Seismic provision of strengthening
Basic concept of retrofitting
Need of retrofitting
Classification of retrofitting Technique
Adding New Shear Walls
Adding Steel Bracings
Types of Base Isolations
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
Detail estimation of all load bearing member
which is seismically weak.
Analysis of condition of the building including
To develop alternative technique which are
feasible to use in particular case
To analysis the cost
To prepare final and the best method for
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
The goal is that the structure may require extensive repair (but not
The lowest level of retrofit applied to bridges.
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
Increasing the ductility and enhancing the energy
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
Buildings that are expanded, renovated or rebuilt .
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
a. Torsional irregularity due to plan symmetry and eccentric mass from water
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
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
Most popular method for strengthening of
Types- 1. Steel jacket 2. Reinforced
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
It is the most powerful tool for passive structural vibration control
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
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
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
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
It mixed just before to use and have low Viscosity.
Injected in fine cracks
Seismic Base Isolation