Geotechnical Earthquake Engineering - PPT - Civil Engineering (CE) PDF Download

 Page 1


Geotechnical Earthquake 
Engineering 
by 
Dr. Deepankar Choudhury 
Professor 
Department of Civil Engineering 
IIT Bombay, Powai, Mumbai 400 076, India. 
Email: dc@civil.iitb.ac.in 
URL: http://www.civil.iitb.ac.in/~dc/ 
Lecture – 13 
Page 2


Geotechnical Earthquake 
Engineering 
by 
Dr. Deepankar Choudhury 
Professor 
Department of Civil Engineering 
IIT Bombay, Powai, Mumbai 400 076, India. 
Email: dc@civil.iitb.ac.in 
URL: http://www.civil.iitb.ac.in/~dc/ 
Lecture – 13 
IIT Bombay, DC 2 
Module – 4 
 
Strong Ground Motion 
Page 3


Geotechnical Earthquake 
Engineering 
by 
Dr. Deepankar Choudhury 
Professor 
Department of Civil Engineering 
IIT Bombay, Powai, Mumbai 400 076, India. 
Email: dc@civil.iitb.ac.in 
URL: http://www.civil.iitb.ac.in/~dc/ 
Lecture – 13 
IIT Bombay, DC 2 
Module – 4 
 
Strong Ground Motion 
IIT Bombay, DC 3 
Strong Ground Motion 
? Evaluation of the effects of earthquakes requires the 
study of ground motion. 
? Engineering Seismology deals with vibrations related to 
earthquakes, which are strong enough to cause damage 
to people and environment. 
? The ground motions produced by earthquakes at any 
particular point have 3 translational and 3 rotational 
components. 
? In practice, generally translational components of 
ground motion are measured and the rotational 
components are ignored. 
 
Page 4


Geotechnical Earthquake 
Engineering 
by 
Dr. Deepankar Choudhury 
Professor 
Department of Civil Engineering 
IIT Bombay, Powai, Mumbai 400 076, India. 
Email: dc@civil.iitb.ac.in 
URL: http://www.civil.iitb.ac.in/~dc/ 
Lecture – 13 
IIT Bombay, DC 2 
Module – 4 
 
Strong Ground Motion 
IIT Bombay, DC 3 
Strong Ground Motion 
? Evaluation of the effects of earthquakes requires the 
study of ground motion. 
? Engineering Seismology deals with vibrations related to 
earthquakes, which are strong enough to cause damage 
to people and environment. 
? The ground motions produced by earthquakes at any 
particular point have 3 translational and 3 rotational 
components. 
? In practice, generally translational components of 
ground motion are measured and the rotational 
components are ignored. 
 
4 
Strong motion seismographs 
• Designed to pickup 
strong, high-amplitude 
shaking close to quake 
source 
• Most common type is 
the accelerometer 
• Directly records ground 
acceleration 
• Recording is triggered 
by first waves 
• Difficult to differentiate 
S and surface waves 
Seismographs in 
India 
Page 5


Geotechnical Earthquake 
Engineering 
by 
Dr. Deepankar Choudhury 
Professor 
Department of Civil Engineering 
IIT Bombay, Powai, Mumbai 400 076, India. 
Email: dc@civil.iitb.ac.in 
URL: http://www.civil.iitb.ac.in/~dc/ 
Lecture – 13 
IIT Bombay, DC 2 
Module – 4 
 
Strong Ground Motion 
IIT Bombay, DC 3 
Strong Ground Motion 
? Evaluation of the effects of earthquakes requires the 
study of ground motion. 
? Engineering Seismology deals with vibrations related to 
earthquakes, which are strong enough to cause damage 
to people and environment. 
? The ground motions produced by earthquakes at any 
particular point have 3 translational and 3 rotational 
components. 
? In practice, generally translational components of 
ground motion are measured and the rotational 
components are ignored. 
 
4 
Strong motion seismographs 
• Designed to pickup 
strong, high-amplitude 
shaking close to quake 
source 
• Most common type is 
the accelerometer 
• Directly records ground 
acceleration 
• Recording is triggered 
by first waves 
• Difficult to differentiate 
S and surface waves 
Seismographs in 
India 
IIT Bombay, DC 5 
Accelerometer 
Types of Accelerometers: 
Electronic : transducers 
produce voltage output 
Servo controlled: use 
suspended mass with 
displacement transducer 
Piezoelectric: Mass attached 
to a piezoelectric material, 
which develops electric charge 
on surface. 
 
Generally accelerometers are placed in three orthogonal directions to 
measure accelerations in three directions at any time. Sometimes 
geophones (velocity transducers) are attached to accelerometers to 
measure the seismic wave velocities. 
Principle: An acceleration a will cause the 
mass to be displaced by  ma/k  or 
alternatively, if we observe a displacement 
of x, we know that the mass has undergone 
an acceleration of  kx/m.