The document discusses seismic retrofitting of buildings to make them more resistant to earthquakes. It describes how seismic retrofitting includes strengthening structural elements like connections, walls, and foundations. It outlines several methods for retrofitting such as adding new structural elements like walls, using innovative materials like fiber reinforced plastics, implementing base isolation systems, and supplemental energy dissipation. The document provides details on evaluating seismic vulnerability and the need for retrofitting to improve building safety, reduce hazards, and limit losses from earthquakes.

1. SEISMIC RETROFIT OF
BUILDING STRUCTURES

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.

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

11. Addition of post cast shear walls

12. TRADITIONAL METHODS OF SEISMIC
RETROFIT
Structural design
Mass reduction

13. Seismic Retrofitting by Mass Reduction (removal of storey)

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.

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

20. Damage controlled structures
= +
Global structure Primary structure Damping system

21. ADVANCED METHODS
 SDOF equivalent systems
 Storey force-displacement (Push over analysis)
 Seismic Resistance in terms of effective Peak Ground
Acceleration(PGA)

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

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

36. SUBMITTED BY
R.Gopinath
V.Umapathi

37. THANK YOU