earthquake risk reduction

7/21/2019 Earthquake Risk Reduction

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2010

ayman

Earthquake efect reduction

2010

Reduction of Eatrhquake

eect

Prepared by:Eng : Ayman Mohamed

Kandeel

Supervisor

PROF.DR : Hamed skarStructural engineering

department


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contents

before start......................................................................................................(2)

Part one : earth quakeefect.........................................................................(3)

h ! :introduction...............................................................................

.........................( " )h # : $hat cau%e% earth

quake................................................................................... .( ")h 3 : %ei%mic efect% on

%tructure%...............................................................................( & )h " : 'e%ign and 'etailing o e$ Structure% or re%i%t

Earthquake......................(!3)Ch 5: reduction of earth quake effect...................................................................(23)

Part t$o :%ummery .......................................................................................(*+)


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,eore %tart

From my first trials in my way on my prefer sciene earthquake engineering

I hope it will be helpfull and easy ....

Part one : earth quake efect

chapter (!)introduction

thi% re%earch i% a-out earthquake efect% on -uilding and$hat are the method% that% -y $e can reduce the efectand ri%k o earthquake.

Earthquake engineering i% ane$ %cience that $e mu%tdeal $ith ho$eer the earthquake action i% not ne$ oru% thereore $e hae the need to produce %ome $ay% inour %tructure% help% the %tructure to %u%tain thearthquake efect or longer time.

/hat% $ay the %cience o earthquake reduction appear tothe lie and in the%e ollo$ing page% $e $ill di%cu%%a-out the earthquake efect and our moderntechnologie% in order to reduce earthquake efect%.


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Ayman kandeel##0!+0#+!+

chapter (#)$hat cau%e% earth quake

/he Earth and it% 1nterior

Long time ago, a large collection ofmaterialmasses coalesced to form the Earth. Largeamount ofheat was generated by this fusion, andslowly as theEarth cooled down, the heavier and densermaterialssank to the center and the lighter onesrose to the top.The dierentiated Earth consists of the

Inner Coreradius !"#$%km&, the Outer Corethickness !##%%km&,the Mantle thickness !#$%%km& and theCrustthickness !' to (%km&. )igure " showsthese layers.The *nner +ore is solid and consists of heavy metalse.g., nickel and iron&, while the +rust consists of lightmaterials e.g., basalts and granites&. The uter +ore is liquid in form and the -antlehas the ability to ow.


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!hat "auses Earthqakes#/he irculation%

+onvection currents develop in the viscous-antle, because of prevailing high

temperature andpressure gradients between the +rust andthe +ore,like the convective ow of water whenheated in abeaker )igure #&. The energy for the abovecirculations is derived from the heatproduced fromthe incessant decay of radioactiveelements in therocks throughout the Earth/s interior. Theseconvectioncurrents result in a circulation of theearth/s mass0 hotmolten lava comes out and the cold rockmass goesinto the Earth. The mass absorbedeventually meltsunder high temperature and pressure and becomes apart of the -antle, only to come out again fromanother location, someday. -any such local

circulations are taking place at dierent regionsunderneath the Earth/s surface, leading to dierentportions of the Earth undergoing dierent directionsof movements along the surface.

Plate /ectonic%

The convective ows of -antle material

cause the+rust and some portion of the -antle, toslide on thehot molten outer core. This sliding of Earth/smasstakes place in pieces called Tectonic Plates.The surfaceof the Earth consists of seven ma1ortectonic plates andmany smaller ones )igure 2&. These platesmove in

dierent directions and at dierent speedsfrom those


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of the neighbouring ones. 3ometimes, the plate in thefront is slower0 then, the plate behind it comes andcollides and mountains are formed&. n the otherhand, sometimes two plates move away from oneanother and rifts are created&. *n another case, twoplates move side4by4side, along the same direction orin opposite directions. These three types of inter4plateinteractions are the convergent, divergent and transformboundaries )igure (&, respectively. The convergentboundary has a peculiarity like at the 5imalayas& thatsometimes neither of the colliding plates wants to sink.The relative movement of these plateboundariesvaries across the Earth0 on an average, it isof the orderof a couple to tens of centimeters per year.

/he Earthquake

Rocks are made of elastic material, and soelasticstrain energy is stored in them during thedeformations that occur due to the gigantictectonicplate actions that occur in the Earth. 6ut, thematerialcontained in rocks is also very brittle. Thus,when therocks along a weak region in the Earth/s +rust reachtheir strength, a sudden movement takes place there)igure '&0 opposite sides of the fault a crack in therocks where movement has taken place& suddenly slipand release the large elastic strain energy stored in theinterface rocks. )or e7ample, the energy releasedduring the #%%" 6hu1 *ndia& earthquake is about (%%times or more& that released by the 194!tom "om#dropped on 5iroshima88The sudden slip at the fault causes t$e

eart$%uake9.a violent shaking of the Earth when largeelastic strainenergy released spreads out through seismicwavesthat travel through the body and along thesurface ofthe Earth. :nd, after the earthquake is over,theprocess of strain build4up at this modi;edinterface

between the rocks starts all over again )igure


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volume, with its long dimension often running intotens of kilometers.

chapter (3)%ei%mic efect% on %tructure%

!.!. $hat are the %eimic efect on%tructure% 2


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#.#. ho$ do earth quake afect reinorced

concrete -uilding


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chapter (")'e%ign and 'etailing o e$ Structure% orre%i%t Earthquake

$.$. %ntroduction

The design of any new item of infrastructure e.g. structure or lifelines& provides bothan opportunity and a challenge to minimi=e earthquake risk to people and propertywithin the resources available. To minimi=e risk, designers must minimi=e the seismicvulnerability of whatever is being designed. :ny given structure may be sub1ect toone or more of the earthquake induced ha=ards, but this chapter is restricted todesign for the basic phenomenon of ground shaking. E7cept for liquefaction, the otherphenomena are largely matters for site selection, site response regional planning, orfoundation design ,rather than the design of superstructure .the designer will have a design brief, which leads to a preferred structural form andconstruction materials. *n addition, the desired performance of the structure will havebeen agreed, and will range from accepting that implied by a code, or performancerequirements for selected ha=ard levels or limit states .

oncrete Structure%

!.#.!. 1ntroduction

There is more information available about the seismic performance of reinforcedconcrete than any other material. >o doubt this is because of its widespread use, andbecause of the di?culties involved in ensuring its adequate ductility robustness&.

@ell designed and constructed reinforced concrete is suitable for most structures inearthquake areas, but achieving both these prerequisites can be problematical even incountries of advanced technology.Reinforced concrete is generally desirable because of its wide availability andeconomy, and its stiness can be used to advantage to minimi=e seismicdeformations and hence reduce damage to non4structure.Ai?culties arise due to reinforcement congestion when trying to achieve highductilities in framed structures, and the problem of detailing beam4column 1oints towithstand strong cyclic loading remains a di?cult and contentious problem. *t shouldbe recalled that no amount of good detailing will enable an ill4conceived structural

form to survive a strong earthquake.

!.#.#. Sei%mic re%pon%e o reinorced concrete

Reinforcement controls and delays failure in concrete members, the degradationprocess generally being initiated by cracking of the concrete. *nelastic elongation ofreinforcement within a crack prevents the latter from closing when the load directionis reversed and cyclic loading leads to progressive crack widening and steel yielding)igure "%."B&. )enwick "$B2& argued that shear in plastic hinge regions of beams isresistedby truss action until the phase of rapid strength degradation in which large shear

displacements occur.

Fi&ure $ : 3igni;cant stages of development of a plastic hinge in reinforced concrete duringcyclic e7ural and shear loading


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!.#.3. elia-le %ei%mic -ehaiour o concrete %tructure%

1ntroduction

)or obtaining reliable seismic response behaviour the principles concerning choice ofform, materials, and failure mode control should be applied to concrete structures.Aesigning for failure mode control requires consideration of the structural form used,

with most of the forms being appropriate for concrete, i.e.C

"& -oment4resisting frames.#& 3tructural walls i.e. shear walls&.2& +oncentrically braced frames.(& 5ybrid structures.


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)or concrete structures, , it should be noted that the essential ob1ectives of failuremode control areC

a& 6eams should fail before columns unless e7tra column strength is provided&.

b& 6rittle failure modes should be suppressed.c& :n appropriate degree of ductility should be provided.

So 4o$ to Make ,uilding% 'uctile or 5ood Sei%mic Perormance2

'uctility

>ow, let us make a chain with links made of#rittleand ductile materials )igure 2&. Each of theselinks willfail 1ust like the bars shown in )igure #. >ow,hold thelast link at either end of the chain and apply aforce (.3ince the same force ( is being transferredthrough allthe links, the force in each link is the same, i.e.,

(. :smore and more force is applied, eventually thechainwill break when the )eakest link in it breaks. *ftheductile link is the )eak one i.e., its capacity to take loadis less&, then the chain will show large ;nal elongation.*nstead, if the brittle link is the weak one, then thechain will fail suddenly and show small ;nalelongation. Therefore, if we want to have such a ductilechain, we have to make the ductile link to be the

)eakest link.

)ig "& C ductile chain design.


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Design

Strong column $eak -eam

6uildings should be designed bedesigned like the ductile residentialapartment construction 4 the multi4storeybuilding made of reinforced concrete. *t

consists of hori=ontal and verticalmembers, namely #eams and columns. Theseismic inertia forces generated at its oorlevels are transferred through the various#eams and columns to the ground. Thecorrect building components need to bemade ductile. The failure of a column canaect the stability of the whole building,but the failure of a beam causes locali=edeect.Therefore, it is better to make #eams to bethe ductileweak links than columns. This method of designingR+ buildings is called the strong*column )eak*#eam design method .

Design)ig #& C column slould be stronger than beams .

4o$ architectural eature% afect -uilding

during earthquake2


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eak-Column


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chapter (*)method% o reductiono earthquake efect

Introduction

There are many modern methods has been

developed to reduce earthquake effect orrisk and this chapter will illustrate this

methods briefly.

onentional Method%

*ncreasing the cross sectional area,increases the rigidity of the structure, so the probability of structural failure isincreased because of the decrease of the natural period of the structure, i.e. thefrequency of the structure within the range of the frequency content of the

earthquake

e%pon%e control method%

:bsorb and reect the energy introduced by dynamic loads


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Seimic isolation and response control

Seismic isolation and response control devices have long been sought to control the displacement and

acceleration response of buildings and thus to control the extent of damage caused by earthquake groundmotion and wind excitation . Historically, buildings have been isolated from input earthquake energy by

putting a layer of sand , or steamed rice, between the base of buildings and the soil, as observed in some

historical buildings in China and Japan .

n modern engineering practice, devices for vibration isolation or the dissipation of input energy were first

applied in the field of mechanical engineering, and included applications such as shock absorbers in

automobiles. n structural engineering, flexible rubber blocks have been used to isolate buildings from

vibration induced by underground trains, vehicle traffic and other forms of ground!borne vibration since

their first application in the "#$%s. &ntil recently, however, these techniques have not been used for the

protection of structures from seismic and wind excitations.

'he first modern attempt to isolate a structure from earthquake ground motion was the Heinrich (estalo))i

School in "#*# in Skop+e, acedonia -in the former ugoslavia/ which utili)ed rubber bearings without

internal reinforcing steel plates. 'he first largescale application of seismic isolation was the use of lead!

rubber bearings for the 0illiam Clayton 1uilding in "#2" in 3ew 4ealand, followed by the 5oothill

Communities 6aw and Justice Center in the &S7 in "#2$. 8wing in part to the progress of computer

analysis capabilities to facilitate non!linear dynamic structural analysis, essential to verify the effectiveness

of devices to control response of buildings sub+ected to earthquake and wind excitations, the application of

response control devices has grown significantly over the last two decades for both new construction and the

retrofit of buildings .

'he favourable response of seismically!isolated buildings observed in the "##9 3orthridge earthquake in the

&S7 and the "##$ Hyogoken!3anbu earthquake in Japan has also contributed to the increased acceptance ofthe technology. 'heir performance and measured response verified the validity and reliability of analytical

procedures developed and accelerated the practical application of seismic isolation and response control

systems and lead to the innovation of a wide variety of devices.

These technologies can be categoried as follows:

1! "eismic Isolation

'his technology utili)es flexible elements such as rubber bearings or sliding or rolling mechanisms,

often coupled with energy absorbing dampers, to reduce structural response. 'he basic concept is to givelonger natural periods and provide higher damping to rigid structures to avoid resonance with the

relatively short period components dominant in earthquake ground motions. :ecently, seismic isolation


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has been utili)ed in more flexible structures to reduce acceleration or displacement response, allowing

designers to minimi)e structural member si)es, or to control damage and improve the post!earthquake

functionality of buildings. Seismic isolation devices demonstrate significant durability and are expected

to function throughout the design life of the structure.

2! #esponse $ontrol "ystems

:esponse control systems can be defined into two categories; direct energy dissipating devices and massdampers.


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Seismically isolated buildings:

Aevices are installed between building and the ground, and they absorbenergy of vibration during the quake. They can reduce vibration of building.6uilding vibration is very slow, there are few possibilities of the foresaidsituations.

Devices for Seismic solation and !esponse

Control

I%T#&'($TI&%

n this following pages we will give an overview of several different response control devices commonly

used in seismic isolation systems and structural control.#esponse control systems are broadly classified into :

"!(assive control

=!Semi!active control

>!7ctive control

9! hybrid control

systems as shown in 'able $.".". 'his classification is based on

S8 >%"% nternational standard ?1asis for design of structures@Seismic action

on structuresA.

$')assi*e control systemsreduce the response of buildings through the use of passive devices which do not require power.

2+"emi+acti*e control systems.

reduce the response of buildings by changing the property of the building structure, i.e., the damping and

stiffness, and requires a relatively small amount of power.

,+-cti*e control systems.reduce the response of buildings by controlling a generated force which resists or reduces the inertia of

buildings.


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+/ybrid control systems.

are composite systems comprising both passive and active systems, where, in general, the active system

assists the passive system.

)assi*e control systems characteried into :

Seismic solation systems.

Bnergy dissipation systems.

7dditional mass effect systems.

"emi+acti*e control systems characteried into :

ariable damping systems

variable stiffness systems

-cti*e control systems characteried into :

mass damper systems .

active tendon systems .

/ybrid control "ystems are :

composite systems comprising both passive and active systems, where, in general, the active system

assists the passive system.

n this Chapter, the construction and performance of popular devices are introduced and discussed. Section

=.= outlines the constructions and performance of isolators for base!isolation system. Section =.> outlines


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dampers commonly used in both baseisolation systems and passive structural control systems. 7ctive and

Semi!active control systems are often pro+ect specific and therefore are briefly shortly.

"assive control s#stems

2.2. I"&-T


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2.2.$.2 %undamental D#namic Characteristic


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Figure 2.2.1 ! )laces of rubber and sliding bearing on aplan of building


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*t utili=es the plasticity property of lead. The hysteretic loop contributes toenergy dissipation. There are two types of lead dampers, one has a roundsection and a curved shape as shown in the Dhotograph and other has acylindrical plug in core of the elastomeric isolator.


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*t utili=es the elasto4plasticity property of steel. The hysteretic loopcontributes to energy dissipation. There are two types of steel dampers, oneis square in section and other is round in section of the rods as shown in theDhotograph.


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Other types o(passive contro)

dampers :


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*'ctive contro) devices

*.$' "+%,E +E-DO-S

'Hyprid "ontro)

7ctuator


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/'Semi 'ctive Devices

Part three


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Summery

!e may conc)ode the above pa&es in some 0ords ...........

/here are %ome $ay% tha% -y $e can reduceearthquake efect% .......

Conventional &ethods :

*ncreasing the cross sectional area, increases the rigidity of the structure, so theprobability of structural failure is increased because of the decrease of the naturalperiod of the structure, i.e. the frequency of the structure within the range of thefrequency content of the earthquake

!esponse control methods :

!0Actie control

E7ternal source powers apply forces to the structure in a prescribed manner

#0Pa%%ie control

Aoes not require an e7ternal power source

304yprid control

+ombined use of active and passive control systems

"0Semi0actie control

3maller e7ternal energy than in active control systems is required, no mechanicalenergy is added to the structure controllable passive control&

nd 0e sti)) search about another techno)o& methods to improve our 0aysto reduce earthquake efect and risk.


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erence%

1&art$%uake tips of indian codes .

2 &art$%uake 'isk 'eduction +.. +o)rick

3Response Control and Seismic Isolation of Buildings asahiko

!igashino and Shin "kamoto

4design of Seismic Isolated Structures# $rom Theory to %ractice.. $.

&aeim and '. . (elly

my best wishes

ayman kandeel

earthquake risk reduction

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