INFLUENCE OF COATED STIRRUPS ON OVER OVERLAPPED RLAPPED SPLICE STRENGTH OF EPOXY COATED DEFORMED BARS


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.

.

INFLUENCE OF COATED STIRRUPS ON OVER OVERLAPPED RLAPPED SPLICE STRENGTH OF EPOXY COATED DEFORMED BARS



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