Connection Capacity of Pultruded GFRP Channels in Multidirectional Loading

2013·4.4 MB·English

by  Wang, Michael

CONNECTION CAPACITY OF PULTRUDED GFRP CHANNELS
IN MULTIDIRECTIONAL LOADING
by
MICHAEL C. WANG
B.S., University of Colorado Denver, 2008

A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fulfillment
of the requirements for the degree of
Master of Science
Civil Engineering
2013
This thesis for the Master of Science degree by
Michael C. Wang
has been approved
for the Civil Engineering Program
by

Yail Jimmy Kim, Advisor

Kevin Rens, Chair

Frederick Rutz

July 12, 2013
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Wang, Michael, C. (M.S., Civil Engineering)
Connection Capacity of Pultruded GFRP Channels in Multidirectional Loading
Thesis directed by Associate Professor Dr. Yail Jimmy Kim

ABSTRACT
Fiber Reinforced Polymer (FRP) composites is a relatively new material that offers
unique advantages for many different engineering applications. While there has been
plenty of research performed to understand composite fiber failure mechanisms
numerically and experimentally, the exact nature of failure based on fiber orientation is
unknown. Due to the complex nature of FRP composites, fiber failure mechanisms are
not clearly understood and the goal of this study is to gain further knowledge regarding
FRP failure, particularly with bolted connections.

The primary objective of this research is to investigate the behavior of bolted Glass Fiber
Reinforced Polymer (GFRP) structural channel members subject to cyclic loading. The
investigation consisted of testing various channel specimens with different flange
geometric configurations. Monotonic loading is performed to determine ultimate strength
of the connection in the axial and transverse directions for the first phase. The second
phase comprises of how unidirectional cyclic loading effects stiffness and the overall
ultimate strength of the connection in the axial and transverse direction. The last phase
studies the behavior and the residual connection capacity of the GFRP specimens subject
to multidirectional cyclic loading. Various load levels for cyclic loading were established
as a fraction of the ultimate strengths obtained from testing.
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The testing showed that the absence of the flange did not have a significant impact with
respect to the ultimate strengths in the axial and transverse directions. Failure modes
observed consisted of initial bearing failure followed by shear-out failure for axial
specimens and net tension splitting for the transverse specimens. The GFRP channel
specimens undergo a period of nonlinear progressive damage after initial failure.
Furthermore, it was found that the residual behavior and strength was affected by
unidirectional and multidirectional load cycles.

A probability-based design was adopted to provide design recommendations and
guidelines. Resistance factors are determined using the Monte-Carlo simulation for the
Load and Resistance Factor Design (LRFD) design method.

The form and content of this abstract are approved. I recommend its publication.
Approved: Jimmy Kim

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ACKNOWLEDGMENTS

My sincere gratitude goes to my advisor Dr. Yail Jimmy Kim and co-advisor Dr. Rui Liu.
It has been a pleasure to work with both and I thank them for their guidance, support, and
time during the preparation of this thesis. They provided me with invaluable knowledge
and expertise necessary for completion of the research project. Also I’d like to thank Dr.
Kevin Rens and Dr. Frederick Rutz for participating on my thesis defense committee.

The material testing conducted in this research study would not have been possible
without the support provided by the following staff and students: Tom Thuis, Jac Corless,
Eric Losty, and Dennis Dunn. A special thanks to Shahlaa Alwakeel, for her guidance
and assistance in the lab. Your hard work is greatly appreciated. Finally, the author
gratefully acknowledges support from International Cooling Towers.

I would also like to express my appreciation to my fellow colleagues and mentors David
Blanchette and Jerry Isler, both have been instrumental in the development of my
professional and academic career.

Lastly, I would like to thank my friends and family for their support and encouragement
along the way.

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TABLE OF CONTENTS
Tables ................................................................................................................................ x
Figures .............................................................................................................................. xi

Chapter
1. Introduction ............................................................................................................. 1
1.1 General .................................................................................................................... 1
1.2 Objectives ............................................................................................................... 2
1.3 Scope ....................................................................................................................... 3
1.4 Outline of Thesis ..................................................................................................... 3

2. Literature Review.................................................................................................... 5
2.1 Introduction. ............................................................................................................ 5
2.2 Overview. ................................................................................................................ 5
2.3 Material Properties of FRP. .................................................................................... 6
2.4 Fabrication of FRP Members .................................................................................. 7
2.5 Bolted FRP Members .............................................................................................. 8
2.6 Fasteners ................................................................................................................. 9
2.7 Failure Modes ......................................................................................................... 9
2.7.1 Tension Failure ..................................................................................................... 10
2.7.2 Shear Failure. ........................................................................................................ 11
2.7.3 Bearing Failure. ..................................................................................................... 11
2.7.4 Cleavage and Pull-out Failure ............................................................................... 12
2.8 Factors Affecting Joint Strength ........................................................................... 12
2.8.1 Fiber Orientation ................................................................................................... 12
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2.8.2 Lateral Contraint ................................................................................................... 13
2.8.3 Stacking Sequence ................................................................................................ 13
2.8.4 Joint Geometry ...................................................................................................... 14
2.9 Static Behavior of Pultruded GFRP Beams. ......................................................... 14
2.9.1 Experimental Setup and Test Procedure. .............................................................. 15
2.9.2 Results and Conclusions. ...................................................................................... 15
2.10 Multi-Bolted Joints For GFRP Structural Members . ........................................... 16
2.10.1 Test Parameters ..................................................................................................... 17
2.10.2 Test Setup and Instrumentation ............................................................................ 17
2.10.3 Experimental Results ............................................................................................ 18
2.10.4 Conclusions ........................................................................................................... 19
2.11 Finite Element Modeling of Damage Accumulation ............................................ 19
2.11.1 Progressive Damage Model .................................................................................. 20
2.11.2 Finite Element Modeling ...................................................................................... 23
2.11.3 Results and Discussions ........................................................................................ 24

3. Experimental Program .......................................................................................... 39
3.1 Introduction ........................................................................................................... 39
3.2 Materials used for Test Specimens ....................................................................... 39
3.2.1 GFRP Channels ..................................................................................................... 39
3.2.2 GFRP Flat Plates ................................................................................................... 40
3.3 Experimental Setup and Loading .......................................................................... 41
3.3.1 Phase I and Phase II Setup for Axial Tests ........................................................... 41
3.3.2 Phase I and Phase II Setup for Transverse Tests .................................................. 42
3.3.3 Phase III Testing Procedure .................................................................................. 42
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4. Finite Element Modeling ...................................................................................... 48
4.1 Introduction ........................................................................................................... 48
4.2 Modeling and Elements ........................................................................................ 48
4.3 Failure Criteria ...................................................................................................... 49
4.4 Model Results ....................................................................................................... 50

5. Test Results and Discussion.................................................................................. 54
5.1 Introduction ........................................................................................................... 54
5.2 Phase I Testing Results of GFRP Channels .......................................................... 55
5.2.1 Phase I Failure Modes of GFRP Channels. .......................................................... 56
5.2.2 Phase I Testing Results of GFRP Thickened Plates. ............................................ 57
5.2.3 Phase I Failure Modes of GFRP Thickened Plates. .............................................. 57
5.3 Phase II Testing Results of GFRP Channels ........................................................ 58
5.3.1 Phase II Failure Modes of GFRP Channels .......................................................... 59
5.4 Phase III Testing Results of GFRP Channels ....................................................... 60
5.4.1 Phase III Failure Modes of GFRP Channels ......................................................... 62
5.5 Comparisons of Phases. ........................................................................................ 63
5.5.1 Comparison Among Different Flange Geometries in Phase I. ............................. 63
5.5.2 Comparison of Post-Cyclic Residual Behavior. ................................................... 63
5.5.3 Effect of Cyclic Loading on Residual Capacity . ................................................. 64
5.6 Design Recommendations. ................................................................................... 64
5.6.1 Monte-Carlo Simulation. ...................................................................................... 64
5.6.2 Calibration of Resistance Factor. .......................................................................... 65

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6. Summary and Conclusions. .................................................................................. 82
6.1 Summary. .............................................................................................................. 82
6.2 Conclusions. .......................................................................................................... 82
6.3 Recommendations for Future Work . .................................................................... 85

Appendix

A Load Displacement Curves for Phase I – Axial and Transverse ...........................86

B Load Displacement Curves for Phase II – Residual Capacity ..............................98

C Load Displacement Curves for Phase III – Residual Capacity ...........................101

D Phase I Testing Failure Photos – Axial and Transverse ......................................103

E Phase II Testing Photos – Damage From Cyclic Loading ..................................113

F Phase III Testing Photos – Damage From Multi Directional Cyclic Loading ....116

G Phase III Testing Failure Photos ..........................................................................118

References ........................................................................................................................119

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LIST OF TABLES

Table
2.1 Comparison of Flexural Rigidity. ............................................................................ 26
2.2 Comparison of Shear Rigidity. ................................................................................. 26
2.3 Geometrical Data for the Investigated Geometry. ................................................... 27
2.4 Elastic Properties of HTA/6376 Material. ............................................................... 27
4.1 Material Properties for GFRP Channel Specimens (Extren). .................................. 51
4.2 Failure Criteria Strength Values. .............................................................................. 51
5.1 Phase I Ultimate Failure Load of GFRP Channel Specimens. ................................ 67
5.2 Phase I Ultimate Failure Load of GFRP Thickened Members. ............................... 67
5.3 Phase II Residual Connection Capacity of Members Subject to Cyclic Loading. ... 68
5.4 Phase III Residual Connection Capacity of Members Subject to Cyclic Loading. .. 68
5.5 Resistance Factor Calibration. ................................................................................. 69

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