This document discusses various techniques for retrofitting existing structures to improve their resistance to seismic activity. It describes adding new shear walls, steel bracing, or jacketing columns as common retrofitting methods. Base isolation, which isolates the structure from foundations, is also discussed. The objectives of retrofitting are outlined as increasing strength, ductility, and protecting life safety. Different classification of retrofitting techniques are provided based on addressing local deficiencies or global irregularities.

2. Topics
 Seismic provision of strengthening
 Retrofitting
 Basic concept of retrofitting
 Retrofitting Objective
 Need of retrofitting
 Classification of retrofitting Technique
 Adding New Shear Walls
 Adding Steel Bracings
 Jacketing
 Base Isolation
 Types of Base Isolations
 Seismic Dampers

3. Seismic Provision of Strengthening
Due to earthquake the loss of property and lives
occurs for not taking care of earthquake
resistance features during construction
.

4. Construction of new structure ,retrofitting of old
construction and restoring the damage building
requires a consideration of important aspects .
“ Huge amount are being spent by Government
and private agency in providing relief to the
affected people and rehabilitation “

5. “ Retrofitting is an art providing additional strength to the building
which are weak due to original structural inadequacies and
material degradation due to time effects or alteration carried out
during use “
It is the modification of existing structures to make them
more resistant to seismic activity, ground motion, or soil failure
due to earthquakes.
Basic Concept of Retrofitting
Up gradation of lateral strength of the structure
Increase in the ductility of the structure
Increase in strength and ductility

6. STRUCTURAL EVALUATION FORSTRUCTURAL EVALUATION FOR
RETROFITTINGRETROFITTING
Detail estimation of all load bearing member
which is seismically weak.
Analysis of condition of the building including
deficiencies
To develop alternative technique which are
feasible to use in particular case
To analysis the cost
To prepare final and the best method for
retrofitting
To evaluate that after applying retrofitting

7. Retrofitting ObjectivesRetrofitting Objectives
Public safety only
 The goal is to protect human life .
 Ensuring that the structure will not collapse
 Under severe seismic conditions the structure may be a total
economic write-off
 Structure survivability
 The goal is that the structure may require extensive repair (but not
replacement)
 The lowest level of retrofit applied to bridges.
 Structure functionality
 Structure unaffected: This level of retrofit is preferred for historic
structures of high cultural significance.

8. Retrofitting Objectives
Increasing the lateral strength and stiffness of the
building.
 Increasing the ductility and enhancing the energy
dissipation capacity.
 Giving unity to the structure.
Eliminating sources of weakness or those that
produce concentration of stresses.
Enhancement of redundancy in the number of
lateral load resisting elements.
The retrofit scheme should be cost effective.
 Each retrofit strategy should consistently achieve
the performance objective

9. Need of retrofittingNeed of retrofittingNeed of retrofittingNeed of retrofitting
 Buildings have been designed according to a seismic
code, but the code has been upgraded in later years .
 Buildings designed to meet the modern seismic codes,
but deficiencies exist in the design and/or construction .
 Essential buildings must be strengthened like hospitals,
historical monuments and architectural buildings .
 Important buildings whose services are assumed to be
essential just after an earthquake like hospitals
,Government office ,school and collage etc.
 Buildings, the use of which has changed through the
years.
 Buildings that are expanded, renovated or rebuilt .

10. Classification of Retrofitting TechniquesClassification of Retrofitting Techniques

11. LOCAL AND GLOBALLocal deficiencies lead to the failure of individual elements of the building
a.Inadequate shear capacity.
b. Lack of confinement of column core. Lack of 135º hooks, with adequate hook length.
c. Faculty location of splice just above the floor, with inadequate tension splice length.
Beams and Beam-to-Column Joints
a.Shear reinforcement not adequate for flexural capacity.
b. Inadequate anchorage of bottom rebar.
c. Inadequate plastic hinge rotation capability due to lack of confinement.
GLOBAL Global deficiencies can broadly be classified as plan irregularities and vertical irregularitie
Plan Irregularities
a. Torsional irregularity due to plan symmetry and eccentric mass from water
tank.
b. Frequent re-entrant corners.
c. Diaphragm discontinuity due to large openings or staggered floors, along with
the absence of collector elements.
d. Out-of-plane offset for columns along perimeter.
e. Nonparallel lateral load resisting systems (not observed in the building studied)

12. Adding New Shear Walls
 Frequently used for retrofitting of non ductile reinforced
concrete frame buildings.
 The added elements can be either cast in place or‐ ‐
precast concrete elements.
 New elements preferably be placed at the exterior of the
building.

13. Adding Steel Bracings
 An effective solution when large openings are required.
 Potential advantages for the following reasons:
• Higher strength and stiffness,
• Opening for natural light,
• Amount of work is less since foundation cost may be minimized
• Adds much less weight to the existing structure

14. Jacketing (Local Retrofitting
Technique)
Most popular method for strengthening of
building columns
Types- 1. Steel jacket 2. Reinforced
Concrete jacket
3.FibreReinforcedPolymerComposite(FRPC)
jacket
 Purpose for jacketing
• To increase concrete confinement
• To increase shear strength
• To increase flexural strength

16. Base Isolation
 Isolation of superstructure from the foundation is known as base
isolation.
 It is the most powerful tool for passive structural vibration control
technique.

17. Retrofitting measure ofRetrofitting measure of
traditionally Built Constructiontraditionally Built Construction
To ensure all elements and member behave as
a single unit
To reduce and remove the irregularity in plan
and elevation
To increase the strength
To increase the stiffness in lateral direction
To import the ductility to the structure .

18. Method Of RetrofittingMethod Of Retrofitting
Providing extra Reinforcement
 Extra reinforcement provide at the end of section
 Concrete cover is remove and steel bar welded for
distance l/5 and the section is covered with high grade of
concrete .

19. Method Of RetrofittingMethod Of Retrofitting
CASING ( Jacketing )
 This technique is applied to load bearing structure to increase the
moment and ductility of structure .
 In this extra reinforcing casing and cover provided by extra quantity
of reinforcement and cover by high concrete

20. Method Of RetrofittingMethod Of Retrofitting
Using steel plate
 Plate bonding technique is use to improve the flexural and shear
strength of beam .
 In this mild steel plate glued to the beam by epoxy material for
improving their strength
 By this method the head room is not decrease
 Construction is speed up

21. Method Of RetrofittingMethod Of Retrofitting
Using of fibre reinforced Plastic (FRP)
 FRP laminas are attached to the beam to increase the flexural strength and
shear strength
 A plate place in narrow space is not easy ,so using light weight plastic
 High tensile strength ,less weight ,not liable to corrosion
 High strength Epoxy material use for adhesion of plate to member
Epoxy Injection technique
 Epoxy material are resinous binding material which use for high
strength
 It mixed just before to use and have low Viscosity.
 Injected in fine cracks
 Seismic Base Isolation