Earth Quake Engineering

7/25/2019 Earth Quake Engineering

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Earthquake

Engineering



What is Earthquake

engineering?

Earthquake engineering is the

application of civil engineering

to reduce life and economic

losses due to earthquakes.

Traditionally, it has been

narrowly defined as the study of

the behavior of structures and

geo-structures subject to

seismic loading.

http://en.wikipedia.org/wiki/Seismic_loading

http://en.wikipedia.org/wiki/Seismic_loading



What is Seismic loading ?

Seismic loading means application of an earthquake-generated excitation to a

structure (or geo-structure. !t happens at contact surfaces of a structure

either with the ground , or with adjacent structures or with gravity waves

from tsunami.

"eismic loading depends primarily on#

• $robable earthquake%s parameters at the site (seismic ha&ard

• 'eotechnical parameters of the site

• "tructure%s characteristics

• haracteristics of the expected gravity waves from tsunami (if applicable



Seismic performance• Seismic performance defines a structure%s ability to sustain

its due functions, such as its safety and serviceability, at and

after a particular earthquake exposure. ) structure is,

normally, considered safe if it does not endanger the lives

and well-being of those in or around it by partially or

completely collapsing. ) structure may be

considered serviceable if it is able to fulfill its operational

functions for which it was designed.



What are the Failure modes? The major reasons of failure :

•

*nreinforced masonry building

• "oft story effect

• "oil liquefaction

• !nsufficient shear reinforcement



Unreinforced masonrybuilding

• The lack of reinforcementcoupled with

poor mortar and inadequate

roof-to-wall ties can result

in substantial damage toa unreinforced masonry

building.



Soft story effect• )bsence of adequate shear walls on the ground level caused

damage to this structure.



Soil liquefaction

Soil liquefaction. !n the cases where the soil consists of loose granular depositedmaterials with the tendency to develop excessive hydrostatic pore water pressure of

sufficient magnitude and compact, liquefaction of those loose saturated deposits may

result in non-uniform settlements and tilting of structures. This caused major damage to

thousands of buildings in +iigata, apan during the /0 earthquake.



Insufficient shear reinforcement1einforced concrete column burst due to insufficient shearreinforcement mode which allows main reinforcement to buckle

outwards.



Some Simple

Design riteria



Simple Design riteria• hoose an adequate lateral load resisting system.



!n adequate lateral load resisting system



Simple Design riteria

•

hoose an adequate lateral load resisting system.

2 3aintain regularity in elevation.



"aintain regularity in ele#ation





2 4nsure connection between structural elements.





Ensure connection bet$een structural elements






2 )void designing in locations of stress concentration.



!#oid designing in locations of stress concentration



Simple Design riteria

• hoose an adequate lateral load resisting system.



2 )void designing in locations of stress concentration.

2 "pacing between buildings to avoid pounding.



!#oid pounding





apacity Designoncepts



apacity Design oncepts

• )n earthquake-resistant

building has a number of special

structural features. !nterior support

walls called shear walls, made of

reinforced concrete, strengthen thestructure and help resist rocking

forces. "hear walls in the center of

a building form a shear core.

ross-bracing reinforces walls with

diagonal steel beams. 5ase

isolators act as shock absorbers,

and a moat allows a building to

bend.



Shear $all and

shear core• Shear wall and shear

core are walls those

made of reinforcementconcrete which are more

stiffer and stronger that

gives the structure more

strength against thelateral load.



%ase Isolation•

) base isolated structure is supported by a series of bearing pads which are

placed between the building and the

building%s foundation.

• ) variety of different types of base

isolation bearing pads have now been

developed.

4xample# 6ead7rubber bearings,

"pherical "liding !solation "ystems



&ead'(ubber %earings

• Lead–rubber bearings. These are among

the frequently7used types of base isolation

bearings. ("ee 8igure ) lead7rubber

bearing is made from layers of rubber

sandwiched together with layers of steel. !n

the middle of the bearing is a solid lead

"plug." 9n top and bottom, the bearing is

fitted with steel plates which are used to

attach the bearing to the building and

foundation. The bearing is very stiff and

strong in the vertical direction, but flexiblein the hori&ontal direction.



Earthquake )eneratedForces

•To get a basic idea of how baseisolation works, first examine8igure. This shows anearthquake acting on both a

base isolated building and aconventional, fixed7base,

building. )s a result of anearthquake, the ground beneath

each building begins to move.!n 8igure , it is shown movingto the right .



Spherical Sliding

Isolation Systems

6ead7rubber bearings are just one ofa number of different types of baseisolation bearings which have now been developed. Spherical SlidingIsolation Systems are another typeof base isolation. The building issupported by bearing pads that have

a curved surface and low friction. :uring an earthquake, the building isfree to slide on the bearings. "incethe bearings have a curved surface,the building slides both hori&ontallyand vertically The force needed tomove the building upwards limits thehori&ontal or lateral forces whichwould otherwise cause buildingdeformations. )lso, by adjusting theradius of the bearing%s curvedsurface, this property can be used todesign bearings that also lengthen the building%s period of vibration.



*uned mass

damper

• Typically, the tuned mass

dampers are huge concrete

blocks mounted in sky

scrapers or other structuresand moved in opposition to

the resonance frequency

oscillations of the structures

by means of some sort ofspring mechanism.



%uilding ele#ation

control

• Building eleation control is a

valuable source of vibration

control of seismic loading.$yramid-shaped skyscrapers

continue to attract attention of

architects and engineers because

such structures promise a betterstability against earthquakes and

winds.



Springs+$ith+damperbase isolator

•

!t is a baseisolation device

conceptually

similar to Lead

Rubber Bearing .



!d#antages !nd

Disad#antages



%raced frame

)dantages

•*sually used in steel structures

•)dd great amount of stiffness

to structure

•"imple to design and analy&e

!isadantages

•3ay require special tools to

install

• +ot energy efficient (steel•"teel is easy to transfer heat. "o, it;s

easy to lose heat during winter

•annot adapt to different load

conditions



%raced frame

)dantages

•*sually used in steel structures

•)dd great amount of stiffness

to structure

•"imple to design and analy&e

!isadantages

•3ay require special tools to

install

• +ot energy efficient (steel•"teel is easy to transfer heat. "o, it;s

easy to lose heat during winter

•annot adapt to different load

conditions



Shear $all

3any materials are used as shear wall

<oods, steel, concrete and masonry

ommonly used in homes

dantages

•$rovides great stiffness

•4asy to install to existing structures

•3any constructors are familiar with it

•heap

!isadantages

•6ess energy dissipation

•ause higher loses to non-structural

components



%ase isolator

)dvantages- =igh energy dissipation

- +ot required electric

- 'ood for using in large structures

- ompact

- =ave both lateral stiffness and >erticalsupport

:isadvantages

- :ifficult to install to existing structures

- $rovides lower stiffness

- "ensitive to near fault ground )cc.



,b-ecti#e of the.resentation



,b-ecti#e of the.resentation• The main objective of this

presentation is to introduceearthquake engineering,

how it works, why it is

needed and also to share the

fundamental concepts thatwe try to gather.



*hank /ou !ll



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Earth Quake Engineering