this presentation is about how you can make a building more resistant to earthquakes. Different techniques and designs are discussed to make a building more resistant to earthquakes. examples of different earthquake resistant buildings are also discussed.

1. Dept. of Earth and Environmental Sciences
Bahria University Islamabad Campus
Earthquake Building Designs

2. Table of contents
 Introduction
 Seismic zones
 Site consideration
 Earthquake building designs
 Diaphragms
 Cross Bracing
 Shear walls
 Moment resisting frames
 Trusses

3. Table of contents
 Base isolators
 Ductility
 Active mass damping
 Rocking frame
 Conclusion
 Refrences

4. Introduction
 When an earthquake occurs, a building will tend
to vibrate around one particular frequency known
as its natural, or fundamental, frequency. When
the building and ground share the building's
natural frequency, they're said to be in resonance.
Resonance amplifies the effects of an
earthquake, causing buildings to suffer damage.
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5. Introduction
 So there is a saying, “Earthquakes don't kill
people, buildings do.“
 Although you can’t control the seismic hazard in
the community where you live or work but you
can influence the most important factor in saving
lives and reducing losses from an earthquake by
the adoption and enforcement of up-to-date
building codes.
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6. Seismic zones
 A seismic zone is a region in which the rate of
seismic activity remains fairly consistent.
OR
 An area with an increased risk of seismic activity.
 Pakistan has been divided into five zones. These
zones are based on the peak ground
acceleration.
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7. 7
Fig: 1.0: Division of seismic zones

8. 8
Site Consideration
 Scope selection of suitable building sites based
on:
1. Geology/stratigraphy,
2. Distance from the causative fault
3. The liquefaction potential of site
4. Earthquake induced land sliding
5. Presence of sensitive clays and any other
relevant geotechnical aspects

9. Earthquake building designs
 Diaphragms
 Cross-bracing
 Shear walls
 Moment-resisting frames
 Trusses
 Base isolation
 Ductility
 Active mass damping
 Rocking frame
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10. Diaphragms
 A diaphragm is a structural element that transmits
lateral loads to the vertical resisting elements of a
structure.
 Diaphragms are a key component of the
horizontal structure
 Includes floor and roof of levels.
 Even symmetrical buildings must be able to
withstand significant lateral forces.
 Engineers counteract these forces in both the
horizontal and vertical structural systems of a
building.
10

11. 11 Fig 2.0: schematics of diaphragms

12. Cross Bracing
 Cross bracing is a system utilized to reinforce
building structures in which diagonal supports
intersect
 It uses two diagonal members in an X-shape, is a
popular way to build wall trusses.
 Cross bracing can increase a building's capability
to withstand seismic activity.
 Bracing is important earthquake resistant building
because it helps keep a structure standing.
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13. 13
Fig 3.1 :Cross-bracing in a 3-storey
frame

14. 14
Fig 3.2: the Hancock tower in Chicago, an example
of cross bracing

15. Shear walls
15
 A shear wall is a structural system composed of
braced panels.
 Used to counter the effects of lateral load acting
on a structure.
 Seismic loads are the most common loads that
shear walls are designed to carry.

16. 16 Fig 4.0: shear walls

17. Moment-resisting frames
17
 In these structures, the columns and beams are
allowed to bend, but the joints or connectors
between them are rigid.
 As a result, the whole frame moves in response
to a lateral force and yet provides an edifice that's
less obstructed internally than shear-wall
structures

18. 18
Fig 5.0: moment resisting frame

19. Trusses
 A truss is a structure that "consists of two-force
members only, where the members are organized
so that the assemblage as a whole behaves as a
single object“.
 The top beams in a truss are called top chords
and are typically in compression.
 The bottom beams are called bottom chords, and
are typically in tension.
 On the roof, where a strong deck isn't always
possible, engineers strengthen the diaphragm
with trusses.
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20. 20
Fig 6.1: schematics of trusses

21. 21 Fig 6.2: example of trusses.

22. Example: The Transamerica Pyramid
22
 The Transamerica Pyramid soars 853 feet (260
meters) into the air and has stood as a symbol of
San Francisco since 1972.
 The pyramid draws its strength from a unique
truss system, which features X-bracing, used
above the first floor.
 The truss system supports both vertical and
horizontal loading, but is particularly resistant to
torsional forces generated by seismic events.
 During the magnitude-7.1 earthquake, which
struck the Santa Cruz Mountains in 1989, the top
story of the pyramid swayed more than 12 inches
(30 centimeters) from side to side, yet suffered no
damage.

23. 23 Fig 6.3 : example of trusses “The Transamerica
pyramid”

24. Base Isolation
 It is one of the most popular means of protecting
a structure against earthquake forces.
 It involves floating a building above its foundation
on a system of bearings, springs or padded
cylinders.
 When an earthquake hits it allows the foundation
to move without moving the structure above it.
 As a result, the building's horizontal acceleration
is reduced and suffers far less deformation and
damage.
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25. 25
Fig 7.1: schematics of base isolator.

26. Example: San Francisco City Hall
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 San Francisco city hall located in San Francisco,
California.
 The present building replaced an earlier City Hall
that was destroyed during the 1906 earthquake.
 In reconstructed building Engineers cut the two-
block-long building from its foundation and floated
it on 530 base isolators.
 If seismic waves roll its way in the future, the
building will sway horizontally up to 26 inches (66
centimeters) without shaking apart.

27. 27
Fig 7.2 : old San Francisco city hall destroyed
in 1906.

28. 28
Fig 7.3 : present San Francisco
city hall

29. Ductility
 Ductility refers to the ability of the material to
undergo large plastic deformations.
 Brick and concrete buildings have low ductility
and therefore absorb very little energy. This
makes them especially vulnerable in even minor
earthquakes.
 Buildings constructed of steel-reinforced
concrete, on the other hand, perform much better
because the embedded steel increases the
ductility of the material.
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30. 30
Fig 8.1 graphical example of ductility.

31. Active Mass Damping
31
 In increasingly more earthquake-resistant
buildings, designers are installing “Damping
Systems”.
 It includes heavy mass mounted to the top of a
building and connected to viscous dampers that
act like shock absorbers.
 During an earthquake when the building begins to
oscillate, the mass moves in the opposite
direction, which reduces the amplitude of
mechanical vibrations.
 It's also possible to use smaller damping devices
in a building's brace system.

32. 32
Fig 9.1: schematics of active mass
damping

33. Example: Taipei 101 in Taiwan
33
 Taipei 101 stood as the world's tallest skyscraper
until the Burj Dubai opened its doors in 2010.
 One of its most impressive features is a 730-ton
(662-metric-ton) active mass damper that resides
at the top of the building, between the 88th and
92nd floors.
 The huge sphere sits in a cradle formed by eight
steel cables and connects to eight viscous
dampers.
 If the building begins to sway, the damper
counteracts the motion, reducing vibrations that
could make inhabitants uncomfortable and could
cause stress on the structure.

34. 34 Fig 9.2: Taipei 101 in Taiwan

35. 35
Fig 9.3: damper in Taipei 101.

36. Rocking Frame
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 It consists of three basic components -- steel
frames, steel cables and steel fuses.
 When an earthquake strikes, the steel frames
rock up and down to their heart's content. All of
the energy gets directed downward to a fitting
that houses several tooth like fuses.
 The teeth of the fuses gnash together and may
even fail, but the frame itself remains intact.
 Once the shaking has stopped, the steel cables in
the frame pull the building back into an upright
position.
 Workers then inspect the fuses and replace any
that are damaged.

37. 37
Fig 10.0 :Schematic diagram of the
rocking frame

38. References
38
 http://science.howstuffworks.com/engineering/stru
ctural/earthquake-resistant-buildings6.htm.
 Eddy, Nathan. "Taipei 101's 730-Ton Tuned Mass
Damper." Popular Mechanics. July 19, 2005.
(Sept. 2, 2011)
 BBC. "Earthquake hits San Francisco." On This
Day: October 17, 1989. (Sept. 2, 2011)
 Living Steel. "Earthquake and Earthquake-
resistant Buildings." Structural Safety Tutorials.
(Sept. 2, 2011)
http://www.livingsteel.org/content/view/75/126/1/6
/
 http://www.urbanunit.gov.pk/PublicationDocs/Othe
r%20Publications/Building%20Codes_2007.pdf

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