During the semester
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Introductions
Basics of earthquakes
History and Recording
Damaging Earthquakes and Understanding seismic exposure
Undertaking loss assessment
• Seismic analysis; and design and detailing
(RCC and Masonry)
We spoke Foundation weakness last
now
Structural Weakness
Basics of Earthquake resistant Construction
We weaken a Structure by weakening/introducing:
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Symmetry
Regularity
Openings
Soft Storey effect
Local eccentricity
Pounding situations
Other
Items with a potential to fall. Such as- Long cantilevers,
partition, badly fixed non-structural components
Basics of Earthquake resistant Construction
• Careful when introducing weakness
• Difference between Centre of Gravity and
Geometry.
• Understand structural properties of
– Stiffness
– Mass
– Strength
– Ductility
– Displacement / deflection
• Distinguish between ‘Structural’ and ‘Nonstructural’ cracks
List of Codes and standards related to
Earthquake Engineering
Internet Sources
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http://nisee.berkley.edu
http://www.bis.org.in/other/quake.htm
http://www.nicee.org/IITK-GSDMA_Codes.php
http://www.eurocodes.co.uk/EurocodeDetail.aspx?Eurocode=8
http://en.wikipedia.org/wiki/International_Building_Code
http://www.asce.org/codes-standards/list/
Recommended Reading
Basics of Earthquake resistant Construction
Performance Levels and Ranges
• Performance based design is a new approach used in
earthquake resistance design and construction.
• FEMA document FEMA356 has more details
Basics of Earthquake resistant Construction
Performance Levels and Ranges
S-1 Immediate Occupancy
S-2 Damage Control Range
S-3 Life Safety
S-4 Limited Safety Range
S-5 Collapse Prevention
S-6 Not Considered
Basics of Earthquake resistant Construction
Performance Levels and Ranges
S-1
Immediate
Occupancy
Structure retains the pre-earthquake design strength and stiffness, and is safe to occupy.
Some minor structural repairs may be appropriate but not necessary to make the building safe to occupy.
This range may be desirable to minimize downtime and repair time, to protect equipment that
Damage
S-2
depends on the survival of the structure for its functionality, or to preserve historic features of
Control Range
the building when its too costly to design for the S-1 damage state.
S-3
Life Safety
The building will retain at least some of its strength against collapse and should prevent loss of
human life. However, there may be injuries and the building could potentially be damaged beyond the
point of economical repair. Some business owners may desire to have a higher standard of design
safety for their building. This is especially true in the case of business’ s that would suffer dramatically
if business was interrupted after a seismic event.
Obviously any building that collapses proposed significant risks to life safety and would not satisfy this
design objective.
S-4
Limited Safety The continuous range of damage states between the Life Safety Structural Performance Level (S-3) and
Range
the Collapse Prevention Structural Performance Level (S-5).
S-5
Collapse
Prevention
The building experience damage to structural components that weaken it so that it retains little or no
lateral resistance against collapse either in part or in full. However, it will still continue to support its own
weight provided that there is no further ground motion. Aftershock activity could cause collapse, but the
initial event did not bring down the building.
S-6
A building rehabilitation that does not address structural performance at all, but instead focuses entirely
Not
on non-structural hazards associated with the building such as anchoring equipment and preventing
Considered
damage to tenant property and improvments.
Which performance level is delivered by the
building you are looking at?
Basics of Earthquake resistant Construction
Summary
- Note different ‘collapse’ modes
- Note different ‘damage’ modes
- Property of ‘Stiffness’ in addition to ‘Strength’
and ‘Ductility’
- Keep ‘Soil – Structure’ interaction in mind
Basics of Earthquake resistant construction
Structure Types
• Classify based on Horizontal Load Resisting
System
• Common types are:
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Frame
Frame with infill wall
Masonry
Reinforced Masonry
Tensile, Membrane, Igloo, and other special systems
Basics of Earthquake resistant Construction
Structure Type: Frame
•Any height
•Materials : Steel, RCC, Timber,
•Any other tensile material
•Non structural Partition
Basics of Earthquake resistant Construction
Structure Type: Frame with infill
•Common types have brick
partition which influence
structural behaviour
•Similarly Basement
Basics of Earthquake resistant Construction
Structure Type: Masonry
•Lower in height
•Use was high in history when buildings
were designed as compression structures
•Materials :
•Walling: Brick, Stone, Rubble, Cement
Blocks
•Mortar: None, Mud, Lime, Cement
•Structural Integrity is important
Basics of Earthquake resistant Construction
Structure Type: Reinforced Masonry
• Usually lower in height structures
• Many house owners unjustifiably use this
because of fear or a misinformed choice
that this will make their house stronger
•Recommended as Horizontal bands and in
vertical direction in zones of high seismicity
•Reinforcing material is any highly tensile
material such as RCC or steel.
•Historical use as timber
Discuss
• Coordinate visit to GSDMA (whole 3rd year?)
• Share what one is reading– Books
– Book Reviews
– Copies of codes such as IS 4326, and IS 13920, IS
1893