Earthquake engineeing

1. EARTHQUA
KE
ENGINEERI
NG

2.  WHAT IS AN EARTHQUAKE?
An earthquake is a shaking of the ground caused by the
sudden breaking and movement of large sections (tectonic
plates) of the earth's rocky outermost crust. The edges of the
tectonic plates are marked by faults (or fractures). Most
earthquakes occur along the fault lines when the plates slide
past each other or collide against each other.

3. STRUCTURE OF THE EARTH
The interior structure of the Earth is layered in spherical
shells, like an onion. These layers can be defined by either
their chemical or their rheological properties. Earth has an
outer silicate solid crust, a highly viscous mantle, a liquid outer core that
is much less viscous than the mantle, and a solid inner core. Scientific
understanding of the internal structure of the Earth is based on
observations of topography and bathymetry, observations
of rock in outcrop, samples brought to the surface from greater depths
by volcanic activity, analysis of the seismic waves that pass through the
Earth, measurements of the gravitational and magnetic fields of the
Earth, and experiments with crystalline solids at pressures and
temperatures characteristic of the Earth's deep interior.

5. HISTORY OF THE EARTH
• The history of Earth concerns the development of the planet Earth from
its formation to the present day. Nearly all branches of natural
science have contributed to the understanding of the main events of the
Earth's past. The age of Earth is approximately one-third of the age of
the universe. An immense amount of biological and geological change
has occurred in that time span.
• Earth formed around 4.54 billion years ago by accretion from the solar
nebula. Volcanic outgassing probably created the primordial
atmosphere, but it contained almost no oxygen and would have been
toxic to humans and most modern life. Much of the Earth was molten
because of frequent collisions with other bodies which led to extreme
volcanism. One very large collision is thought to have been responsible
for tilting the Earth at an angle and forming the Moon. Over time, the
planet cooled and formed a solid crust, allowing liquid water to exist on
the surface.

7. HISTORY OF THE EARTH
• The first life forms appeared between 3.8 and 3.5 billion years ago. The earliest
evidences for life on Earth are graphite found to be biogenic in 3.7-billion-year-
old metasedimentary rocks discovered in Western Greenland and microbial
mat fossils found in 3.48-billion-year-oldsandstone discovered in Western
Australia. Photosynthetic life appeared around 2 billion years ago, enriching the
atmosphere with oxygen. Life remained mostly small and microscopic until about
580 million years ago, when complex multicellular life arose. During
the Cambrian period it experienced a rapid diversification into most major phyla. More
than 99 percent of all species, amounting to over five billion species,[that ever lived on
Earth are estimated to be extinct.[10][11] Estimates on the number of Earth's
current species range from 10 million to 14 million,[12] of which about 1.2 million have
been documented and over 86 percent have not yet been described.
• Geological change has been constantly occurring on Earth since the time of its
formation and biological change since the first appearance of life. Species
continuously evolve, taking on new forms, splitting into daughter species, or going
extinct in response to an ever-changing planet. The process of plate tectonics has
played a major role in the shaping of Earth's oceans and continents, as well as the life
they harbor. The biosphere, in turn, has had a significant effect on the atmosphere and
other abiotic conditions on the planet, such as the formation of the ozone layer, the
proliferation of oxygen, and the creation of soil.

8. EARTHQUAKE MECHANISM
• The focal mechanism of an earthquake describes the
deformation in the source region that generates
the seismic waves. In the case of a fault-related event it
refers to the orientation of the fault plane that slipped and
the slip vector and is also known as a fault-plane solution.

9. PROPAGATION OF SEISMIC WAVES
• The full elastic seismic wavefield that propagates through an
isotropic Earth consists of a P-wave component and two shear (SV
and SH) wave components. Marine air guns and vertical onshore
sources produce reflected wavefields that are dominated by P and
SV modes. Much of the SV energy in these wavefields is created by
P-to-SV-mode conversions when the downgoing P wavefield
arrives at stratal interfaces at nonnormal angles of incidence.
Horizontal-dipole sources can create strong SH modes in onshore
programs. No effective seismic horizontal-dipole sources exist for
marine applications.

11. EARTHQUAKE PHENOMENA
• The phenomena of earthquakes differ greatly in accordance with the
number, duration, and intensity of the shocks, and with the distance
of the place of observation from that of the origin of the disturbance.
One of the greatest of modern earthquakes is that of northern India of
1897, which is well summed up in the official report.

12. EARTHQUAKE MEASUREMENTS
• The Richter magnitude scale was developed in 1935 by
Charles F. Richter of the California Institute of Technology
as a mathematical device to compare the size
of earthquakes. The magnitude of an earthquake is
determined from the logarithm of the amplitude of waves
recorded by seismographs.

14. SEISMICITY- GLOBAL &
LOCAL

15.  EARTHQUAKE VIBRATIONS
• Our servo-hydraulic shake table can also be used for
simulating vibration in vehicles. We carry out vibration
testing not only of transported goods, but also of
equipment that is secured to or in vehicle. The
equipment is suitable for testing large, heavy items at
low and moderate frequencies, while smaller and lighter
items can be tested at high frequencies on SP's
electromagnetic vibration rigs

16. FREE & FORCE VIBRATIONS FOR SINGLE DEGREE OF
FREEDOM SYSTEM
• This document describes free and forced dynamic responses of single
degree of freedom (SDOF) systems. The prototype single degree of
freedom system is a spring-mass-damper system in which the spring has
no damping or mass, the mass has no stiffness or damping, the damper
has no stiffness or mass. Furthermore, the mass is allowed to move in
only one direction. The horizontal vibrations of a single-story building
can be conveniently modeled as a single degree of freedom system. Part 1
of this document describes some useful trigonometric identities. Part 2
shows how damped SDOF systems vibrate freely after being released
from an initial displacement with some initial velocity. Part 3 covers the
resposne of damped SDOF systems to persistent sinusoidal forcing.

17. FREE & FORCE VIBRATIONS FOR SINGLE DEGREE OF
FREEDOM SYSTEM
• Consider the structural system shown in Figure 1, where:
• f(t) = external excitation force
• x(t) = displacement of the center of mass of the moving object
• m = mass of the moving object, fI = d dt(mx˙(t)) = mx¨(t)
• c = linear viscous damping coefficient, fD = cx˙(t) k = linear
elastic stiffness coefficient, fS = kx(t)

18. STRONG MOTION VIBRATION RECORDS
• The strong motion records were provided by the U.S.
Geological Survey (USGS) National Strong-Motion
Program (NSMP). At least one strong-motion record is
available and has been processed for each building, and as
many as sixteen seismic records are available for some
buildings. Ambient vibration records were collected using
velocimeters (velocity transducers). In order to test the
efficiency of the ambient vibration for defining the dynamic
parameters of structure, a set of three permanently
instrumented buildings has been monitored using ambient
vibration.

19. EARTHQUAKE SPECTRUM AND DESIGN
SPECTRUM
• Earthquake Spectra, the professional journal of the
Earthquake Engineering Research Institute (EERI), is
published quarterly in both printed and online editions
in February, May, August, and November. The printed
edition is sent to EERI members as part of their
membership benefits. The online edition is available
free to EERI members who register for the online
access.

20. EARTHQUAKE SPECTRUM AND DESIGN
SPECTRUM
Strength reduction factors (SRFs) continue to play a key role in obtaining
inelastic spectra from the elastic design spectra for the ductility-based earthquake
resistant design. This study proposes a new model to estimate the SRF spectrum in
terms of a pseudo-spectral acceleration spectrum and ductility demand ratio with
the help of two coefficients. The proposed model is illustrated for an elastoplastic
oscillator in case of five recorded accelerograms and three ductility ratios. The
model is used to carry out a parametric study for the explicit dependence of SRF
spectrum on strong motion duration, earthquake magnitude, site conditions, and
epicentral distance. It is shown that there is no clear and significant dependence of
SRF spectrum on strong motion duration, while the dependence on earthquake
magnitude, site conditions, and epicentral distance conforms to the trends reported
by earlier investigations. In particular, it is confirmed that the dependence of SRF
spectrum on earthquake magnitude cannot be ignored.

21. GROUND MOTION- EFFECT OF GROUND
CONDITIONS
• The overall objective of this research is to improve the understanding of the
damaging ground motions produced in earthquakes in order to develop better
methods for seismic hazard assessment and mitigation in urban areas. Past
earthquakes have shown that the amplification of motions due to surface-to-
bedrock geology, 3D crustal structure, and topography have a major influence on
seismic damage and loss in urban areas. Also of significant importance are the
details of the rupture process on the fault, and the way a built structure is
engineered.

22. GROUND MOTION- EFFECT OF GROUND
CONDITIONS
• Two important local geologic factors that affect the level of shaking experienced in
earthquakes are (1) the softness of the surface rocks and (2) the thickness of surface
sediments. This image of the Los Angeles region combines this information to predict
the total amplification expected in future earthquakes from local geologic conditions or
site effects.
• As the waves propagate they are affected by the earth structure, such as changes in
elastic properties resulting in effects such as constructive and destructive interference
and basin amplification. Near the ground surface, strong shaking can result in nonlinear
soil behavior or raise pore fluid pressure causing liquefaction. Likewise, the geometry of
a man-made structure, the construction materials, the type of ground, and its anchorage
in the ground affect its vulnerability to damage during the shaking. This research aims to
understand each of these processes and to work with the seismic engineering community
to bring the best estimates of strong ground shaking to engineering practice.

23. GROUND MOTION- EFFECT OF GROUND
CONDITIONS
• Two important local geologic factors that affect the level of
shaking experienced in earthquakes are (1) the softness of the
surface rocks and (2) the thickness of surface sediments. This
image of the Los Angeles region combines this information to
predict the total amplification expected in future earthquakes
from local geologic conditions or site effects.

24.  EARTHQUAKE DAMAGES TO VARIOUS CIVIL
ENGINEERING STRUCTURES
• Civil engineering structures were subject to enormous damage, considered to be worse than that incurred
during the Great Kanto Earthquake, and this included the collapse of overhead Shinkansen rails, the
collapse of overhead rails belonging to the Hanshin Hankyu Electric Railways, and the collapse and
overturning of the main supports of the expressway.
• This exceedingly shocking form of damage occurred to the sc overhead support--Mos, considered modern
when built, between Ashiya Post Office and Uozaki. Many of the other overhead supports which received
damage were constructed between 1965 and 1975, and most of them were designed and installed in
accordance with the design policies of the day. The removal of these damage supports was carried out at a
frantic pace in order to secure emergency transportation routs and enable recovery work to continue.
• Damage also occurred in underground structures made of the same material in the metropolis.
Underground structures were always considered safe from the effects of earthquakes until now, but
subsidence also occurred to the roads which inters ect the Kobe Expressway. This subsidence caused the
central pillar on the underground platform and the station ceiling of Daikai Station to collapse. It is
thought that the main reason for the collapse of the underground station's central pillar was the fact that the
epicenter of the quake was nearby and the fact that the rate of lateral movement was greater than originally
provided for in the design, which indicates that greater care should be taken on cause surveys in the
future.

25.  EARTHQUAKE DESIGN PROCEDURES
• Modern earthquake design has its genesis in the1920’s and1930’s. At that time earthquake design
typically involved the application of 10% of the building weight as a lateral force on the structure,
applied uniformly up the height of the building. Indeed it was not until the
1960’sthatstronggroundmotionaccelerographsbecame more generally available. These instruments
record the ground motion generated by earthquakes. When used in conjunction with strong motion
recording devices which were able to be installed at different levels within buildings themselves, it
became possible to measure and understand the dynamic response of buildings when they were
subjected to real earthquake induced ground motion. By using actual earthquake motion records as
input to the, then, recently developed inelastic integrated time history analysis packages, it became
apparent that many buildings designed to earlier codes had inadequate strength to withstand design
level earthquakes without experiencing significant damage. However, observations of the in-service
behaviour of buildings showed that this lack of strength did not necessarily result in building failure or
even severe damage when they were subjected to severe earthquake attack. Provided the strength could
be maintained without excessive degradation as inelastic deformations developed, buildings generally
survived and could often be economically repaired. Conversely, buildings which experienced
significant strength loss frequently became unstable and often collapsed.

26. With this knowledge the design emphasis moved to ensuring that the retention of post-elastic
strength was the primary parameter which enabled buildings to survive. It became apparent that
some post-elastic response mechanisms were preferable to others. Preferred mechanisms could be
easily detailed to accommodate the large inelastic deformations expected. Other mechanisms were
highly susceptible to rapid degradation with 2 collapse a likely result. Those mechanisms needed to
be suppressed, an aim which could again be accomplished by appropriate detailing. The key to
successful modern earthquake engineering design lies therefore in the detailing of the structural
elements so that desirable post-elastic mechanisms are identified and promoted while the formation
of undesirable response modes are precluded. Desirable mechanisms are those which are
sufficiently strong to resist normal imposed actions without damage, yet are capable of
accommodating substantial inelastic deformation without significant loss of strength or load
carrying capacity. Such mechanisms have been found to generally involve the flexural response of
reinforced concrete or steel structural elements or the flexural steel dowel response of timber
connectors. Undesirable post-elastic response mechanisms within specific structural elements have
brittle characteristics and include shear failure within reinforced concrete, reinforcing bar bond
failures, the loss of axial load carrying capacity or buckling of compression members such as
columns, and the tensile failure of brittle components such as timber or under-reinforced concrete.
Undesirable global response mechanisms include the development of a soft-storey within a
building (where inelastic deformation demands are likely to be concentrated and therefore make
high demands on the resistance ability of the elements within that zone), or buildings where the
structural form or geometry is highly irregular, which puts them outside the simplifications made
within the engineering models used for design.

27.  DESIGN CODES
• A design code is a document that sets rules for the design of a new development in
the United Kingdom. It is a tool that can be used in the design and planning process, but
goes further and is more regulatory than other forms of guidance commonly used in the
English planning system over recent decades. It can be thought of as a process and
document – and therefore a mechanism – which operationalises design guidelines or
standards which have been established through a masterplan process. The masterplan or
design framework is the vision. It should be accompanied by a design rationale that
explains the objectives, with the design code providing instructions to the appropriate
degree or precision of the more detailed design work.
• In this way a design code may be a tool which helps ensure that the aspirations for
quality and quantity for housing developments, particularly for large-scale projects,
sought by the Government and other agencies are actually realised in the final schemes.
It has the potential to deliver the consistency in quality exposed as lacking
by CABE’s Housing Audit(2004).

28. • The following codes and standards have been identified as applicable, in whole or in
part, to civil engineering design and construction of power plants.
• • American Association of State Highway and Transportation Officials (AASHTO)—
Standards and Specifications
• • American Concrete Institute (ACI) - Standards and Recommended Practices
• • American Institute of Steel Construction (AISC) - Standards and Specifications
• • American National Standards Institute (ANSI) - Standards
• • American Society of Testing and Materials (ASTM) - Standards, Specifications, and
Recommended Practices
• • American Water Works Association (AWWA) - Standards and Specifications •
• American Welding Society (AWS) - Codes and Standards
• • Asphalt Institute (AI) - Asphalt Handbook
• • State of California Department of Transportation (CALTRANS) Standard
Specification • California Energy Commission - Recommended Seismic Design
Criteria for Non-Nuclear Generating Facilities in California, 1989
• • Concrete Reinforcing Steel Institute (CRSI) – Standards

29. • Factory Mutual (FM) - Standards
• National Fire Protection Association (NFPA) -
Standards
• California Building Standards Code (CBC) 2001
• Steel Structures Painting Council (SSPC) - Standards
and Specifications