Graduation Project 1 Strengthening of an existing reinforced concrete structure

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Graduation Project (1)Strengthening of an
existing reinforced concrete structure
United Arab Emirates University College of
Engineering Civil and Environmental Department
Instructor Dr. Ashraf Biddah

• Student Name ID No.
• Nabil Raweh Qahtan 980410066
• Mohammed Eisa Al-Harrasi 980710101
• Hazem Bakri Al-Naser 199901443

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Introduction

• Exclusive Summary
• The general idea of the project.
• Problems Facing reinforced concrete structures.

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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 commercial building.
• According to change in the use of existing
  structure, the structural system of the building
  will be modified to fit the new changes.
• PROBLEM   The old building cannot carry the new
  loads that come from the changes.
• DESIGN BRIEF Design a strengthening system that
  can increase the capacity of the existing
  structural system to be able to carry the new
  loads that come from the changes.

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Problems Facing Reinforced Concrete 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 REINFORCED CONCRETE STRUCTURES BY
BONDING STEEL PLATES

• Strengthening is the process of adding capacity
  to a member of structure.
• Attachment of steel to concrete
• Adhesive connecting mechanism.
• Bolting connecting mechanism.

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Explanatory Sketch
Fig. 1 Techniques of plating reinforced concrete
beams.
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STRENGTHENING REINFORCED CONCRETE STRUCTURES BY
PRESTRESSING CABLES

• Post-tensioning is a technique used to prestress
  reinforced concrete after concrete is placed.
• The tensioning provides the member with an
  immediate and active load-carrying capability.

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External Post-tensioned picture
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The advantages of External Prestressing

• Ability to restress, destress and exchange any
  external prestressing cable.
• Crack free members.
• Reduce deflection.
• High fatigue and impact resistance.

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The Disadvantages of External Prestressing

• Usually requiring a greater section depth.
• More exposed to environmental influences (fire,
  vandalism, aggressive chemicals etc.).
• Handling of the tensioning devices may 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 existing
  structural 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 or flexural capacity.

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Column Compressive strengthening by Section
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 ties that 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 new material 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, an
  excellent material for column enlargements.

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Disadvantages of the concrete jackets

• 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 Reinforced Polymer
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Fiber Reinforced Polymer (FRP)

• FRP is a new class of composite material for the
  development and repair of new and deteriorating
  structures in Civil Engineering.
• Search for alternatives to Steel and alloys to
  combat the high costs of repair and maintenance
  of structures damaged by corrosion and heavy use.

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FRP Laminate Structure

• FRPs are organized in a laminate structure.
• each lamina (flat layer) contains an arrangement
  of unidirectional fibers fabrics embedded within
  a thin layer of light polymer matrix material.
• FRP consists of two main components
• Fibers.
• Resin or Matrix. 

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FRP Laminate Structure
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Types of FRP

• The three main types of fibers used are
• Carbon.
• Glass.
• Aramid.

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Suitability of FRP for Uses in Structural
Engineering

• FRP properties and advantages makes it ideal 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 members improves
  dramatically.
• They are ideal for external application.

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Advantages of FRP

• They are extremely durable.
• They are available in various forms sheets,
  plates, fabric, etc.
• They are available in long lengths that
  eliminates joints   and splices.
• 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
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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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Experimental lab test on FRP material.

• The main objective of this experiment was to
  study the effect of different environments on the
  behavior of FRP material.

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Beams Details

• This experiment consists of 16 beams and 6 cubes.
• Beams were divided to 4 groups, each group
  consists of 4 beams with four different
  reinforcements.
• Beams dimensions were 10cm x 10cm x 50cm.
• Minimum reinforcement of one bar with 6mm
  diameter (1F6) was used.

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Groups Environment

• Each group was exposed to four different
  environments 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 24 hours.

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Equipments

• Digital balance.
• Molds of beams and cubes.
• Mixer.
• Vibrator.
• Hot water tank.
• Oven.
• Cube test machine.
• Beam test machine.

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Materials

• Concrete mix water, cement, sand, coarse and
  small aggregates.
• Plastic sheet.
• FRP strips.
• Strain gages.

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Procedures

• Steel reinforcements were prepared.
• Strain gages were fixed on the steel
  reinforcement.
• Concrete ingredients were calculated, weighted
  and mixed 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 in potable water for 14 days.
• Beams and cubes were exposed to air drying in
  laboratory.

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Procedures

• FRP was applied with layer of epoxy.
• Beams were exposed to the different environments
  for 1000 hours.
• 3 cubes was tested after 28 days.
• All beams was tested after 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

• Effect of Fiber Reinforcement Polymer (FRP) on
  strengthening the beams
• One FRP strip increased the beam's capacity by
  about 100 for all environments.
• Two strips of FRP increased the beam's capacity
  by about 200 for all environments.
• All reinforced beams strengthen with FRP failed
  on de-bonding of the FRP at the end of strips due
  to the shear force at this location.

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Experimental Observations

• Environmental effect on the beams
• The effect of environment on reinforced concrete
  beams with steel only is negligible.
• Plain concrete with one strip of FRP (shear
  force) was affected in hot environments (humid
  and dry). Where the effect of outdoor and indoor
  environments was negligible.

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Experimental Observations

• The reinforced concrete beams strengthen with
  FRP (bond capacity between the FRP and the
  concrete) was affected in hot and humid
  environment.
• Although the FRP in the outdoor environment was
  subjected to the Ultra Violet during the 1000 hrs
  exposure, no reduction in the beam capacity was
  noticed.

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Cost Estimation
Total Cost 1496 Dhs (within the budget)
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Analysis background

• The most important and most difficult task faced
  by the structural designer is the accurate
  estimation of the loads that may be applied to
  the structure during its life.
• The next problem is to decide the worst possible
  combinations of these loads that might occur at
  one time.

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Analysis background

• The loads that will be used in this project are
  dead and live loads.
• Dead loads are loads of constant magnitude that
  remain in one position.
• Live loads are loads that can change in magnitude
  and position.

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Analysis background

• ACI code (9.2) states that the required ultimate
  load carrying ability of the member U provided to
  resist the dead load D and the live load L must
  at least equal
• U 1.4D 1.7L

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Analysis background

• The Loads carried by the structure are
  transferred from one structural element to
  another until it reaches its final destination to
  the supporting ground.
• The loads that come from slabs to beams can be
  estimated according to the slabs design system
  and the geometry of these slabs.

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Analysis background

• In one direction slabs the beam is carrying half
  of the slab as a rectangular or square shape.
• In two way slabs the each beam around the slab is
  carrying triangle or trapezoidal shape of the
  slab.

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Prokon Structural Analysis Design

• Prokon structural analysis and design is a useful
  tool for analysis and design of structures.
• The PROKON suite has two main components
• 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 two way solid slabs.
• Types of columns Rectangular and circular.
• There are projected beams and hidden beams.

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Structural system of the building

• The Floor cover 2 KN/m2.
• The Live load 2 KN/m2.

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Hurdy slab load

• The unfactored loads calculation of the one way
  Hurdy slabs.

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Comparison between hand Prokon results

• Hand results

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Comparison between hand results and Prokon results

• PROKON results

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Conclusion

• It was learned some modern technologies in
  strengthening concrete structures.
• It was learned a new computer software program.
• The a knowledge that we gained from structural
  analysis and design courses were applied.

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Conclusion

• From the experimental results, it was found that
  the FRP was effected by 20 in the hot (0
  humidity) environment.
• It was decided to use FRP to strength the
  building.
• It was learned how to analyze one way Hurdy slabs
  and beams.

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Thank Youfor Listening