earthquake engineering part1

Tishk International University

Civil Engineering Department

Third Year (2020-2021)

Earthquake Engineering

Asst. Prof. Dr. Najmadeen Mohammed Saeed

[email protected]

Part 1Earthquake Engineering

Introduction to Earthquakes I

Part 1: Introduction to Earthquakes I

Asst. Prof. Dr. Najmadeen 2

Dynamic Characteristics of Structures

Part 1: Introduction to Earthquake I

Natural DisastersIntroductionTerminologiesInternal Structure of EarthEarthquake Fatalities



Earthquake Tornado, Cyclone

FireFloods

Natural Disasters



VolcanoHurricane

Natural Disasters



Global Loss Due To Natural Disasters

Loss of life from natural disasters(Source: Herath and Katayama, 1994)

Loss of built environment

from natural disasters (Source: Andrew and Robin, 2002)



Earthquake Shaking

Earthquakes are UNPREDICTABLE!!!



Dead & Live Loads

Direction Of Dead

& Live loads

Depends on self

weight and

functional aspects

of building

Direction Of Dead

& Live loads

Depends on self

weight and

functional aspects

of building



Wind Loads

Direction Of wind loads

Depends on Wind

intensity and exposed

area of the building

&

Distribution is uniform

along the height

F = p * area



Seismic Loads

Direction of seismic forces

Depends on acceleration

and weight of the building

&

Distribution is not uniform

Earthquake motion

F = Mass *Acceleration



Effects of Earthquake

ACCELERATION

DECELERATION

Inertia Force F = m a



Static Vs Dynamic Loading

P

Y

Y(t)

Static Loading Dynamic Loading

F = m a

Y(t)

P(t)



Types of Dynamic Loading

RAPID OR TRANSIENT LOADING

MONOTONIC LOADING

SLOW

LOADING

TIME

CYCLIC OR REPETITIVE

LOADING

LO

AD



Earthquake Engineering:

Earthquake engineering can be

defined as the branch of

engineering dedicated for

minimizing earthquake hazards.

Introduction

■ An Earthquake :is the motion or vibration, sometimes

violent, of the earth’s surface that follows a release of

energy in the earth’s crust. This energy can be generated

by a sudden dislocation of segments of the crust, by a

volcanic eruption, or even by manmade explosions.



Scope:

Earthquake engineering involves planning, designing,

constructing and managing earthquake-resistant

structures and facilities.

• Seismicity ,Nature, Measures and Recording of

earthquakes.

• Planning for Seismic Risk Assessment &

Mitigation

• Analysis, Design and Construction of Earthquake

Resistant Structures

• Evaluation of Buildings for Earthquake Resistance

• Retrofitting of Earthquake damaged Structures

Introduction



Main causes of earthquake: tectonic ground motions,

Volcanism, landslides, rock bursts, and man-made

explosions. Among these, naturally occurring tectonic-

related earthquakes are the largest and most important.

Causes of Earthquake



Causes of Earthquake



- Tectonic-related earthquakes are caused by the fracture and sliding of

rock along faults within the Earth’s crust.

- A fault is a zone of the earth’s crust within which the two sides have

moved .

- faults may be hundreds of miles long, from one to over one hundred

miles deep, and are sometimes not readily apparent on the ground

surface.

- Earthquakes initiate a number of phenomena or agents, termed seismic

hazards, which can cause significant damage to the built environment,

these include fault rupture, vibratory ground motion , tsunami, dam

failure, fire.

- For most earthquakes, shaking is the dominant and most widespread

agent of damage.

* The word seismology originated from Greek words,

‘seismos’ meaning earthquake and ‘logos’ meaning science.

Terminologies



- Fault rupture is a process that takes seconds or at most a few minutes.

- Shaking near the actual earthquake rupture lasts only during the time

when the fault ruptures.

- The seismic waves generated by the rupture propagate long after the

movement on the fault has stopped, however, spanning the globe in

about 20 min. Typically, earthquake ground motions are powerful

enough to cause damage only in the near field (i.e., within a few tens

of kilometers from the causative fault)

- in a few instances, long period motions have caused significant

damage at great distances, to selected lightly damped structures. A

prime example of this was the 1985 Mexico City Earthquake, where

numerous collapses of mid- and high-rise buildings were due to a

magnitude 8.1 Earthquake occurring at a distance of approximately

400 km from Mexico City.

Terminologies



Tsunami or Harbor Wave: This Japanese

word is represented by two Characters;

(Tsu=Harbor) and (Nami=Wave).

Why did the earthquake cause a tsunami?

- Shallow focus earthquake

- Large volume of oceanic crust displaced

- The movement of the crust also

displaces a large volume of water.

Terminologies



Terminologies

Japan Tsunami, 2011



The earth’s shape is an oblate spheroid with a diameter along the

equator of about 12740 km with the polar diameter as 12700km.

The higher diameter along equator is caused by the higher

centrifugal forces generated along the equator due to rotation of

earth.

Interior of the earth can be classified into three major categories as

Crust, Mantle and Core

Internal Structure of Earth



• The earth's radius is 6371 km.

The Crust:

• The crust is a thin outer shell, about 30 km in thickness on average.

• Its thickness exceeds 70 km in some mountain belts, such as the

Himalayas.

• Its thickness ranges from 3 km to 15 km in oceanic crust.

The Mantle:

• It is a solid rocky layer.

• It extends to a depth of about 2900 km.

The core:

Inner core:

• Its radius is 1200 km.

• The inner core is solid due to generated pressure.

• It is made of iron.

Outer Core:

· Its radius is about 2200 km.

· It is made of iron mixed with other elements.




Region Radius

(km)

Inner Core 1200

Outer Core 2200

Mantle 2900

Crust 5 to 70

Anatomy of Earth



- The upper most part of the earth is considered to be divided into two

layers with different deformation properties.

- The upper rigid layer, called the lithosphere, is about 100 km thick

below the continents, and about 50 km under the oceans, and consists

of Crust and rigid upper-mantle rocks.

- The lower layer, called the asthenosphere, extends down to about 700

km depth.

- The rigid lithospheric shell is broken into several irregularly shaped

major plates and a large number of minor or secondary plates.

- The lithospheric plates are not stationary, on the contrary, they float in

a complex pattern, with a velocity of some 2-10 cm/year on the soft

rocks of the underlying asthenosphere like rafts on a lake.




- This theory requires a source that can generate great force is

acting on the plates.

- The widely accepted explanation is based on the force offered by

convection currents created by thermo-mechanical behavior of

the earth’s subsurface. The variation of mantle density with

temperature produces an unstable equilibrium. The colder and

denser upper layer sinks under the action of gravity to the

warmer bottom layer which is less dense. The lesser dense

material rises upwards and the colder material as it sinks gets

heated up and becomes less dense (refer to the figure in previous

slide).

- These convection currents create shear stresses at the bottom of

the plates which drags them along the surface of earth.

Theory of occurring earthquakes



Earthquake Fatalities

Bam earthquake struck the Kerman

province of southeastern Iran



Earthquake Victims



• UBC, “Structural engineering design provisions. In: Uniform Building Code.

International Conference of Building Officials”, vol. 2. 1997

• BS EN. 1998-1: Eurocode 8, “Design of structures for earthquake resistance. Part 1:

General rules, Introduction seismic actions and rules for buildings”, 2004

• IBC 2012, “ International Building Code”, International Code Council, 2011

• American Society of Civil Engineers, ASCE 7-10 ,“Minimum Design Loads for

Buildings and Other Structures”, 2010

• FEMA 356, “Prestandard and commentary for the seismic rehabilitation of buildings”,

Washington. DC: Federal Emergency Management Agency, 2000

• American Society of Civil Engineers, ASCE 41-06 , “Seismic Rehabilitation of

Existing Buildings”, 2007

• ACI 318-11, “ Building Code Requirement for Structural Concrete and Commentary”,

American, Earthquake Engineering & Structural Dynamics – 2012 Concrete Institute,

Detroit, 2011

• NZS 1170.5, “Structural Design Actions-Part 5 : Earthquake actions New Zealand”,

Standards, Association of New Zealand, 2004

• DIN 4149, “Buildings in Germany earthquake areas - Design loads, analysis and

structural design of buildings”, German Safety Standard Commission, 2005

Bibliography - Codes

earthquake engineering part1

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