Presentarion

Master of Science Thesis
Submitted by
Eng. Mohammad Fawzy Farouk Sayed
SHEAR BEHAVIOR OF EXTERNALLY
PRESTRESSED CONCRETE T-BEAMS
USING FRP TENDONS
Supervisors
Prof. Dr. Ahmed Sherif
Professor of Reinforced Concrete Structures
Structural Engineering Department, Ain Shams University
Dr. Ahmed Ghallab
Associate Professor of Structural Engineering
Structural Engineering Department, Ain Shams University
Dr. Mohamed A. Khafaga
Associate Professor of Structural Engineering,
Housing and Building National Research Center

CONTENTSCONTENTS OF THEOF THE
PRESENTATIONPRESENTATION

4- Analytical Work
2- Experimental Program
5- Conclusions and Recommendations
3- Test Results and Discussions
1- Introduction
CONTENTS OF THE PRESENTATIONCONTENTS OF THE PRESENTATION

INTRODUCTIONINTRODUCTION
Increased traffic loading
External prestressing system can be an effective solution
Many bridges all over the world require structural strengthening due to:
There are many ways of strengthening
Research MotivationResearch Motivation
Material defects
Problems in design

Moreover External Prestressing Is Used For New Constructions, Especially
Segmental Bridges.
External PrestressingExternal Prestressing

External PrestressingExternal Prestressing
Main Components of External Prestressing SystemMain Components of External Prestressing System
Prestressing tendons are unbonded and are outside the concrete section
DeviatorsEnd PlatesDucts/Tendons
Prestressing
Force

Advantages of External Prestressing:Advantages of External Prestressing:
Smaller Concrete Sections, Saving In Construction Cost .
Tendons Profile Not Restricted to Sec. Dimensions.
External Tendons Can Be Removed And Replaced Easily.
Friction Losses Are Significantly Reduced.
Easier And Faster To Construct.
FRP Tendons Are Highly Corrosion Resistance.

Disadvantages of External Prestressing:Disadvantages of External Prestressing:
Less Fire Resistance Especially When We Use FRP Tendons.
Long Term Performance Has Not Yet Been Explored.
Insufficient Ductility.
External Tendons Are Subjected To Vibrations And So Their Free Length
Should Be Limited

Aspects of the behavior include:
Experimentally Investigating the Shear Behavior of External Prestressing
Using Parafil Ropes, of Simply Supported T-section Beams.
Research ObjectiveResearch Objective
Cracking Patterns
The Shear Cracking and Shear Ultimate Loads
Mode of Failure
Prestressing Force in Parafil Ropes

EXPERIMENTALEXPERIMENTAL
PROGRAMPROGRAM

Four Prestressed R.C. T-Sec Concrete Beams Were Tested up to
Failure
EXPERIMENTAL PROGRAMEXPERIMENTAL PROGRAM
The Parameters Investigated Are:
1- Effective Shear Span to Depth Ratio (a/d).
2- Value of External Prestressing Force (P EXT).
Moreover, One More Beam With No External Prestressing (Control
Beam) Was Also Tested Up to Failure.

(mm) Pex Pex/Pult (N/mm 2
)
PS 1-1 G1 733 2.62 36 0.31
PS 1-2 G1 300 1.07 36 0.31
PS 1-3 G1,G2 450 1.61 36 0.31
PS 2-1 G2 450 1.61 48 0.41
RC G2 450 1.61 - -
Beam no. Group a/d
External
prestressing
force (kN)
36.3
f cu
Effective Shear
Span (a)

36 kN 36 kN
733 mm
PS 1-1 G1

36 kN 36 kN
300 mm
PS 1-2 G1

36 kN 36 kN
450 mm
PS 1-3 G1,G2

48kN 48kN
450 mm
PS 2-1 G2

450 mm
R.C. G2

Test SetupTest Setup
Using 2 Point Loading Mechanism.

InstrumentationInstrumentation

Properties of Materials Lab, Housing and Building National ResearchProperties of Materials Lab, Housing and Building National Research
Center.Center.

TEST RESULTSTEST RESULTS
AND DISCUSSIONSAND DISCUSSIONS

TEST RESULTS AND DISCUSSIONSTEST RESULTS AND DISCUSSIONS
Effect of Shear Span to Depth Ratio (a/d)Effect of Shear Span to Depth Ratio (a/d)
In All of The Tested Beams, Flexural Cracks Appeared First
Between The Two Concentrated Loads. Except Beam PS 1-2
(a=300 mm) The Shear Cracks Appeared First
Then Shear Cracks Appeared On The Shear Span at Higher
Load.
The Widths of The Shear Cracks Increased With The Increase In
Loading Until It Reached The Load of Failure.
The Cracking Load At Which The Cracks Were Observed Is Used
To Compare The Cracking Patterns Of The Tested Beams.
Cracking Patterns

PS1-3
PS1-3PS1-3
PS1-3
PS 1-1
PS 1-2
PS 1-3
PS1-2
PS1-2
PS1-2
PS1-2PS1-3
PS1-3
PS1-3
PS1-3
PS1-3
PS1-3
Cracking Patterns

Cracking and Ultimate Loads
PS 1-2a=300 mm
PS 1-1a=733 mm
PS 1-3a=450 mm

Relation Between
P & (a/d)
PS 1-2a=300 mm
PS 1-1a=733 mm
PS 1-3a=450 mm

a=300 mm
PS 1-1
Flexure
Failure
PS 1-2
Shear Failure
PS1-2
Mode Of Failure
PS 1-3
PS 1-3
PS 1-3
Shear Failure
a=733 mm
a=450 mm
PS1-2

Group 1
a/d
Variable
PS 1-2a=300 mm
PS 1-1a=733 mm
PS 1-3a=450 mm
Increase in External Prestressing Force

Relation Between Increase
In Tendon Force & (a/d)
PS 1-2a=300 mm
PS 1-1a=733 mm
PS 1-3a=450 mm

Effect of External Prestressing Force (PEffect of External Prestressing Force (PEXTEXT))
In All of The Tested Beams, Increasing The External Prestressing
Force Delayed The Appearance of Flexural Cracks And Decreased
The Rate of Crack Propagation
Increasing The External Prestressing Force Increased Its Vertical
Component And Hence Increased Shear-Cracking Load And
Reduced Number Of Diagonal Cracks.
Cracking Patterns

Pext =48 kNPext =36 kN
R.C.
Cracking Patterns
PS 2-1
PS2-1
PS2-1
PS2-1
PS2-1
PS2-1
PS1-3
PS1-3PS1-3
PS1-3
PS 1-3PS1-3
PS1-3
PS1-3
PS1-3
Pext = 0 kN

PS 1-3Pext =36 kN
RCPext = 0 kN
PS 2-1Pext =48 kN

Relation Between P & Pext
PS 1-3Pext =36 kN
RCPext = 0 kN
PS 2-1Pext =48 kN

Relation Between Increase
in Applied Load (%)P & Pext
PS 1-3Pext =36 kN
RCPext = 0 kN
PS 2-1Pext =48 kN

PS 1-3
Shear Failure
PS 2-1 R.C.
Shear Failure
PS 1-3 PS2-1
Shear Failure
PS 1-3
Mode of Failure

Group 2
Pext Variable
PS 1-3Pext =36 kN
PS 2-1Pext =48 kN

Relation Between The Increase In
Tendon Force & The Initial Pext
PS 1-3Pext =36 kN
PS 2-1Pext =48 kN

Shear Cracking and Ultimate LoadsShear Cracking and Ultimate Loads

ANALYTICAL WORKANALYTICAL WORK

Methods to Calculate the Ultimate Shear
Force of Prestressed Concrete Beams
Code Equations Proposed Equations By
Researchers
As Conventional Beams
With Normal Force
As Prestressed Beam

Beam Centre Line
Pext
Θ = 8°
Pext Cos θ
Pext Sin θ
Why Do We Think of The Conventional Beams??Why Do We Think of The Conventional Beams??
0.99Pext
0.14Pext
Almost ALL The Prestressing Force Converts to
Axial Compression Force on the Beam

Proposed Equations By Researchers
Code Equations
Methods to Calculate the Ultimate Shear Strength of Prestressed Concrete
Beams
Egyptian Code of Practice [ECP-203-2007]
ACI 318[2005]
Euro Code (BS EN1992-1-1:2004)
Australian Standard (AS 3600-2001)

Code Equations
ACI 318[2005]
Proposed Equations By Researchers
Methods to Calculate the Ultimate Shear Strength of Prestressed Concrete
Beams
Shaaban’s equation

Equations to Predict The Shear Strength And TheEquations to Predict The Shear Strength And The
Factors Taken Into Consideration For Each EquationFactors Taken Into Consideration For Each Equation
Axial Force Stirrups
Prestressing
Force
a/d
ECP [2007] √ √ √ √
ACI [2005] √ √ √ ----
Euro [2004] √ √ ---- √
AS [2001] √ √ √ √
Farahat [2003] ---- √ ---- √
Shaaban [2004] √ √ ---- √

Code EquationsCode Equations
s
cu
q
q
capacitytion +=
2
sec
sb
fnA
q
sys
s
)/( γ
=
)/07.01(24.0 c
c
cu
cu AN
f
q +=
γ
U
PU
C
cu
cu
M
dQf
q 6.3045.0 +=
γ

ACI 318[2005]
Un VV ≥φ
SCn VVV +=
)
14
1('17.0
g
U
wcc
A
N
dbfV +=
sdfAV yVS /=
db
M
dV
fV W
U
PU
cc 





+= 8.4'05.0

RdEd VV ≤
SRdCRdRd VVV ,, +=
( )( ) dbkfkCV wcpckCRdCRd σρ 1
3/1
1,, 100 +=
θcot, ywd
sw
sRd fZ
S
A
V =

*
VVu ≥φ
SUCUu VVV +=
vfsySVUS sdfAV θο cot)/( .=
3/1
'
321 





=
ο
οβββ
db
fA
dbV
v
cst
vuc
V
v
cptst
vuc PV
db
fAA
dbV ++







 +
= ο
ο
οβββ
3/1'
321
)(

Values of the Experimental and Predicted ShearValues of the Experimental and Predicted Shear
Strength Using the Different CodesStrength Using the Different Codes
Beam
PULT
Experimental
Ultimate
Shear Force,
kN
Predicted, kN Experimental / Predicted
ECP
[2007]
ACI
[2005]
EU
[2004]
AS
[2001]
ECP
[2007]
ACI
[2005]
EU
[2004]
AS
[2001]kN
PS 1-1 171 72.90 50.76 49.97 58.33 41.04 1.44 1.46 1.25 1.78
PS 1-2 293 138.10 49.52 48.50 53.83 62.33 2.79 2.85 2.57 2.22
PS 1-3 263 122.04 49.84 48.87 54.97 50.17 2.45 2.50 2.22 2.43
PS 2-1 269 120.90 49.69 48.70 54.43 49.97 2.43 2.48 2.22 2.42
RC 1 150 75.00 58.44 45.56 44.83 46.40 1.28 1.65 1.67 1.62

Relation between the Experimental and Predicted Results
from the ECP (2007) Equation

ACI 318[2005]
from the ACI (2005) Equation

from the Euro Code (EN2004) Equation

from the Australian Code (AS2001) Equation

The Methods Proposed by the Researcher to
Improve the Equations of the Egyptian Code
Neglecting the Limit
Stating That “the
shear stress before
reduction should
not be higher than
0.7 √(fcu/γc)” for a/d
≤ 2
Using the Full
Strength Rather
Than Half of the
Concrete Shear
Strength

Proposed Modifications By ResearcherProposed Modifications By Researcher
from the ECP [2007] Equation before and after Modification
(Complete Value of qcu) As Prestressed Beam

Proposed Modifications By ResearcherProposed Modifications By Researcher
from the ECP [2007] Equation before and after Modification
(2d/a) As Prestressed Beam

General Comparison Between Codes
Relation between the Effect of Shear Span to Depth
Ratio in Different Codes

General Comparison Between Codes
Relation between the Effect of Prestressing Force in
Different Codes

ycU fvadfV ρρ ++= /93'114.0
Proposed Equations By ResearchersProposed Equations By Researchers
Relation between the experimental and predicted results from
Farahat [2003] equation multiplied by the factor (1+0.07 N/Ac)
ycU fvadfV ρρ ++= /217'132.0
for a/d <3
for a/d ≥3

Proposed Equations By ResearchersProposed Equations By Researchers
Relation between the experimental and predicted
results from Shaaban [2004] equation
)/07.01](/9.0)/'13[( 3/1
cyvcU ANsdfAbdadfV ++= ρ
)/07.01](/9.0)/()/'660[( 3/43/1
cyvcU ANsdfAbdadadfV ++= ρ
For a/d ≥2.5
And for a/d <2.5

CONCLUSIONS ANDCONCLUSIONS AND
RECOMMENDATIONSRECOMMENDATIONS

Effect of Shear Span to Depth Ratio:Effect of Shear Span to Depth Ratio:
The Shear Span to Depth Ratio Governed The Crack Pattern Even
Flexure or Shear Crack Patterns.
Before Cracking, The Shear Span To Depth Ratio Has No Significant
Effect On The Increase of The Rope Load. But After Cracking It
Increases The External Prestressing Force Till Ultimate .
CONCLUSIONS AND RECOMMENDATIONSCONCLUSIONS AND RECOMMENDATIONS
The Shear Span To Depth Ratio Should Be Taken Into Consideration
When Analyzing And Designing Beams For Shear
Increasing Shear Span To Depth Ratio Increased The Appearance
Of Cracks And Increased The Cracks Propagation
Increasing the shear span to depth ratio from 1.07 to 1.61 decreased
shear cracking load by about 29%, and decreased the ultimate load
by about 11 %

Effect of External Prestressing Force:Effect of External Prestressing Force:
Cracking Load Increased To 117% When Strengthening The Tested
Beams Using External Prestressing Technique
Crack Widths and Cracks Propagation on The Strengthened Beams
Were Smaller Than on The Unstrengthened Beams.
The Gain In The Crack And Ultimate Shear Loads Due To The Increase
In External Prestressing Force From 36 kN To 48 kN Is Relatively Small
And Can Be Neglected.
The Value of The Initial External Prestressing Force Has a Negligible
Effect on The Increase In External Prestressing Force at Cracking Stage,
While at Ultimate Stage Increase In The External Prestressing Force
Increases as The Initial Prestressing Force Increase.
The Presence of External Prestressing Force Increases The Ultimate
Load of The Tested Beams By About 79 %

Analytical Investigation:Analytical Investigation:
Using Codes Equations For Ultimate Shearing Force Give Conservative
Results
The Australian Code As 3600-2001 Is Less Complicated, Time Consuming
And Give Fairly Conservative Results
Although the Inclination Angle of the Parafil Rope Is Too Small, Considering
The External Force As Prestressed Force And Using The Prestressing
Equations Give Much Better Accuracy, Than Considering It As Axial Force
Only And Using The Conventional RC Equations
Using The Full Strength Rather Than Half Of The Concrete Shear
Strength Improves The Accuracy of The Predicted Shear Strength
Of The Prestressed Beams
Neglecting The Limit Stating That “The Shear Stress Before
Reduction Should Not Be Higher Than 0.7 √(fcu/γc)” (for a/d ≤ 2)
Giving Higher Shear Accuracy Than Using This Limit
INECP-203
[2007]

RecommendationsRecommendations
From the Economic View, It Is Better to Use Moderate External
Prestressing Force. This Leads to Significant Improvement In The
Properties of Beams, in Addition to Using A Lower Capacity
Hydraulic Jack And Speeds The Strengthening Process.

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