Cable Guardrail End Terminal Simulation FHWA Center of Excellence in DYNA3D Analysis
John Reid, Nicholas Hiser
The objective of this simulation research is to develop detailed finite element models of a new cable barrier end terminal being developed at the Midwest Roadside Safety Facility. The primary complicated feature of the end terminal is the slip base mechanism used on the first post in the system. Model development involved locating and isolating the physical phenomenon that occurs within the slip base mechanism, including fricitonal sliding behavior, friction coefficients, and bolt preloading. These phenomena were individually modeled, tested, and evaluated prior to application within a more complex model, incrementally validating the model components until a complete slip base model was attained. Two bolt preloading techniques were developed and evaluated, including one method which utilized a discrete spring element, and a second method which utilized pre-stressed bolt shaft elements. Both methods produced desired bolt preload, as well as acceptable correlation with data obtained from tensile testing of a slip base joint. However, after incorporation of both preloading techniques into post and slip base models, preliminary impact simulations indicated that the model using pre-stressed solid elements was significantly more accurate and thus, was used for further study. Additionally, results from a friction investigation showed that mesh size is critical for contact stability and for capturing theoretical slip behavior. The verified post and slip base model was then incorporated into the new cable guardrail system end terminal model. Performance of the slip base model was acceptable in both end-on impact and length-of-need impact simulations. Thus, the model was deemed appropriate for use in further development and analysis of existing cable systems, as well as alternate slip base applications.
LS-DYNA Simulation, Cable Guardrail End Terminal, Three Strand Cable, Nonlinear Finite Element Analysis