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Graduation Project (1) Strengthening of an existing reinforced concrete structure

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Title: Graduation Project (1) Strengthening of an existing reinforced concrete structure


1
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

2
Introduction
  • Exclusive Summary
  • The general idea of the project.
  • Problems Facing reinforced concrete structures.

3
Exclusive Summary
  • The main achievements
  • Studying the Strengthening Methods.
  • Selection of an exiting building.
  • Experimental Test.
  • Beginning of Structural Analysis.

4
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.

5
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.

6
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.

7
Explanatory Sketch
Fig. 1 Techniques of plating reinforced concrete
beams.
8
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.

9
External Post-tensioned picture
10
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.

11
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.

12
Concrete Jackets(Section Enlargement)
13
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.

14
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.

15
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.

16
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.

17
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.

18
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.

19
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.

20
Fiber Reinforced Polymer
21
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.

22
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. 

23
FRP Laminate Structure
24
Types of FRP
  • The three main types of fibers used are
  • Carbon.
  • Glass.
  • Aramid.

25
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.

26
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.

27
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.

28
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.

29
Decision
30
Introduction
  • M.S.Project gantt chart.
  • Lab tests on FRP material.
  • Cost estimation for G.P.1

31
M.S. Project Gantt Chart
32
M.S. Project Gantt Chart
33
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.

34
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.

35
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.

36
Equipments
  • Digital balance.
  • Molds of beams and cubes.
  • Mixer.
  • Vibrator.
  • Hot water tank.
  • Oven.
  • Cube test machine.
  • Beam test machine.

37
Materials
  • Concrete mix water, cement, sand, coarse and
    small aggregates.
  • Plastic sheet.
  • FRP strips.
  • Strain gages.

38
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.

39
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.

40
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.

41
Experimental Result
42
Experimental Results
43
Experimental Results
44
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.

45
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.

46
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.

47
Cost Estimation
Total Cost 1496 Dhs (within the budget)
48
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.

49
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.

50
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

51
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.

52
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.

53
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 .

54
Prokon Structural Analysis Design
  • PROKON interface.

55
Prokon Structural Analysis Design
  • Input parameters.

56
Prokon Structural Analysis Design
  • Section dimensions.

57
Prokon Structural Analysis Design
  • Spans lengths.

58
Prokon Structural Analysis Design
  • Input loads.

59
Prokon Structural Analysis Design
  • Shear and Moment diagrams.

60
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.

61
Structural system of the building
  • The Floor cover 2 KN/m2.
  • The Live load 2 KN/m2.

62
Hurdy slab load
  • The unfactored loads calculation of the one way
    Hurdy slabs.

63
Comparison between hand Prokon results
  • Hand results

64
Comparison between hand results and Prokon results
  • PROKON results

65
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.

66
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.

67
Thank Youfor Listening
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