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CANDE Newsletter #4
CANDE Newsletter #4
Mar 1, 2013
The latest CANDE version, called CANDE-2013, may be downloaded free of charge from CandeForCulverts.com website. New capabilities and improvements in CANDE-2013, listed below, are provided gratis as a result of industry sponsored developments.
1. Deeply corrugated steel structures. Recently, AASHTO adopted a new combined moment-thrust design criterion that applies to deeply corrugated steel structures with corrugation heights greater than 5 inches. The combined thrust-moment design criterion (AASHTO Equation 126.96.36.199-1) incorporates the plastic moment of the corrugated section as a resistance measure in addition to the thrust yield stress. Also, AASHTO introduced a new equation to predict the global buckling resistance of deeply corrugated structures (Equation 188.8.131.52-1). These new design criteria are programmed into CANDE-2013 Steel pipe type and may be activated at the user’s discretion. (Industry sponsors Atlantic Industries and Contech Construction Products)
2. Variable plastic profile properties. Typically, the section properties of plastic profile pipe are uniform around the pipe’s periphery; hence, previous versions of CANDE were restricted to uniform section properties per pipe group. However, arch-shaped storm water chambers often employ changes in the plastic profile geometry from top to bottom. CANDE-2013 has been revised to allow variable profile geometries around the structure. This applies to all types of plastic including HDPE, PVC, and PP. (Industry sponsors Advanced Pipe Services and Prinsco)
3. Link elements with death option. Links, which are new constraint-type elements in CANDE-2013, are useful for connecting one beam-element group to another in either a pinned connection or fixed-moment connection. More importantly, the link element offers a user-specified death option that allows the simulation of temporary support removal during construction. Alternatively, by placing links around a group of soil elements, it is possible to simulate soil removal (excavation) or the creation of voids during the loading schedule. (Industry sponsors Contech Construction Products and MGK Consulting)
4. CONRIB pipe type. CONRIB is a new pipe type in CANDE-2013 that offers modeling capabilities for rib-shaped reinforced/concrete cross-sections in addition to standard wall cross sections. More significantly, the concrete constitutive model offers the option to simulate the nonlinear ductile behavior of fiber reinforced concrete (FRC) in tension as well as the standard nonlinear behavior in compression. Applications include all concrete culverts and foundation walls with or without steel reinforcement. (Industry sponsor Con/Span Bridge Systems)
5. CONTUBE pipe type. CONTUBE is another new pipe type added to the pipe library that permits modeling circular-shaped concrete cross sections encased in tubes spaced at uniform distances. Applications for the CONTUBE pipe type include arch-shaped soil bridges as well as pile-support systems based on the new AASHTO publication LRFD Guide Specifications for Design of Concrete-Filled FRP Tubes. (Industry sponsor Advanced Infrastructure Technologies)
In addition to the new capabilities listed above, several corrections and improvements have been reprogrammed in CANDE-2013 that are transparent to the user and are listed below:
• Corrected a small error in predicting the percentage of plastic penetration in the cross-section of corrugated steel. Specifically, the old plastic-penetration algorithm slightly over-predicted the amount of plastic penetration by a few percentage points when thrust loading was dominant.
• Improved the internal selection criteria for bisecting quadrilateral elements into component triangles to maximize numerical integration accuracy and element robustness. The revision avoids division by zero during static condensation of badly distorted elements.
• Introduced new error messages to alert the user whenever an incorrect name was input for a canned Duncan or Duncan/Selig soil model. Previously, the old program would stop with an ill-defined execution error.
To get the CANDE-2013 package follow the steps below.
1. To begin with, you must have CANDE-2007 with 2011 Update from the TRB website already installed in your computer.
2. Go to home page on CANDE web site and down load the CANDE-2013 package which includes the executable program, installation directions, an updated user manual and an updated theoretical manual.
3. Save the package on your computer, and read the simple installation direction to patch-in the new options.
Comments on CANDE-2013
• All CANDE input files that worked with CANDE-2007/2011will work the same way with CANDE-2013
• To utilize any new option, the input data must be entered directly on the input file (batch mode) because the input GUI menu is not updated.
• Although the new options have been tested for a year or more, they are still viewed as undergoing experimental beta testing – so your feedback is welcomed in the CANDE Forum.
• It is anticipated that CANDE-2013 will eventually become part of another TRB/NCHRP upgrade project wherein the GUI will be updated and extended. CANDE has shown itself to be a great example of industry-government cooperation and technology transfer thanks to the user community.