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