Download Rehabilitation and Retrofitting of Structures Notes (RRS)

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LECTURE NOTES ON
Rehabilitation & Retrofitting of structure
Department of Civil Engineering
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UNIT-1
INTRODUCTION
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Cracks in the building are of common occurrence in a building
It is due to exceeding stress in a building components
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Causes of the cracks are mainly by increase in live load and dead load, seismic oad etc.,
Classification of cracks
Cracks can be classified into two categories viz.,
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Structural cracks
Non-structural cracks
Structural cracks
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It arises due to incorrect designs, overloading of structural c mp nents
Expenses cracking of foundation walls, beams and columns
slab etc.,
PHOTO OF STRUCTURAL CRACKS
They are due to internal forces developed in materials due to moisture variations,
temperature variation, crazing, effects of gases ,liquids etc.,
Non structural cracks
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They can be broadly classified into vertical, horizontal, diagonal, smoothened cracks
PHOTO OF NON S RUC URAL CRACKS
DIREC ION OF HE CRACKS
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Vertical
Horizontal
Diagonal
Straight
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Toothed
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Variable and irregular
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WIDTH OF CRACKS
It can be measured through instrument and tell-tale signs.
The changes in the length of the cracks should be noted.
Cracks measuring devices
CAUSES OF CRACKS
Major causes of cracks
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Movements of the ground
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Over loading
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Effect of gases, liquids and solids
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Effect of changes of temperature
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General causes such as vibrations
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Movements of grounds
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Due to mining subsidence, land slips, earthquakes, moisture changes due to shrinkable soils.
Overloading
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Overloading of the building
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Overloading of the building parts
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cracks Overloading forced may be due to
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External ( excessive wind/snow loads)
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Internal ( from heavy machinery
 etc.,)
Effects of gases, liquids and solids
Gases
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Only gases like Co2 (carbon dioxide) is likely to produce cracks.
It causes Carbonation of porous cement products
Leads into an overall shrinkage crazing cracks
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Liquids
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Water is the most commonly used liquid when not taken care it can be hazardous
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Construction water
 i.e., that in the utilization of water during the construction
process Effects of water
Physical(i.e. due to change in water content)
Chemical ( directly or indirectly affecting other
materials) General vibrations
Vibrations can cause cracks in buildings only when their amplitude of vib ations a e high.
Apart from vibrations caused due to earthquakes, the vibrations caused due to heavy machinery,
traffic, sonic booms are also responsible for the occurrence of cracks in buildings.
THERMAL MOVEMENT
All materials expand on heat and contract on cool.
Thermal movement in components of structure creates cracks due to tensile f shear stresses
One of the most potent causes of cracking in buildings and need attention
GENERAL PRECAUTION TO AVOIDING CRACKS
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Before laying up foundation,the type of foundation to be used should be decided based on the
safe bearing capacity of soil.
Providing R.C deep beam or an involved T -beam with adequate reinforcements
to withstand the
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stress due to differential ground movements. This method is expensive
Construction operations such as cutting for roads drainages etc., close to the structures
should be avoided this will results in reduction
of soil moisture with consequent shrinkage of
soil beneath the foundation of the structure.
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In buildings close to the water courses are noticed in many places
PLACI G OF CO CRETE
Concrete should not be placed in heavy rains unless suitable shelter is provided.
To avoid segregation, concrete should not be dropped from a height of more than 1m.
Working on freshly laid concrete should be avoided
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While placing
 the concrete in R.C.C members the alignment of formwork should not be
disturbed.
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Concrete should be laid continuously to avoid irregular and unsightly lines.
Internal surface of the forms either
 steel or wood should have even surfaces and should be oiled so that
the concrete may not stick to it
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MATERIAL QUALITY
Aggregate should be hard, sound, durable, non-absorbent and capable of of developing good bond with
mortar.
Water shall be clean and free from alkaline and acid materials and suitable for drinking purposes.
TEST TO BE CARRIED OUT
Slump test to be carried out for the control of addition of water and wo kabi ity.
Consistency of concrete should also be tested.
A slump of 7.5 to 10cm may be allowed for building work
LAYING TECHNIQUE AND CURING METHOD
Concrete should be laid in layers and should be compacted while laying with wooden tamping
rods with mechanical vibrators until a dense concrete is obtained
After two hours of laying concrete, when the concrete has begun to harden, it shall be kept damp
by covering with wet gunny bags or wet sand for 24 hours
Evaluation of cracks
To determine the effects of cracks in the building.
First the cracks location and extent should be noted down for the adopting suitable methods of
repair and the future problems due to that cracks.
Crack widths should be measured to the accuracy of 0.001 in (0.025mm) using a crack
comparator. Movements should be recorded with movement sensors.
Based on the reports from the location and width the suitable methods is adopted
Crack as narrow as 0.002 in can be bonded by the injection of epoxy.
Epoxy injection can alone be used to restore the flexural stiffness.
For water retaining structure cracks it can be repaired by the autogenous
healing. Repairing of cracks
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Routing and sealing.
Stitching.
Additional reinforcement.
Gravity filling
Grouting
Dry packing
Polymer impregnation
Routing and sealing
Routing and sealing of cracks can be used in conditions requiring remedial epair and whe e structural
repair is not necessary.
Routing and sealing is used to treat both fill pattern cracks and larger, is lated cracks.
The sealants may be any of several materials, including ep xies, urethanes, silic nes, polysulfide,
asphaltic materials, or polymer mortars
Process of routing and sealing
stitching
Stitching involves drilling holes on both sides of the crack and grouting in U-shaped metal units with
short legs (staples or stitching dogs) that span the crack.
Stitching a crack tends to stiffen the structure, and the stiffening may increase the overall
structural restraint.
The stitching procedure consists of drilling holes on both sides of the crack, cleaning the holes, and
anchoring the legs of the staples in the holes, with either a non shrink grout or an epoxy resinbased bonding system
Figure showing stitching
Additional reinforcements
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Conventional reinforcement-Cracked reinforced concrete bridge girders have
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repaired by inserting reinforcing bars and bonding them in place with epoxy .
This technique consists of sealing the crack, drilling holes that intersect the crack plane at
approximately 90º ,filling
the hole and crack with injected epoxy and placing a reinforcing
bar into the drilled hole
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Prestressing steel-Post-tensioning is often the desirable solution when a major portion of a
member must be strengthened or when the cracks that have formed must be closed.
Adequate anchorage must be provided for the prestressing steel, and care is needed so that the
problem will not merely migrate to another part of the structure
Fig showing additional reinforcements
grouting
Portland cement grouting-Wide cracks, particularlyWorldingravitydamsandthickconcretewas,maybe repaired by filling with portland cement grout.
Gravity filling
This method is effective in stopping water leaks, but it will not structu ally bond c acked sections.
Low viscosity monomers and resins can be used to seal cracks with su face widths f 0.001 to 0.08 in.
(0.03 to 2 mm) by gravity filling.
Dry packing
High-molecular-weight methacrylates, urethanes, and s me l w visc sity ep xies have
been used successfully.
The lower the viscosity, the finer the cracks that can be filled.
Polymer impregnation
Drypacking is the hand placement of a low water content mortar followed by tamping ramming of the mortar
into place, producing intimate contact between the mortar and the existing concrete.
Monomer systems can be used for effective repair of some cracks. A monomer system is a
liquid consisting of monomers which will polymerize into a solid.
The most common monomer used for this purpose is methyl methacrylate.
The procedure consists of drying the fracture, temporarily encasing it in a watertight (monomer
proof) band of sheet metal, soaking the fractures with monomer, and polymerizing the monomer
conclusion
The discussion on our project mainly focused on the cracks deals with failure due to improper settlement
of foundation and poor construction.
By the following discussed remedies and instruction what we have concentrated helps to reducing the
cracks and move on to the next level in the construction.
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Content
1. Introduction
2. Rehabilitation
A. Why Rehabilitation
B. What Is Rehabilitation
3. Inspection
4. Common Defects And Possible Causes
5. Common Remedies
6. Composite Wraps For Durability
7. Conclusion
Introduction
Deterioration of reinforced concrete structure due to corrosion of steel is a cause of global concern.
The losses due to corrosion every year run in to millions of rupees and any solution to this
universal problem of corrosion has a direct bearing economy of the country.
It is estimated that about 30 to 40% of steel produce each year is used to replace corroded material.
Main objective of rehabilitation in the construction industry to reinstate rejuvenate strengthen
and upgrade existing concrete structure.
Various causes which needs rehabilitation of a building are such as environment degradation,
design inadequacies, poor construction practices, lack of maintenance, increase in load, unexpected
seismic loading condition in addition to corrosion induced distress.
Why rehabilitation
The chief aim of rehabilitation is to restore a prematurely distressed building back to it’s original
standard and to improve the facilities depending upon the needs and the technological advances.
In the field of building construction, after rehabilitation the building is expected to give a trouble free
service up-to it’s expected life.
What is rehabilitation
There is basic difference between the words “repair and rehabilitation”. The word repair normally
indicates small and petty repairs more or less cosmetic, which are not of structural significance.
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A building is said to require rehabilitation, when structural stability and safety of building and occupant
is in danger.
Basic advantage of rehabilitation on repair1. Repair building required frequent repair again because these are up to small extent and less
durable so the expenditure spent on repair required more. The life of rehabilitated building is
comparatively more than that of a repair building and economical too.
2. In repair what we apply is plaster only that does not last long hence eads eakage in pipe ine,
terrace, therefore there is corrosion in reinforcement of RCC structure but in rehabi itation we
can approach the problem by the identification of main culp its esponsib e for ete ioration.
Plastering is nothing but the waste of money only. So rehabilitation is effective than epair.
Causes of distress
1. Design deficiency:
1. underestimation of loads, deflection, shear f rces and m ments
2. environmental condition for durability neglected wr ngly specifying concrete grade,
maximum water to cement ratio and minimum cement content
3. Poor detailing especially at beam and column junction
4. fault analysis and earth quake & wind forces not considered at all
2. Material deficiency:
a. Poor quality cement
b. Poor quality steel
c. Contaminated water
d. Contaminated aggregates
3. Construction deficiency:
a. inadequate cover of concrete to steel reinforcement
b. use of poor quality cover blocks
c. poor formwork and staging
d. poor preparation of construction joints
4. chemical/environmental attacks:
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a. moisture and chloride attack
b. carbonation
c. sulphate attacks
d. thermal variation, hot and cold cycles
e. erosion
f. biological(insects and fungus) attacks
5. Natural causes:
a. earth quakes
b. floods
c. fires
6. Mechanical causesa. over loading
b. fatigue
c. impact
7. Foundation problema. failure of load bearing strata
b. soil consolidation
c. soil shrinkage and swelling
d. ground movement
8. Manmade causesa. blasting
b. poor and no maintenance
Cracks in buildings and it’s components
Cracks in column
Cracks in slabs
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Cracks in beam
Philosophy of rehabilitation
Inspection
Systematic detailed inspection is the key to success of any rehabilitation scheme and is done to
achieve the following objectives.
1. Preparation of complete defect catalogue
2. Evaluate the existing (safety and serviceability) condition of the bui ding and assess the
possible rate of future
3. Decide further course of action
Items needed during inspection1. Completion drawing for detailing
2. Mason’s tool kit- plumb bob, hammer, chisel, punch etc.
3. Measuring instrument- steel tap, scale, ladder, torch, safety belt etc.
4. Labour
5. Details of repairs
Common remedies
1. Jacketing of columnJacketing (provision of additional cross section) is done to strengthen column by removing loose
concrete and treating the reinforcement with protection treatment like providing shear anchor of
10mm–12mm diameter with a spacing 20–30cm c/c and then concreting is done (M25).
Polymer modified concrete which have good bonding quality and flexural strength, can be used.
2. Patch repairing by polymer mortarPatching is done by removing loose concrete and rust of reinforced. Sometimes extra reinforcement is
also provided. after removal of rust a bond coat is applied evenly in order to attain sufficient strength
between old concrete and new polymer mortar then polymer mortar is applied which is prepared by
weight (one part of polymer latex liquid, 5 part of cement and 15 part of quartz sand). Mortar is applied
by hand by pressing it to the damaged or cracked surface.
Column jacketing
3. Repairing of toilet block and GI pipe line-
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To avoid leakage problem from toilet, they should be made water proof. for this the seats are broke and
cleaned then the surface is applied with suitable polymer coating. After this a coating of 20 mm thick
plaster in cm 1:3 with w/c ratio of 0.4 provided. And joints between the seats are sealed with polymer
mortar.
Pipes which are leaked should be replaced.
4. Grouting-
5. Shotcretingmethod mortar or concrete is conveyed at a highWorldvelocityntoareceptivesurfacebytheapplicationof compressed air for moving concrete. the cement, sand mix and water are kept in
separate containers, which are connected to a nose pipe. Compressed air is f rced into these c ntainers
FIBER REINFORCED POLYMER COMPOSITE
through a motor.
Grouting is used to repair deep structural cracks by injecting grout material ike cement grout or resin. It
is very effective method for repairing RCC or masonry structure. admixture are a ed to re uce
shrinkage problem of cement grout so that it can reach upto the deepest c ack in the st uctu e and fill
the pores.
Shotcreting is a technique to achieve better structural capability f walls an ther elements. In this
Fiber reinforced polymer (FRP) is a composite material made by combining two more materials to give a
new combination of properties.
It is composed of fiber and matrix, which are bonded.
In this case, the reinforcing fiber provides FRP composite with strength and stiffness, while the matrix
gives rigidity and environmental protection.
Formation of Fiber Reinforced Polymer Composite
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A fiber is a material made into a long filament with a diameter generally in the order of 10 mm.
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he main functions of the fibers are to carry the load and provide stiffness, strength, thermal
stability, and other structural properties in the FRP.
To perform desirable functions, the fibers in FRP composite must have1. High Modulus of Elasticity for use as reinforcement;
2.
High Ultimate Strength;
3.
Low variation of strength among fibers;
4.
High Stability of their strength during handling; and
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5.
High Uniformity of diameter and surface dimension among fibers.
Matrix
Matrix material is a polymer composed of molecules made from many simpler and smaller units called
monomer.
The matrix must have a lower modulus and greater elongation than those of fibers, so that fibers
can carry maximum load.
Made from Metal, Polymer or Ceramic
Some Ductility is Desirable
TYPES OF FRP MATERIALS
USES
To strengthen the structures due to:1) Loading Increase
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Increasing the Live Load in warehouses
Increased traffic volume on Bridges
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Installation of Heavy machinery in Industrial Building
Vibrating Structures
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Change of Building utilization
2) Damage to Structural parts
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Ageing of Construction material
Steel Reinforcement corrosion
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Vehicle Impact
Fire
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Earthquakes
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3) Serviceability Improvement
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Decrease of Deformation
Stress reduction in steel reinforcement
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Crack width reduction
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4) Change in Structural System
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Removals of walls or columns
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Removal of slab section for openings
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5) Design or Construction Defects
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Insufficient reinforcement
Insufficient Structural Depth
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advantages
Low in weight
Available in any Length, no joints required
Low overall thickness
Easy to transport
Laminate Intersections are simple
Economical application- no heavy handling and installation equipment
Very high strength
High modulus of elasticity
Outstanding fatigue resistance
High alkali resistance
No corrosion
conclusion
1. With careful planning and close supervision, expected result can be achieved.
2. We can protect many buildings having historic, cultural, monumental, archeological
importance by rehabilitation.
3. Can save lot of money by rehabilitation.
4. Rehabilitation increases the life of building and any type of structure.
5. FRP gives the strength of the structural member.
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UNIT-2
Structure Repairs & Rehabilitation In Low Strength Masonry Buildings
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Structure Repairs & Rehabilitation
Low Strength Masonry Building is Laid in
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Fired brick work in clay & mud mortar
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Random rubble ; Uncoursed, Undressed stone masonry in weak mo ta s ma e of cement-sand ,
lime-sand & clay-mud.
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Structure Repairs & Rehabilitation
Component Of Low Strength Masonry Building:
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Foundation
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Flooring
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Brick/ Stone Columns
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Brick Work
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Stone Masonry
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Wood Work
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Slab
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Slopping Wooden frame Roof
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Plaster
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Structure Repairs & Rehabilitation
Life Of Structure Depend Upon:
A. Geography Of Location
B. Building Material
C. Technology
D. Workmanship
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Structure Repairs & Rehabilitation
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A . Geography Of Location:
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Type of Strata
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Water Table
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Earth Quack, Wind, Cyclone, Flood, Snow
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Pollutant
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Land Slide
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Tree location w.r.t. building
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Structure Repairs & Rehabilitation
B . Building Materials
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Cement
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Lime
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Fine Sand
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Coarse Sand
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Coarse Aggregate
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Quality of Water
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Bamboo/Wood
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Brick
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Structure Repairs & Rehabilitation
C. Technology
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Architectural Design
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Structural Design Based On Load Bearing Wall
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Construction Methods
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Quality Practices
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Construction Management
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Structure Repairs & Rehabilitation
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D Workmanship
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Structural Work
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Finishing Work
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Water Proofing Work
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Development of Drainage (Internal & External)
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Maintenance Of Building
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Structure Repairs & Rehabilitation
Building Needs Repairs & Retrofitting
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Crack & Spalling In Structural Members
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Crack & Settlement In Flooring
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Crack & Spalling in Non Structural Members
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Leakage In Water Supply & Drainage System
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Redesigning existing structure for nature forces
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Changed functional requirements
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Structure Repairs & Rehabilitation
Crack & Spalling In Structural Members
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Cracks Occur Due To Settlement In Foundation
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Cracks Due o Earth Quack ,Wind
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Crack Due o Overloading Of Structure
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Crack Due o Reduction in Load Carrying Capacity of Structure Due To Weathering
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Crack Due To Improper Design Of Structure
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Crack due to Poor connection Of Structural Members Resulted From Poor Workmanship
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Structure Repairs & Rehabilitation
Crack & Settlement In Flooring
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Due To Improper Plinth Filling
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In case of black cotton soil in foundation not replaced up to sufficient depth by Good Soil under
plinth (For generating enough Counter weight upon black cotton soil)
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Water Table vary within the Plinth Sub base (this occur in frequent flooding area & near
sea soar)
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Improper curing, Improper laying, Poor Quality of workmanship.
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Improper design for loading i.e. thickness & type of flooring.
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Structure Repairs & Rehabilitation
Crack & Spalling in Non Structural Members
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Crack In Plaster
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Crack In Finishing
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Crack In Water Proofing Work
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Vertical cracks in long boundary wall due to thermal m vement Or Shrinkage.
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Crack Induced due to thermal changes, change in moisture content in building material,
Chemical Reactions
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Structure Repairs & Rehabilitation
Leakage In Water Supply & Drainage
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It may result from structural cracks & settlement
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Improper selection of pipe thickness
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Improper selection of Supports & its spacing to Pipe
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Improper making Of joints
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on Provision for contraction & expansion (Particularly when pipe is passing over different
type of long structures)
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on Testing of Pipe before & after laying
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Insufficient soil cover over pipe
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Structure Repairs & Rehabilitation
Redesigning existing structure to meet functional requirement as well as forces generated by Nature
It is a comprehensive task & require planning which include following Information gathering.
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Field investigations including details of sub strata, foundation details
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Type of Existing structure & its members stability
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Design Data Collection
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Identification of components required to be strengthened, replaced.
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Cost Estimates (it is feasible up to 60% of new construction)
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Method or Procedure to be fallowed.
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Structure Repairs & Rehabilitation
Crack Investigation
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Location
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Profile (vertical, Horizontal, Diagonal)
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Crack Size throughout length (Width,Depth & length)
Thin crack< 1mm
Medium Crack >1 to 2 mm
Wide Crack > 2 mm
Crack may be non-uniform width. i.e. Tapper in width(narrow at one end & wider at other end. )
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Static or Live cracks
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Structure Repairs & Rehabilitation
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Cracks are static or live, is monitored & recorded by “Tell-Tale” method
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
Construction Details Of Bearing Of R.C.C. Roof Slab Over a Masonry Wall
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation
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Structure Repairs & Rehabilitation World
When two adjacent walls shake in different directions, their joint at corners comes un er a lot
of stress. This causes crack at the junction of two walls.
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Structure Repairs & Rehabilitation
When the long wall bends outward or inwards vertically in the midd e of its ength, this
stretching causes tension and causes vertical cracks in the walls.
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Structure Repairs & Rehabilitation
Similarly when the walls bends outward or inwards h riz ntally in the middle of its height,
this stretching causes tension and causes horiz ntal cracks in the walls. This happens at the
base of gable wall.
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Structure Repairs & Rehabilitation
Many times the wall gets pulled from its corners. This results in to tearing f wall in diagonal
direction. In the wall if there is a window a door, then the diagonal crack occur at their
corners.
Structure Repairs & Rehabilitation
Flexural Tension Cracks At Lintel Level Due to Shrinkage & contraction of R.C.C. Slab
Structure Repairs & Rehabilitation
If the window is very large or if there are many doors and windows in a wall, then it tears
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even more easily in an earthquake.
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Structure Repairs & Rehabilitation Many times the roof slides on top
of the walls on which it is sitting on
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Structure Repairs & Rehabilitation
Structural Repairs
Load Bearing Walls: PROCEDURE IN NEXT SLIDE
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Structure Repairs & Rehabilitation
Repairing Of Crack Due To Structural Cause
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Replace all cracked bricks
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Use R.C.C. Stitching Block In Vertical Spacing In Every 5th or 6th Course ( 0.5 meter apart ).
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• Stitching block
Width=equal to wall width,
Length = 1.5 to 2 bricks,
Thick =1 or 2 bricks as per severity of cracks
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Mortar For Repairs 1:1:6 (1 Cement :1 lime: 6 sand)
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Structure Repairs & Rehabilitation
load bearing walls(May be Brick or Stone) have inbuilt deficiency.
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Each Brick have different strength
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Thickness of Mortar Joints are not also uniform.
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Bricks are not perfectly laid horizontally & vertically
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Opening in walls
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Improper staggered joints
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Use of unwanted Brick bats
1. These resulted in cumulative effect & concentration of stress in particular section of wall is more
than other section.
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Structure Repairs & Rehabilitation
Corrective Measures For Load Bearing Wall Building
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herefore Shifting of Window, Door ,Inbuilt construction of Almirah should be carried out with
due consideration to IS code 13828:1993
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Proper Bearing to lintel over brick work to avoid diagonal cracks & it can be done in
retrofitting work.
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It is advisable to keep window width as less as feasible while height can be increased with
fixed glass pans on top portion as per slide 41.
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Structure Repairs & Rehabilitation
Importance Factor(I) Depend Upon
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Functional Use Of Structures
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Hazardous Consequences Of Its Failure
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Post Earthquake Personal needs
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Historical Value
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Economic Importance
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School Building Have “I” value=1.5
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Structure Repairs & Rehabilitation
Elevation : Distance b1 to b8 changes as per Building
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Retrofitting
Need
Structure Repairs & Rehabilitation Table
:Size, Position Of Opening In Above Figure
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Structure Repairs & Rehabilitation
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Strengthening Of Window When Its Position
Is Not As Per Table Above Slide No 42.
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Structure Repairs & Rehabilitation
Strengthening Arrangements Recommended For low Strength Masonry Building
b
= Lintel Bend
C
= Roof Bend, Gable bend
d
= Vertical steel at corners & junctions of wall
f = Bracing in plan at tie level of Pitched Roofs
g = Plinth band
For Building of Category ‘B’ in two storey constructed with stone masonry in weak mortar,
provide vertical steel of 10 mm dia in both storey.
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Structure Repairs & Rehabilitation
Strengthening Arrangements Recommended For Elements of low Strength Masonry Building
•
Structure Repairs & Rehabilitation
•
Seismic wave propagation increases as height of wall/structure increases.
•
Seismic wave expansion pushes bricks of corner of wall out of building.
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•
Movement of Seismic wave through joints of similar or dissimilar component of building ,makes
joint open, resulting in falling of component of the building.
•
Structure Repairs & Rehabilitation
Possibility For Old Masonry Structures Strength
•
Plinth Belt in lieu of plinth band
•
Lintel level belt in lieu of band
•
Roof level/ gable level band
•
Corner steel
•
Shape, Size & location of Window In Wall
•
Wall length to Height Ratio
•
Cross wall/ Brick Pillar/counter fort
•
Structure Repairs & Rehabilitation Reinforced band n t p f gable wall It
will reduce bending of gable wall
•
Structure Repairs & Rehabilitation
In long walls introduce buttress
to strengthen it.
•
Structure Repairs & Rehabilitation
Low Strength Masonry Building Retrofitting
For Brick Masonry Structure
•
Height of the building in B.W. shall be restricted to the following.
1. For retrofitting category of building A,B,C up to3 storey with flat roof or 2 storey plus Attic
for pitched roof.
2. For category D up to 2 storey with flat roof or one storey plus Attic for pitched roof.
where each storey height shall not exceed 3.0 m. Cross wall spacing should not be more than 16
times the wall thickness CONTD.
•
Structure Repairs & Rehabilitation
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3. Minimum wall thickness in brick masonry shall be one brick for one & two storey construction,
while in case of three storey, the bottom storey wall thickness is one & half brick.
4. Use brick from kiln only after 2 weeks when work is in summer & 3 week when work in winter.
5. Use leaner mortar preferably also adding lime for repairing cracks in particular& in masonry in
general. It can be 1:1:6,1:2:9,1:3:12 as per need.
•
Structure Repairs & Rehabilitation
For Stone Masonry
•
Height of the building in Stone Masonry shall be restricted to the fo owing
1. For retrofitting category of building A,B,—2 storey with flat oof or 1 sto ey p us Attic for pitched
roof .In case cement sand mortar 1:6, the building up to 2 st ey plus Attic f pitched roof.
2. 2. For category C,D– 2 storey with flat roof 2 st rey plus Attic f
sand mortar or 1 storey plus Attic for pitched r f with lime- sand
pitched oof with Cement
r mud m rtar.
CONTD.
•
Structure Repairs & Rehabilitation
3. Maximum wall thickness in stone masonry shall be 450 mm & preferably 350 mm. ,
•
Each storey height shall not exceed 3.0 m and span of walls between cross wall is limited to
5.0m
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•
Structure Repairs & Rehabilitation
•
Cross wall connection In steps
•
Structure Repairs & Rehabilitation
Wall to wall joints are to be made
by building wall ends in steps form
•
Structure Repairs & Rehabilitation Vertical reinforcement within the masonry in
corners increases wall’s capacity to withstand Horizontal cracks due to bending.
•
Structure Repairs & Rehabilitation
In Each Layer Staggered Toothed Joint
Y A
B
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X
PLAN
•
Structure Repairs & Rehabilitation
Recommended Longitudinal steel in Reinforcement Concrete Bends
•
Structure Repairs & Rehabilitation
•
Steel Profile In Band At Corner & Junction
•
Structure Repairs & Rehabilitation
Bonding Elements
A.
ood Plank
( 38x38x450 mm)
B. R.C.C. Block
(50x50x450 & 8 mm)
C. 8 or 10 mm Hook
or “S” shape bent Bar
Plan showing Through Stone
Through stone = Bonding Element
•
Structure Repairs & Rehabilitation
“S” shaped steel rod placed in a through hole in random rubble wall and fully
encased in concrete
•
Structure Repairs & Rehabilitation
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Plan showing Center bar in Casing
Casing in every 0.6 m is lifted & M15 or Mortar 1:3 is Compacted a ound bar.
•
Structure Repairs & Rehabilitation
•
roof from getting distorted and damagedWorld Structure Repairs & Rehabilitation Installing multiple strands of galvanized iron wires pulled and
•
•
Half Split Bamboo Ties To Rafter
•
Brace the Rafter to 50 mm Dia Bamboo (B)
•
Seismic Bend & Rafter should be tied Properly
•
Structure Repairs & Rehabilitation Diagonal tying on the upper
underside of the roof Prevents
twisted to pretension
•
Structure Repairs & Rehabilitation
Vertical steel at corners and junction of walls up to 350 mm thick should be embedded in plinth
masonry of foundations, bands, roof slab as per table
•
Structure Repairs & Rehabilitation
One Brick Thick
One & Half Brick Thick
-------- Contain One Bar At Centre
•
Structure Repairs & Rehabilitation
Seismic Belts & closing a opining with pockets made in jams of masonry.
•
Structure Repairs & Rehabilitation
Encasing masonry column in cage of steel rods and encased in micro concrete.
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•
Structure Repairs & Rehabilitation Anchoring the roof rafters and trusses with steel angles
or other means
•
Structure Repairs & Rehabilitation
Weld mesh belt approximately 220mm wide all
around the openings and anchored to masonry wall and encased in cement mortar
•
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Vertical deformed steel encased in concrete bar from foundation to roof, anchored to both
masonry walls at wall junctions with special connectors.
• Structure Repairs & Rehabilitation
Seismic belt in lieu of Seismic Band is made of weld mesh app oximate y 220mm wide
anchored to masonry wall and encased in cement mortar.
• Structure Repairs & Rehabilitation
Use smaller glass panes for windows Prevents the shattering f glass in ea thquake and cyclone
•
Structure Repairs & Rehabilitation Anchoring
prevent the roof from getting blown off
•
Structure Repairs & Rehabilitation Prolonged flooding can weaken the mortar, especially if it is
mud mortar, and hence,
f to wall &, reducing r f verhangs,
the wall, causing cracking in walls or collapse.
•
Structure Repairs & Rehabilitation
If the ground is sandy in which the foundation is sitting, then high speed flood/surge water can
scour the land around and under the foundation of your school, leading to settlement and/or
cracking of the wall.
•
Structure Repairs & Rehabilitation
Simple erosion of wall near its bottom, or cracking, plaster peeling off and settlement
in floor.
•
Structure Repairs & Rehabilitation
•
Structure Repairs & Rehabilitation
Extensive cracking of walls caused by differential settlement due to flood
•
Structure Repairs & Rehabilitation High
plinth level to avoid entering flood
•
Structure Repairs & Rehabilitation
Use of pilasters strengthens walls against flowing water
•
Structure Repairs & Rehabilitation
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•
This Presentation was focused on Low Strength Masonry Buildings therefore for framed
structures & rich cement mortar building ,certain slides are in-valid. In next Presentation this
balance portion will be highlighted.
•
This Presentation was aiming to provide some technical input to site peoples so that we could
point out any doubtful detailing in drawings to Structural/Architectural Designer.
•
It is possible that features of Flood, Heavy Rain fall, Cyclone, earth quack may colli e but We
have to look priority of our geographical requirement.
Thank You
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UNIT-3
Definition of Corrosion
though the amount of metal destroyed is quiteWorldsmall.
Corrosion is the deterioration of materials by chemical interaction with their environment. The
term corrosion is sometimes also applied to the degradation of plastics, concrete and woo , but
generally refers to metals.
Anodic & Cathodic Reactions
Effects of corrosion
The consequences of corrosion are many and varied and the effects of these on the safe,
reliable and efficient operation of equipment or structures are ften m
e se i us than the simple loss
of a mass of metal. Failures of various kinds and the need f expensive eplacements may occur even
Underground corrosion
Buried gas or water supply pipes can suffer severe corrosion which is not detected until an
actual leakage occurs, by which time considerable damage may be done.
Electronic components
In electronic equipment it is very important that there should be no raised resistance at
low current connections. Corrosion products can cause such damage and can also have sufficient
conductance to cause short circuits. These resistors form part of a radar installation.
Corrosion influenced by flow-1
he cast iron pump impeller shown here suffered attack when acid accidentally entered the
water that was being pumped. he high velocities in the pump accentuated the corrosion damage.
Corrosion influenced by flow – 2
his is a bend in a copper pipe-work cooling system. Water flowed around the bend and then
became turbulent at a roughly cut edge. Downstream of this edge two dark corrosion pits may be seen,
and one pit is revealed in section.
Safety of aircraft
The lower edge of this aircraft skin panel has suffered corrosion due to leakage and spillage
from a wash basin in the toilet. Any failure of a structural component of an aircraft can lead to the most
serious results.
Influence of corrosion on value
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A very slight amount of corrosion may not interfere with the usefulness of an article, but can
affect its commercial value. At the points where these scissors were held into their plastic case some
surface corrosion has occurred which would mean that the shop would have to sell them at a
reduced price.
Damage due to pressure of expanding rustWorld
Motor vehicle corrosion and safety
The safety problems associated with corrosion of motor vehicles is illustrated by the holes
around the filler pipe of this petrol tank. The danger of petrol leakage is obvious. Mud and irt thrown
up from the road can retain salt and water for prolonged periods, forming a corrosive “pou tice”.
Corrosion at sea
Sea water is a highly corrosive electrolyte towards mild steel. This ship has suffe ed severe
damage in the areas which are most buffeted by waves, where the p otective coating of paint has been
largely removed by mechanical action.
Aluminium Corrosion
The current trend for aluminium vehicles is not with ut pr blems. This aluminium alloy chassis
member shows very advanced corrosion due to contact with ad salt fr m gritting perations or use in
coastal / beach regions.
The iron reinforcing rods in this garden fence post have been set too close to the surface of the
concrete. A small amount of corrosion leads to bulky rust formation which exerts a pressure and causes
the concrete to crack. For structural engineering applications all reinforcing metal should be covered by
50 to 75 mm of concrete.
“Corrosion” of plastics
Not only metals suffer “corrosion” effects. This dished end of a vessel is made of glass fibre
reinforced PVC. Due to internal stresses and an aggressive environment it has suffered “environmental
stress cracking”.
Galvanic corrosion
This rainwater guttering is made of aluminium and would normally resist corrosion well.
Someone tied a copper aerial wire around it, and the localised bimetallic cell led to a “knife-cut” effect.
Galvanic corrosion
The tubing, shown here was part of an aircraft’s hydraulic system. The material is an aluminium
alloy and to prevent bimetallic galvanic corrosion due to contact with the copper alloy retaining nut this
was cadmium plated. The plating was not applied to an adequate thickness and pitting corrosion
resulted.
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Galvanic corrosion
This polished Aluminium rim was left over Christmas with road salt and mud on the rim.
Galvanic corrosion has started between the chromium plated brass spoke nipple and the
aluminium rim.
Galvanic corrosion
Galvanic corrosion can be even worse underneath the tyre in bicycles used all winter. Here
the corrosion is so advanced it has penetrated the rim thickness.
Corrosion prevention
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UNIT-4
DAMAGE IN STRUCTURES DUE TO FIRE
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DAMAGE IN STRUCTURES DUE TO FIREWorld
PART 1: Fire Induced Damages in Structures
PART 2: Fire Rating of Structures


PART 3: Phenomenon of Desiccation

DAMAGE IN STRUCTURES DUE TO FIRE

PART 1: Fire Induced Damages in Structures
Part I: Fire Induced Structural Damages


Uneven volume changes in affected members, resulting in dist rti n, buckling and cracking. The
temperature gradients are extreme - from ambient
70 F (21 C), to higher than 1500oF (800oC) at

the source of the fire and near the surface.
Spalling of rapidly expanding concrete surfaces from extreme heat near the source of the
fire. Some aggregates expand in bursts, spalling the adjacent matrix. Moisture
 rapidly
changes to steam, causing localized bursting of small pieces of concrete.
The cement mortar converts
to quicklime at temperatures of 750 F (400oC), thereby causing
disintegeration of concrete.
Reinforcing steel loses tensile capacity as the temperature rises.

Once the reinforcing steel is exposed by the spalling action, the steel expands more rapidly
than the surrounding concrete, causing
 buckling and loss of bond to adjacent concrete where
the reinforcement is fully encased.
Concrete undergoes cracking,
spalling, and experiences a decrease in stiffness and strength as the

temperature increases.
Concrete has low thermal conductivity, which allows it to undergo
 heating for longer durations
before the temperature increases significantly and damage occurs.
The concrete compressive strength
starts decreasing rapidly after its temperature reaches

approximately 400°C (750°F).
At temperatures of around 
500oC (932oF), the concrete compressive strength is reduced to
50% of its nominal strength.
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
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The tensile yield strength of the steel decreases gradually up to 500oC (932o F). It is reduced to
o
about 50% of its nominal yield strength at 600oC (1112
 F). This essentially eliminates any
factor of safety, which is usually between 1.5 and 2.0.
o
The steel yield strength decreases more rapidly for temperatures greater than 500oC (932
F),
and failure may be inevitable if temperatures keep increasing while the loading is sustained.
Stages of deterioration due to Fire

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DAMAGE IN STRUCTURES DUE TO FIRE
PART 2: Fire Ratings of Structures

PART 2: Fire Ratings

Structures What is Fire Rating?

of
A fire rating refers to the length of time that a material can withstand c mplete c mbustion during a
standard fire rating test. Fire testing of building materials and c mp nents f buildings -- such as joists,
beams and fire walls -- is required in most places by building codes.
Other fire tests for things such as appliances and furniture are voluntary, ordered by manufacturers
to use in their advertising. Wall and floor safes are examples of products for which fire resistance is a
key selling point.

PART 2: Fire Ratings of Structures
What is Fire Rating?
With the required tests, the results are measured in either units of time, because the emphasis is on
holding up under fire (literally) long enough for the occupants of a home or building to escape, or by
classification designations. his does not mean, necessarily, that the components of every new
structure have to be fire tested. In most cases, the fire rating has been already established by
testing the product before it is even put on the market.
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DAMAGE IN STRUCTURES DUE TO FIRE
PART 3: Phenomenon of Desiccation
PART 3: Phenomenon of Desiccation


Desiccation
 is a phenomenon referring to dryness of the material induced by the loss of
moisture
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UNIT-5
DISTRESS OF CONCRETE STRUCTURES & THEIR REPAIR TECHNIQUES
World
INTRODUCTION
If a building has given about 25v to 30 years of service without much maintenance or repair then it
is reasonable to expect that it would need some repair sooner later.
CATEGORIES OF REASONS DISTRESS OF CONCRETE STRUCTURES
1. WEATHERING
2. AGEING
3. ENVIRONMENTAL EFFECTS
4. INADEQUATE MAINTENANCE
5. POOR DESIGNING AND CONSTRUCTION QUALITY
6. CHANGE OF LOADING PATTERN OR NON CONVENTIONAL LOADING ON STRUCTURE
7. WATER LEAKAGE LEADING TO CORROSION OF CONCRETE STRUCTURE
JNTUCAUSESOFEARLYDETERIORATIONOFCONCRETE STRUCTURES
EFFECTS OF CRACKING ON LIFE OR D RABILIY OF STRUCTURE
IDENTIFICATION OF DISTRESSED LOCATIONS ON STRUCTURES
MATERIALS AND ME HODS FOR CRACK REPAIR
SOME SPECIFIC REPAIR ECHNIQUE FOR CONCRETE SURFACE
ASSESMENT OF QUALI Y OF S RUC URE SOON AFTER ITS CONSTRUCTION
REQUIREME
FOR TRAINING FOR CONCRETE REPAIR AND CONCRETE WORKERS
THA K YOU
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UNIT-6
METHODS OF REPAIRING CONCRETE STRUCTURES
1. INTRODUCTION
Cracking, Spalling and Disintegration
2. Repairing cracks
3 Basic symptoms of distress in a concrete structureWorld
Reasons for their development may be poor materials, poor design, poor const uction p actice, poor
supervision or a combination
repair of cracks usually does not involve strengthening
repair of a structure showing spalling and disintegration, it is usual to find that there have been
substantial losses of section and/or pronounced corrosi n f the reinf rcement
In order to determine whether the cracks are active dormant, periodic observations are done utilizing
various types of telltales



by placing a mark at the end of the crack
a pin or a toothpick is lightly wedged into the crack and it falls out if there is any extension of the
defect
A strip of notched tape works similarly :
Movement is indicated by tearing of the tape

he device using a typical vernier caliper is the most satisfactory of all.
Both extension and compression are indicated

If more accurate readings are desired, extensometers can be used




Where extreme accuracy is required resistance strain gauges can be glued across the crack
2.1
Types of cracks
•
active cracks and dormant cracks
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•
the proper differentiation between active and dormant cracks is one of magnitude of
movement, and the telltales are a measure of the difference
•
If the magnitude of the movement, measured over a reasonable period of time (say 6
months or 1 year), is sufficient to displace or show significantly on the telltales, we can treat the
crack as an active one.
Regular patterns of cracks may occur in the surfacingWorldofconcreteandinthinslabs.Thesearecalled
pattern cracks
• If the movements are smaller, the crack may be considered as dormant.
Cracks can also be divided into solitary or isolated cracks and pattern cracks
Generally, a solitary crack is due to a positive overstressing of the conc ete either ue to oad
shrinkage
Overload cracks are fairly easily identified because they follow the lines demonst ated in aboratory load
tests
In a long retaining wall or long channel, the regular formati n f cracks indicates faults in the design
rather than the construction, but an irregular distributi n f s litary cracks may indicate poor
construction as well as poor design
Methods of repairing cracks
1. Bonding with epoxies
Cracks in concrete may be bonded by the injection of epoxy bonding compounds under
pressure Usual practice is to




inject water or a solvent to flush out the

defect
allow the surface to dry
surface-seal the cracks between the injection


drill into the crack from the face of the concrete at several locations
to
inject the epoxy until it flows out of the adjacent sections of the crack or begins
bulge out the surface seals
Usually the epoxy is injected through holes of
inch deep at 6 to 12 inches centers

points

Smaller spacing is used for finer cracks
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about ¾ inch in diameter and ¾
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
The limitation of this method is that unless the crack is dormant or the cause of
cracking is
possibly

removed and thereby the crack is made dormant, it will probably recur,
somewhere else in the structure
Also, this technique is not applicable if the defects are
actively leaking to the extent that they
cannot be dried out, or where the cracks are numerous
2. Routing and sealing
•
This method involves enlarging the crack along its exposed face and fi ing and sea ing it with a
suitable material
The routing operation
placing the sealant
This is a method where thorough water tightness of the j int is n t required and where appearance is
not important
3. Stitching
Concrete can be stitched by iron or steel dogs
A series of stitches of different lengths should be used
bend bars into the shape of a broad flat bottomed letter U between 1 foot and 3 feet long and with
ends about 6 inches long
The stitching should be on the side, which is opening up first
if necessary, strengthen adjacent areas of the construction to take the additional stress
the stitching dogs should be of variable length and/or orientation and so located that the tension
transmitted across the crack does not devolve on a single plane of the section, but is spread out over
an area
In order to resist shear along the crack, it is necessary to use diagonal stitching
The lengths of dogs are random so that the anchor points do not form a plane of weakness
4. External stressing
cracks can be closed by inducing a compressive force, sufficient to overcome the tension and to
provide a residual compression
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The principle is very similar to stitching, except that the stitches are tensioned; rather than plain
bar dogs which apply no closing force to the crack
Some form of abutment is needed for providing an anchorage for the prestressing wires or rods
5. Grouting




installing built-up seats at intervals along the crack
same manner as the injection of an epoxyWorld cleaning the concrete along the crack
sealing the crack between the seats with a cement paint
g out
flushing the crack to clean it and test the seal; and then grouting the whole
6. Blanketing
similar to routing and sealing
applicable for sealing active as well as dormant
cracks Preparing the chase is the first step
Usually the chase is cut square
The bottom should be chipped as smooth to facilitate breaking the bond between sealant and
concrete The sides of the chase should be prepared to provide a good bond with the sealant material
The first consideration in the selection of sealant materials is the amount of movement
anticipated and the extremes of temperature at which such movements will occur
elastic sealants
mastic sealants
mortar-plugged joints
7. Use of overlays
Sealing of an active crack by use of an overlay requires that the overlay be extensible and not flexible
alone
Accordingly, an overlay which is flexible but not extensible, ie. can be bent but cannot be stretched, will
not seal a crack that is active
Gravel is typically used for roofs
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concrete or brick are used where fill is to be placed against the overlay
An asphalt block pavement also works well where the area is subjected to heavy traffic
Repairing spalling and disintegration
In the repair of a structure showing spalling and disintegration, it is usual to find that there have
been substantial losses of section and/or pronounced corrosion of the reinforcement
Both are matters of concern from a structural viewpoint, and repair genera y invo ves some urgency
and some requirement for restoration of lost strength
1. Jacketing
primarily applicable to the repair of deteriorated columns, piers and piles
Jacketing consists of restoring or increasing the section f an existing membe , p incipally a compression
member, by encasement in new concrete
The form for the jacket should be provided with spacers to assure clearance between it and the
existing concrete surface
The form may be temporary or permanent and may consist of timber, wrought iron, precast concrete or
gauge metal, depending on the purpose and exposure
Timber, Wrought iron Gauge metal and other temporary forms can be used under certain conditions
Filling up the forms can be done by pumping the grout, by using prepacked concrete, by using a
tremie, or, for subaqueous works, by dewatering the form and placing the concrete in the dry
The use of a grout having a cement-sand ratio by volume, between 1:2 and 1:3 , is recommended
The richer grout is preferred for thinner sections and the leaner mixture for heavier sections
The forms should be filled to overflowing, the grout allowed to settle for about 20 minutes, and
the forms refilled to overflowing
The outside of the forms should be vibrated during placing of the grout
2. Guniting
Gunite is also known as shotcrete or pneumatically applied mortar
It can be used on vertical and overhead, as well as on horizontal surfaces and is particularly useful
for restoring surfaces spalled due to corrosion of reinforcement
Gunite is a mixture of Portland cement, sand and water, shot into the place by compressed air
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Sand and cement are mixed dry in a mixing chamber, and the dry mixture is then transferred by air
pressure along a pipe or hose to a nozzle, where it is forcibly projected on to the surface to be coated
Water is added to the mixture by passing it through a spray injected at the nozzle
The flow of water at the nozzle can be controlled to give a mix of desired stiffness, which will adhere to
the surface against which it is projected
3. Prepacked concrete
This method is particularly useful for carrying out the repair under water and e sewhere where
accessibility is a problem
Prepacked concrete is made by filling forms with coarse aggregate and then fi ing the voids of the
aggregate by pumping in a sand-cement grout
Prepacked concrete is used for refacing of structures, jacketing, filling and f cavities in and under
structures, tings
underpinning and enlarging piers, abutments, retaining walls and f
Pumping of mortar should commence at the lowest point and pr ceed upward
Placing of grout should be a smooth, uninterrupted operation
4. Drypack
Drypacking is the hand placement of a very dry mortar and the subsequent tamping of the mortar
into place, producing an intimate contact between the new and existing works
Because of the low water-cement ratio of the material, there is little shrinkage, and the patch remains
tight. The usual mortar mix is 1:2.5 to 1:3
5. Replacement of concrete
This method consists of replacing the defective concrete with new concrete of conventional
proportions, placed in a conventional manner
This method is a satisfactory and economical solution where the repair occurs in depth (at least
beyond the reinforcement), and where the area to be repaired is accessible
This method is particularly indicated where a water-tight construction is required and where
the deterioration extends completely through the original concrete section
Overlays
In addition to seal cracks, an overlay may also be used to restore a spalled or disintegrated surface
Overlays used include mortar, bituminous compounds, and epoxies
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They should be bonded to the existing concrete surface
Conclusions
When repairing cracks, do not fill the crack with new concrete or mortar
A brittle overlay should not be used to seal anWorldactivecrack
The restraints causing the cracks should be relieved,
accommodating future movements
otherwise the repair must be capable of
Cracks should not be surface-sealed over corroded reinforcement, without encasing the bars
The methods adopted for repairing spalling and disintegration must be capab e of esto ing the ost
strength
References
[1]
Champion, S. Failure and Repair of Concrete Structures. J hn Wiley & S ns Inc. New York, 1961
[2]
Sidney.M.Johnson. Deterioration, Maintenance and Repair f Structures. Mc Graw-Hill Book
Company. New York, 1965.
[3]
Lee How Son and George C.S. Yuen . Building Maintenance Technology. Macmillan Distribution
Ltd. England. 1993.
[4]
Thomas H. McKaig. Building Failures.
Mc Graw-Hill Book Company. New York,
1962.
[5] Jagadish, R. Structural Failures - Case Histories. Oxford & IBH Publishing Co. Pvt.
New Delhi.1995.
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UNIT-7
Repair and Strengthening of Reinforced Concrete Beam-Column Joints: State of the Art
CONTENT
1. INTRODUCTION
1.1 RESEARCH SIGNIFICANCE
2. REPAIR AND STRENGTHENING TECHNIQUES FOR BEAM-COLUMN
JOINTS 2.1 Epoxy repair
2.2 Removal and replacement
2.3 Concrete jackets
2.4 Reinforced masonry blocks
2.5 Steel jackets and external steel elements
2.6 Fiber-reinforced polymeric composites
3. APPENDIX
4. CONCLUSIONS
5. REFERENCES
1. INTRODUCTION
RESEARCH SIGNIFICANCE
2.REPAIR AND S RENG HENING ECHNIQUES FOR BEAM-COLUMN JOINTS
2.1 Epoxy
repair
2.3 Concrete jackets
Concrete jackets continues…
2.5 Steel jackets and external steel elements
2.6 Fiber-reinforced polymeric composites
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APPENDIX
3. CONCLUSIONS
From the literature review on the performance, repair, and strengthening of nonseismically detailed RC
beam-column joints presented in this paper, the following conclusions were drawn:
1. The critical nonseismic joint details in existing RC structures have been well-identified as shown in Fig. 1; however, the investigation of their
effects on seismic behavior have been limited to testing of isolated one-way joints (no floor slab, transverse beams, bidirectional loads) to a
very arge extent, and 1/8-and 1/3-scale building models that may not accurately simulate the actual behavior of structural etails;
The authors believe that injection of epoxyWorldintojointssurrundedbyflmembeswouldbesimilarly
difficult;
2. Epoxy repair techniques have exhibited limited success in restoring the bond of einfo cement, in
filling the cracks, and restoring shear strength in one-way joints, although some autho s be ieve it to be
inadequate and unreliable.13
Conclusion
3. Concrete jacketing of columns and encasing the joint region in a reinforced fillet is an effective but
the most labor-intensive strengthening method due to difficulties in placing additional joint transverse
reinforcement.
Welding an external steel cage around the joint instead of adding internal steel has also proven effective
in the case of a three-dimensional interior joint test. These methods are successful in creating strong
column-weak beam mechanisms, but suffer from considerable loss of floor space and disruption to
building occupancy;
4. An analytical study showed that joint strengthening with reinforced masonry units can lead to
desirable ductile beam failures and reduction of interstory drifts; however, no experimental data
are available to validate their performance;
Conclusion
5. Grouted steel jackets tested to date cannot be practically applied in cases where floor members are
present. If not configured carefully, such methods can result in excessive capacity increases and
create unexpected failure modes.
Externally attached steel plates connected with rolled sections have been effective in preventing
local failures such as beam bottom bar pullout and column splice failure; they have also been
successfully used in combination with a reinforced concrete fillet surrounding the joint;
6. Externally bonded FRP composites can eliminate some important limitations of other
strengthening methods such as difficulties in construction and increases in member sizes.
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The shear strength of one-way exterior joints has been improved with ±45-degree fibers in the joint
region; however, ductile beam failures were observed in only a few specimens, while in others,
composite sheets debonded from the concrete surface before a beam plastic hinge formed. Reliable
anchorage methods need to be developed to prevent debonding and to achieve full development of
fiber strength within the small area of the joint, which can possibly lead to the use of FRPs in
important that testing programs be extendedWorldtoincludecriticaljinttypes(fexample,corner)under bidirectional cyclic loads.
strengthening of actual three-dimensional joints; and
Conclusion
7. Most of the strengthening schemes developed thus far have a limited range of app icabi ity, if any,
either due to the unaccounted floor members (that is, transverse beams and f oor s ab) in eal
structures or to architectural restrictions.
Experiments conducted to date have generally used only unidirectional load histo ies. The efore, the
research in this area is far from complete, and a significant am unt f w k is necessa y to a ive at
reliable, cost-effective, and applicable strengthening meth ds. In devel ping such methods, it is
REFERENCES
Engindeniz, M.; Kahn, L. F.; and Zureick, A., “Repair and Strengthening of Non-Seismically Designed RC
Beam-Column Joints: State-of-the- Art,” Research Report No. 04-4, Georgia Institute of Technology,
Atlanta, Ga., Oct. 2004, 58 pp. (available online at http:// www.ce.gatech.edu/groups/struct/reports)
Repair and Strengthening of Reinforced Concrete Beam-Column Joints: State of the Art. by Murat
Engindeniz, Lawrence F. Kahn, and Abdul -Hamid Zureick ,ACI Structural Journal, V. 102, No. 2,
March-April 2005.
THANK YOU

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UNIT-8
The Absolutes of Life
Some Other Absolutes of Life (other than Death and
Taxes) The Gosain Dictum No. 1
“So long as structures will keep on
getting built, failures will keep on occurring.”
The Gosain Dictum No. 2
“Failures will keep Forensics Engineers busy for a long time”
Primary Causes of Engineering Failures
Deferred maintenance
Design flaws
Material failures
Overloading
Combination of all the above
Gosain and Prasad Observation No. 1
Fear of failure will spur some owners to
action! Gosain and Prasad Observation No. 2
An action may be Structural Health Monitoring!
Some failures are sudden and catastrophic, and some failures just take their time…
Structural Health Monitoring (SHM) can be very helpful in serving as an alarm system for
preventing both types of failures ………….
But what is Structural Health Monitoring?
What is Structural Health Monitoring (SHM)?
Definition: The process of implementing a distress or damage detection strategy for aerospace,
mechanical and civil engineering structures is referred to as Structural Health Monitoring or
SHM.
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Not a new concept
Has been around for several decades
Advances in electronics made it easier to implement.
Several non-destructive evaluation (NDE) tools available for monitoring.
How old is SHM?
SHM work goes back almost 80
years. Limited to major structures
Dams
Bridges
Some early high rises
Unique structures
Significant interest in the past 10
years. Life-safety issues
Economic benefits
Performance evaluation
Affordable
Case History from the Past …
San Jacinto Monument
Built 1936
La Porte, exas
San Jacinto Monument Mat Foundation SHM
San acinto Monument Mat Foundation SHM
San acinto Monument Mat Foundation SHM
San acinto Monument Mat Foundation SHM
San Jacinto Monument Mat Foundation SHM
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San Jacinto Monument Mat Foundation SHM
San Jacinto Monument Mat Foundation SHM
San Jacinto Monument Mat Foundation SHM
San Jacinto Monument Mat Foundation SHM World
Objectives of Structural Health Monitoring: Farrar and Worden (2007)
1. Modifications to an existing structure,
2. Monitoring of structures affected by external factors,
3. Monitoring during demolition,
4. Structures subject to long-term movement degradati n f mate ials,
5. Feedback loop to improve future design based n experience,
Objectives of Structural Health Monitoring
6. Fatigue assessment,
7. Novel systems of construction,
8. Assessment of post-earthquake structural integrity, and
9. Growth in maintenance needs.
Instrumentation used for SHM
1. Strain gages,
2. Inclinometers,
3. Displacement transducers,
4. Accelerometers,
5. Temperature gages,
6. Pressure transducers,
7. Acoustic sensors,
8. Piezometers, and
9. Laser optical devices
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Instrumentation used for SHM
Most of these sensors can be wirelessly connected.
Technology using solar energy is very common in instrumentation.
Latest technology even has self powered systems, i.e. no external power required.
Some Recent Work…
Case History 1
Health Monitoring of a Stadium Truss During Erection
Health Monitoring of a Stadium Truss During Erection
Segmented Erection.
Monitor strains and stresses at various stages of erecti n.
Verification of predicted behavior was needed
Key Challenges
Non-interference with the construction schedule.
No wires were allowed to run from one segment to the
other. No main power supply.
No drilling or welding on to the frame.
Each segment needed to be prepared and instrumented in a narrow 2 day interval.
No lift access after erection.
Health Monitoring of a Stadium russ During Erection
Instruments
MicroStrain V-Link
4 Strain gauges could be attached to the device.
Fully ruggedized for exterior applications.
One laptop with data querying software was sufficient to access all boxes.
Low duty cycle can give up to 1 year of battery life.
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Case History 2
Health Monitoring of a Data Center
Health Monitoring of a Data Center
Health Monitoring of a Data Center
World
Key Challenges
Needed to prevent undesirable vibrations in the data center.
Quantify sensitivities of many high-performance computing systems.
Needed to inform the contractor immediately upon discovery of an issue.
Alarm system to alert Walter P Moore and the contract .
Health Monitoring of a Data Center
Instruments
Pre-construction Testing.
National Instruments dynamic data acquisition system.
PCB mG scale accelerometers.
Construction and Operations Time Monitoring
Instantel Blastmate device.
Case History 3
Health Monitoring of a Parking Garage Structure
Health Monitoring of a Parking Garage Structure
Key Challenges
Selection of monitoring location.
Selection of types of measurements.
Need to operate during power outages.
Sensor installation.
Data logger installation.
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Remote communication setup.
Alarm system to alert engineer and the
client. Instruments
Campbell Scientific CR10X logger with DC
backup. Inclinometers with temperature sensors.
Anemometer.
Rain gauge.
Health Monitoring of a Parking Garage Structure
Health Monitoring of a Parking Garage Structure
Case History 4
Health Monitoring of a Bridge Essential to Business Operati ns
Health Monitoring of a Bridge Essential to Business Operations
Key Challenges
Installation of inclinometers under girders.
Access was difficult.
Night time installation was preferred.
Installation has to be stopped when a train passed by under the
bridge. The whole system needed to be run with solar power.
Remote communication setup.
Alarm system to alert the engineer and the
client. Instruments
Campbell Scientific CR1000 logger with solar
power. Tilt beams with temperature sensors.
Cellular TCP/IP modem facilitates accessing data over the
internet Evaluate need
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Discuss the motivation in implementing SHM with the client and the benefits to be accrued
Discuss the period of time for monitoring
Have a clarity on how the damage or distress is to be defined and measured
Select the appropriate instrumentation and data acquisition system
Environmental conditions
Extract meaningful data
Presentation to client in a meaningful and understandable
format Reduce the implementation cost.
Improved hardware.
Extensive usage by the industry.
Implement wireless and self powered technology.
Facilitates usage even in remote areas.
Simplifies installation.
Insensitive to local power outages.
Estimate potential savings of using SHM.
Develop models to show potential savings in using SHM vs. periodic physical
inspections. Deferred Maintenance and SHM
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