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GFRP Barrier Testing Evaluation and Repair Strategies

Description:

Deterioration of bridge decks and safety barriers in salt exposure conditions using traditional steel reinforced concrete, or even using epoxy coated steel, has demonstrated the inability of steel reinforcement to satisfy today’s desired 100-year service life due to the susceptibility of traditional steel reinforcement to galvanic corrosion. While the AASHTO LFRD Specifications do not specify a specific service life for bridges more recent guides provide a path for selecting a target service life including life cycle cost analysis approaches. Other international standards such as the British Standards set a specific required 120-year service design life.

One solution to address the long-term service life target of 100 years that many DOT’s desire in their bridge deck systems is to use noncorrosive reinforcing materials such as glass fiber reinforced polymer (GFRP) in lieu of traditional steel or steel coated systems. Since the late 1990’s and early 2000’s, GFRP materials have been demonstrated in bridge elements including bridge decks in both hybrid reinforced deck applications or more recently fully steel free GFRP reinforced decks. However, a few challenges in the 2000’s and 2010’s have slowed the widespread implementation of steel free GFRP usage into bridge deck systems. These are generally perceived as 1.) AASHTO design standards developed for using these materials, 2.) remaining concerns on the materials long-term durability, and 3.) development of barrier systems along with physical crash testing and repair strategies for damaged barrier systems. Fortunately, in recent years, efforts have been made to address challenges one and two. Late in 2018, AASHTO produced the second edition of the GFRP Design Guide Specification (AASHTO, 2018). In addition, several states including Florida, Ohio, and Missouri have initiated efforts to develop and standardize GFRP reinforced barriers. The first major effort to thoroughly investigate a significant number of GFRP RC bridge decks after 15-20 years of service exposure has been completed showing no signs of degradation in the reinforcing materials. In this investigation, eleven bridges situated mostly in aggressive northern climates were inspected, sampled, and studied in depth including microstructure analysis.

It appears that the remaining issue to have a fully validated steel free deck system including the bridge barrier is to 1) develop repair strategies on the barrier configurations developed/under development by the aforementioned DOT’s, 2) conduct full scale crash testing on both undamaged GFRP RC barriers as well as repaired GFRP impact damaged barriers, and 3) benchmark the test results in objective 2 to currently available crash test data for traditional reinforced barriers. This NCHRP project statement aligns well with ASSHTO strategic efforts to extend the service life of the transportation infrastructure, reduce bridge maintenance costs, and extend efforts to be more sustainable and environmentally sensitive.

Objective:

The objective of this project will be to build on existing research on GFRP RC barriers in terms of both crash testing and tested design repair strategies for impact damaged GFRP RC barriers to restore full crash test capacity to damaged GFRP RC barriers. The desire in terms of the repair strategies is to examine anchorage and internal continuity detailing such as innovative couplers and splicing details.

Related Research:

GFRP reinforcement has recently drawn tremendous amount of interest in engineering practice. Years of research together with successful pilot implementation projects have provided confidence to engineers for field implementation of GFRP in bridge structures. GFRP is a composite that combines the high strength and stiffness of the glass fiber and the ductility of the soft resin. This combination has given GFRP superior mechanical performance and durability in comparison with steel reinforcement. The GFRP rebars have been extensively investigated and validated as sound alternative reinforcing materials.

There have been both field implementations of GFRP bars and design code (AASHTO, 2009; CSA, 2000) in terms of development length and bar strength limit. Field implementation of GFRP bars in reinforced concrete superstructures are still in the early stage. In North America, there are several examples of field implementation that have demonstrated the validity of using GFRP reinforcement in a traffic barrier. Current efforts to develop standardized GFRP barriers in Florida, Ohio, and Missouri (see Fig. 1) have undergone design development with some laboratory testing such as pendulum testing. However, a gap exits in terms of full-scale crash testing that this effort proposes to investigate and validate the full crash testing validation of the barriers. Secondly, questions have arisen by barrier designers and experts, what approaches would be taken to repair impact damaged GFRP RC barriers and if proposed repair designs would be resilient to a secondary crash testing. This project statement proposes to address both of these issues.

Tasks:

Major tasks will include:

  • A State DOT survey and literature review to collect all information on current DOT GFRP RC Barrier systems such as Florida, Missouri, Ohio, etc. along with any laboratory and field-testing undertaken to date.
  • A literature review to identify promising coupler and continuity devices that have demonstrated experimental results to develop full tensile capacity in discontinuous GFRP bars. These are to be considered in the repair strategies.
  • To design and evaluate GFRP RC barriers developed with repair strategies under finite element method (FEM) modelling and laboratory static and cyclic evaluation.
  • To compare existing data on baseline RC control barriers (w/steel and GFRP) to the same barriers that have been incorporated the repair strategy in the prior task.
  • Undertake full scale crash testing and FEM modelling on undamaged GFRP RC barriers as well as damaged GFRP RC barriers that have undergone the repair strategy. MASH TL-4 impact conditions for initial testing and repair, which will consider static/dynamic component testing for investigations/verifications as required. Results from these field tests are to be benchmarked to existing crash tested steel RC barriers of the same size and cross section.

Deliverables will include:

  • Interim report on the first three major tasks to the project panel prior to proceeding to the laboratory and field-based crash testing.
  • A final publication synthesizing the findings of the project for practitioners – including DOT survey results, literature review, repair strategies, design approach, FEM modeling, experimental findings and crash testing results.
Implementation:

This research builds on GFRP barrier systems that State DOT’s have very recently designed and developed, but not demonstrated full-scale crash testing worthiness. This effort will allow bridge designers and their DOT’s to directly implement GFRP RC barrier systems with known impact resistance. Furthermore, it will provide a path forward to address GFRP RC barrier systems that are exposed to vehicular impact damage. AASHTO Committees T-6, T-7, T-10 and T-1 will be able to directly communicate the results broadly to State DOT’s in the US. Furthermore, it is anticipated that TRB Committees AKB10 and AKB30 can develop co-sponsored Webinars and Workshops at future TRB events to communicate the findings and results to the broader bridge design community and technical societies including ACI, PCI and ASCE.

Relevance:

Addressing the research gap in crash testing and repair strategies for GFRP RC barriers is required to move GFRP technology to full implementation of steel free deck systems. Transitioning away from bridge decks and barriers that use reinforcing steel will address concerns with reinforcing corrosion and greatly extend the service design life of bridge deck systems. The benefits to DOT’s that move to the implementation of GFRP RC barrier systems include cost savings due to longer service design life and reduced maintenance costs over the life of the bridge deck and barrier system.

Sponsoring Committee:AKB10, Innovative Highway Structures and Appurtenances
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Bryan A. Hartnagel, Missouri DOT & Taya Retterer, Texas DOT
Source Info:RNS Authors:
John Myers, Ph.D., P.E. , Missouri Univ. of Science & Technology
Tim Bradberry, P.E., Texas DOT
Chenglin (Bob) Wu, Ph.D., Missouri Univ. of Science & Technology
Ron Faller, Ph.D., P.E., University of Nebraska-Lincoln

Others Supporting the Problem Statement
AASHTO Committees T-1, T-6, T-7, T-10 (T-6 possible lead) as well as TRB Committees AKB10 Innovation Highway Structures and Appurtenances and AKB30 Concrete Bridge support this problem statement.
Date Posted:06/28/2021
Date Modified:07/09/2021
Index Terms:Glass fiber reinforced plastics, Barriers (Roads), Repairing, Service life, Life cycle costing, Bridge design,
Cosponsoring Committees: 
Subjects    
Design
Maintenance and Preservation
Materials
Bridges and other structures

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