that a designer has to incorporate in the design of buildings

to make buildings resist earthquake.

5. With support of neat sketches recommend the different construction feature that need to

The building during earthquake.

6.With support of neat sketches recommend the different construction features that

need to be integrate in design of load bearing structures to make them resist the

earthquake.