This report summarizes the finite element modeling and simulation efforts on evaluating the performance of cable median barriers including the current and several proposed retrofit designs. It also synthesizes a literature review of the performance evaluation of cable median barriers, existing finite element modeling and simulation work on roadside safety, and an analysis of crash data collected by the North Carolina Department of Transportation.
Two retrofit options were proposed for this project, and several designs for each option were evaluated using the full-scale finite element simulations of a vehicle crashing into a cable median barrier. The simulation results showed that the potential of vehicle under-riding in back-side impacts was higher than that for front-side impacts, because the vehicle’s suspension was compressed and there was less median traversal width for back-side impacts. The evaluation of different retrofit options indicated that lowering the middle and bottom cables and changing the sides of all cables on the posts could increase the likelihood of redirecting small vehicles for back-side impacts without sacrificing the CMB¿s performance for front-side impacts and for large vehicle impacts. For each of the two retrofit options, a new design was developed and evaluated. The simulation results showed that the newly developed three-cable and four-cable retrofit designs could improve the performance relative to the current design in back-side impacts without sacrificing its performance in front-side impacts.
The simulation results of this project should only be used to investigate performance trends for evaluating the CMBs; they should not be used to draw definitive conclusions about CMB performance for a specific crash event, because many factors affecting CMB performance were not considered in the simulations. Finite element analysis was shown to be a useful tool in crash analysis and could be used in future research to investigate these remaining issues.
