Transcript STRENGTHENING REINFORCED CONCRETE STRUCTURES BY …

United Arab Emirates University
College of Engineering
Civil and Environmental Department
Graduation Project (1)
Strengthening of an existing
reinforced concrete structure
Instructor: Dr. Ashraf Biddah
Student Name
Nabil Raweh Qahtan
Mohammed Eisa Al-Harrasi
Hazem Bakri Al-Naser
ID No.
980410066
980710101
199901443
Introduction
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Exclusive Summary
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The general idea of the project.
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Problems Facing reinforced concrete
structures.
Exclusive Summary
The main achievements:
 Studying the Strengthening Methods.
 Selection of an exiting building.
 Experimental Test.
 Beginning of Structural Analysis.
The general idea of the project
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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.
Problems Facing Reinforced
Concrete Structures
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Load increases.
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Damage to structural parts.
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Improvements in suitability for use.
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Modification of structural system.
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Errors in planning or construction.
STRENGTHENING REINFORCED
CONCRETE STRUCTURES BY BONDING
STEEL PLATES:
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Strengthening is the process of
adding capacity to a member of
structure.
Attachment of steel to concrete:
Adhesive connecting mechanism.
Bolting connecting mechanism.
Explanatory Sketch
Fig. 1 Techniques of plating reinforced concrete beams.
STRENGTHENING REINFORCED
CONCRETE STRUCTURES BY
PRESTRESSING CABLES:
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Post-tensioning is a technique
used to prestress reinforced concrete
after concrete is placed.
The tensioning provides the member
with an immediate and active loadcarrying capability.
External Post-tensioned picture
The advantages of External
Prestressing
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Ability to restress, destress and
exchange any external prestressing
cable.
Crack free members.
Reduce deflection.
High fatigue and impact resistance.
The Disadvantages of External
Prestressing
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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.
Concrete Jackets
(Section Enlargement)
Concrete Jackets
(Section Enlargement)
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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.
Concrete Jackets
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In most cases, the
enlargement must be
bonded to the existing
concrete to create a
monolithic member for
additional shear or
flexural capacity.
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.
Section Enlargement
Method 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.
Section Enlargement
Method 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.
Section Enlargement
Methods 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.
Disadvantages of the concrete
jackets
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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.
Fiber Reinforced
Polymer
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
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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:
1.Fibers.
2.Resin or Matrix.
FRP Laminate Structure
Types of FRP
The three main types of fibers
used are:
• Carbon.
• Glass.
• Aramid.
Suitability of FRP for Uses in
Structural Engineering
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FRP properties and advantages makes it
ideal for wide spread applications in
construction worldwide.
FRP has a few disadvantages.
Advantages of FRP:
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Corrosion Resistance.
Lightweight.
Ease of installation.
Less Finishing.
Less maintenance.
Ductility of FRP wrapped members
improves dramatically.
They are ideal for external
application.
Advantages of FRP
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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.
Disadvantages of FRP
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High cost, susceptibility to
deformation under long-term loads
Temperature and moisture effects,
lack of design codes, and most
importantly, lack of awareness.
Decision
Steel plates
Concrete
jacketing
FRP
High Corrosion
Medium Corrosion
Corrosion resistance
Low Cost
High Cost
High Cost
High Installation
cost
High Installation cost Ease of installation.
more Maintenance
more Maintenance
Less Maintenance
Heavy Weight
Heavy Weight
light Weight
Introduction
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M.S.Project gantt chart.
Lab tests on FRP material.
Cost estimation for G.P.1
M.S. Project Gantt Chart
M.S. Project Gantt Chart
Experimental lab test on FRP
material.
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The main objective of this experiment
was to study the effect of different
environments on the behavior of FRP
material.
Beams Details
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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 (1Φ6) was used.
Groups Environment
Each group was exposed to four different
environments as follows:
Group 1:
o
 Room temperature with 26 C.
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.
Equipments
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Digital balance.
Molds of beams and cubes.
Mixer.
Vibrator.
Hot water tank.
Oven.
Cube test machine.
Beam test machine.
Materials
Concrete mix: water,
cement, sand, coarse
and small aggregates.
 Plastic sheet.
 FRP strips.
 Strain gages.
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Procedures
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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.
Procedures
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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.
Procedures
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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.
Experimental Result
Experimental Results
Experimental Results
Experimental Observations
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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.
Experimental Observations
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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.
Experimental Observations
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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.
Cost Estimation
Item # Item Description
Manufacturers
Cost/
unit
# units
Total
Cost
Dhs
1
5MM Steel Strain Gages Single
INSTALLATION
middle east
25
25
625
2
Super Glue 5g Bottle
INSTALLATION
middle east
22
2
44
3
Fiber Reinforcement Polymer Sika Company
strips (Sika Carbodur S type)
75
Dhs/m
7m
525
4
FRP Epoxy
normal)(6kg)
25
6
150
5
Reinforcement Steel Bars (#6)
2
12
24
6
Drawings Copying
4
17
68
7
Reinforcement Steel Welding
5/beam
12
60
(Sikadur
30 Sika Company
Al-Moazam stores
Total Cost = 1496 Dhs (within the budget)
Analysis background
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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.
Analysis background
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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.
Analysis background
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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
Analysis background
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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.
Analysis background
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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.
Prokon Structural Analysis &
Design
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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 .
Prokon Structural Analysis & Design
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PROKON interface.
Prokon Structural Analysis & Design
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Input parameters.
Prokon Structural Analysis & Design
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Section dimensions.
Prokon Structural Analysis & Design
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Spans lengths.
Prokon Structural Analysis & Design
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Input loads.
Prokon Structural Analysis & Design
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Shear and Moment diagrams.
Structural system of the building
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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.
Structural system of the building
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The Floor cover = 2 KN/m2.
The Live load = 2 KN/m2.
Hurdy slab load
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The unfactored loads calculation of
the one way Hurdy slabs.
Comparison between hand &
Prokon results
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Hand results:
KN
KN

0
.
2
m

0
.
8
m

4
m
m3
KN
Wa ll weig h t  5.7 5
m
S elf Weig h t  2 5
KN
KN
KN
4
)  13.65
m
m
m
Wu  (l ) 2
13.65  (5.2) 2
Mu 

 46.137 KN .m
8
8
Wu  l
13.65  5.2
Vu 

 35.5 KN
2
2
Wu  1.4 ( 5.75
Comparison between hand results
and Prokon results
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PROKON results:
Conclusion
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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.
Conclusion
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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.
Thank You
for Listening