Evaluation of technical and economic effectiveness of Fiber Reinforced Polymer (FRP) solutions in repair/strengthening of steel bridges in Vietnam

Based on norms, documents, announcements of Vietnam, research has estimated the unit price for three methods of reinforcement, repair for a horizontal/collar beam replacing collar beams,

VIETNAM NATIONAL UNIVERSITY

VIETNAM JAPAN UNIVERSITY

NGUYEN HUU HOE

EVALUATION OF TECHNICAL AND ECONOMIC EFFECTIVENESS OF FIBER

REINFORCED POLYMER (FRP)

SOLUTIONS IN REPAIRING/STRENGTHENING OF STEEL

i

ACKNOWLEDGEMENT

At the very beginning, I would like to express my deepest gratitude to Vietnam National University - Vietnam Japan University (VJU) that gave me the chance to learning and studying VJU gives me a modern international and professional environment The studying opportunity which I had at Vietnam Japan University was

a great chance for learning and professional development Therefore, I consider myself a very lucky individual as I was provided with an opportunity to be a part of

it I am also grateful for having a chance to meet so many wonderful people and professionals who led me through this studying and researching period The studying time at VJU is a really valuable time for me

I express my deepest thanks and gratefulness to Assoc Prof Luong Xuan Binh for his careful and precious guidance which were extremely valuable for my study both theoretically and practically I choose this moment to acknowledge his contribution gratefully

I would like to express my deepest gratitude and special thanks to Prof Miyajima in Kanazawa University who in spite of being extraordinarily busy with his duties, took time out to hear, guide and keep me on the correct path and allowing me

to carry out my research at his lab and extending during the internship

It is my radiant sentiment to place on record my best regards, deepest sense of gratitude to Prof Nguyen Dinh Duc, Prof Hironori Kato, Prof Dao Nhu Mai, Dr Phan Le Binh, Dr Nguyen Tien Dung, and all professors, lecturers from the program

of Infrastructures Engineering for their useful orientations and their willing advices

to help me complete this thesis

Sincerely yours,

Nguyen Huu Hoe

ii

TABLE OF CONTENTS

Page

LIST OF FIGURES iv

LIST OF CHARTS v

LIST OF TABLES vi

LIST OF NOMENCLATURES AND ABBREVIATIONS vii

UNIT OF SI SYSTEM viii

ABSTRACT 1

INTRODUCTION 2

1 The necessary of the study 2

2 The objective of the study 2

3 Methodology 3

4 The object and scope of the study 3

5 The layout of the thesis 3

Chapter 1 : LITERATURE REVIEW 4

Chapter 2 : OVERVIEW OF TECHNICAL ISSUES OF REPAIRING AND STRENGTHENING STEEL BRIDGE STRUCTURE IN VIETNAM 7

2.1 Typical forms of damages of steel bridge structure in Vietnam 7

2.2 Traditional solutions to repair and reinforce steel bridges 7

2.2.1 Repair solutions 7

2.2.2 Some methods of reinforcing the steel span structure 13

2.3 Technical requirements of steel bridge repair and reinforcement 13

2.4 Develop criteria for selecting FRP materials for the repair and reinforcement of steel bridges 14

Chapter 3 : SOME EXPERIMENTAL RESEARCHES USING FRP MATERIALS IN REPAIRING, STRENGTHENING STEEL STRUCTURE AND ANALYSIS OF TECHNICAL EFFICIENCY OF SOLUTIONS 16

3.1 Experiment 1: Experiment on glue resistance of TYFO WS 16

3.1.1 Experimental purpose 16

3.1.2 Experimental setup 16

3.1.3 Processing experimental data 23

3.1.4 Comment and conclusion on experimental results 27

3.2 Experiment 2: Bending test of steel samples reinforced with FRP materials 28

3.2.1 Experimental purpose 28

3.2.2 Experimental setup 28

iii

3.2.3 Processing experimental data 33

3.2.4 Comment and conclusion on experimental results 41

3.3 Conclusion of technical efficiency 42

Chapter 4 : EVALUATE THE ECONOMIC EFFICIENCY OF THE SOLUTIONS USING FRP MATERIALS ON REPAIRING STEEL BRIDGE STRUCTURE IN VIETNAM, CASE STUDY LONG BIEN BRIDGE 44

4.1 Causes and deterioration of Long Bien Bridge 44

4.1.1 Overview of history, operation of Long Bien Bridge 44

4.1.2 Damaged condition of the Long Bien bridge 46

4.1.3 Damaged classification: 48

4.2 Protection and reinforcement measures have been used 49

4.2.1 Use U-shaped steel plate to cover the collar beam 49

4.2.2 Use steel plates to compensate for corrosion, puncture with welding or rivets for bonding Then use special paint to paint on 51

4.2.3 Replace collar beam by new one 52

4.3 Develop solutions for repairing and strengthening Long Bien Bridge 53 4.3.1 The advantages of repair and reinforcement with FRP materials 53

4.3.2 Select FRP materials following the criteria and technical requirements: 53

4.3.3 Calculation and design of reinforcement solutions for Long Bien bridge collar beams using FRP-Tyfo materials 54

4.4 Estimate the unit price for methods of repairing and reinforcement collar beams of Long Bien bridge 63

4.4.1 Bases for calculation of repair and reinforcement prices 63

4.4.2 Volume of repair and reinforcement methods 66

4.4.3 Unit price for methods of repairing and reinforcement collar beams of Long Bien bridge 69

4.5 Analysis, evaluation of economic efficiency 77

CONCLUSION 79

REFERENCES 80

iv

LIST OF FIGURES

Page

Figure 2.1 Repair the crack in steel structures 9

Figure 2.2 Corrosion in steel structures 10

Figure 2.3 Flatting steel structures 12

Figure 3.1 Model of pulling test on compressed tractor multimeter HFM 16

Figure 3.2 Simulation image of Tyfo WS foundation adhesion structure 19

Figure 3.3 Creating test samples for pulling test 20

Figure 3.4 Sample after maintenance 21

Figure 3.5 Sample of test before pulling 21

Figure 3.6 Pull the sample on the machine 22

Figure 3.7 Experimental samples were split when pulled 22

Figure 3.8 Model of bending reinforced thick steel beams 30

Figure 3.9 Model of bending reinforced thin steel beams with two layers 30

Figure 3.10 Model of bending reinforced thin steel beams with three layers 30

Figure 3.11 Thick beams and thin beams after maintenance 31

Figure 3.12 Bending steel beams on compressors with 32

Figure 3.13 Model of bending steel beams 33

Figure 4.1 Picture of Long Bien Bridge 44

Figure 4.2 Rail way of Long Bien Bridge 45

Figure 4.3 Horizontal/collar beam of Long Bien Bridge 46

Figure 4.4 Damaged image of the upper flange 46

Figure 4.5 Describe damage on the upper flange 47

Figure 4.6 The damage of web of beam of Long Bien Bridge 47

Figure 4.7 Description of web’s damage 47

Figure 4.8 Description of lower flange’s damage 48

Figure 4.9 U-shape steel structure 50

Figure 4.10 Method of steel plate and protective coating 51

Figure 4.11 Construction method to replace collar beams 52

Figure 4.12 Original I section and force components 55

Figure 4.13 Cross section severely damaged by 20% and forces 58

Figure 4.14 Cross section damaged by 10% and forces 60

Figure 4.15 Cross section damaged by 5% and forces 62

Figure 4.16 The figure shows the size of the collar beam 66

Figure 4.17 The area reinforced by gluing stell plates method 67

Figure 4.18 The area reinforced by FRP material method 69

v

LIST OF CHARTS

Page

Chart 3.1 Experiment to determine the pulling force -Sample 1 23

Chart 3.2 Experiment to determine the pulling force -Sample 2 23

Chart 3.3 Experiment to determine the pulling force -Sample 3 24

Chart 3.4 Experiment to determine the pulling force -Sample 4 25

Chart 3.5 Experiment to determine the pulling force -Sample 5 26

Chart 3.6 Experiment to determine the pulling force -Sample 6 26

Chart 3.7 Load and deformation relationship of bending test 34

Chart 3.8 Force and deflection relationship of thin beams 37

vi

LIST OF TABLES

Table 2.1 Criteria of FRP material 15

Table 3.1 Record the test results of pulling test samples without sand blasting 25

Table 3.2 Record the test results of pulling test 27

Table 3.3 Experimental data of thick steel beam bending test 33

Table 3.4 Maximum stress sheet of steel and FRP sheets 35

Table 3.5 Compare the load value of beams at the same deflection 35

Table 3.6 Table of data for calculation of thin beams reinforced with FRP sheet 37

Table 3.7 Calculate the maximum stress on thin steel beams 38

Table 3.8 The maximum stress table on thin beams is reinforced with 2 layers 39

Table 3.9 The maximum stress table on thin beams is reinforced with 3 layers 41

Table 4.1 Parameters of Tyfo SCH - 41 57

Table 4.2 Parameters of Epoxy Tyfo S 57

Table 4.3 Calculation for number of FRP layer (Group I-20%) 59

Table 4.4 Calculation for number of FRP layer (Group II-10%) 61

Table 4.5 Calculation for number of FRP layer (Group III-5%) 62

Table 4.6 Price of materials, labours, equipments 64

Table 4.7 Calculate the weigh of horizontal/collar beam 66

Table 4.8 Volume of steel plate use for a reinforced collar beam 68

Table 4.9 Volume of FRP materials use for a reinforced collar beam 69

Table 4.10 Unit price for production and manufacturing collar beams 70

Table 4.11 Unit price for dismantling, removing horizontal/collar beam 71

Table 4.12 Unit price for install horizontal/collar beam 71

Table 4.13 Unit price of paint steel by normal paint 72

Table 4.14 Unit price for replace horizontal/collar beam and painting 72

Table 4.15 Unit price for attach/glue steel plates 73

Table 4.16 Unit price for reinforced collar beam by gluing steel plate method 73

Table 4.17 Unit price for cleaning steel surface before attachment 74

Table 4.18 Unit price for sticking glass fiber on the steel 75

Table 4.19 Unit price for sticking carbon fiber 75

Table 4.20 Unit price for painting surface of FRP layer with Tyfo U Coating 76

Table 4.21 Unit Price for reinforcement using FRP (for one collar beam) 76

Table 4.22 The cost of methods within 50 years 77

E Young module of elasticity

FRP fiber reinforcement Polymer

σch the yield stress of steel

σgh the yield stress of FRP

n number of FRP layer

viii

UNIT OF SI SYSTEM

Intensity of force mega pascal MPa

Area squared millimeter mm2

Density gram to cubed centimeter g/cm3

Moment of mass cubed millimeter mm3

Moment of inertia millimeter to the power of four mm4

Stress newton to millimeter square N/mm

1

ABSTRACT

Through the experience results, the thesis has useful comments on the quality

of the processing of steel structure surface to the adhesion effect between epoxy glue and reinforced structure This is an important basis to build instructions on construction technology steps to apply FRP materials on steel structures Experimental research has also evaluated the effect of reinforcing the bearing capacity of FRP materials for steel structures

Through a survey of the deterioration and degradation of Long Bien Bridge, the thesis has proposed a solution to apply FRP materials to repair, reinforce collar beams within the range of train operation of Long Bien bridge Find out some advantages and disadvantages of using the FRP material method and other traditional methods have been used

The thesis has proposed a set of criteria to select FRP materials suitable for repairing and strengthening requirements of steel structures in Long Bien Bridge project in particular and steel bridges in Vietnam in general Research proposed a method of calculation to determine the number of layers of FRP material to reinforce bending capacity for the collar beam’s section of Long Bien Bridge (corresponding

to the level of damages 20%, 10%, and 5%)

Based on norms, documents, announcements of Vietnam, research has estimated the unit price for three methods of reinforcement, repair for a horizontal/collar beam (replacing collar beams, gluing steel plates and using FRP material) Thereby, comparing the effectiveness of the method of using FRP with the other methods Through the calculation of unit prices and comparative analysis, research point out the economic efficiency of the solution using FRP materials, especially if considering the more effective aspects, and other advantages of FRP such as: do not have to stop operation, protecting human health and protect the environment

2

INTRODUCTION

In Vietnam, hundreds of steel bridges are being degraded and damaged due to many different reasons It does not ensure conditions for operation and using They need to be repaired, upgraded and even replaced the structure The new replacement method requires huge financial resources that are difficult to meet Therefore, the repair and reinforcement solution is often considered the most optimal solution There have been many methods of reinforcement and repair that are proposed, including methods of using FRP materials (carbon fiber, glass fiber and aramid fiber combined with Epoxy glue)

For Vietnam, this is still a new technology solution applied in the last 10 years and is mainly used for repairing and reinforcing reinforced concrete structures This technology solution has good economic and technical efficiency for reinforced concrete structures

For steel bridge structures in particular and steel structure in general, there are not many works using FRP materials to repair and reinforce, because, in fact, there are not many theoretical and real types of researches evaluating the economic and technical efficiency of using FRP materials for steel structures in Vietnam

Therefore, this research will contribute to evaluate the effectiveness of using FRP materials for steel bridges, which will be a help deciding on the application of solutions for using FRP materials for repair and strengthen the steel bridge project in Vietnam

Select appropriate FRP materials for repairing and strengthening of steel bridges with the typical damages

Evaluate the technical and economic effectiveness of the FRP solution

3

Evaluate technical efficiency:

Conduct a few experiments to evaluate effectiveness

Evaluate economic efficiency:

Comparison between cost of FRP solution and cost of traditional solution to evaluate economic efficiency

Using case study: Long Bien Bridge

The steel structures in steel bridge in Vietnam which are needed to repair and upgrade

The FRP material (carbon fiber, glass fiber, aramid fiber and epoxy)

In addition to the abstract, introduction, conclusion, list of references there are

4 chapters

Chapter 1: Literature review

Chapter 2: Overview of technical issues of repairing and strengthening steel bridge structures in Vietnam

Chapter 3: Some experimental researches using FRP materials in repairing, strengthening steel structures and analysis of technical efficiency of solutions

Chapter 4: Evaluate economic efficiency of the solutions using FRP materials

in repairing, strengthening steel bridge structures in Vietnam, case study Long Bien Bridge

4

Chapter 1 : LITERATURE REVIEW

Since the 1980s, external adhesive fiber materials have been widely used in both Europe and Japan to enhance the bearing capacity of the structure being used

In Europe, FRP materials have been developed to replace structural reinforcement with steel plates The method of gluing steel plates in the tensile zone

is a feasible technique to increase bending resistance for structures (Fleming and King 1967) This technique has been used to enhance many bridges and buildings around the world However, after a period of use, steel is corroded and reduced bearing capacity significantly On the other hand, using a steel plate method is difficult to work in narrow areas

The application of using FRP materials to replace the steel plate method is applied in strengthening structures that have been reported in Germany (Wolf and Miessler 1989), in Switzerland (Meier 1987, Rostasy 1987)

In Japan, the fabric system was first applied to enhance earthquake resistance

in the 1980s (Fardis and Khalili 1981; Katsumata et al 1987), especially after the Hyogoken-Nanbu earthquake in 1995 (Nanni 1995)

Researchers in the US have been studying the application of reinforcing fibers for structures since the 1930s However, began in the 1980s through national scientific initiatives, research activities led to the development of technical standards and design guidelines ACI440R in 2000 for using FRP materials

In the past ten years, glass fiber reinforced polymer materials and soft carbon fiber reinforcement have been widely applied in strengthening the bridge structure of normal reinforced concrete beams and prestressed reinforced concrete structures in Vietnam

In the Journal of Science and Technology Development, Tuong, N.Q (2007)

has introduced the maintenance process of reinforced concrete structures by using

5

FRP materials Currently, the most popular are the two methods for sheet and fabric FRP materials That is a dry lay-up and wet lay-up method This paper also provides

a method for calculating the bearing capacity of the reinforced concrete beam which

is reinforced by FRP materials This calculation method is based on ACI 318-85 (1999)

In 2017, in the doctoral dissertation by author Nguyen Chi Thanh - Vietnam Institute of Water Resources Research The author has studied the factors affecting the bearing capacity of reinforced concrete structures which are reinforced by composite sheet applied to irrigation works This research is a basis to propose the process and method of calculation of reinforcement design This is a pioneering study

in the field of reinforcement of irrigation works in Vietnam using the FRP material method The author focuses on studying the behavior of the structure of reinforced concrete irrigation works before and after reinforcement, clarifying the applicability

in irrigation works in water condition (with high humidity), the effectiveness of reinforcement methods, methods of calculating reinforcement structure as well as the scope of effective application of the method The research’s results contribute to the scientific basis for the development of the process of calculating and designing the reinforcement of reinforced concrete structures using FRP materials for irrigation works

Ghadir Mehramiz and Kambiz Narmashiri (2014) by selecting various, widely-used structural sections and through using ABAQUS software-modeling based on finite element method, studied the created shear capacity, stresses and maximum strains in steel beams Also, this article proposes two modes of applying the steel reinforcement plate and FRP reinforcement sheets Then, they are compared

in all cases to estimate how many percents are those effective as compared to the original one In the conclusion, this research stated that it is always necessary to do analyses of any reinforcement methods in each particular project since the complexity

in Hanoi, find out actual damage, technical requirements, design solutions to repair, estimate cost prices, analysis economic efficiency, from which to draw conclusions about the effectiveness of reinforced technology solutions with FRP materials

7

Chapter 2 : OVERVIEW OF TECHNICAL ISSUES OF REPAIRING

VIETNAM

2.1 Typical forms of damages of steel bridge structure in Vietnam

Some major damages often appear in the structure of steel bridges as follows:

- Rust and corrosion cause dissipation of the area section of the structure

- Cracking steel structure, cracking reinforced concrete plates

- Curve, buckling, local instability of beam flank

- Damage link parts with rivets, high strength bolts, loss of rivets, loss of bolts, corroded nail heads, loose rivets, cracking of welding seams

Damage of steel bridge structure, depending on its properties, is divided into categories: damage of link parts (studs, bolts, welds); damaged by the fatigue of materials, due to metal corrosion, brittle damage and mechanical damage

2.2 Traditional solutions to repair and reinforce steel bridges

it can significantly increase bonding wear and fatigue resistance

 Repair of welding lines:

If there are cracks, puffs, etc on the welding line, it is necessary to remove all defects Particularly, the crack must be removed for each side at least 10mm

8

Clean the surface, weld the cut-off part, clean and paint the surface

 Repair high strength bolt links:

Removing damaged high-strength bolts If bolts, gaskets, and nuts are corroded, it needs to be replaced Otherwise, it needs to be cleaned and be used again

Clean the nail hole, use the Cle to tighten the bolt and then apply force to the design torque Carry out paint or grease protection on bolts

2.2.1.2 Damages caused by cracking of steel

 With cracks that can be repaired by welding, do the following:

Drill two cracked ends with a diameter of 14-18mm to reduce stress to concentrate two crack heads Processing cracks surface into K-shaped (when beveled from both directions of one side of crack), V-shaped (when beveled one directions from the both sides of crack) or X (when bevelled from both sides and both directions

of the crack) Depending on the thickness of the main steel plate and the construction conditions to select the appropriate treatment method, wider the crack of at least 10mm, heating the crack to a temperature of 1500C to 2000C and then proceeding welding, soldering and welding protective coatings

9

Figure 2.1 Repair the crack in steel structures

(Source: Lectures on operation and testing of bridges in Vinh University)

 With a small crack and at the edge of the rivet hole, do the following:

Drilling holes to block crack head to avoid concentrated stress, proceed to remove rivets, clean the bonding surface to replace with high strength bolts, paint or mulch protection after repair

 With a large crack, it is not possible to weld directly, do the following:

Using an additional steel plate with the same steel properties as the original steel, drilling holes to block the two ends of the crack, installing the covering plate to cover the crack (Covering both sides is better In difficult conditions, it is possible to cover one side ) Then use high strength bolts or weld lines to link the plate to the structure, cleaning, painting to protect structures

2.2.1.3 Damage caused by metal corrosion

The structure of steel bridges along with the operation time, all of these have got damages due to the phenomenon of metal corrosion The extent of these damages depends primarily on measures to protect steel from corrosion and maintenance

10

Steel rust, corrosion (Figure 2.2) makes the section of the element weakened and the bearing capacity also decreases In particular, the simultaneous impact of rusty and cyclic loads easily makes rust - fatigue in the structure appear

Figure 2.2 Corrosion in steel structures

The rate of rust development depends on a variety of factors: the chemical composition of steel, the technology of fabricating components, anti-rust, anti-corrosion measures, climatic zones, environment, and stress state

Solution:

- Use of paint in steel bridges: Usually the paint life is at least 4 years, each set

of paint will consist of three layers: a primer (anti-rust), intermediate coating and top coating However, recently, steel bridge structures have to be used epoxy to paint having a lifespan up to 20 years, after painting will create a protective layer of high durability

- Repair method when rust, corrosion appears:

+ If the rust, corrosion greatly reduces the area of the cross-section, it is necessary to have a solution to compensate for the cross section before fixing it

11

+ In the case of rust on the surface of the old paint film, you need to use a brushed version, brush the dust, use the liquid soap, dilute the alkaline to clean, then rinse with clean water and brush and rinse before painting

+ Finished surface needs to be painted immediately, for more than 3 days need

b Solution:

Mechanical impact method: bent steel elements should be straightened or

flattened again under normal temperature conditions because the molecular structure

of the steel is easily changed under the effect of heat Only use the heating method in special cases Local curvature areas are flattened by vam (Figure 2.3a) The angle steel, U steel, and steel plates bent on small lengths can be flattened by clamps (Figure 2.3b) The small protruding points on the steel plate can be overcome by using a sledgehammer on it through a cushion Large distortions, such as deformation of solid

by jacks (Figure 2.3d)

Figure 2.3 Flatting steel structures

(Source: Lectures on operation and testing of bridges in Vinh University) Thermal processing method: This method is to use a flame of acetylene + gas

+ oxygen gas to create new deformation to eliminate old deformation Because this method affects the properties of the steel structure, it is necessary to have a design to designate the allowed range of heating, permissible temperature, heating speed, and cooling, etc, supporting equipment during construction The order of processing recommendations is as follows:

13

+ Using the flame to heat treatment position to design temperature

+ Correct only when the temperature is indicated to 7500C (red-purple) and only allowed up to 8500C (red color) to avoid reducing the intensity of steel

+ When heating, you can attach supporting equipment to adjust

+ Heating and cooling speed must be following the specified design

+ After adjusting, check the surrounding locations to promptly detect secondary arising damages

+ Carry out cleaning and paint to protect the surface

2.2.2 Some methods of reinforcing the steel span structure

- Enhance the sectional structure along with strengthening their links if necessary

- Structure of additional frames or beams

- Include additional structures in the span structure diagram

- Reinforcement by changing the structure of beams: Using the tension bar below the beam, adding the third bar, continuously aligning the span or simple beams

- Construction of supporting pillars (temporary or long-term), reducing the calculated span length

- Changing steel beams into steel-concrete beams by casting more concrete slabs to work with steel beams

- Reinforce individual structures by adding steel in different directions

2.3 Technical requirements of steel bridge repair and reinforcement

Bridge projects are the parts connecting the network of roads, resistant under the effect of the transport operation, must serve continuous full-time

vibration-14

operation, working in humid conditions and even deep in the water From this characteristic of working conditions, it is possible to identify basic technical requirements for repairing, and strengthening bridge structure as follows:

i) Response to vibration conditions due to live load;

ii) Constantly operation on the bridge during repairing, and strengthening; iii) Applicable in wet conditions;

iv) Quick and simple construction;

v) Limit the weight gain of the structure itself, with little effect on the existing structural status

2.4 Develop criteria for selecting FRP materials for the repair and reinforcement of steel bridges

Currently, there are many types of FRP materials supplied in domestic and foreign markets To select FRP materials following the technical requirements of the bridge repair, and reinforcement work in Vietnam, several selection criteria are proposed as shown in Table 2.1

15

Table 2.1 Criteria of FRP material

1 Meet the requirements of repairing bridge

structures in wet condition or deep under

the water

It is not controlled by moisture, can use in water or

wet conditions

2 Ensure continuous traffic on the bridge

during repair, and reinforcement time

Resistant to vibration during

freezing

3 Ensure the quality requirements in each

construction phase and the quality of the

whole project

Has strict quality control

system

4 Epoxy glue can penetrate into pores,

cracks, help improve sticking quality

Epoxy glue has low intrinsic

viscosity

5 The quality of fiber must go hand in hand

with the quality of epoxy glue That can

produce good quality composite products

Fiber, epoxy and auxiliary materials must be synchronized by a same manufacturer

6 Ensuring no bad effects on the environment

and human health

There are full certificates of environmental safety, health safety

7 Support, technical guidance as well as

technology transfer from suppliers and

manufacturers

Having a team of technical

support experts in Vietnam

8 Attach the manufacturer's long-term

responsibility with the quality of the

17

Selecting laboratory samples:

+) When conducting experiments to determine the plucking resistance of Tyfo

WS combined with carbon fiber and glass fiber, the pulling force must be perpendicular to the surface of the sample, to meet this requirement the pulling force must be placed in the center so that the tensile stress is evenly distributed on the section of the sample

+) The size of the sample should neither be too large causing eccentricity nor too small since difficult to conduct experiments

To meet the requirements of the laboratory sample and based on the laboratory's available conditions as well as the limitations of this thesis, research selected a sample of two round flanges The diameter is 60mm, 20mm thickness is conveniently threaded on one side

Samples were made in two groups: In which the sample group 1 was cleaned only without surface roughness and the sample group 2 was sanded with small particles to clean and create striations

The samples are fabricated as follows: Between 2 Tyfo WS glue layers, 2 layers of SEH 25A glass fiber are arranged and 1 layer of SCH 41 carbon fiber is saturated with Tyfo S substrate (order: Steel plate, Tyfo WS, SEH 25A, SCH 41, SEH 25A, Tyfo WS, steel plate)

The process of the experiment:

Step 1: Prepare the specimen

- Prepare laboratory samples

+) Prepare 2 small, soft paint brushes

+) Prepare 12 cylindrical steel samples with thickness b = 20 mm, two round flanges with the same diameter a = 60 mm Carrying thread turning for the sample,

18

the threaded hole is in the center of the cylinder center, the threaded hole diameter is 10mm, the thread depth is 15mm

+) Prepare 4 threaded axes with 10mm diameter

+) Prepare 6 samples of cylindrical PVC pipes with internal diameter is 60mm and 50mm high

+) Using scissors to cut 8 glass fiber samples and 4 layers of circular carbon fiber with a diameter of 60mm Use a paint brush to remove dirt from the fabric surface

Step 2: Sand blasting and create a rough surface for steel plates

Sand blasting is a method of smoothing, flattening and cleaning hard surfaces

by moving high-speed solid particles across the surface to be treated

- Leave 6 original samples corresponding to 3 pairs of manufactured samples without sand blasting, those only to be cleaned by the normal way Numbering 1, 2 and 3 respectively for 3 pairs fabricated samples

- Conduct sand blasting for 6 samples used for experiments corresponding to

3 pairs of samples after gluing Numbering 4, 5, and 6 respectively for 3 pairs fabricated samples

19

Step 3: Conduct the creation of the sample

Figure 3.2 Simulation image of Tyfo WS foundation adhesion structure

combined with glass fiber, carbon fiber

Mixing Tyfo WS glue and Tyfo S according to the volume ratio

Experiment to determine the pulling resistance of Tyfo WS combined with glass fiber, carbon fiber: put a steel sample created in PVC pipe so that the thread is directed downwards, sweeping a glue Tyfo WS-1mm thick on the surface of the steel plate, place a layer of SEH 25A glass fiber on top, Tyfo S, then a SCH 41 carbon fiber layer, then sweep a Tyfo S layer, then place a layer of SEH 25A glass fiber up, finally sweep Tyfo S Ensure 3 layers of fibers including 2 layers of glass fiber and one layer of carbon fiber must be saturated with Tyfo S Finally put a steel sample that has swept Tyfo WS on the bottom surface, so that the thread is directed upwards

After being created, the test samples will be tested for balance in 3 positions,

in which 2 outside are near the edge of the sample and one is at the center to ensure concentricity and balance If not balanced, it neccessary to recreate other samples

20

Figure 3.3 Creating test samples for pulling test

(Source: Research team)

Step 4: Maintenance 3 days after fabrication

Proceed to remove the PVC layer, use a file to clean the glue on the side of the sample

Step 5: Install the sample and proceed to pull the sample on the universal compression tractor

Insert the shaft into the threaded hole, then twist to excess half of the threaded ring due to the deformation of the steel and FRP plate will cause eccentricity, then the threaded shaft acts as a portable bearing to ensure that it is not eccentric when pulling

Placing the samples on the tractor in the center, so that the traction force must

be perpendicular to the surface of the material sample to determine the plucking resistance of Tyfo WS and the plucking resistance of Tyfo WS combined with glass fiber sheet, carbon fiber sheet

Sample steel is Q345 steel

21

Total samples: 6 samples (3 samples pulling up Tyfo WS combined with glass fiber and carbon fiber are not made the rough surface, 3 samples pulling up Tyfo WS combined glass fiber and carbon fiber surface roughness)

Start the system for the machine to increase the load on the sample from zero until the FRP sheet is peeled off, then stop saving the test data

Figure 3.4 Sample after maintenance

(Source: Research team)

Figure 3.5 Sample of test before pulling

(Source: Research team)

22

Figure 3.6 Pull the sample on the machine

(Source: Research team)

Figure 3.7 Experimental samples were split when pulled

(Source: Research team)

23

3.1.3 Processing experimental data

3.1.3.1 Tensile testing of specimens without surface roughness

Chart 3.1 Experiment to determine the pulling force of samples without sand

blasting-Sample 1 (Source: Research team)

Chart 3.2 Experiment to determine the pulling force of samples without sand

blasting-Sample 2 (Source: Research team)

24

Chart 3.3 Experiment to determine the pulling force of samples without sand

blasting-Sample 3 (Source: Research team)

In which:

P: Critical tensile force (N);

d: Sample diameter (mm);

A: Sample area (mm2)

25

Tensile strength stress value of Tyfo WS sample is calculated and displayed

on the computer screen at the time of destructive sample

Table 3.1 Record the test results of pulling test samples without sand

3.1.3.2 Tensile testing of specimens - the sample to be roughened

Chart 3.4 Experiment to determine the pulling force of the sample sandblasting on

HFM 500 KN compressors-Sample 4

(Source: Research team)

26

Chart 3.5 Experiment to determine the pulling force of the sample sandblasting on

HFM 500 KN compressors-Sample 5

(Source: Research team)

Chart 3.6 Experiment to determine the pulling force of the sample sandblasting on

HFM 500 KN compressors-Sample 6

(Source: Research team)

27

Table 3.2 Record the test results of pulling test on specimens sand blasted to

create surface roughness

3.1.4 Comment and conclusion on experimental results

For samples not be created roughly by sand blasting:

The maximum intensity measured is 9.85 N / mm2

The smallest intensity measured is 8.09 N / mm2

The average intensity measured is 8.97 N / mm2

For samples of sand blasting to create surface roughness:

The maximum intensity measured is 18.74 N / mm2

The smallest intensity measured is 15.59 N / mm2

The average measured intensity is 17.26 N / mm2

Experimental results show that surface roughed has much better plucking resistance than not creating roughness for the sample

- Compare experimental results of 2 groups of experimental samples

∆kTB = kTB2 - kTB1 = 17.26 - 8.97 = 8.29 (N/mm2)

28

=> ∆kTBkTB1 x 100% = 8.29

8.97 x 100% = 92.42 (%) The test sample is roughened before bonding for 92.42% higher plucking resistance than non-roughened samples

CONCLUSION:

When increasing the surface roughness for samples by sand blasting method, the bearing capacity of the sample is nearly doubled compared to the original, the rougher the surface, the higher the strength of the sample Roughness and surface cleanliness are important determining factors for the strength of the sample

To make more effectiveness of TyFo WS glue in combination with glass fiber and carbon fiber as a bonding material for structures, it is necessary to clean and create surface roughness for components and structures by sand blasting before pasting Therefore, make steel structure surface to be roughness and cleanliness are very important

3.2 Experiment 2: Bending test of steel samples reinforced with FRP materials

Selecting experimental samples: Conduct experiments with thin beams having

a thickness close to the thickness of FRP sheets (simulated beams) and types of beams have a thickness much larger than FRP sheet’s thickness (beams with a thickness equivalent to real beam structures)

29

The fabricating samples are as follows:

+) Creating a thick beam test specimen: The surface is reinforced by the glue Tyfo WS layer, then arranges a layer of SEH 25A glass fiber and 2 layers of SCH

41 carbon fiber (orderly: Steel beam, Tyfo WS, SEH 25A, SCH 41, SCH 41)

+) Create thin beam test samples, divided into the following two types:

• Thin beams are reinforced with two layers of carbon fiber SCH 41: Reinforcing in the tensile area, using Tyfo WS glue, two layers of SCH 41 carbon fiber (orderly: Steel beam, Tyfo WS, SCH 41, SCH 41)

• Thin beams are reinforced with three layers of carbon fiber SCH 41: on the one side of steel beam reinforced by TYFO WS glue, incorporates three layers of SCH 41 carbon fiber (orderly: steel beam, Tyfo WS, SCH 41, SCH 41, SCH 41)

The experiment’s process:

Step 1: Prepare the sample

- Prepare 2 paint brushes

- Prepare 4 steel plates with dimensions are 600mm x 100mm x 20mm

- Prepare 10 steel samples with dimensions are 600mm x 60mm x 5mm

- Cut 6 samples of SCH 41 carbon fiber and 3 SEH 25A glass fiber samples with the size is 580mm x 100mm

- Cut 20 carbon fiber samples SCH41 with the size is 580mm x 60mm

Step 2: Use sand blasting method and make the surface to be roughed for 3

thick steel beams and 10 thin steel beams reinforced by FRP material

Use a brush to clean dust on the cuting fabric surface

30

Step 3: Conducting to paste the FRP materials for 3 thick steel beams,

according to the design below; one thick steel beam to be original

Figure 3.8 Model of bending reinforced thick steel beams

Figure 3.9 Model of bending reinforced thin steel beams with two layers of

31

Use a paint brush to apply Tyfo WS coating on the surface of the beam; use another paint brush to saturate Tyfo S glue into pre-prepared carbon fiber and glass fiber sheets Pasting SEH 25A glass fiber sheet saturated with Tyfo S on top of the steel beam Attach two SCH 41 carbon fiber sheets saturated with Tyfo S on the previous glass fiber layer

With thin steel beams reinforced with two layers of carbon fiber:

Use a paint brush to apply a Tyfo WS coating on the steel beam surface; use another paint brush to saturate the Tyfo S glue on the SCH 41 carbon fiber sheet, then lay two layers of carbon SCH 41 fibers saturated Tyfo S on the steel beam, then apply glue Tyfo S until saturation With samples reinforced three layers of carbon fiber do the same way

Step 4: Maintain the samples 3 days after fabrication Using a machine,

remove excess fabric from the steel plate

Figure 3.11 Thick beams and thin beams after maintenance

(Source: Research team)

Step 5: Put the samples on the tractor-compressed universal machine Place

the sample so that the reinforced surface is below The force that the machine operates