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Publication Number: FHWA-HRT-04-096
Date: August 2005

Evaluation of LS-DYNA Wood Material Model 143

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10 - Validation Criteria for the Wood Material Model

To validate the wood material model, several criteria must first be developed in order to determine whether the model is working as desired. To this end, the validation process at the user’s facility consisted of verifying that the results were similar on different computer platforms (chapter 11) by simulating single-element models in order to check basic fundamental behavior (chapter 12), simulating static wood post tests (chapter 13), simulating dynamic wood post tests (chapter 14), checking the sensitivity of the simulation models by varying numerous parameters (throughout chapters 12, 13, and 14), and by simulating wood-cube crushing tests performed in parallel with this project. Because of time constraints, the cube crushing test and simulation were not revisited in this final report. Interested readers are urged to contact the user for details.

10.1 - NDOR Tests: Performance Envelopes

In 1995, the user ran a series of static and dynamic post testing for the Nebraska Department of Roads (NDOR). The series consisted primarily of 152.4-mm by 203.2 mm by 1828.8-mm (6-inch by 8-inch by 72-inch) southern yellow pine of various grades and ages. The wood posts were obtained from previously installed guardrail systems throughout Nebraska. A smaller series of dynamic tests using frozen southern yellow pine and Douglas fir wood posts were also conducted.

Data collected from the 1995 NDOR project were to be used for validating the wood material model. Based on several meetings and discussions, the simulation user community requested that the wood material model have specific options for selecting southern yellow pine of grades DS-65 and 1/1D (among other options). In order to validate the material model for those specific cases, the 1995 NDOR data were completely analyzed to determine the appropriate tests with which to compare the simulation results. The details for the results of this analysis are not presented herein; however, interested readers are urged to contact the user for details. Grades 1 and 1D wood post test results showed very little difference in behavior; thus, this report will use the terminology of grade 1 to represent the combined grades 1 and 1D.

Performance envelopes were constructed using the most typical behavior of the desired wood and grades for both static and dynamic test conditions (see figure 56). Force-deflection and energy-deflection results from the simulations would need to fall within the performance envelopes in order to be considered validated. Photographs from the testing are presented in figures 57 through 61.

Figure 56a.
(a) Grade DS-65 force
Figure 56b.
(b) Grade 1 force
Figure 56c.
(c) Grade DS-65 energy
Figure 56d.
(d) Grade 1 energy
Figure 56. Performance envelopes from 1995 NDOR testing.

Figure 57.

Figure 57. Static post setup.

Figure 58a.
(a) Post and bogie vehicle
Figure 58b.
(b) Post
Figure 58. Dynamic post setup.
Figure 59a.
(a) DS-65 post
DS-65 Figure 59b.
(b) DS-65 closeup
Figure 59c.
(c) Grade 1D post
Grade 1D Figure 59d.
(d) Grade 1D closeup
Figure 59e.
(e) Grade 1 post
Grade 1 Figure 59f.
(f) Grade 1 closeup
Figure 59. Typical static post test results
Figure 60a.
(a) DS-65 breakage
DS-65 Figure 60b.
(b) DS-65 post
Figure 60c.
(c) Grade 1D breakage
Grade 1D Figure 60d.
(d) Grade 1D post
Figure 60e.
(e) Grade 1 breakage
Grade 1 Figure 60f.
(f) Grade 1 post
Figure 60. Typical dynamic post test results
Figure 61a.
(a) Clean break
Figure 61b.
(b) Atypical behavior
Figure 61. Other dynamic post test results.

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