Repair Concrete

8/3/2019 Repair Concrete

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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
http://www.engg.uaeu.ac.ae/index.html


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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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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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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 interface.


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Input parameters.


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Section dimensions.


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Spans lengths.


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Input loads.


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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

Repair Concrete

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