6. Waves of different periods
If the ground is shaken by earthquake waves that have short periods, then
short period buildings will have large response.
Similarly, if the earthquake ground motion has long period waves, then long
period buildings will have larger response.
Dr. N. Subramanian
7. Soil condition at site may influence
damage
Different Buildings
Respond Differently
to Same Ground
Vibration
Dr. N. Subramanian
8. Design Codes
IS 13920, 1993, Indian Standard Code of Practice
for Ductile Detailing of Reinforced Concrete
Structures Subjected to Seismic Forces
IS 1893 (Part I), 2002, Indian Standard Criteria
for Earthquake Resistant Design of Structures
(5th Revision)
IS 4326, 1993, Indian Standard Code of Practice
for Earthquake Resistant Design and
Construction of Buildings (2nd Revision)
Dr. N. Subramanian
14. Earthquakes do not kill people;
man in his role as a builder, kills
people.
Total Horz. EQ Force increases downwards along its height
Collapse of partially open GF building in Bhuj EQ, with vertical split at
the middle! Dr. N. Subramanian
19. Detailing of columns in seismic zones
180 links are necessary to prevent the
135 tie from bulging outwards
Dr. N. Subramanian
20. Shear failure of column
Large spacing of ties and lack of 135 hook ends caused
brittle failure of columns during 2001 Bhuj earthquake
Dr. N. Subramanian
24. Short Column effect
Short columns are stiffer and attract larger forces during
earthquakes – this must be accounted for in design
Dr. N. Subramanian
36. Collapse of nominally connected
water tank
IS 1893 – Connections designed for five times the design
horizontal acceleration coefficient
Dr. N. Subramanian
37. Bare Vs infilled frame
Predominant frame action Predominant shear action
Dr. N. Subramanian
41. Effect of Staircases
Diagonal slabs or beams in staircases attract large
seismic forces-sliding supports limits the seismic forces
Dr. N. Subramanian
44. Base Isolation Technology
One of the most
significant
developments in
earthquake
engineering in the
past 35 years.
It provides the
design profession
the ability to design
a building that is
“operational” after a
major earthquake
Base isolated structure Conventional structure
Dr.N.Subramanian 44
45. BASE ISOLATOR
Base isolators may be
either coiled springs
or laminated rubber-
bearing pads, made of
alternate layers of
steel and rubber, and
have a low lateral
stiffness.
Dr.N.Subramanian 45
46. Examples of Base Isolated Systems
Base Isolated LA City Hall
Base isolator being installed. during a seismic
event. Every isolator will extend in any
direction 21 inches.
San Francisco Airport International
Terminal is the World’s Largest Base
Isolated Building
Dr.N.Subramanian 46
47. Energy Absorbing Devices
• “Passive energy dissipation is an emerging
technology that enhances the performance of
buildings by adding damping to buildings.”
• (ASCE/SEI 41-06, pg 280)
Dr.N.Subramanian 47
48. Commonly used dampers
Viscous dampers (They consist of a piston-cylinder
arrangement filled with a viscous silicon based fluid,
which absorbs the energy)
Friction dampers (energy is absorbed by the friction
between two layers, which are made to rub against
each other).
Hysteretic dampers (energy is absorbed by yielding
metallic parts)
Visco-elastic dampers (containing visco-elastic
material, sandwiched between two steel plates, which
undergoes shear deformation, thus dissipating energy.
Dr.N.Subramanian 48
49. Other Types Of Dampers
Tuned mass dampers (TMD)- They are extra
masses attached to the structure by a spring-
dashpot system and designed to vibrate out of
phase with the structure.
Tuned liquid dampers (TLD) – They are essentially
water tanks mounted on structures and dissipate
energy by the splashing of the water.
Hydraulic activators- They are active vibration
control devices and have a sensor to sense the
vibration and activate the activator to counter it. -
Require external energy source and are expensive.
Dr.N.Subramanian 49
50. Why Use Dampers?
Dampers dramatically decrease earthquake induced
motion .
Less displacement : over 50% reduction in drift in
many cases
Decreased base shear and inter-story shear, up to 40%
Much lower “g” forces in the structure. Equipment
keeps working and people are not injured
Reduced displacements and forces can mean less
steel. This offsets the damper cost and can sometimes
even reduce overall cost.
Dr.N.Subramanian 50
53. Tuned Mass Damper (TMD)
Taipei 101, the world's second tallest skyscraper is equipped with a tuned mass
damper. This 18 feet dia.,730-ton TMD acts like a giant pendulum to counteract the
building's movement--reducing sway due to wind by 30 to 40 %. Cost: $4 million
Dr.N.Subramanian 53