ETAG certified rockfall barriers — new design approach according to UNI 11211:4/2012

Abstract

European Technical Approval Guideline (ETAG) 027 ensures that a tested falling rock protection kit (interception structure, support structure and connection elements) is able to withstand a series of impacts for a fixed energy level. The main manufacturers of flexible rockfall barriers have tested and certified their products in compliance with this guideline. To take into account the differences between the field tests, which are carried out in controlled state, and the real conditions in situ, a new guideline was developed in January 2012 by the Italian Organization for Standardization, Ente Nazionale di Unificazione (UNI), named UNI 11211-4:2012. The purpose of this guideline is to ensure a high level of safety for the structures protected by the flexible rockfall barriers considering all the possible uncertainties that are normally found during the design process (height of the bounce, mass of the rock, velocity etc.). The calculation methodology suggested by the UNI 11211 4:2012 is the well-known limit state design approach. The purpose of this paper is to present the differences between tests and real in situ conditions, and to introduce the new design approach proposed by the UNI 11211:4/2012. Some practical aspects on the installation of the rockfall barriers that need to be considered during the design stage will also be highlighted.