A Simulation Study On The Effect Of Soil Foundation On The Crashworthiness Of The Guardrail

W-beam guardrail as an important road-safety protection equipment has been widely used in highway around China.Soil foundation can be very significant to the Crashworthiness of the guardrail ,the stiffness of the guardrail will reduce when the soil foundation can not meet the requirements, and this will weaken the protection of the gardrail because of the larger lateral deflection when impact accident happends. Therefore, the study on the effect of soil foundation on the guardrail is very important.Finite element method is a fundamental part of the analysis and design of roadside guardrail.This paper starts with explaining the theories of basic F.E.algorithms of impact problems , and then discuss the basic typical impact simulation .The paper introduces the soil constitutive model and soil material model in F.E. code LS-DYNA, Base on that, NO.78 material model of F.E.code LS-DYNA has been tested. The Model of soil-post quisa-static loading has been developed using the Lagrange formulation and Euler multi-material formulation ,A systematic parametric study is consequently carried out to understand the effect of the strength of the soil . Since it is expensive to include the soil F.E. model in the impact simulation, The paper discuss a method which involves the use of the discrete spring element to correctly simulation the soil-post interaction. On the basis of above work, The w-beam guardrail F.E. model had been developed and validated. Finally, a 2000kg vehicle traveling at 100 km/h was used to impact the guardrail at an angle of 20 degrees, the Crashworthiness of guardrail which post in different foundation has been discussed.The study shows that the lateral deflection of guardrail systems is governed by the degree of compaction, and when the degree of compaction reach 96% , the lateral deflection is governed by the post failure.The changing of the cross-section force is the same as the lateral deflection.All these work in this article will provide a guideline for developing a safer guardrail.