Road safety barriers are a passive safety system and usually they are made of steel or cement concrete. Ac-tually, road barriers made of wood and steel are located in context of particular environmental value (moun-tains, countryside, or along a road close to a park or in a park). The aim of this research is a new safety road barrier made completely of wood. Wood is a material with a complex structure, whose main features are anisotropy and hygroscopicity. It al-so possesses greatly different mechanics characteristics between the longitudinal direction and the tangential and radial direction. In Europe, road safety barriers have to pass crash tests required by EN1317 before their location. So in this study, several barriers have been designed and modelled and, for each of them, impact with a vehicle has been simulated with the software Ls-Dyna, following EN 1317 prescriptions. Analysis of the different models and their compliance with the requirements of the Standard, has allowed the authors to identify the optimal sec-tion of beams and posts, the distance between beams and between posts of the new barrier. Furthermore, a parametric analysis has been conducted, to examine how temperature and humidity can modify mechanical characteristics of wood and so performance of the new barrier. The results appeared interesting: the new barrier satisfied all requirements prescribed by the Regulation and the parametric study highlighted that THIV (Theoretical Head Impact Velocity) and ASI (Acceleration Severity Index) vary with temperature and humidity but their values were always below the limit imposed by EN 1317. This study represents only one step of the research which needs more data to individuate a correlation be-tween temperature and humidity and ASI and THIV indexes, and a real scale test to calibrate the model.
Environmentally friendly road barriers
MALTINTI, FRANCESCA
2014-01-01
Abstract
Road safety barriers are a passive safety system and usually they are made of steel or cement concrete. Ac-tually, road barriers made of wood and steel are located in context of particular environmental value (moun-tains, countryside, or along a road close to a park or in a park). The aim of this research is a new safety road barrier made completely of wood. Wood is a material with a complex structure, whose main features are anisotropy and hygroscopicity. It al-so possesses greatly different mechanics characteristics between the longitudinal direction and the tangential and radial direction. In Europe, road safety barriers have to pass crash tests required by EN1317 before their location. So in this study, several barriers have been designed and modelled and, for each of them, impact with a vehicle has been simulated with the software Ls-Dyna, following EN 1317 prescriptions. Analysis of the different models and their compliance with the requirements of the Standard, has allowed the authors to identify the optimal sec-tion of beams and posts, the distance between beams and between posts of the new barrier. Furthermore, a parametric analysis has been conducted, to examine how temperature and humidity can modify mechanical characteristics of wood and so performance of the new barrier. The results appeared interesting: the new barrier satisfied all requirements prescribed by the Regulation and the parametric study highlighted that THIV (Theoretical Head Impact Velocity) and ASI (Acceleration Severity Index) vary with temperature and humidity but their values were always below the limit imposed by EN 1317. This study represents only one step of the research which needs more data to individuate a correlation be-tween temperature and humidity and ASI and THIV indexes, and a real scale test to calibrate the model.
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