Numerical Simulation And Analysis Of Semi-rigid Guardrail When Crashed With The Carriage

Over 110 thousand people caused by traffic accidents die annually in China and about one third of fatal accidents are single-vehicle accidents involving the impact between vehicles and roadside guardrails, which result in numerous casualty and property losses. As one of the most important traffic safety appurtenances on expressway, guardrail plays a key role in reducing the severity and property losses of road accident. As a result, the research of the impact between vehicles and guardrails has many realistic meaning. In this thesis, taking the W3beam semi-rigid guardrail with BHI distant spacer and the DD6980 carriage produced by the HuangHai car company as the researching objects, some research on the recovery ability of the guardrail and the factors which affect the recovery ability of the guardrail are analyzed. The main aspects are as follows:In the first, background of highway development and data collecting and statistics analysis of highway accidents at home and abroad are carried out. Researches of vehicle-barrier crash accidents on highway are compared between in and outside China.Secondly, the basis principle and relating algorithms of dynamic explicit finite element method are introduced. Topics discussed include the governing equation, shell element algorithms material model, stress modify, time integration, contact-impact interface and etc, which offer the academic foundation for later chapter.Thirdly, based on ANSYS/LS-DYNA, a finite element calculational and analytic model for the whole "carriage -guardrail" crashing system is established. In this model, some predigestion of the carriage model and some suppose of the crashing are allowed, the shape and geometry dimension of the carriage and the material and connecting method of the guardrail are taken into account, all contact parts between the carriage and guardrail are subdivided, and the effect of friction is thought over.Finally, the recovery ability to the carriage of the W3beam semi-rigid guardrail with BHI distant spacer is evaluated by using the value index for the recovery ability of guardrails accepted in the world. By adjusting the initial impactive velocity, impactive angle and the frictional modulus between the carriage and guardrail, the impacting process between the carriage and guardrail is simulated and studied, and the fators which affect the recovery ability of guardrail is analyzed. In this thesis, a series of conclusions are made: The guardrail has a good recovery and guiding ability when the carriage crashed the guardrail; The factors such as initial impactive velocity, impactive angle and the frictional modulus between the carriage and guardrail can affect the recovery ability of the guardrail; With the increase of that three factors, the resultant acceleration of the carriage centroid will increase and the risk of the passenger damage will be bigger. Based on the analysis of the stumbling process when the carriage crashed the post, this thesis proposes two measures to avoid stumbling. The results from this study indicate that increasing the block's transverse length and the post's thickness can all avoiding the stumbling, but the latter has better performance than the first one in improving the defending ability of the guardrail.