STRUCTURAL PERFORMANCE OF A HYBRID GLASS FIBER REINFORCED POLYMER BRIDGE DECK SYSTEM

ABSTRACT

 

A lightweight composite bridge deck system was developed as part of a Highway for LIFE Technology Partnerships Program from the Federal Highway Administration (FHWA). The deck panel consists of pultruded trapezoidal GFRP tubes and glass fiber outer wrap, and is designed to be filled with grout if higher stiffness is needed. The performance of tubes and panels with different grout and grouting patterns was evaluated in single span tests. Also, two-span flexure tests were performed on grouted and non-grouted panels to evaluate their structural behavior in both positive and negative bending regions. Test results showed that the epoxy grouted panel met the AASHTO deflection requirement (L/800) and had promising advantages over the cementitious grouted panel in terms of flexural stiffness. Different types of potential failure modes of pultruded tubes were evaluated in order to predict the governing failure mode, and it was found the predicted failure mode and corresponding failure load matched well with those from experimental tests. Failure mode of non-grouted panel was found to be preferable since it was localized failure, which did not lead to collapse. An analytical model was developed to predict the load-deflection relation of grouted and non-grouted panels in different loading conditions, and when compared to experimental data, it was able to predict the panel deflection well even at 3 times the service load within 11.1% error.

   

 

 

TABLE OF CONTENTS

List of Figures ………………………………………………………………………………………………………………. vi

List of Tables ……………………………………………………………………………………………………………….. viii

Acknowledgements……………………………………………………………………………………………………….. ix

Chapter 1 INTRODUCTION …………………………………………………………………………………………. 1

1.1 Objective …………………………………………………………………………………………………………. 3

1.2 Research Tasks ………………………………………………………………………………………………… 3

Chapter 2 LITERATURE REVIEW ………………………………………………………………………………. 5

2.1 FRP Pultruded Shapes ………………………………………………………………………………………. 5

2.1.1 Lateral-torsional Buckling ………………………………………………………………………. 5

2.1.2 Local Buckling of Flanges and Webs due to In-plane Compression …………… 6

2.2 All-FRP Bridge Deck ……………………………………………………………………………………….. 8

2.2.1 Outer wrap: ……………………………………………………………………………………………. 10

2.3 Hybrid Bridge System ………………………………………………………………………………………. 12

Chapter 3 EXPERIMENTAL PROGRAM ……………………………………………………………………… 15

3.1 Description of Specimens …………………………………………………………………………………. 15

3.2 Single Span Flexure Test of Pultruded tubes ………………………………………………………. 17

3.2.1 Test Setup ……………………………………………………………………………………………… 17

3.2.2 Results and Discussion …………………………………………………………………………… 20

3.3 Single Span Flexure Test of Panels ……………………………………………………………………. 26

3.3.1 Test Setup ……………………………………………………………………………………………… 26

3.3.2 Results and Discussion …………………………………………………………………………… 29

3.4 Two-span Flexure Test of Panels ………………………………………………………………………. 32

3.4.1 Test Setup ……………………………………………………………………………………………… 33

3.4.2 Results and Discussion …………………………………………………………………………… 35

Chapter 4 ANALYTICAL PROGRAM ………………………………………………………………………….. 41

4.1 Calculation of      and          ………………………………………………………………………………. 42

4.2 Failure Analysis of Pultruded Tubes ………………………………………………………………….. 47

4.1.1 Non-grouted Tubes ………………………………………………………………………………… 47

4.1.2 Grouted Tubes ……………………………………………………………………………………….. 48

4.3 Timoshenko Beam Theory in Different Loading Conditions ……………………………….. 50

4.4 Comparison of Analytical Model with Experimental Data ………………………………….. 54

Chapter 5 CONCLUSIONS AND RECOMMENDATIONS ……………………………………………. 57

5.1 Conclusions ……………………………………………………………………………………………………… 57

5.2 Recommendations for Future Work …………………………………………………………………… 59

References ……………………………………………………………………………………………………………………. 61

Appendix A  Calculations ……………………………………………………………………………………………… 65

A.1 Calculation of      and          ……………………………………………………………………………… 65

A.2 Calculation of failure load of pultruded tubes ……………………………………………………. 67

A.2.1 Non-grouted Tube …………………………………………………………………………………. 67

A.2.2 Grouted Tube ………………………………………………………………………………………… 69

A.3 Calculation Related to Timoshenko Beam Theory …………………………………………….. 72

Appendix B  MATLAB Program …………………………………………………………………………………… 79

Appendix C  Material Information …………………………………………………………………………………. 90

Chapter 1  

 

INTRODUCTION

According to the data from Federal Highway Administration in 2009, almost 22% of nation’s 603,310 bridges are either structurally deficient or functionally obsolete [1]. This is due to accumulated degradation of conventional materials used in bridge structures, such as steel and concrete. Steel is known to be susceptible to corrosion while concrete could crack and spall due to substandard loading or freeze-thaw process. Thus, it is necessary to build or replace bridge systems, especially bridge decks, with durable materials and new structure systems. FRP composites are competitive materials in solving the problems on existing bridges due to their superior material properties such as low weight, corrosion immunity, and high fatigue strength. In the last few decades, structural applications of FRP composites started to appear in civil infrastructure systems, such as FRP sheet for bonded reinforcement, FRP tendon for internal reinforcement and FRP pultruded shapes for highway structures. Among the new applications of FRP composites in highway structures, bridge decks for rehabilitation and new construction have drawn most attention because of their inherent advantages in strength and stiffness per unit weight as compared to traditional steel reinforced concrete deck [2].

Various all-FRP deck systems have been developed and implemented in USA and

Canada, such as Hardcore system, EZSpan system, Superdeck system and DuraSpan system. These all-FRP deck systems can be classified into two major categories according to their construction – sandwich and adhesively bonded pultruded shapes [2]. Sandwich decks provide design flexibility for deck depth and face sheet, while decks assembled by adhesively bonded pultruded shapes could achieve good quality control in the factory and optimized design of cross section. In addition, the typical weight of all-FRP bridge deck is only about 20% percent of conventional concrete bridge deck [3], which facilitates the transportation and installation.

Despite the advantages of all-FRP bridge deck systems, they are still too expensive to compete with conventional materials. Bakis et al. [2] indicated that the cost of a FRP deck in unit of per square feet is more than twice the cost of a deck made of conventional materials. Karbhari and Cheng [4] also indicated that the design of all-FRP bridge deck is driven by stiffness after reviewing FRP bridges from 1980 to 2006. In order to reduce the cost and enhance the performance of FRP bridge system, hybrid bridge system combining FRP composites with components made of traditional materials, such as concrete, was developed. The hybrid concept was first brought up by Bakeri and Sunder [5], with the idea that the compressive force is carried by the concrete at the top and the tensile force is taken by FRP at the bottom. Many other researchers have extended hybrid concept to various bridge applications, such as hybrid girders and decks. Deskovic et al. [6] investigated the short-term behavior of hybrid glass fiber reinforced plastic (GFRP) box beams with a layer of concrete on top flange and a carbon fiber reinforced plastic laminate on bottom flange. Chakrabortty et al. [7] conducted tests of beams formed by wrapping up a GFRP pultruded profile, a CFRP laminate and a concrete block using filament winding technique. Aref [8, 9] performed various tests and analysis on a hybrid FRP-concrete bridge superstructure system comprised of a layer of concrete and three trapezoidal GFRP tubes surrounded by an FRP outer shell. Johnson et al. [10] compared the performance of GFRP bridge deck system with and without concrete topping through experimental testing.

Among all these application of hybrid concept to bridge decks and girders, concrete was the major material used at top side of the structure. However, in case when the deck is lying on multi-girder bridge and subjected to negative bending above interior girders, the concrete would be vulnerable to tensile crack. Thus, a substitute material to concrete may need to be investigated to meet the need in such circumstance.

1.1 Objective

The primary objective of this study was to experimentally investigate the flexural behavior of a newly developed hybrid deck system combining the GFRP pultruded tubes with different grout materials and grouting pattern, and verify the feasibility of such deck panel in multi-girder bridges. Two types of grout and two grouting patterns were evaluated in terms of flexural stiffness and failure mode. Experimental tests of grouted and non-grouted deck panels were performed in single span and two-span conditions to assess the flexural behaviors of the panels in positive bending and negative bending regions. An analytic model was developed to predict the load-deflection response of these deck panels with and without grout. In this study, the behavior of the hybrid system in different loading conditions is discussed and comparisons of the analytical model and experimental data are presented.

1.2 Research Tasks

In order to achieve the objective, the following tasks were performed:

• Task 1: Single span flexural test of pultruded tubes. Tests in elastic range and to failure were performed on pultruded tubes with and without grout to evaluate the failure mode and compare the performance of different grout.
• Task 2: Single span flexural test of panels. Grouted and non-grouted panels were tested in single span condition to compare the stiffness increment by using different grout and grouting pattern.
• Task 3: Two-span flexural test of panels. A non-grouted panel and an epoxy grouted panel were tested in two-span loading condition to evaluate the behavior of such hybrid panel in both positive and negative bending moment region, and prove the feasibility of the use of the hybrid deck panel on multi-girder bridges.
• Task 4: Failure analysis of pultruded tubes. Existing analytical failure mechanisms were evaluated for this new type of pultruded tubes in order to predict the governing failure mode as well as the corresponding failure load.
• Task 5: Analytical model for predicting load-deflection behavior of panels. An analytical model based on the transformed section method and Timoshenko’s beam theory was developed to predict load-deflection relations in single span and two-span loading conditions.

STRUCTURAL PERFORMANCE OF A HYBRID GLASS FIBER REINFORCED POLYMER BRIDGE DECK SYSTEM

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