EARTHQUAKE

RESISTANT DESIGNS

Submitted by-

PRATEEK SRIVASTAVA

Guided by – AR. Madhura YadavRoll no - 27

S.Y. B.ARCH

SEMINAR PROJECT

Contents

What is earthquake?

Why is it deadly?

India’s profile

Need for earthquake resistant design.

Important considerations for design

Sesmic vibration control

What is Earthquake

An earthquake (also known as

a quake, tremor or temblor) is the result of a

sudden release of energy in the Earth’s crust that

creates seismic waves.

In its most general sense, the word earthquake is

used to describe any seismic event — whether

natural or caused by humans — that generates

seismic waves

The most recent large earthquake of magnitude

9.0 or larger was a 9.0 magnitude earthquake in

Japan in 2011 (as of March 2011), and it was the

largest Japanese earthquake since records began.

CONTINENTL DRIFT

Source: from internet

Fault

A fault is nothing but a crack or weak zone inside the Earth. When two blocks of rock

or two plates rub against each other along a fault, they don’t just slide smoothly.

As the tectonic forces continue to prevail, the plate margins exhibit deformation as

seen in terms of bending, compression, tension and friction. The rocks eventually

break giving rise to an earthquake, because of building of stresses beyond the

limiting elastic strength of the rock.

Effects of earthquakes

Types-

Shaking and

ground rupture

Landslides and

avalanches

Fires

Soil liquefaction

Tsunami

Floods

M > 8 Great Very great

7 - 7.9 Major Great

6 - 6.9 Strong Moderate

5 - 5.9 Moderate Moderate

4 - 4.9 Light Slight

3 - 3.9 Minor Slight

M < 3 Micro

earthquake

EARTHQUAKE MAGNITUDE CLASS

USGS IMD

Magnitude Annual Average No.

M > 8 2

7 - 7.9 20

6 - 6.9 100

5 - 5.9 3000

4 - 4.9 15,000

3 - 3.9 >100,000

GLOBAL EARTHQUAKE OCCURRENCE

Records of Worlds Largest

Earthquakes

Earthquake as the deadliest

Natural Disaster

The Vulnerability Profile - India

59% of land mass prone to earthquakes

40 million hectares (8%) of landmass prone to floods

8000 Km long coastline with two cyclone seasons

Hilly regions vulnerable to avalanches/landslides/Hailstorms/cloudburst

68% of the total area susceptible to drought

Different types of manmade Hazards

Tsunami threat

1 million houses damaged annually + human, economic, social and

other losses

More than 60 % area is earthquake prone.

Zone V 12 %

Zone IV 18 %

Zone III 26 %

Zone II 44 %

Fig. courtesy: nicee

Casualties during past events

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Earthquake Do Not Kill people

Improperly Designed

Structures Do!

Earthquake Design Philosophy

Need for Earthquake Resistant

Design Earthquake Resistant Design is the scientific field

concerned with protecting society, the natural and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels.

Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismic loading, thus considered as a subset of both structural and geotechnical engineering.

However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of civil engineering and from the social sciences, especially sociology, political sciences, economics and finance.

Earthquake Resistant Design

The main objectives of earthquake engineering

are:

Foresee the potential consequences of

strong earthquakes on urban areas and civil

infrastructure.

Design, construct and maintain structures

to perform at earthquake exposure up to the

expectations and in compliance with building

codes.

A properly engineered structure does not

necessarily have to be extremely strong or

expensive. It has to be properly designed to

withstand the seismic effects while sustaining an

acceptable level of damage.

IMPORTANT CONSIDERATIONS TO MAKE A

BUILDING EARTHQUAKE RESISTANT

1. Configuration

2. Ductility

3. Quality control

4. Base Isolation

5. Passive Energy Dissipating Devices

6. Active Control Systems

A terminally ill patient , however

effective the medication, may

eventually die.

Similarly, a badly configured building Cannot be engineered for an improved performance beyond a certain limit.

1. Configuration

Regular Configuration

Regular configuration is seismically ideal. These configurations have low heights to base ratio, symmetrical plane, uniform section and elevation and thus have balanced resistance.

These configurations would

have maximum torsional

resistance due to location

of shear walls and

bracings. Uniform floor

heights, short spans and

direct load path play a

significant role in seismic

resistance of the building.

Irregular Configuration

Buildings with irregular configuration

Buildings with abrupt changes in lateral

resistance

Buildings with abrupt changes in

lateral stiffness

Re-entrant corner

Discontinuity in diaphragm Stiffness

Discontinuity in Diaphragm Stiffness

FLEXIBLE

DIAPHRAGM

R I G I D

D I A P H R A G MO P E N

Vertical Components of Seismic Resisting System

Out of plane Offsets

Shear Wall

Out-of-Plane Offset

in Shear Wall

Shear

walls

Non-parallel

system

ELEVATION IRREGULARITIES

1) Soft-Storey/Pan-caked 2) Set-backs 3) Connections

Pancaking

Soft storey

ELEVATION IRREGULARITIES

4) Pounding 5) Breaks in

Columns

or Beams

6) Staggered

Levels

7) In-fills

Open ground storey building (soft storey)

Right or Wrong…?

Short column effect

Ductility

Let us first understand how different materials behave.

Consider white chalk used to write on blackboards and steel pins with solid

heads used to hold sheets of paper together. Yes… a chalk breaks easily!!

On the contrary, a steel pin allows it to be bent back-and-forth. Engineers define

the property that allows steel pins to bend back-and-forth by large amounts, as

ductility; chalk is a brittle material.

The currently adopted performance criteria in the earthquake codes are

the following:

i. The structure should resist moderate intensity of earthquake shaking

without structural damage.

ii. The structure should be able to resist exceptionally large intensity of

earthquake shaking without collapse.

The strength of brittle construction materials, like masonry and concrete, is highly sensitive to the

1. quality of construction materials

2. workmanship

3. supervision

4. construction methods

Quality control

special care is needed in construction to ensure that the elements meant to be ductile are indeed provided with features that give adequate ductility.

Thus, strict adherence to prescribed standards of construction materials and construction processes is essential in assuring an earthquake-resistant building.

Elements of good quality control.

1.Regular testing of construction materials at qualified laboratories (at site or away)

2. Periodic training of workmen at professional training houses, and

3. On-site evaluation of the technical work

Prepared by CT.Lakshmanan

Seismic vibration control

After the seismic waves enter a superstructure, there are a number of ways to control them in order to soothe their damaging effect and improve the building's seismic performance, for instance:

to dissipate the wave energy inside a superstructure with properly engineered dampers.

to disperse the wave energy between a wider range of frequencies

to absorb the resonant portions of the whole wave frequencies band with the help of so called mass dampers

Oldest Technique

However, there is quite another approach: partial suppression of the seismic energy flow into the superstructure known as seismic or base isolation.

For this, some pads are inserted into or under all major load-carrying elements in the base of the building which should substantially decouple a superstructure from its substructure resting on a shaking ground.

The first evidence of earthquake protection by using the principle of base isolation was discovered in Pasargadae, a city in ancient Persia, now Iran: it goes back to 6th century BCE. Below, there are some samples of seismic vibration control technologies of today.

Mausoleum of Cyrus,

the oldest

base isolated

structure in the world

Dry –stone walls control

Dry-stone walls of Machu Picchu Temple of the

Sun, Peru

Dry-stone walls control

People of Inca civilization were masters of the polished 'dry-stone walls', called ashlar, where blocks of stone were cut to fit together tightly without any mortar. The Incas were among the best stonemasons the world has ever seen, and many junctions in their masonry were so perfect that even blades of grass could not fit between the stones.

Peru is a highly seismic land, and for centuries the mortar-free construction proved to be apparently more earthquake-resistant than using mortar. The stones of the dry-stone walls built by the Incas could move slightly and resettle without the walls collapsing, a passive structural control technique employing both the principle of energy dissipation and that of suppressing resonant amplifications.

Base isolators

Prepared by CT.Lakshmanan

Basic example

Lead rubber bearing

Lead Rubber Bearing or LRB is a type of base isolation employing a heavy damping. It was invented by Bill Robinson, a New Zealander.[24]

Heavy damping mechanism incorporated in vibration control technologies and, particularly, in base isolation devices, is often considered a valuable source of suppressing vibrations thus enhancing a building's seismic performance.

However, for the rather pliant systems such as base isolated structures, with a relatively low bearing stiffness but with a high damping, the so-called "damping force" may turn out the main pushing force at a strong earthquake.

The bearing is made of rubber with a lead core.

Many buildings and bridges, both in New Zealand and elsewhere, are protected with lead dampers and lead and rubber bearings.

Te Papa Tongarewa, the national museum of New Zealand

New Zealand Parliament Buildings

Both have been fitted with the bearings.

Both are in Wellington, which sits on an active earthquake fault.

Te Papa Tongarewa,

the national

museum of New

Zealand

New Zealand

Parliament

Buildings

Simple roller bearing

Simple roller bearing is a base isolation device which is intended for protection of various building and non-building structures against potentially damaging lateral impacts of strong earthquakes.

This metallic bearing support may be adapted, with certain precautions, as a seismic isolator to skyscrapers and buildings on soft ground. Recently, it has been employed under the name of Metallic Roller Bearing for a housing complex (17 stories) in Tokyo, Japan

Tuned mass damper

Typically, the tuned mass dampers are huge concrete blocks mounted in skyscrapers or other structures and moved in opposition to the resonance frequency oscillations of the structures by means of some sort of spring mechanism.

Taipei 101 skyscraper needs to withstand typhoon winds and earthquake tremors common in its area of the Asia-Pacific. For this purpose, a steel pendulumweighing 660 metric tons that serves as a tuned mass damper was designed and installed atop the structure. Suspended from the 92nd to the 88th floor, the pendulums sways to decrease resonant amplifications of lateral displacements in the building caused by earthquakes and strong gusts.

Tuned

Mass

Dampers

Taipei101

Building

Elevation

Control

Transamerica

Pyramid

Building,

San Francisco,

USA

Building elevation control Building elevation control is a valuable source of vibration

control of seismic loading. Pyramid-shaped skyscrapers continue to attract attention of architects and engineers because such structures promise a better stability against earthquakes and winds. The elevation configuration can prevent buildings' resonant amplifications because a properly configured building disperses the shear wave energy between a wide range of frequencies.

Earthquake or wind quieting ability of the elevation configuration is provided by a specific pattern of multiple reflections and transmissions of vertically propagating shear waves, which are generated by breakdowns into homogeneity of story layers, and a taper. Any abrupt changes of the propagating waves velocity result in a considerable dispersion of the wave energy between a wide ranges of frequencies thus preventing the resonant displacement amplifications in the building.

A tapered profile of a building is not a compulsory feature of this method of structural control. A similar resonance preventing effect can be also obtained by a proper tapering of other characteristics of a building structure, namely, its mass and stiffness. As a result, the building elevation configuration techniques permit an architectural design that

Building during

Earthquake

CROSS-BRACING

The vertical structural system of a building consists of columns, beams and bracing, and functions to transfer seismic forces to the ground. Engineers have several options when building the vertical structure. They often build walls using braced frames, which rely on trusses to resist sideways motion. Cross-bracing, which uses two diagonal members in an X-shape, is a popular way to build wall trusses. Instead of braced frames or in addition to them, engineers may use shear walls --vertical walls that stiffen the structural frame of a building and help resist rocking forces. Engineers often place them on walls with no openings, such as those around elevator shafts or stairwells.

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