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PPT =RETROFITTING
Er. SHISH PAL
LECTURER IN CIVIL ENGINEERING
GOVT. POLYTECHNIC AMBALA CITY
1
Introduction
• Earthquake creates great devastation in terms of life, money
and failures of structures.
• Earthquake Mitigation is an important field of study from a
long time now.
• Seismic Retrofittingis a collection mitigation techniques for
Earthquake Engineering.
• It is of utmost importance for historic monuments, areas prone
to severe earthquakes and tall or expensive structures.
2Er. SHISH PAL
Seismic Retrofitting
Definition
It is the modification of existing structures to make
them more resistant to seismic activity, ground motion,
or soil failure due to earthquakes.
The retrofit techniques are also applicable for other
natural hazards such as tropical cyclones, tornadoes and
severe winds from thunderstorms.
3Er. SHISH PAL
When is Seismic Retrofitting
Needed ?The two circumstances are:-
Earthquake damaged buildings
Earthquake-vulnerable buildings (with no exposure to
severe earthquakes)
4Er. SHISH PAL
Retrofit Performance Objectives
• Public safety only: The goal is to protect human life, ensuring
that the structure will not collapse upon its occupants or passers-
by, and that the structure can be safely exited. Under severe
seismic conditions the structure may be a total economic write-
off, requiring tear-down and replacement.
• Structure survivability: The goal is that the structure, while
remaining safe for exit, may require extensive repair (but not
replacement) before it is generally useful or considered safe for
occupation. This is typically the lowest level of retrofit applied to
bridges. 5Er. SHISH PAL
Retrofit Performance Objectives
(Contd.)Structure functionality: Primary structure undamaged and the
structure is undiminished in utility for its primary application.
Structure unaffected: This level of retrofit is preferred for
historic structures of high cultural significance.
6Er. SHISH PAL
Need of Retrofitting in Existing
Earthquake Vulnerable Buildings
• 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;
• Buildings, the use of which has changed through the years;
Buildings that are expanded, renovated or rebuilt.
7Er. SHISH PAL
Problems faced by Structural
Engineers are :-• Lack of standards for retrofitting methods
• Effectiveness of each methods varies a lot depending upon
parameters like type of structures, material condition, amount of
damage , etc.
8Er. SHISH PAL
Basic Concept of Retrofitting
• The aim is at (CEB1997):-
Up gradation of lateral strength of the structure;
Increase in the ductility of the structure
Increase in strength and ductility
9Er. SHISH PAL
Earthquake Design Philosophy
• Under minor but frequent shaking, the main members of the building
that carry vertical and horizontal forces should not be damaged; however
building parts that do not carry load may sustain repairable damage;
• Under moderate but occasional shaking, the main members may
sustain repairable damage, while the other parts of the building may be
damaged such that they may even have to be replaced after the
earthquake; and
• Under strong but rare shaking, the main members may sustain sever
(even irreparable) damage, but the building should not collapse.
10Er. SHISH PAL
Classification of Retrofitting
Techniques
11Er. SHISH PAL
Some Conventional ApproachesAdding 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.
Not preferred in the interior of the structure to avoid interior mouldings
12Er. SHISH PAL
Some Conventional Approaches
(Contd.)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
13Er. SHISH PAL
Adding Shear Walls and
Bracings
Fig: Effect of Adding Shear Walls and Bracings
14Er. SHISH PAL
Adding Steel Bracings
Fig: RC Building retrofitted by steel bracing
15Er. SHISH PAL
Some Conventional Approaches
(Contd.)• Jacketing (Local Retrofitting Technique)
Most popular method for strengthening of building columns
Types-1. Steel jacket, 2. Reinforced Concrete jacket,
3. Fibre Reinforced Polymer Composite(FRPC) jacket
Purpose for jacketing:
To increase concrete confinement
To increase shear strength
To increase flexural strength
16Er. SHISH PAL
Jacketing
Fig: Column JacketingFig: Beam Jacketing
17Er. SHISH PAL
Retrofit of Structures using Innovative
Materials
• Current research on advanced materials has mainly
concentrated on FRP composites.
• Studies have shown that externally bonded FRP
composites can be applied to various structural
members including columns, beams, slabs, and walls to
improve their structural performance such as stiffness,
load carrying capacity, and ductility.
18Er. SHISH PAL
Effectiveness of FRPC as a Retrofitting
Material
Fig: A 3-D Model of aBuilding
Fig:ARetrofitApplication combining Conventional and Composites Retrofitting
(a) Wall Stresses
before
Retrofitting
(b) After
installation of
Steel Window
frames
(c) Additional
FRP
Retrofitting
19Er. SHISH PAL
Base Isolation (or Seismic
Isolation)
Isolation of superstructure from the foundation is known as base
isolation.
It is the most powerful tool for passive structural vibration control
technique
20Er. SHISH PAL
Concept of Base Isolation
• Significantly Increase the Period of the Structure and the
Damping so that the Response is Significantly Reduced.
Fig: Spectral Response for a Typical Base Isolation System
21Er. SHISH PAL
Types of Base Isolations
• Base isolation systems which uses Elastomeric Bearings
• Base isolation systems with Sliding System
22Er. SHISH PAL
Elastomeric Base Isolation Systems• This is the mostly widely used Base Isolator.• The elastomer is made of either Natural Rubber or Neoprene.
• The structure is decoupled from the horizontal components of the
earthquake ground motion
A layer with low horizontal stiffness is
introduced between the structure and the foundation.
Fig: Steel Reinforced Elastomeric Isolators
23Er. SHISH PAL
Sliding Base Isolation Systems• It is the second basic type of isolators.
• This works by limiting the base shear across the isolator
interface.
Fig: Metallic Roller Bearing
24Er. SHISH PAL
Spherical Sliding Base Isolators
• The structure is supported by bearing pads that have
curved surface and low friction.
• During an earthquake, the building is free to slide on the
bearings.
Fig: Spherical Sliding Base Isolator
25Er. SHISH PAL
Friction Pendulum Bearing• These are specially designed base isolators which works on
the principle of simple pendulum.
• It increases the natural time period of oscillation by causing
the structure to slide along the concave inner surface through the
frictional interface.
• It also possesses a re-centering capability.
Fig: Cross-section of Friction Pendulum Bearing
26Er. SHISH PAL
Friction Pendulum Bearing (Contd.)• Typically, bearings measure 3 feet in dia., 8 inches in height and weightbeing
• 2000 pounds
• Benicia Martinez Bridge, California is one of the largest bridges to date toundertake a seismic isolation retrofit.
• Largest seismic isolation bearings, measuring 13 feet in diameter, andweighing 40,000 pounds. They have a lateral displacement capacity of 53inches, a 5 million pound design dead plus live load, and a 5 second period.
• Fig: Bearing used in Benicia Martinez Bridge (left) and Benicia Martinez Bridge (right)
27Er. SHISH PAL
Advantages of Base Isolation
• Isolates Building from ground motion
Lesser seismic loads, hence lesser damage to the structure.
Minimal repair of superstructure.
• Building can remain serviceable throughout construction.
• Does not involve major intrusion upon existing superstructure.
28Er. SHISH PAL
CRACK REPAIR TECHNIQUES Epoxy-injection Grouting
Routing and Sealing
Flexible Sealing
Stitching
Providing additional Reinforcement
Drilling and plugging
Pre-stressing steel
Grouting
Dry packing
Surface Coatings
29Er. SHISH PAL
CRACK REPAIR TECHNIQUES Epoxy-injection Grouting
Cracks as narrow as 0.002 in. (0.05 mm) can be bonded by the
injection of epoxy. The technique generally consists of
establishing entry and venting ports at close intervals along the
cracks, sealing the crack on exposed surfaces, and injecting the
epoxy under pressure. Epoxy injection has been successfully used
in the repair of cracks in buildings, bridges, dams, and other types
of concrete structures. However, unless the cause of the cracking
has been corrected, it will probably recur near the original crack.
The general procedure are given below.
30Er. SHISH PAL
CRACK REPAIR TECHNIQUES
Clean the cracks: The first step is to clean the cracks that have
been contaminated; to the extent this is possible and practical.
Contaminants such as oil, grease, dirt, or fine particles of
concrete prevent epoxy penetration and bonding, and reduce the
effectiveness of repairs. Preferably, contamination should be
removed by vacuuming or flushing with water or other specially
effective cleaning solutions.
Seal the surfaces: Surface cracks should be sealed to keep the
epoxy from leaking out before it has gelled. A surface can be
sealed by applying an epoxy, polyester, or other appropriate
sealing material to the surface of the crack and allowing it to
harden. If a permanent glossy appearance along the crack is
objectionable and if high injection pressure is not required, a
strippable plastic surface sealer may be applied along the face of
the crack.31Er. SHISH PAL
CRACK REPAIR TECHNIQUES
When the job is completed, the surface sealer can be stripped
away to expose the gloss-free surface. Cementitious seals can
also be used where appearance of the completed work is
important. If extremely high injection pressures are needed,
the crack can be cut out to a depth of 1/2 in. (13 mm) and
width of about 3/4 in. (20 mm) in a V-shape, filled with an
epoxy, and struck off flush with the surface.
Install the entry and venting ports. Two methods are in general
use: Fittings inserted into drilled holes: This method was
the first to be used, and is often used in conjunction with V-
grooving of the cracks. The method entails drilling a hole into
the crack, approximately 3/4 in. (20 mm) in diameter and 1/2
to 1 in. (13 to 25 mm) below the apex of the V grooved
section.
32Er. SHISH PAL
CRACK REPAIR TECHNIQUES
Bonded flush fitting: When the cracks are not V grooved , a
method frequently used to provide an entry port is to bond a fitting
flush with the concrete face over the crack. The flush fitting has an
opening at the top for the adhesive to enter and a flange at the
bottom that is bonded to the concrete.
33Er. SHISH PAL
CRACK REPAIR TECHNIQUESMix the epoxy: This is done either by batch or continuous methods. Inbatch mixing, the adhesive components are premixed according to themanufacturers instructions, usually with the use of a mechanical stirrer,like a paint mixing paddle. Care must be taken to mix only the amountof adhesive that can be used prior to commencement of gelling of thematerial.
Inject the epoxy: Hydraulic pumps, paint pressure pots, or air- actuatedcaulking guns may be used. The pressure used for injection must beselected carefully. Increased pressure often does little to accelerate therate of injection. If the crack is vertical or inclined, the injection processshould begin by pumping epoxy into the entry port at the lowestelevation until the epoxy level reaches the entry port above. Forhorizontal cracks, the injection should proceed from one end of thecrack to the other in the same manner. The crack is full be maintained. Ifthe pressure can not be main.
epoxy is still flowing into unfilled portions or leaking out of the crack.
34Er. SHISH PAL
CRACK REPAIR
TECHNIQUES
Remove the surface seal: After the injected epoxy has cured, the
surface seal should be removed by grinding or other means as
appropriate.
35Er. SHISH PAL
CRACK REPAIR
TECHNIQUES
36Er. SHISH PAL
CRACKS REPAIR BY
ROUTING AND SEALING• The Crack sealers should ensure the structural integrity and
service ability .in addition they provide protection from the
ingress of harmful liquids and gases.
• Routing and sealing of cracks can be used in condition
requiring remedial repair and where structural repair is not
necessary .the method consist of enlarging remedial repair and
where structural repair is not necessary . The method consist of
enlarging the crack along its length on exposed surface called
chasing or routing and sealing it with a suitable joint sealant.
37Er. SHISH PAL
CRACKS REPAIR BY
ROUTING AND SEALING•This is a very common technique for crack treatment and is
relatively simple in comparison to the procedures and the training
required for epoxy injection .The procedure is most applicable to
flat horizontal surface such as floors and pavements. However this
method can be accomplished on vertical surface as well as on
curved surfaces.
•This method is used to repair both fine pattern cracks and larger
isolated cracks .a common and effective use is for waterproofing by
sealing cracks on the concrete surface where water stands or where
hydrostatic pressure is applied.
38Er. SHISH PAL
CRACKS REPAIR BY
ROUTING AND SEALING• The sealant may be of sereval materials ,including epoxies silicones
urethanes poly sulfides asphaltic materials polymers mortars. Cement
grouts should be avoided due to the like hood of cracking .For floors
the sealant should be sufficiently rigid to support the anticipated
traffic.
•The procedure consists of preparing a groove at the surface ranging
in depth typically from 6 to 25mm.A concrete saw , hand tools or
pneumatic tools may be used .This groove is then clean by last or sir
blasting and allowed to dry . A sealant is placed into the dry groove
and allowed to curd.
39Er. SHISH PAL
CRACKS REPAIR BY
ROUTING AND SEALING
40Er. SHISH PAL
CRACKS REPAIR BY ROUTING
AND SEALING
41Er. SHISH PAL
CRACKS REPAIR BY
ROUTING AND SEALING
42Er. SHISH PAL
CRACKS REPAIR BY
STITICHING
•The stitching procedure consist of drilling holes on both
slides of the cracks cleaning the holes and an the legs of the
stitching dogs that span the cracks which either a non –shrink
grout or an epoxy bonding system .The stitching dogs
should be variable in length and orientation or both and
should be so located that the tension transmitted across the
cracks is not applied to single to a single plan but spread over
area.
•Stitching may be used when tensile strength must be
established across major cracks .stitching a crack tend to
stiffen the structure the overall structural restraint causing
concrete to cracks elsewhere.
43Er. SHISH PAL
REPAIR OF CRACK STITCHING
44Er. SHISH PAL
CRACKS REPAIR BY
STITCHING
45Er. SHISH PAL
REPAIR BY PROVINDING
EXTRA RAINFORCEMENT Structurally deficient beams and columns are provided extra
reinforcing material at end section. The concrete cover is remove
and steel bar are welded for distance of L/5 for extra end bed
section is coverd with the help strength
46Er. SHISH PAL
DRILLING AND PLUGGINGThis method consist of drilling down the length of the crack and
grouting its to from a key. A hole typically 50 to 75 mm in
diameter should be drilled. The drilled hole should be cleaned
made tight to be filled to be grout. The grout key to prevent
transverse movement of the section of concrete adjacent to the
crack. The key will be also reduce the heavy leakage through the
crack and loss if soil from behind the leaking wall.
47Er. SHISH PAL
DRILLING AND PLUGGING
48Er. SHISH PAL
USING STEEL PLATE
•In this technique Mild steel are glued to beam by epoxy
material for improve flexural and shearing strength of
the member main advantage of the technique are
simplicity and speed construction while the structure is
in used. The head does not reduce considerably and
additional weight edit to the structure by applying plate
very small
49Er. SHISH PAL
USING STEEL PLATE
50Er. SHISH PAL
GROUTINGGrouting is a process of injecting mixture of cement, sand
water at high pressure in the cracks, joints, voids etc.
Purpose of grouting:
To strengthen the porous Concrete
To prevent the seepage in dam and water retaining
structures
To reduce uplift pressure below dam
To fill the cracks in concrete structure
51Er. SHISH PAL
GROUTINGProcedure for grouting:
Drilling of Grouting holes
For drilling grouting holes, equipment's like jack hammer, diamond drill, shot
drill etc are used. The choice of type of drilling equipment depends upon the
type of stone, size of hole and depth of hole.
Arrangement of grout pipes
Grout pipes of 4 to 5 cm dia and 45 to 90 cm length are inserted in the grout
holes. The space surrounding the pipe is filled with cement mortar. The top
end of the pipe is connected to the pump.
Cleaning of cracks
Before injecting grout mixture in the cracks, it is necessary to clean the cracks.
Inserting grout in holes
Normally grout is inserted in the holes at a pressure 0.65kg/cm2 36 depth hole.
52Er. SHISH PAL
GROUTINGTypes of grouting:
1. Consolidation Grouting:
This type of grouting is used for shallow depthgrouting holes. Normally pressure below 3 kg/cm2 is
known as low pressure grouting.
2. Stage grouting:
When thick layers are to be grouted the total thickness of layer isdivided into stages of 1m each and grouting of each layer is carriedout one by one. Grouting of upper layer is started only after thegrout in the lower layer had properly set.3. Curtain Grouting:
This type of grouting is done to prevent the seepage of water belowfoundation of dam. Grouting holes are drilled in the upstream sideof dam in the bed rock and impermeable grout wall is created.
53Er. SHISH PAL
CRACKING REPAIR BY
GROUTING•Based on grouting materials used there three types :
•Portland cement grouting
•Chemical grouting
•Epoxy grouting
54Er. SHISH PAL
PORTLAND CEMENT
GROUTING • It is the process in which fine cement mortar (1:2) used to fill the crack
developed wall.
•For grouting a low pressure grouting pump is required to transfer the
grout in the wall required depth.
55Er. SHISH PAL
CHEMICAL GROUTING•Chemical used for grouting are sodium silicate, urethanes and
acry lamide. Two or more chemical are combined to from gel, a
solid precipitate or a from as opposed to cement grout that
consist of suspension of a solid particles in a fluid. the
advantage of chemical grout include applicability in moist
environment and their ability to be applied in very fine crack.
56Er. SHISH PAL
CHEMICAL GROUTING
57Er. SHISH PAL
EPOXY METHOD•Epoxy Injection technique : Epoxy materials are
resinous binding material which posses high tensile
strength.
•Epoxy injection consist of high strength epoxy
material into the crack concrete filling the voids and
rebinding the affected members
58Er. SHISH PAL
EPOXY METHOD
59Er. SHISH PAL
PROVIDING SEISMIC BELT
•Belt are providing in building to preventopening of brick masonry walls particularlyat joint.
•Seismic belt are provided both side of wall above lintel of opening . if the height of story is 3.0m then one belt is sufficient, but the height is more than 3m then 2 belt are provided.
60Er. SHISH PAL
SESMIC BELT
61Er. SHISH PAL
•In this method mortar or concrete is conveyed through a
hose(pipe) under high pressure pneumatically on to the surface
to be treated called shortcrete method.
•For treating a damaged wall a layer of 75 mm thick layer of
shortcrete is sufficient to against earthquake.
SHORTCRETE METHOD OF
TREATMENT
62Er. SHISH PAL
SHORTCRETE METHOD
OF TREATMENT
63Er. SHISH PAL
BENEFIT OF RETROFITTING
•Saving on capital expenditure while benefiting from new
technologies
•Optimization of existing plant components
•Adaptation of the plant for new or changed products
•Increase in piece number and cycle time
•Guaranteed spare parts availability
•Reduced maintenance costs and increased reliabilit
64Er. SHISH PAL
LIMITATIONS OF
RETROFITTING
•Lack of confidence of engineers and builders.
•Ignorance of general public.
•Disturbance during retrofitting work.
•Original importance and aesthetic value of building is
likely to be lost.
•Retrofitting sometimes causes reduction of usable space.
65Er. SHISH PAL
Indian Codes for Earthquake Design
• IS: 1893-2002 (part-1) Criteria for Earthquake Resistant Design of Structures (Part 1 :
General Provision and Buildings) - Code of Practice
• IS: 4326-1993 Earthquake Resistant Design and Construction of Buildings – Code of
Practice
• IS: 13920-1993 Ductile Detailing of Reinforced Concrete Structures subjected to
Seismic Forces – Code of Practice
• IS: 13935-1993 Repair and Seismic Strengthening of Buildings – Guidelines
• IS: 13828-1993 Improving Earthquake Resistance of Low Strength Masonry
• Buildings - Guidelines
• IS: 13827-1993 Improving Earthquake Resistance of Earthen Buildings – Guidelines
66Er. SHISH PAL
Conclusion
• Seismic Retrofitting is a suitable technology for protection of a
variety of structures.
• It has matured in the recent years to a highly reliable
technology.
• But, the expertise needed is not available in the basic level.
• The main challenge is to achieve a desired performance level at
a minimum cost, which can be achieved through a detailed
nonlinear analysis.
• Optimization techniques are needed to know the most efficient
retrofit for a particular structure.
• Proper Design Codes are needed to be published as code of
practice for professionals related to this field.67Er. SHISH PAL
REFRENCES:-
• Agarwal, P . and Shrikhande M.2006, Earthquake resist design of structure,
2nd edition, Prentice hall of India private limited ,New Delhi.
• EERI 1999, Lesson learnt over Time- Learning for Earthquake.
• Series volume II Innovative recovery in India, Earthquake engineering
research institute, Oakland (CA),USA.
• Murty, C.V.R , 2004, IITK-BMTPC Earthquake Tip NEW DELHI.
• Constantinou, Mc, syamn , M. D, TSOPELAS ,P., and Taylor, D.P., 1993
Fluid viscous dampers in application of seismic energy dissipation and
seismic isolation , ATC,-17, applied technology council ,san Francisco .
• Cardone , D . And dolce , M., 2003, seismic protection of light secondary
• Systems through different base isloation systems , journal of earthquake
engineering , 7(2) ,223-250.
Er. SHISH PAL 68
THANK YOU
69Er. SHISH PAL
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