Conclusions

These tractor-semitrailer vehicle FEM models are the best 36000V class vehicle FEM models currently available to the roadside safety research. As of this writing they are the most advanced FEM models publicly available of this vehicle in terms of physical function, geometric detail and material property accuracy. These models are computationally quite robust given their complexity. They have been extensively debugged and exercised hundreds of times for the cases within the range of NCHRP Report 350 TL-5 speeds and impact angles.

In developing these FEM models, computational efficiency is considered wherever possible, but computational efficiency is considered second to fidelity. The philosophy is that today's computational resources are small relative to the next generation.

These FEM models fulfill their intended application for evaluating the crash performance of roadside safety features based on the crash test guidelines of National Cooperative Highway Research Program (NCHRP) Report 350 Recommended Procedures for the Safety Performance Evaluation of Highway Appurtenances for Test Level 5. In such applications, these tractor-semitrailer models serve as "bullet" vehicles, whose purpose is to accurately simulate the load transfer from the vehicle to the barrier during and after impact.

In validation phase of this project, representative tractor FEM models were created for comparison to the MwRSF test TL5CMB-2 and the TTI test 7069-13 which reflected more closely the geometry of the crash test vehicles. These FEM models were validated using the verification and validation procedures of NCHRP Project 22-24. Based on the metrics used in these verification and validation procedures, the simulation of the MwRSF test TL5CMB-2 compared very well with the crash test data and is considered a validated FEM model. Based on these same metrics, the simulation of the TTI test 7069-13 did not compare very well with the crash test data, and is cannot yet be considered a validated FEM model. The procedures used and the results of the quantitative validations of both simulations to their respective tests are described in detail in the project reports. By studying these cases the reader can see a real-world example of a well-validated and a non-validated FEM simulation performed according to the objective criteria set forth in the validation procedures.