The soil material model using the Nebraska soil parameters provided by the developer do not accurately simulate the physical testing (as shown in the following figures).
Using
different computer platforms, a comparison of three different models using the FHWA soil model in LS-DYNA is made. Results from an Intel ®-based PC (using Windows) are
provided by both the developer and the user, while UNIX-based results from an
SGI Octane ® (using
UNIX) are provided by the user.
The user's SGI results were obtained using LS-DYNA, Version 970 Beta, Revision
1812, June 7, 2002, for an SGI Workstation IRIX64 6.5.
The developer's PC results were obtained using LS-DYNA, Version 970 Beta, Revision
1812, June 7, 2002, for a PC (Intel) Windows 2000.
Although the results are shown to be different in the latter
stages of the simulations on the different computer platforms, they appear to
be within an acceptable range based on previous experience with using different
computers.
Two single element models were run to check the consistency
between the PC (Intel)-based computers and the SGI-based computers. Specific
results for each model are described below. The developer supplied only the d3plot files from these runs; thus, the
comparison is limited to the information stored in those files.
The deformed geometry of the single element models appeared
to be the same and, thus, are not shown.
The
internal energy for the hydrostatic tension runs are shown in figure 26. The results are nearly identical until 35
ms. After 35 ms, the results for the
SGI and PC begin to diverge. There was
no discernible difference between the developer's PC and the user's PC results. The difference between the SGI and PC
results after 35 ms is attributed to the significant plasticity that the
element has undergone after that time. Once plasticity becomes great enough, round-off errors between the
computer platforms begin to influence the results. This, however, is only conjecture.
The internal energy and effective stress for the triaxial
compression runs are shown in figures 27 and 28. The results are nearly identical, with the exception that the
single element in the user's SGI run fails a few cycles before the PC runs.
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