1973-76. The first version of CANDE was released in 1976 under the sponsorship of Federal Highway Administration (FHWA). The development work, a three-year research program, was conducted at the Naval Civil Engineering Laboratory in Port Hueneme California under the direction of Dr. Michael G. Katona. The original release of the CANDE program contained the following options and features:
- Execution mode choice: Analysis or Design.
- Solution level choice: Level 1, 2 or 3. Level 1 is a modified elasticity solution, Level 2 is a finite element solution with an automated mesh for circular culverts, and Level 3 is a finite element solution with a user-defined mesh.
- Pipe type choice: Corrugated aluminum, basic, reinforced concrete, plastic, and corrugated steel.
- Soil model choice: Linear elastic, overburden dependent, and nonlinear hyperbolic model by Hardin.
- Interface choice: Bonded, frictionless, or friction at soil-structure interface.
1978-79. FHWA awarded the University of Notre Dame a research contract under the direction of Dr. Katona to extend the CANDE program by adding an automated Level-2 finite element mesh for reinforced concrete box culverts along with an improved concrete constitutive model. Also, this research effort included installing the Duncan hyperbolic soil model originally developed at University of California at Berkeley.
1981-82. FHWA awarded the University of Notre Dame another research contract under the direction of Dr. Katona to develop a special joint model for corrugated metal culverts to simulate the behavior of slotted joints. This combined experimental and analytical study demonstrated that slotted joints, which allow slippage and circumferential shortening of the culvert, are very effective in reducing the thrust stress in the culvert wall.
1987-89. FWHA awarded a contract to Syro Steel Company, which at the time was using CANDE on a daily basis to design long-span arch culverts, to unify and extend CANDE. The project was headed by Mr. Samuel Musser of Syro Steel Company along with Dr. Katona (then employed with the Ballistic Missile Division of TRW) and Professor Ernest Selig at the University of Massachusetts, Amherst. One purpose of this contract was to produce a unified user manual, which incorporated all the previous upgrades to CANDE and to ensure that the input/output programming was compatible with personal computers. In addition, a new Level-2 capability for arch culverts was developed along with a revised form of the hyperbolic soil model, referred to as the Duncan/Selig model. The final product of the FHWA contract was called CANDE-89, a public domain program available through McTrans.
2005-07. Under the sponsorship of AASHTO, the National Cooperative Highway Research Program negotiated a contract with Michael Baker Jr. Inc. to modernize and upgrade CANDE-89. The project, known as the CANDE Upgrade project and designated as NCHRP 15-28, was headed by Mr. Mark Mlynarski of Michael Baker Jr. Inc. along with Dr Katona (then a Professor at Washington State University), and Dr. Timothy McGrath of Simpson, Gumpertz & Heger Inc. The CANDE Upgrade project targeted the following three areas for enhancement:
- Pre- and Post-processing with modern computer technology. Previous versions of CANDE operated in a batch input mode without dedicated graphical software to aid the user in data preparation and output interpretation. CANDE 2007 is now equipped with a Windows®-based, menu-driven format for interactive data input and real-time control of data output along with a context-sensitive help system and numerous graphical plotting options.
- New analysis capabilities and architecture. The new architecture installed in CANDE-2007 allows the use of multiple pipe groups, thereby allowing an analysis of several culverts placed side-by-side pipe, or a retrofit design, say a plastic pipe inserted inside a corrugated steel pipe. Also, an updated Lagrange formulation has been incorporated into CANDE-2007 that provides an accurate and robust algorithm for predicting large deformations along with a methodology for predicting buckling capacity at the end of each load step. Also, the architecture was expanded to include an automated bandwidth minimizer.
- Improved design criteria for all culvert types, including LRFD methodology. A complete and AASHTO-compatible set of design criteria, applicable to both working-stress and LRFD methodologies, was identified for common culvert materials; corrugated metal, reinforced concrete, and thermoplastic pipe. These design criteria are now used to evaluate the structural responses of each pipe type used in CANDE-2007 program. More importantly, the user now has the option to choose either service load (working-stress evaluation of the design criteria) or factored loading with factored resistance (LRFD evaluation of the design criteria.)
The CANDE-2007 program along with its three documentation manuals are the final deliverables for the CANDE Upgrade project.
2011. As a follow-on to NCHRP project 15-28, TRB funded Mr. Mark Mlynarski of Michael Baker Jr. Inc to upgrade CANDE to be compatible with 64-bit operating systems like Windows 7. At the same time, Dr. Katona provided corrections and improvements to the original CANDE-2007 program. Improvements included; a new capability to specify initial gap distances for interface elements, a more general capability to prescribe displacement boundary conditions in sequential load steps, a better working bandwidth minimizer when node numbers are missing, faster convergence algorithms for the Duncan/Selig soil model and the reinforced concrete model. Corrections included; eliminating an ambiguity between canned parameters for Duncan model versus Duncan/Selig model, correcting concrete shear-strength capacity for multiple pipe groups and correcting radial tension capacity for intermediate span lengths, and avoiding potential division by zero problems in the plastic pipe subroutines.
The CANDE-2007 program with 2011 upgrade (CANDE-2007/2011) is a complete replacement for the original CANDE-2007 program. It is operable in both 32-bit and 64-bit architecture and on all standard operating systems including Windows 7. The 2011 Upgrade will generally produce slightly different answers than original CANDE-2007 program due to improved convergence techniques.
2013. CANDE-2013 is an extension of the AASHTO/TRB version CANDE-2007/2011 with five new capabilities listed below, which are provided freely to the engineering community as a result of industry sponsored developments.
- CONRIB pipe type. This is a new pipe type in CANDE-2013 with modeling capabilities for rib-shaped reinforced/concrete cross-sections. Also, the concrete stress-strain model has the ability to model fiber reinforced concrete. (Con/Span Bridge Systems)
- CONTUBE pipe type. This is another new pipe type added to the pipe library that permits modeling circular-shaped concrete cross sections encased in fiber-reinforced plastic tubes spaced at uniform distances. Useful for new soil-bridge systems and piles. (Advanced Technologies Infrastructure)
- Link elements with death option. Links are useful for connecting one beam-element group to another in either a pinned connection or fixed-moment connection. Also, the link element offers a death option that allows simulating strut removal, culvert erosion, and creation of soil voids. (Contech Construction Products and MGK Consulting)
- Deeply corrugated steel structures. CANDE’s corrugated steel pipe type now includes the new AASHTO combined moment-thrust design criterion and new global buckling equation for deeply corrugated steel structures. Also, the plastic-penetration algorithm has been improved. (Atlantic Industries and Contech Construction Products)
- Variable plastic profile properties. The input data defining plastic profile section properties has been expanded to allow variable profile geometry around the pipe’s periphery. This is useful for arch-shaped storm-water chambers that vary the plastic profile geometry from top to bottom. (Advanced Pipe Services and Prinsco)
2015. CANDE-2015 is a further extension of new capabilities beyond those listed in CANDE-2013 with two new soil models added to the suite of soil model choices. Again, these capabilities are freely distributed as a result of industry sponsored developments.
Mohr/Coulomb plasticity model. The classical Mohr/Coulomb elastic-perfectly plastic model is now included in the suite of available constitutive models that may be assigned to continuum elements to describe soil behavior. (Industry sponsors Contech Engineered Solutions and MGK Consulting)
Modified Duncan/Selig model for plastic-like behavior. Katona's modification to the original Duncan and Duncan/Selig soil models produces permanent deformations upon unloading similar to advanced plasticity models. The user has the option to use either the Original or Modified version. (Industry sponsors Contech Engineered Solutions and MGK Consulting)
2017. CANDE-2017 offers two additional new capabilities, gratis industry sponsored research.
- Continuous Load Scaling (CLS). A revolutionary new method to accurately simulate longitudinal load spreading from live loads. CLS is a superior alternative to the traditional reduced surface load procedure.
- Extended Mohr/Coulomb plasticity model. The Mohr-Coulomb model was expanded to allow the option for non-associative flow rules, and the option to control the tensile stress limit for new and improved tension cut-off algorithm.
2019. CANDE-2019 offers further advancements in 2D live-load analysis including the CANDE Tool Box (CTB), which is a stand-alone program that greatly eases the input burden for developing meshes for load rating and evaluating load-rating factors.
- 3D Stiffness Effects (3DSE). To simulate 3DSE for shallow buried culverts, CANDE-2019 offers improved methods for either Reduced Surface Load (RSL) or Continuous Load Scaling (CLS) procedures using the Wmin and Wcritical concepts.
- CANDE Tool Box. Having successfully completed alpha and beta testing, the CTB now offers four easy-to-use options to modify meshes for load rating along with a simple command to compute load rating factors.
2022. CANDE-2022 includes two new capabilities beyond the previous version, gratis industry sponsored support.
- Full Benefit of Pavements for live loads (AMMP-Ø*). A new procedure based on the Fox elasticity solution to account for the pavement-enhanced out-of-plane load spreading from live-loads. Correspondingly, the CTB-2022 box was updated to compute the required input parameters for RSL and CLS procedures.
- Composite Link Element. This capability allows the user to combine two distinct pipe-element groups to act as a composite whole for simulating stiffeners, pipe rehabilitation or new composite cross sections.
It is anticipated that CANDE-2022 will undergo further enhancements in the future, particularly by upgrading the Graphical-User-Interface, which has not kept pace with new capabilities installed in CANDE since 2011. CANDE has shown itself to be a great example of industry-government cooperation and technology transfer.
Developers and contributors of the CANDE program are listed in the following link, Developers.