A Study of the Deflections of Metal Road Guardrail Post

This article reports on a study of the deflections of differently-shaped metal road guardrail posts. The authors analyzed the deformation processes of the sigma(Σ)-shape and double T-shape metal posts of guardrails, using a mathematical model. The analysis used one-dimensional first-order finite elements, and considered elastic deformations, as well as the effect of soil on the buried post section of the guardrail. The deflections of Σ-shape and double T-shape metal posts caused by the impact of a motor vehicle moving at varying speed are then determined. The authors found that the deformation of the sigma-shape post is not so heavy compared to the double T-shape post deformation. This property of the sigma-shape post was found irrespective of the post location (on the road shoulder or on a bridge) or the motor vehicle’s speed at the moment of collision. The authors conclude that guardrails with high deformation behaviors, such as the sigma-shape post, are most effective in keeping travel along the longitudinal axis of the guardrail and/or fully stopping the vehicle.