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14 program. These and other improvements are discussed in the Process 12-50 tags fully documented in the CANDE-2007 CANDE-2007 User Manual and Guideline. User Manual and Guideline. The FORTRAN code has also been updated from the After beta testing was completed and the panel viewed the 1989 code to provide a clearer more structured architecture. results, a list of items that were beyond the scope of this The FORTRAN analysis program is now compiled as a research effort was added to a future development list. These DLL that is called directly from the GUI. items include the following: 1. Element death option to simulate removal of temporary Testing and Evaluation bracing, excavating of soil, or loss of structural elements Checking and testing the accuracy and validity of the new due to aging and corrosion/abrasion. capabilities and modifications include comparing CANDE- 2. Reformulating the Duncan and Duncan/Selig soil model 2007 solutions with older versions of CANDE, closed form into a plasticity-based model to properly simulate un- solutions, simplified AASHTO solutions, and general loading. purpose finite element programs conducted. This type of 3. Incorporating shear deformation into structural beam- testing, called alpha testing, was accomplished by the proj- column elements. ect team during and after the development phase of each 4. Possible incorporation into the AASHTOWareTM suite of new capability. The results of the alpha-testing phase products such as Virtis or Opis. indicated that the new capabilities were accurate and func- 5. Enhanced mesh generation capabilities. tioning as planned. 6. Load rating capabilities. The beta-testing phase, involving CANDE-2007 testers outside the project team, began in May 2007 with the NCHRP project panel serving as the initial beta testers. Sub- Applications--Tutorials sequently, the beta testing was expanded with 35 beta-tester The applications of the new CANDE-2007 program are volunteers from the culvert community over a testing period best demonstrated with the CANDE tutorial problems. For a of 3 months. Beta testers had access to a project website and complete understanding, the reader is invited to peruse the software to easily record all problems and comments. Of the companion document entitled, CANDE-2007 Tutorial of 35 beta testers and 10 panel members, 16 testers recorded Applications. problem reports on the project website. By the end of beta testing, 141 beta incidents were logged on the website. The entire list of beta incidents was reviewed by the project panel List of Tutorial Problems at an October 2007 meeting. The vast majority of issues dealt with questions about interpretation of input variables. Listed in Table 1 are the 16 tutorial examples (Note: Accordingly, the CANDE-2007 User Manual and Guideline examples 15 and 16 are only input files and do not include the was revised to address these questions. Some comments led problem description/narration) that cover all aspects of to the discovery of bugs in the CANDE-2007 program, which CANDE-2007 capabilities including multiple structures and were corrected. Another class of beta-testing comments dealt retrofit problems. with desires for future additions to CANDE-2007. These comments will continue to be maintained by the project team Illustration of Tutorial for the purposes of building a list of possible future enhance- ments for the CANDE software. Tutorial examples (Tutorials 114) describe the physical The beta-testing phase proved to be very effective in un- nature of the problem to be solved followed by step-by-step covering problem areas in the software as well as areas of input instructions as well as illustrations of graphical solutions potential misunderstanding on the part of the user that could and an evaluation of the culvert safety in terms of design cri- be addressed by enhancements to the CANDE documenta- teria. To illustrate the contents of the CANDE-2007 Tutorial tion. All beta-testing incidents have been addressed and of Applications, Tutorial Example #4 is highlighted below. resolved except for those issues that are classified as a future Tutorial Example #4 seeks a design solution for a 60-in. enhancement. inside diameter corrugated aluminum pipe with 30 ft of fill To enhance future regression testing of the software over the top of the pipe using the Working Stress (service) (i.e., comparing a revised version of the software numerically Design method. The problem is shown schematically in with a previous version), the NCHRP Process 12-50 (8) has Figure 9. The problem employs Solution Level 2, using an been incorporated into the CANDE Engine with the new automated finite element pipe mesh for a trench installation

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15 Table 1. Tutorial Example Descriptions. Problem Description 1 Level-1, Corrugated Steel Pipe, Design mode (LRFD). Design a 60 in. inside diameter corrugated steel pipe with 30 ft of fill over the top of the pipe using LRFD design. The design will be with Level 1, which is based on the Burns and Richard elasticity solution. The desired result is the corrugation size and thickness. 2 Level-1, Reinforced Concrete Pipe, Design mode (LRFD). Design a 60 in. inside diameter reinforced concrete pipe with 30 ft of fill over the top of the pipe using LRFD design. The design will be with Level 1, which is based on the Burns and Richard elasticity solution. The desired result is the required inner and outer reinforcement. 3 Level-1, HDPE Plastic Pipe, Design mode (LRFD). Design a 36 in. outside diameter smooth wall HDPE plastic pipe with 40 ft of fill over the top of the pipe using LRFD design. The design will be with Level 1, which is based on the Burns and Richard elasticity solution. The desired result is the wall thickness. 4 Level-2, Corrugated Aluminum Pipe, Design mode (Working Stress). Design a 60 in. inside diameter corrugated aluminum pipe with 30 ft of fill over the top of the pipe using Working Stress (service) design. The design will be with Level 2, using an automated finite element pipe mesh for a trench installation having no interface elements. The desired result is the corrugation size and thickness. 5 Level-2, HDPE Plastic Pipe, Analysis mode (Working Stress). Analyze a 36 in. outside diameter smooth wall HDPE plastic pipe with 40 ft of fill over the top of the pipe using Working Stress (service) analysis. The analysis will be with Level 2, using an automated finite element pipe mesh for an embankment installation having no interface elements. 6 Level-2, Reinforced Concrete Arch, Analysis mode (LRFD). Analyze a 237-in. span (90-inch rise) reinforced concrete arch supported on spread footings with 2 ft of fill over the top of the arch, using LRFD analysis. The analysis will be with Level 2, using an automated finite element arch mesh for a trench installation having interface elements. The automated finite element mesh will be modified using Level 2-extended to apply point loads depicting a LRFD design truck at the ground surface above the crown of the arch. Additionally, the live load rating procedure will be demonstrated using CANDE output. 7 Level-2, Reinforced Concrete Box, Analysis mode (LRFD). Analyze a 120 in. x 84 in. reinforced concrete box culvert with standard ASTM steel placement with 2 ft of fill over the top of the culvert using LRFD analysis. The analysis will be with Level 2, using an automated finite element box mesh for an embankment installation. 8 Level-2, Corrugated Steel Pipe, Analysis mode (LRFD). Analyze a 144 in. corrugated steel pipe with 8 slotted joints and 60 ft of fill over the top of the pipe using LRFD analysis. The analysis will be with Level 2, using an automated finite element pipe mesh for an embankment installation having no interface elements. The automated finite element mesh will be modified using Level 2-extended to reduce the thickness of the construction steps above the crown of the pipe. 9 Level-2, Corrugated Steel Long Span, Analysis mode (Working Stress). Analyze a 217-in. span (82-inch rise) 3-segment type corrugated steel long span arch supported on spread footings with 3 ft of fill over the top of the arch, using Working Stress (service) analysis. The analysis will be with Level 2, using an automated finite element arch mesh for a trench installation having interface elements. The automated finite element mesh will be modified using Level 2-extended to apply point loads depicting an LRFD design truck at the ground surface above the crown of the arch. 10 Level-2, Reinforced Concrete Pipe, Design mode (LRFD). Design a 72 in. inside diameter concrete pipe set on gravel bedding with 60 ft of fill over the top of the pipe using LRFD design. The analysis will be with Level 2, using an automated finite element pipe mesh for an embankment installation having a 6 in. layer of soft backpacking soil around the circumference of the pipe and no interface elements. The desired result is the required inner and outer reinforcement. 11 Level-2, Plastic Pipe (Profile), Analysis mode (Working Stress). Analyze a 48 in. inside diameter corrugated plastic (profile) pipe with 40 ft of fill over the top of the pipe using Working Stress (service) analysis. The analysis will be with Level 2, using an automated finite element pipe mesh for a trench installation having interface elements. The automated finite element mesh will be modified using Level 2-extended to change the haunch zones to a user-defined soil material and the thickness of bedding layer to 6 in.

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16 Table 1. (Continued). Problem Description 12 Level-3, Reinforced Concrete Box, Analysis mode (LRFD). Analyze a 120 in. x 84 in. reinforced concrete box culvert with standard ASTM steel placement with 2 ft of fill over the top of the culvert using LRFD analysis. The analysis will be with Level 3, using a user-generated finite element mesh for an embankment installation. This problem analyzes the reinforced concrete box culvert from Tutorial Problem 7, which was performed using a Level 2 analysis. 13 Level-3, Corrugated Steel Long Span, Analysis mode (Working Stress). Analyze a 217-in. span (82-inch rise) 3-segment type corrugated steel long span arch setting on concrete footings with 3 ft of fill over the top of the arch using Working Stress (service) analysis. The analysis will be with Level 3, using an imported finite element arch mesh in XML format from Tutorial Problem 9 for a trench installation having interface elements. This problem analyzes the corrugated steel long span arch from Problem 9, which was performed using a Level 2 analysis. 14 Level-3, Reinforced Concrete and Corrugated Aluminum Arch, Analysis mode (Working Stress). Analyze a two-material structure composed of a reinforced concrete U-shaped base with 15-ft span and 5-ft rise supporting a pin connected, corrugated aluminum arch-shaped roof with 13 ft of fill over the top of the arch. The analysis will be with Level 3, using an imported finite element mesh in XML format. 15 Level-3, Multiple Plastic Arches, Analysis mode (LRFD). Analyze three corrugated plastic arches with 42 in. span and 27 in. rise placed side by side with 8.5 in. spacing between the legs (storm water retention chambers) with 2 ft of soil over the top of the arches. The analysis will be with Level 3, using a user-generated finite element mesh for a trench installation. The desired analysis result is to evaluate LRFD local and global buckling. (INPUT FILE ONLY) 16 Level-3, Corrugated Steel Pipe Retrofitted with Plastic Pipe Liner, Analysis mode (Working Stress). Analyze a 48 in. corrugated steel pipe with an eroded invert and retrofitted with a profile plastic pipe with 5 ft of fill over the top of the pipe. The analysis will be with Level 3, using a user- generated finite element mesh for a trench installation. (INPUT FILE ONLY) without interface elements. The desired results are the corru- corrugation tables for aluminum culverts and lists the least gation profile and sheet thickness and a final evaluation. weight design solution for each corrugation size. The tutorial leads the user through 10 GUI-input screens From the list of acceptable corrugation sizes, CANDE that convey the above physical information into a complete selects the corrugation with a combined minimum thrust CANDE input document. After executing the input file, area and moment of inertia for a final analysis and evalua- CANDE generates the symmetric mesh shown in Figure 10 tion. In this example, the selected corrugation profile is wherein the shaded/numbered layers of soil are construction 2-2/3 in. (period) by 1/2 in. (height) with a metal thickness increments. The initial configuration, shown shaded with a of 0.135 in. numeric "1" in each box , includes the in situ soil bedding, and After performing another analysis cycle, the CANDE culvert. Next, three layers of trench fill soil are placed to the Output report provides a final evaluation of the selected cor- top of the trench (designated with load step numbers 2-4), rugation as shown in Figure 12. All safety factors meet or followed by one larger layer of overfill (load step 5) to a fill exceed the user-specified requirements. Excess safety occurs height of 1.5 diameters above the crown. The remaining over- because the available manufactured section properties exceed fill soil loading is placed in five load steps using equivalent the minimum required section properties. overburden pressure loading. This example, as do all the tutorial examples, demon- The design solution, taken directly from the CANDE strates how CANDE-2007 differs from general purpose fi- output report, is shown in Figure 11, wherein three design- nite element programs. That is, CANDE sorts through all iteration cycles were required to determine the required the mechanistic responses of deformations, stresses, thrust area, moment of inertia, and section modulus to sus- strains, thrust, moments, and shears and summarizes the tain the soil loading with the desired safety factors. Using the pipe performance in terms of safety factors or demand-to- required section properties, CANDE searches through the capacity ratios.

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17 Soil Zone Type of Soil Young's Poisson's Soil Modulus Ratio Density (psi) (lb/ft3) In situ Hard clay 6,000 0.35 120 Bedding Compacted sand 2,600 0.19 120 Backfill in Compacted sand 2,600 0.19 120 trench Overfill above Lightly 800 0.23 120 trench compacted silt Figure 9. Illustration of Tutorial Example #4 with soil zone properties.

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18 Figure 10. Soil construction increments for Tutorial Example #4 from GUI.

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19 Figure 11. Design solutions for Tutorial Example #4.

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20 Figure 12. Final evaluation of selected design.