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21 CHAPTER 4 Conclusions and Recommendations Assessment 2. Reformulating the Duncan and Duncan/Selig soil model into a plasticity-based model to properly simulate unloading. Every objective for the new CANDE capabilities and user- 3. Incorporating shear deformation into structural beam- friendly GUI options has been met or exceeded. Of course, column elements. the user community will make the final judgment on the 4. Possible incorporation into the AASHTOWareTM suite of utility of CANDE-2007 after it is released into the public products such as Virtis or Opis. domain. Since the older versions of CANDE have been ex- 5. Enhanced mesh generation capabilities. tensively used during the last 30 years to design highway 6. Load rating capabilities. culverts and other soil-interaction structures, it is reasonable to expect that engineers will continue to use CANDE in its As in the past, it is quite likely that some researchers will newest version. In particular, when engineers are confronted undertake incorporating one or more of the above capabilities with specialized installations that do not lend themselves to into CANDE-2007 using their own research funds. This is an simplified or routine design methods, it is anticipated that advantage of public domain software, like CANDE, wherein the CANDE-2007 will be the tool of choice. Moreover, because entire user community contributes to future developments. of the new user-friendly interface and the new LRFD design methodology, the CANDE usage may expand to include more routine culvert designs. Implementation It is recommended that AASHTO pursue all avenues of technology transfer for the CANDE software, not only its in- Future Research house methodology for software transfer and maintenance. As with any successful computer program, future upgrades In summary, the researchers are confident that the new and enhancements are a continuing process. Based on the CANDE-2007 program is the best available tool for culvert comments of beta testers and survey results, the next recom- design and analysis. Further, the researchers believe CANDE mended set of new capabilities to be incorporated into will continue to be the tool-of-choice well into the future pro- CANDE-2007 include the following: vided that CANDE's successful attributes are maintained. These attributes include formulations that are based on sound 1. Element death option to simulate removal of temporary principles of soil-structure interaction and a well-documented bracing, excavating of soil, or loss of structural elements source code to allow other researchers to develop and test new due to aging and corrosion/abrasion. theories and concepts in soil-structure interaction.