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21.1 Problem Statement 1.1.1 Certification of Rockfall Fence Systems in the United States Rockfall fence systems are used to mitigate rockfall and generally consist of flexible nets or panels that are connected to a post system with energy absorbing braking elements. Rockfall fence systems are currently designed and given an energy rating based on full-scale field testing to determine the energy capacity or energy reduction of a single rockfall event with variable considerations for serviceability after specific impacts. Most of the current tested and rated rockfall fence systems manufactured today were developed in Europe and are specific to a manufacturer system. Before 2003, no widely accepted means were available to test and certify fences sold in the United States. In 2003, NCHRP Project 20-07/Task 138, âRecommended Procedures for the Testing of Rock-Fall Barriersâ (Higgins 2003) was submitted to the AASHTO. This task report recommended acceptance of the Swiss testing standard and certification process developed by the Swiss Agency for the Environment, Forests and Landscape (SAEFL) and the Swiss Federal Research Institute (WSL) (Gerber 2001). In 2008, the EU implemented standardized testing and certification of rockfall fences known as ETAG 27 for Falling Rock Protection Kits (European Organisation for Technical Approvals [EOTA] 2008). ETAG 27 differs signifi- cantly from the Swiss standard. Most European manufac- turers 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 fence systems. 1.1.2 Asset Management of Flexible Rockfall Fence Systems MAP-21, the Moving Ahead for Progress in the 21st Cen- tury Act (P.L. 112-141), was signed into law July 6, 2012, and took effect October 1, 2012. The bill provides funds for surface transportation investments in fiscal years 2013â14, and also establishes a new performance-based management frame- work. While the language mandates an inventory of pavement and bridge assets on the National Highway System (NHS), it also encourages states to include all infrastructure assets within the right-of-way corridor, requires states to achieve or make significant progress toward achieving its performance targets, and establishes penalties for non-compliance. MAP-21 does not approve or certify a stateâs asset management plans, but certifies the process used in developing such plans. At the time, it did not specifically contain references for asset management related to geotechnical features but many departments of trans- portation (DOTs) are developing such processes. By including geotechnical assets within an agencyâs asset management plan, the potential benefits and staying power of best-practice asset management will be enhanced. Overall, the desired outcome of geotechnical asset manage- ment is the establishment of more predictable and sustainable funding allocation policies and program management deci- sions. A difficulty that will need to be overcome in develop- ing asset management related to geotechnical features is that steel, concrete, and pavement have well-defined and mea- sureable parameters that relate well to performance-based management systems, whereas soil and rock are generally not well defined and have wide ranges in measurable and non- measureable parameters. 1.2 Research Objectives The objective of this research was to produce guidelines on rockfall fence systems for transportation agencies that address the following: ⢠Testing, approval, and certification methodologies, as well as proposed performance-based specifications for flexible rockfall fence systems and components thereof C H A P T E R 1 Background
3 ⢠Inspection, maintenance, and repair procedures for flex- ible rockfall fence systems ⢠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, and replacement decisions for flexible rockfall fence systems This guidebook presents the results of the research effort. A detailed discussion of the research can be found in the Final Report, which is available on the NCHRP Project 24-35 web page at www.trb.org.
