2. EARTHQUAKE
An earthquake (also known as a quake, tremor or temblor)
is the result of a sudden release of energy in the Earth's crust
that creates seismic waves.
The seismicity, seismism or seismic activity of an area
refers to the frequency, type and size of earthquakes
experienced over a period of time.
3.
4.
5. INTRODUCTION
• Seismic retrofitting of constructions are vulnerable to
earthquake. Most of the Indian building stock is vulnerable to
seismic action even if located in areas that have long been
considered of high seismic hazard. In the past thirty years
moderate to severe earthquakes have occurred in India at
intervals of 5 to 10 years. Such events have clearly shown the
vulnerability of the building stock in particular and of the built
environment in general
• Aim is to focus on a few specific procedures which may
improve the state-of-the-art practice for the evaluation of
seismic vulnerability of existing reinforced concrete buildings
and for their seismic retrofitting by means of innovative
techniques such as base isolation and energy dissipation.
6. SEISMIC RETROFITTING
To provide existing structures with more resistance to
seismic activity due to earthquake
Includes strengthening of weak connections found in the
roof to wall connections, continuity ties, shear walls and roof
diaphragm.
7. NEED FOR SEISMIC
RETROFITTING
To ensure the safety and security of a building,
employees, structure functionality, machinery and
inventory
Essential to reduce hazard and losses from non-structural
elements
Predominantly concerned with structural improvement to
reduce seismic hazard
8. SIX MORE REASONS TO SEISMIC
RETROFIT
Marketability of the building is improved
The risk of injury and legal litigation is reduced
Earthquake coverage
Lenders
Insurance companies
Tenants
9. METHODS FOR SEISMIC
RETROFITTING
Conventional Strengthening Methods
Traditional Methods of seismic retrofitting
Retrofit of structures using innovative materials
Base Isolation
Supplemental Energy Dissipation and Structural Control
10. CONVENTIONAL
STRENGTHENING METHODS
Conventional retrofitting method include addition of new
structural elements to the system and enlarging the existing
members. Methods such as
Addition of post cast shear walls
Additional foundation to support the shear walls to be
constructed around the stairs
Concrete jacketing of a column
Addition of column members to vertical irregularities
14. RETROFIT OF STRUCTURES USING
I N N O VAT I V E M AT E R I A L S
High Performance Concrete
High Performance Steel
Fibre Reinforced Plastic
15. BASE ISOLATION
Placing flexible isolation systems between the foundation
and the superstructure.
Provides safety against collapse.
Also used in the seismic retrofitting of historic structures
without imparting their architectural characteristics by
reducing the induced seismic forces.
16.
17. S U P P L E M E N TA L E N E R G Y D I S S I PAT I O N
AND STRUCTURAL CONTROL
Cost efficient retrofitting strategy compared to base isolation is
installation of supplemental energy devices in structures as a means
for passive or active structural control
Objective of structural control is to reduce structural vibrations
for improved safety and serviceability under wind and earthquake
loadings
18. Other methods used for seismic retrofit are:
Carbon fiber retrofit
Mending Application of Reinforced Sheets
Aramid Fiber Retrofitting System
Precast Retrofit Shear Wall System
Pitacolumn Method
Tufnes Method
Outer-frame brace
Taisei Anchor-less Retrofit system
19. I N N O VAT I V E A P P R O A C H E S
Stiffness reduction
Ductility increase
Damage controlled structures
Composite materials
Active control
21. ADVANCED METHODS
SDOF equivalent systems
Storey force-displacement (Push over analysis)
Seismic Resistance in terms of effective Peak Ground
Acceleration(PGA)
22.
23.
24.
25.
26.
27.
28.
29.
30. Table 4: Relative Seismic Resistance R (%) of the Retrofitted Building
Seismic Zone Transverse Direction Longitudinal Direction
Original Building 43 66
High Seismicity
Building + Walls 75 60
SR+W 135 135
Original Building 60 92
Medium Seismicity
Building + Walls 104 84
SR+W 189 189
Original Building 100 153
Low Seismicity
Building + Walls 174 140
SR+W 315 315
31. Table 5: Seismic Vulnerability V (%) of the Retrofitted Building
Seismic Zone Transverse Direction Longitudinal Direction
Original Building 57 34
High Seismicity
Building + Walls 25 40
SR+W 0 0
Original Building 40 8
Medium Seismicity
Building + Walls 0 16
SR+W 0 0
Original Building 0 0
Low Seismicity
Building + Walls 0 0
SR+W 0 0
32. Table 6: Seismic Over-resistance OR (%) of the Retrofitted Building
Seismic Zone Transverse Direction Longitudinal Direction
Original Building 0 0
High Seismicity
Building + Walls 0 0
SR+W 35 35
Original Building 0 0
Medium Seismicity
Building + Walls 4 0
SR+W 89 89
Original Building 0 0
Low Seismicity
Building + Walls 74 40
SR+W 215 215
33. Table 8: Angular Inter-storey Drifts (%) at Limit Base
Displacement
Direction First Storey Second Storey Third Storey Fourth Storey
Transverse 0.09 0.18 0.20 0.19
Longitudinal 0.20 0.16 0.12 0.07
34.
35. CONCLUSION
This paper considers the retrofitting of buildings vulnerable to
earthquakes and briefly discuss about the traditional, conventional
and innovative methods of seismic retrofitting.
In conclusion it is hoped that the material presented in this paper
will be useful in understanding of the earthquake engineering
problems and of seismic retrofitting