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Graduation Project (1)
Strengthening of an existing
reinforced concrete structure
Student Name ID No.Nabil Raweh Qahtan 980410066
Mohammed Eisa Al-Harrasi 980710101
Hazem Bakri Al-Naser 199901443
United Arab Emirates University
College of Engineering
Civil and Environmental Department
Instructor: Dr. Ashraf Biddah
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Introduction
Exclusive Summary
The general idea of the project.
Problems Facing reinforced concretestructures.
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Exclusive Summary
The main achievements:
Studying the Strengthening Methods.
Selection of an exiting building. Experimental Test.
Beginning of Structural Analysis.
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The general idea of the project The owner of a residential building wanted
to convert his building to a commercialbuilding.
According to change in the use of existingstructure, the structural system of thebuilding will be modified to fit the newchanges.
PROBLEM: The old building cannot carrythe new loads that come from the changes.
DESIGN BRIEF : Design a strengtheningsystem that can increase the capacity of theexisting structural system to be able tocarry the new loads that come from the
changes.
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Problems Facing ReinforcedConcrete Structures
Load increases.
Damage to structural parts.
Improvements in suitability for use.
Modification of structural system.
Errors in planning or construction.
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STRENGTHENING REINFORCEDCONCRETE STRUCTURES BY BONDINGSTEEL PLATES:
Strengthening is the process ofadding capacity to a member ofstructure.
Attachment of steel to concrete:1. Adhesive connecting mechanism.
2. Bolting connecting mechanism.
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Explanatory Sketch
Fig. 1 Techniques of plating reinforced concrete beams.
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STRENGTHENING REINFORCEDCONCRETE STRUCTURES BYPRESTRESSING CABLES:
Post-tensioning is a techniqueused to prestress reinforced concreteafter concrete is placed.
The tensioning provides the memberwith an immediate and active load-carrying capability.
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External Post-tensioned picture
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The advantages of ExternalPrestressing
Ability to restress, destress andexchange any external prestressingcable.
Crack free members.
Reduce deflection.
High fatigue and impact resistance.
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The Disadvantages of ExternalPrestressing
Usually requiring a greater sectiondepth.
More exposed to environmentalinfluences (fire, vandalism,aggressive chemicals etc.).
Handling of the tensioning devicesmay be more difficult.
High cost.
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Concrete Jackets(Section Enlargement)
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Concrete Jackets(Section Enlargement)
Enlargement is the
placement of additional
concrete and reinforcing
steel on an existingstructural member.
Beams, slabs, columns,
and walls, if necessary,
can be enlarged to add
stiffness or load-carrying
capacity.
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Concrete Jackets
In most cases, the
enlargement must be
bonded to the existing
concrete to create a
monolithic member for
additional shear orflexural capacity.
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Column Compressive strengthening bySection Enlargement
Enlarging the cross section of
an existing column will
strengthen the column by
increasing its load carrying
capacity.
A column can be enlarged in
various configurations.The drying shrinkage effects in
the concrete used to enlarge the
column must be considered.
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Section EnlargementMethod A
In the illustration, Method A
will accomplish efficient load
transfer if the new portion is cast
with a bond breaker between the
new and old concrete.
After most of the drying
shrinkage has occurred, the tiesthat link the old and new
concrete can be installed.
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Section EnlargementMethod A
The gap between the new
portion of the column and the
existing member (to be partially
supported by this column) can
be filled with dry packing
material.
This will allow the newmaterial to share its portion of
the load.
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Section EnlargementMethods B & C
When Methods B and C are used,
extreme care should be exercised to
select concrete mix designs with very
low shrinkage rates.
Pre placed aggregate concrete
generally offers the lowest drying
shrinkage; it is, therefore, anexcellent material for column
enlargements.
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Disadvantages of the concretejackets
Increasing the size of the element, which make
its usage very limited.
Difficult to construct in some active buildings
such as hospitals, schools because of the noise
of equipments.
Needs shuttering, formworks, reinforced steel,concrete, concrete pumps, vibrators, etc.
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Fiber ReinforcedPolymer
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Fiber Reinforced Polymer (FRP)
FRP is a new class of compositematerial for the development and
repair of new and deterioratingstructures in Civil Engineering.
Search for alternatives to Steel andalloys to combat the high costs of
repair and maintenance of structuresdamaged by corrosion and heavy use.
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FRP Laminate Structure
FRPs are organized in a laminatestructure.
each lamina (flat layer) contains anarrangement of unidirectional fibersfabrics embedded within a thin layerof light polymer matrix material.
FRP consists of two maincomponents:
1.Fibers.
2.Resin or Matrix.
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FRP Laminate Structure
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Types of FRP
The three main types of fibersused are:
Carbon. Glass.
Aramid.
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Suitability of FRP for Uses inStructural Engineering
FRP properties and advantages makes itideal for wide spread applications in
construction worldwide.
FRP has a few disadvantages.
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Advantages of FRP:
Corrosion Resistance.
Lightweight.
Ease of installation.
Less Finishing.
Less maintenance.
Ductility of FRP wrapped membersimproves dramatically.
They are ideal for external
application.
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Advantages of FRP
They are extremely durable.
They are available in variousforms:sheets, plates, fabric, etc.
They are available in long lengthsthat eliminates joints andsplices.
They cure within 24 hours.
Versatility.
Anti-seismic behavior.
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Disadvantages of FRP
High cost, susceptibility to
deformation under long-term loads Temperature and moisture effects,
lack of design codes, and most
importantly, lack of awareness.
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Decision
FRPConcretejacketing
Steel plates
Corrosion resistanceMedium CorrosionHigh Corrosion
High CostHigh CostLow Cost
Ease of installation.High Installation costHigh Installationcost
Less Maintenancemore Maintenancemore Maintenance
light WeightHeavy WeightHeavy Weight
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Introduction
M.S.Project gantt chart. Lab tests on FRP material.
Cost estimation for G.P.1
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M.S. Project Gantt Chart
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M.S. Project Gantt Chart
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Beams Details
This experiment consists of 16 beams and 6cubes.
Beams were divided to 4 groups, each groupconsists of 4 beams with four differentreinforcements.
Beams dimensions were 10cm x 10cm x50cm.
Minimum reinforcement of one bar with 6mmdiameter (16) was used.
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Groups Environment
Each group was exposed to four differentenvironments as follows:
Group 1: Room temperature with 26oC.Group 2: Hot water tank with 100 % humidity at 45oC.Group 3: Oven (0% humidity) at 45oC.
Group 4: Outside exposed to sun radiation and the
variation in temperature through the 24hours.
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Digital balance.
Molds of beams and cubes.
Mixer. Vibrator.
Hot water tank.
Oven.
Cube test machine.
Beam test machine.
Equipments
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Procedures
Steel reinforcements wereprepared.
Strain gages were fixed on thesteel reinforcement.
Concrete ingredients werecalculated, weighted andmixed using a big mixer.
Concrete was poured in the
molds of beams and cubes. Concrete was vibrated and
covered by plastic sheet.
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Procedures
3 cubes were tested after 7 days.
Concrete beams and cubes were
removed from molds and cured inpotable water for 14 days.
Beams and cubes were exposed to
air drying in laboratory.
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Procedures
FRP was applied withlayer of epoxy.
Beams were exposed tothe differentenvironments for 1000hours.
3 cubes was tested after28 days.
All beams was testedafter 1000 hours.
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Experimental Result
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Experimental Results
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Experimental Results
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Experimental Observations
1. Effect of Fiber Reinforcement Polymer(FRP) on strengthening the beams:
One FRP strip increased the beam'scapacity by about 100% for allenvironments.
Two strips of FRP increased the beam'scapacity by about 200% for allenvironments.
All reinforced beams strengthen with FRPfailed on de-bonding of the FRP at the endof strips due to the shear force at this
location.
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Experimental Observations
2. Environmental effect on thebeams:
The effect of environment on reinforced
concrete beams with steel only isnegligible.
Plain concrete with one strip of FRP(shear force) was affected in hot
environments (humid and dry). Wherethe effect of outdoor and indoorenvironments was negligible.
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Experimental Observations
The reinforced concrete beams strengthenwith FRP; (bond capacity between theFRP and the concrete) was affected in hot
and humid environment. Although the FRP in the outdoor
environment was subjected to the UltraViolet during the 1000 hrs exposure, noreduction in the beam capacity wasnoticed.
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Cost Estimation
Total Cost = 1496 Dhs (within the budget)
Total
Cost
Dhs
# unitsCost/
unit
ManufacturersItem DescriptionItem #
6252525INSTALLATIONmiddle east
5MM Steel Strain Gages Single1
44222INSTALLATIONmiddle east
Super Glue 5g Bottle2
5257 m75Dhs/m
Sika CompanyFiber Reinforcement Polymerstrips (Sika Carbodur S type)
3
150625Sika CompanyFRP Epoxy (Sikadur 30normal)(6kg)
4
24122Al-Moazam storesReinforcement Steel Bars (#6)5
68174Drawings Copying6
60125/beamReinforcement Steel Welding7
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Analysis background
The most important and mostdifficult task faced by the structuraldesigner is the accurate estimation
of the loads that may be applied tothe structure during its life.
The next problem is to decide the
worst possible combinations of theseloads that might occur at one time.
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Analysis background
The loads that will be used in thisproject are dead and live loads.
Dead loads are loads of constantmagnitude that remain in oneposition.
Live loads are loads that can changein magnitude and position.
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Analysis background
ACI code (9.2) states that therequired ultimate load carryingability of the member U provided to
resist the dead load D and the liveload L must at least equal:
U = 1.4D + 1.7L
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Analysis background
The Loads carried by the structure aretransferred from one structural element toanother until it reaches its final destination
to the supporting ground.
The loads that come from slabs to beamscan be estimated according to the slabs
design system and the geometry of theseslabs.
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Analysis background
In one direction slabs the beam iscarrying half of the slab as arectangular or square shape.
In two way slabs the each beamaround the slab is carrying triangle
or trapezoidal shape of the slab.
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Prokon Structural Analysis & Design
Prokon structural analysis and designis a useful tool for analysis anddesign of structures.
The PROKON suite has two maincomponents:
PROKON Calcpad. PROKON analysis and design
modules .
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Prokon Structural Analysis & Design
PROKON interface.
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Prokon Structural Analysis & Design
Input parameters.
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Prokon Structural Analysis & Design
Section dimensions.
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Prokon Structural Analysis & Design
Spans lengths.
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Prokon Structural Analysis & Design
Input loads.
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Prokon Structural Analysis & Design
Shear and Moment diagrams.
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Structural system of the building
Area = 750 m2.
It consists of two stories.
Types of slabs: One way Hurdy
slabs, two way hurdy slabs and twoway solid slabs.
Types of columns: Rectangular and
circular. There are projected beams and
hidden beams.
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Hurdy slab load
The unfactored loads calculation ofthe one way Hurdy slabs.
Comparison between hand &
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Comparison between hand &Prokon results
Hand results:
mKNweightWall
m
KNmm
m
KNWeightSelf
75.5
48.02.0253
KNlWu
Vu
mKNlWuMu
m
KN
m
KN
m
KNWu
5.352
2.565.13
2
.137.468
)2.5(65.13
8
)(
65.13)475.5(4.1
22
Comparison between hand results
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Comparison between hand resultsand Prokon results
PROKON results:
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Conclusion
It was learned some moderntechnologies in strengtheningconcrete structures.
It was learned a new computersoftware program.
The a knowledge that we gained
from structural analysis and designcourses were applied.
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Conclusion
From the experimental results, it wasfound that the FRP was effected by20 % in the hot (0% humidity)
environment. It was decided to use FRP to strength
the building.
It was learned how to analyze oneway Hurdy slabs and beams.
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Thank You
for Listening