Digital Simulation Analysis for Evaluating Earth Berm Design and Vehicle Dynamics.

摘要

This study deals with the evaluation and modification of the original North Carolina earth berm based on the generalized vehicle dynamic analysis and computer-aided design using digital simulation techniques. Simulation runs of vehicle-berm interaction were made on both main and transition sections of the original N. C. and the modified berm. The modified berm design RS with energy-dissipating steps would safely redirect a vehicle impacting the berm at 60mph with an approaching angle up to 20degrees while the maximum safe approaching angle for the original N. C. earth berm was 11degrees. Three types of median-curb configurations were investigated to determine the vehicle behavior. The maximum vehicle encroachment angles were evaluated for two maximum steer angles at 45and 60mph speeds. The effects of soft soil on vehicle dynamic behavior were studied extensively. The original and modified earth berms with soft earth were capable of redirecting a vehicle approaching at 13and 24degree angle respectively with 60mph speed. Analytical movie techniques were applied to demonstrate the vehicle dynamics and vehicle-berm interactions. Simulation runs on the modified berm without steps showed that the maximum safe approaching angle was 14degrees on the soft-surfaced and 11degrees on the hard-surfaced berm. In order to facilitate the interpretation of massive output data from a simulated event,computer graphic displays were used to show the detailed perspective and top views of the vehicle dynamics and designed roadside geometric configuration as seen from a selected viewing position and time intervals.