INFLUENCE OF COATED STIRRUPS ON OVER OVERLAPPED SLAPPED SPLICE STRENGTH OF EPOXY COATED DEFORMED BARS
ABSTRACT.
This paper investigates the influence of coated stirrups on overlapped splice strength of epoxy coated deformed bars. Six (6) beams of length 2550mm Image 300mm Image with lapped splice bars in constant moment region were cast and tested. The beams where cast with 16mm high yield diameter bars for both compression and Tension zone, 8mm high yield stirrups were used over the lap splices.
The ultimate moment from the test were used to determine the stress developed in the bars. The ratios of the test bond stresses and bond stress values using the tensile reinforcement yield stressImage , were used for comparison of the parameter under investigation. Coated and uncoated Transverse reinforcement was found to increase the splice strength of epoxy coated deformed bars, but uncoated transverse reinforcement was found to increase the splice strength of epoxy coated bars more than coated transverse reinforcement.
TABLE OF CONTENTS PAGE
Title page…………………………………………………………………………...i
Certification………………………………………………………………………... ii
Dedication………………………………………………………………………….iii
Acknowledgement……………………………………………………………….....iv
Abstract………………………………………………………………………..…....v
Table of contents…………………………………………………………….……..vi
Notations……………………………………………………………………………ix
List of Tables……………………………………………………………………….xi
List of Figures……………………………………………………………………..xii
List of Plates………………………………………………………………………xii
CHAPTER ONE – INTRODUCTION
1.1 Background of study………………………………………………………...1
1.2 Aim and Objectives……………………………………………………...….2
1.3 Scope of Investigation…………………………………………………….. 2
1.4 Significance of Investigation………………………………………………..2
1.5 Mechanism of Bond failure……………………………………………….. 2 - 5
1.6 Factors affecting Bond……………………………………………………..5- 11
1.7 Code provision for Bond strength………………………………………… 12
CHAPTER TWO – LITERATURE REVIEW
2.1 Review on lap splice, bond strength and pull out test…………………. 13- 19
2.2 Review on parameter effect on bond……………………………………….19
2.2.1 Effect of stirrups………………………………………………………….19 - 21
2.2.2 Effect of coating……………………………………………………………22 - 24
2.2.3 Effect of concrete strength…………………………………………………24 - 25
2.2.4 Effect of depth of casting……………………………………………………25 - 27
CHAPTER THREE – METHODOLOGY
3.1 Fabrication of the test specimen………………………………………………28
3.11 Mix Proportions for the Investigation………………………………………..28
3.12 Steel Reinforcement Preparation……………………………………………..28
3.13 Preparation and Application of Coating Materials…………………………….28 – 29
3.14 Formwork Preparation…………………………………………………………..29
3.15 Casting of the Beams……………………………………………………………29
3.16 Specimen Identification……………………………………………………………29
3.17 Curing……………………………………………………………………………. 30
3.18 Specimen Description……………………………………………………………30 - 31
3.2 Quality control of materials used for the investigation……………………………32
3.2.1 Concrete……………………………………………………………………..32 -33
3.2.1.2 Sieve analysis……………………………………………………………….. 33
3.2.1.3 Silt test………………………………………………………………….. 34
3.2.1.4 Slump test………………………………………………………………….34
3.2.1.5 Compressive strength of concrete cubes………………………………………..34
3.2.1.6 Tensile strength on steel reinforcement……………………………………………35
3.2.2 Water……………………………………………………………………………….35
3.2.3 Cement………………………………………………………………………………35
3.3 Calculation of quantities of materials used for the investigation…………....... 35 - 37
CHAPTER FOUR – INSTRUMENTATION AND TEST PROCEDURE
4.1 Compression testing machine…………………………………………………38
4.2 Concrete mixer……………………………………………………………………38
4.3 Poker vibrator……………………………………………………………………38 – 39
4.4 Weighing balance……………………………………………………………………39
4.5 Dial gauge……………………………………………………………………............39
4.6 Hydraulic jack……………………………………………………………………39
4.7 Crane……………………………………………………………………………39 - 40
4.8 Test procedure………………………………………………………………………41
CHAPTER FIVE – ANALYSIS AND DISCUSSIN OF TEST RESULT
5.1 Analysis of test result…………………………………………………. 42- 57
5.2 Discussion of test result………………………………………………….. 58 - 61
CHAPRET SIX- CONCLUSION AND RECOMMENDATION
6.1 Conclusions………………………………………………………………….63
6.2 Recommendation……………………………………………………………63
References……………………………………………………………………….
NOTATION
ld Development length
MU Ultimate test bending moment
Q Applied load
ImageBS Ultimate bond stress recommended in BS 8110 : 1997
Imagecal Theoretical bond stress
Imaget Test bond stress
X Depth to neutral axis
Image Steel ratio, AS /bd
Imagee Effective bar size
Imagecu Strain in concrete in compression
Images Strain in tension reinforcement
Image Bond coefficient
As Area of steel
fs Stress in steel
ls Splice length
db Nominal bar diameter
Atr Area of transverse reinforcement
fcu Characteristics strength of concrete
av Shear span
St Spacing of transverse reinforcement
Ecs + Ustr Epoxy coated splice + uncoated stirrups
Ecs + Cstr Epoxy coated splice + coated stirrups
Ucs + Nstr Uncoated splice + no stirrup.
Tables
Table 1: Cube compressive strength result on trial mix
Table 2: Sieve analysis for fine aggregate
Table 3: sieve analysis for coarse aggregate
Table 4: Tensile test results
Table 5: Beam parameters
Table 6: Characteristics of hognestad stress block
Table 7: Beam data
Table 8: Strength achieved for control cubes
Table 9: Beam test results
Figures
Figure 1: Diagram showing side split failure
Figure 2: V-notch failure
Figure 3: Face-and-side split failure
Figure 4: Pull out failure
Figure 5: Beam with no transverse reinforcement in the splice region
Figure 6: Beam with transverse reinforcement overlap
Figure 7: Shear force and bending moment diagrams
Figure 8: Schematic of test set-up
Figure 9: Strain and stress distribution at failure
Figure 10: Hognestad and Evans stress block………………………………………..
Figure 11: Graph of sieve analysis for fine aggregate……………………………….
Figure 12: Graph of sieve analysis for coarse aggregate………………………..
Figure 11: Effect of coating of stirrups on bond efficiency………………..
Figure 12: Effect of coating of stirrups on bond efficiency……………………
Figure 13: Effect of coating of stirrups on bond efficiency…………………….
Plates
1. Trial Mix
(a) Sieve analysis of coarse aggregate for Trial mix
(b) Batching of coarse aggregate by weight for Trial mix
(C) Sieving of aggregate for Trial Mix
(d) Trial Mix freshly cast
2. Compressive strength of trial mix
(a) Weighing of Trial mix cube
(b) Compression testing machine
(c) Cube placed in compression testing machine
(d) Cube being taken out after crushing
3. Silt Test
(a) Sand and Salt Solution being mixed together
(b) Settling of particles in the measuring cylinder
4. Epoxy coated reinforcement
(a) Mixing of the coating material
(b) Spraying of the reinforcement
(c) Epoxy coated reinforcement
(d) Coated steel bars kept in the lab
5. Formwork in place
6. Reinforcement cages placed inside the formwork.
7. Slump test carried out in-situ
(a) Slump test being carried out
(b) Difference in height being measured
8. Beam specimen freshly demoulded
9. Curing process
10. Tensile strength
(a) Tensile testing machine
(b) Reinforcement being fixed in machine
(c) Tensile machine gripping the reinforcement
(d) Result being printed out
11. Crack pattern in beam with coated stirrups on coated splice region
(a) Splitting in the splice region.
(b) Cracks in the shear region.
12. Crack pattern in beams without stirrups on uncoated splice region
(a) Splitting in the splice region.
(b) Cracks in the shear region.
13. Crack pattern in beams with uncoated stirrups on coated splice region
(a) Splitting in the splice region.
(b) Cracks in the shear region.
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