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FIELD PERFORMANCE OF A NEW FIBER REINFORCED POLYMER BRIDGE DECK
Abstract
The field performance of a new bridge deck system composed of pultruded trapezoidal fiber reinforced polymer (FRP) tubes wrapped with a filament wound outer layer is described in this study. The proof of concept FRP deck was installed on a rehabilitated bridge in Bolivar, NY, in 2012 as part of the Highways for Life Technology Partnerships Program from the FHWA. The information gathered from the field test was used to study the in-situ performance of the prefabricated FRP panels and their interaction with the steel wide flange support girders. Field data gathered in this investigation was used to evaluate the composite action developed by the bolted deck to girder connection system; establish girder live load distribution factors; and evaluate the serviceability of the bridge. Results were compared to the AASHTO LRFD Specifications. Data indicates that the live load is transferred transversely through the deck to the girders without developing composite action. The lever rule conservatively predicts twice the maximum field measured distribution factor on any interior girder while timber and open steel grate distribution factors are non-conservative. The AASHTO S/800 deflection limit was found to be inadequate to govern the rehabilitated bridge serviceability. Measured girder deflections and calculated accelerations were compared against appropriate standards and found to exceed comfort limits by 125% and 245% respectively. Deck deflections relative to the support girders in regions not under service loads were determined to be negligible. A laboratory test also indicated that there is limited movement of the
hollo-bolt connection under service loads. _ Table of Contents
List of Figures ……………………………………………………………………………………………………………………………… v
List of Tables ……………………………………………………………………………………………………………………………. viii Acknowledgements …………………………………………………………………………………………………………………….. ix
- Introduction ………………………………………………………………………………………………………………………… 1
1.1. Project background ……………………………………………………………………………………………………….. 1
- Deck development and testing ………………………………………………………………………………………. 4
- Bridge rehabilitation …………………………………………………………………………………………………….. 5
- Live load testing ……………………………………………………………………………………………………………. 6
- Instrumentation ……………………………………………………………………………………………………………. 9
- Maximum displacement and strains ………………………………………………………………………………. 12
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Composite action ………………………………………………………………………………………………………………. 14
- Literature Review ………………………………………………………………………………………………………… 14
3.3. Global versus local deformation ……………………………………………………………………………………. 15
3.3. Neutral Axes ……………………………………………………………………………………………………………….. 17
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Distribution Factors …………………………………………………………………………………………………………….. 19
- Literature Review ………………………………………………………………………………………………………… 19
- Field Results ……………………………………………………………………………………………………………….. 21
- AASHTO Distribution Factors at 0.61 m Girder Spacing ……………………………………………………. 23
- AASHTO specifications versus field results ……………………………………………………………………… 24
- Distribution factors and changing girder spacing ……………………………………………………………. 26
- Recommendations ……………………………………………………………………………………………………… 29
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Serviceability ……………………………………………………………………………………………………………………… 30
- Background ………………………………………………………………………………………………………………… 30
- Girder Serviceability …………………………………………………………………………………………………….. 30
- Deck Serviceability ………………………………………………………………………………………………………. 33
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Two span test ……………………………………………………………………………………………………………………. 35
- Purpose and test set up ……………………………………………………………………………………………….. 35
- Hollo-bolt connection movement ………………………………………………………………………………….. 37
- Panel deflection behavior …………………………………………………………………………………………….. 39
- Conclusions ……………………………………………………………………………………………………………………….. 41
- Recommendations for Future Research ………………………………………………………………………………… 43
References ……………………………………………………………………………………………………………………………….. 44
Appendix A: Composite Action ……………………………………………………………………………………………………. 45
Appendix B: Distribution factor calculations and data ……………………………………………………………………. 51
Appendix C: Serviceability …………………………………………………………………………………………………………… 57
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Introduction
- Project background
About 25% of the United States’ 600,000 bridges are classified as structurally deficient or functionally obsolete (ASCE 2013). These bridges require rehabilitation to repair decaying members or meet new design standards. Specifically, there is a need to rehabilitate bridges with decks at the end of their design life or that have deteriorated from environmental effects and road salts. Fiber reinforced polymer (FRP) bridge decks provide a fatigue and corrosion resistant alternative to traditional deck replacement materials. Light weight FRP decks can be installed on load posted bridges, reducing the dead load and therefore increasing live load carrying capacity. The prefabricated decks require reduced installation time, limiting road closings and detours. Due to high initial material costs and lack of experience with FRP decks, designers often revert to traditional concrete or timber decks even though their lifetime costs due to required maintenance may be higher.
The FHWA’s Highways for Life Technology Partnerships program joined with Bridge Composites, LLC to develop, produce, and test a new economical FRP deck that can be routinely used for rehabilitation. The team was tasked with refining existing materials, practices, and construction details to limit costs and to verify the results through a proof of concept installation on a steel girder bridge (O’Connor 2013). The new deck, based on studies previously concluded at the University of Buffalo, was installed on the rehabilitated Pleasant St Bridge in Bolivar, NY in August 2012.
The purpose of this study is to determine the level of composite action developed by the new deckgirder connection; establish live load distribution factors for the steel girders; and observe the serviceability performance of the bridge. Results are compared with the AASHTO LRFD 2012 specifications and recommendations provided. Performance of the deck to girder connection is characterized.
- Research tasks
Task 1: Characterize the composite action developed by the hollo-bolt connection.
Displacements and strains will be used to characterize local and global load transfer in the FRP deck and girders. Mid span longitudinal strains taken on the bottom flange and one third the steel girder height will be used to create strain profiles assuming a linear strain distribution. Neutral axes locations and additional observations will establish the level of composite action.
Task 2: Determine maximum distribution factors and compare to AASHTO guidelines.
With the measured girder strains, the field distribution factors will be determined for the various tested loading conditions assuming symmetry along the roadway centerline. Results will be compared to AASHTO recommendations for concrete slab, timber, and open steel grating on steel girders as well as the lever rule. Applicability and limitations of the current AASHTO (2012) guidelines will be determined up to the maximum FRP deck girder spacing.
Task 3: Compare field results to AASHTO serviceability requirements.
Current optional AASHTO (2012) deflection limits are imposed to limit wearing surface damage and user discomfort. Applicability of these limits to new FRP deck bridges will be discussed. Measured global deflections of the girders and local deflections of the FRP deck will be compared to limits specified in the AASHTO LRFD (2012) design specifications, the Canadian and Ontario codes, and those from other research projects. Design recommendations for the new deck will be made.
Task 4: Describe range of connection motion through a two span test.
A two span lab test designed to closely mimic the actual bridge deck to girder connection detail will be used to observe the hollo-bolt and clip connection movement and panel bending behavior.
FIELD PERFORMANCE OF A NEW FIBER REINFORCED POLYMER BRIDGE DECK
