BACKGROUND
Flexible rockfall protection systems have been in service along roadways in Europe and the United States for more than 40 years. In the United States, thousands of rockfalls occur each year along highways; consequently, rockfall protection systems have become an important component of highway safety and maintenance. Flexible rockfall protection systems that are intended to control rockfall and/or reduce the potential for rock debris to fall within highway alignments include ring-net barrier fences, cable-net barrier fences, draped cable-net, draped wire-mesh, attenuators, and other systems. The flexible rockfall protection systems include components such as wire rings, wire rope, wire rope nets, wire mesh, posts, pins, fasteners, connections, braking elements, and anchors. Flexible rockfall protection fence systems are usually designed and rated based on full scale testing of energy capacity or energy reduction of a single rockfall event with some consideration for serviceability after specific impacts. Many of these systems were developed in Europe and are proprietary. Prior to 2003, no widely accepted means were available to test and certify flexible rockfall protection fence systems sold in the United States. In 2003, NCHRP Project 20-07, Task 138, “Recommended Procedures for the Testing of Rockfall Barriers” (Higgins 2003) was submitted to AASHTO. This task report recommended acceptance of the Swiss testing standard and certification process (Gerber 2001). In 2008, the European Union (EU) implemented standardized testing and certification of rockfall fences known as ETAG 27 (from the European Technical Approval Guidelines). ETAG 27 differs from the Swiss standard. All European manufacturers are now certifying their products in accordance with ETAG 27. Currently, U.S. transportation agencies do not have testing standards and certification procedures for these rockfall protection fence systems. Guidance is required to address these issues.In addition, the long-term performance and maintenance issues of these systems are a growing concern since many departments of transportation that have installed these systems are faced with significant maintenance, repair, and/or replacement costs. Currently, there are no well-defined provisions or protocols for condition assessment and service-life modeling of rockfall protection systems. Asset management offers a framework for monitoring performance of rockfall protection systems and understanding the condition/deterioration time-line so the owners can make informed life cycle cost-based decisions about these assets. Combining technical analysis with asset management principles can yield a more efficient and fiscally responsible transportation system that focuses on preservation of assets while maintaining the required level of service set by owners.
OBJECTIVE
The objective of this research is to produce a guidebook on flexible rockfall protection systems for transportation agencies that addresses the following:
- Inspection, maintenance, and repair procedures for flexible rockfall protection systems (e.g., drapes, pinned mesh, attenuators, and barriers).
- Testing, approval, and certification methodologies, as well as proposed performance-based specifications for flexible rockfall fence systems and components thereof.
- Development of an asset management plan, including long-term performance and condition measures; and establishment of critical factors and key components in determining estimates of future performance, life-cycle cost, and cost/benefit analysis for maintenance, repair, or replacement decisions for flexible rockfall protection systems.
- Creation of a database capable of recording and suitable for analyzing the asset management plan information for flexible rockfall protection systems.
RESEARCH PLAN
Proposers are asked to develop and include a detailed research plan for accomplishing the project objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective. The work proposed must be divided into tasks and proposers must describe the work proposed in each task in detail. The research plan should build in appropriate deliverables, in addition to the required quarterly reports, that include, at a minimum, an interim report that describes the work done in early tasks (covering the first third to half of the research) and updates the work plan for the remaining tasks; the guidebook; a final report providing background information used in the development of the guidebook; and a PowerPoint presentation describing the background, objectives, research method, findings, and conclusions. The research plan should build in a face-to-face interim report review meeting. The research team will be expected to present the project results at a meeting of a relevant national organization to be determined by the panel. The schedule should include 1 month for NCHRP review and comment on the interim report and 3 months for panel review and for contractor revision of the preliminary draft guidebook and final report. Proposers should provide their initial thinking on the format of the final deliverables (e.g., guidebook, final report documenting the research, PowerPoint presentation, etc.).
In developing the research plan and proposed deliverables, proposals should:
- Include a literature search necessary to support the project objectives.
- Review ETAG technical approval procedures.
- Prepare a communication plan for disseminating the results of this research.
STATUS
A copy of NCHRP Report 823 Guidelines for Certification and Management of Flexible Rockfall Protection Systems is available HERE.
A copy of the Final Report for NCHRP Project 24-35 is available HERE.
