In addition to the above new features, many additional modifications have been made to improve the program and ease the burden of user input. For example, a simplified method of defining interface angles is now operational in the.
This type of testing, called alpha testing, was accomplished by the proj- ect team during and after the development phase of each new capability. The results of the alpha-testing phase indicated that the new capabilities were accurate and func- tioning as planned.
Sub- sequently, the beta testing was expanded with 35 beta-tester volunteers from the culvert community over a testing period of 3 months. Beta testers had access to a project website and software to easily record all problems and comments.
Of the 35 beta testers and 10 panel members, 16 testers recorded problem reports on the project website. By the end of beta testing, beta incidents were logged on the website. The entire list of beta incidents was reviewed by the project panel at an October meeting. The vast majority of issues dealt with questions about interpretation of input variables. These comments will continue to be maintained by the project team for the purposes of building a list of possible future enhance- ments for the CANDE software.
The beta-testing phase proved to be very effective in un- covering problem areas in the software as well as areas of potential misunderstanding on the part of the user that could be addressed by enhancements to the CANDE documenta- tion. All beta-testing incidents have been addressed and resolved except for those issues that are classified as a future enhancement.
To enhance future regression testing of the software i. After beta testing was completed and the panel viewed the results, a list of items that were beyond the scope of this research effort was added to a future development list.
These items include the following: 1. Incorporating shear deformation into structural beam- column elements. Enhanced mesh generation capabilities.
Load rating capabilities. Tutorial Example 4 seeks a design solution for a in. The problem is shown schematically in Figure 9. The problem employs Solution Level 2, using an automated finite element pipe mesh for a trench installation.
Design a 60 in. 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. The desired result is the required inner and outer reinforcement. Design a 36 in. The desired result is the wall thickness. The design will be with Level 2, using an auto ma ted finite elem ent pipe me sh for a trench installation having no interface elem ents.
Analyze a 36 in. The analysis will be with Level 2, using an autom ated finite elem ent pipe me sh for an em bankm ent installation having no interface elem ents. Analyze a in. The analysis will be with Level 2, using an autom ated finite elem ent arch me sh for a trench installation having interface elements.
The automated finite element mesh will be modified using Level 2-extended to apply p oint loads depicting a LRFD design truck at the ground surface above the crown of the arch.
The analysis will be with Level 2, using an autom ated finite element box mesh for an embankment installation. The analysis will be with Level 2, using an auto mated finite elem ent pipe me sh for an em bankm ent installation havi ng no interface elem ents. The autom ated finite element mesh will be m odified using Level 2-extended to reduce the thickness of the construction steps above the crown of the pipe.
The analysis will be with Level 2, using an automated finite element arch mesh for a trench installation having interface elem ents. The autom ated finite element mesh will be m odified using Level 2-extended to apply point loads depicting an LRFD design truck at the ground surface above the crown of the arch.
Design a 72 in. The analysis will be with Level 2, using an automated finite elem ent pipe me sh for an em bankm ent installation having a 6 in. The desired result is the required inner and outer reinforcem ent. Analyze a 48 in. The analysis will be with Level 2, using an auto ma ted finite elem ent pipe me sh for a trench installation having interface elem ents. The automated finite element mesh will be m odified using Level 2-extended to change the haunch zones to a user-defined soil material and the thickness of bedding layer to 6 in.
Table 1. Tutorial Example Descriptions. The analysis will be with Level 3, using a user-generated finite elem ent me sh for an em bankm ent installation. This problem analyzes the reinforced concrete box culvert from Tutorial Problem 7, which was perform ed using a Level 2 analysis.
The analysis will be with Level 3, using an imported finite element arch mesh in XML form at from Tutorial Problem 9 for a trench installation having interface elem ents. This problem analyzes the corrugated steel long span arch from Problem 9, which was perform ed using a Level 2 analysis.
The draft final report as submitted by the research agency can be downloaded. This is an ISO file. AS2 F Steel area for inner wall of bottom slab. AS3 F Steel area for inner wall of side sl abs. AS4 F XL1 F Uniform concrete cover thickness to all steel centers. TC F Case4 Specifi ed wall thickness and working stress design. Specify a non-zero value.
Note the design solution will provide required steel reinforcement area Steel yielding safety factor PFS 1 F Typically this safety factor is specified in the range from 1. Typical range is 1. Satisfying this safety factor may require the designer to use traverse steel. If needed, the excess shear force to be carried by stirrups.
If needed, excess load to be carried by stirrups. Resistance factor for radial concrete tension PHI 4 F CANDE approximates the crack width at service loading by dividing steel stress in crack width formulas by load factors. In the analysis mode, CANDE will show the five numerical values of the above factored resistances along with the corresponding factored demands.
Pl astic Plasti c load controls. If need be, the problem can be run twice, once with short duration properties and once with long duration properties to bracket the responses of each load step.
If left blank, default values from Table 5. Poisson s ratio PNU F Poissons ratio is taken the same for short and long term loading Density of plastic material used for body weight.
This value produces the self-weight of the plastic structure in the loading schedule. Although the CANDE solution for structural responses is based on either short-term or long- term properties depending on choice of LOADT , both short-term and long-term properties must be input or defaulted for each problem.
This is because the both the short-term and long-term properties are used in the evaluation of the plastic pipe performance in terms of design criteria. Short-term properties are appropriate for shallow burial situations wherein live loads dominate.
Long-term properties are suitable to deep burial conditions wherein design life for soil weight is on the order of 50 years. The table below shows the range of short-term and long-term properties for three common types of plastics used as culverts and storm chambers. Default values are in parenthesis. Sometimes it is wise to run the same problem twice, once with short term and once with long-term properties. Pl astic. Smooth Cross-sectional properti es of plastic wall for smooth or general.
Parameter columns format units Input Options Description Total height of wall cross section. PT F This completes smooth wall input. Area of general wall- section per unit length of pipe PA F PC F The value is used to compute maximum fiber stresses. The repeating profile shape always includes two web elements. By themselves, the two webs may be used to form a saw-tooth profile.
The k-value may be taken as 4. For a freestanding element with only one edge supported, the k-value is 0. Otherwise, Set B is complete. Profile Additional cross-sectional properti es of plastic wall for wall type Profile. Note, Line B-3b is repeated for the number of specified horizontal elements, i. The length of the liner 2 or link 4 element does not include the web thicknesses. The thicker the element the more it resists local buckling.
See comments below. CANDE uses the web and horizontal element input data to calculate the cross-sectional area per inch, the moment of inertia per inch, and the distance to the neutral axis measured from the inner fiber. Comment on Local Buckling. If so, the cross-sectional properties are appropriately reduced, which results in increased stresses due to loss of effective area. Subsequent load steps utilize the reduced section properties, which in turn can lead to an increased rate of local buckling.
Every element of the pipe group is examined to determine its individual state of local buckling. WSD Working Stress safety factors and performance requirements.
This safety factor guards against material failure of entire cross section. The default safety factor is typically used. Typical PFS range is 1. For automated design, the allowable displacement is used as a performance limit. For automated design, the allowable tensile strain is used as a performance limit. Comment: CANDEs working-stress automated design methodology will determine the required smooth- wall thickness such that the controlling desired safety factor nearly matches the corresponding actual safety factor.
The remaining actual safety factors will be equal to or greater than the corresponding desired safety factors. Also the selected wall thickness will limit the maximum displacement and tensile strain to be less than or equal to the allowable limits. Typically this weight is always 1 for plastic structures. See comment below. Comment: The above design weights give the designer control over the degree of conservatism for the LRFD process.
Resistance factor for global buckling PHI 2 F Resistance factor for limiting stain PHI 3 F CANDE estimates the service load deflections by dividing by the specified load factors. CANDE estimates the service load strains by dividing by the specified load factors. In the analysis mode CANDE will show the numerical values of the above factored resistances along with the corresponding factored responses as well as the service limits along with the corresponding service responses.
Steel Material properties and control Use if Comments A Leave blank to ignore self-weight. It is the slope of the stress-strain curve after yielding. Centroid is assumed at mid-depth of cross section. WSD Design safety factors for working stress design. Comment: Similar to the working-stress approach, the above design weights give the designer control over the degree of conservatism for the LRFD process. Steel Joint properties Use if Comments A Lighter gauges e. For standard keyhole slots, a travel length of 1.
See comment for Level 2. This occurs in level 2 meshes when the axis of symmetry cuts through a joint at the crown or invert, which produces a half- joint with the same properties as a full joint except the slot length is one-half its full value. Steel Joint locations and properties Use if Comments A Level 2 elements are numbered clockwise starting with no. The format for column data is up to 15 fields of I4 integers. Consider, for example, a circular pipe with a total of four slipping joints that are located near the crown, invert and each spring line.
Steel Joint locations and properties 2 Use if Comments A This is useful for correctly defining joints that are on lines of symmetry whose slot length is of standard. The criterion applies to service loading conditions, which is approximated by reducing the predicted displacements by the load factors.
In the design mode, the designer is given additional control on line B-2 to design with more or less conservatism or turn off any of the criterion to fit the problem at hand. It is suggested that designers evoke this criterion for all metal culverts. The solution level input is specified in command A-1 see Section 5. L1 Major input parameters Use if Comments A This applies to all circular pipe types in deep burial installations.
A typical range of soil density is to pcf. CANDE uses soil density to assign increments of overburden pressure to the pipe-soil system. This, in turn, will permit the change of soil stiffness properties as a function of the current fill height in line C Comment: Level 1 is based on the Burns and Richard elasticity solution for a deeply buried circular pipe in an ideal homogenous soil system wherein the fill height above the crown is at least 2 pipe diameters.
Level 1 is not appropriate for shallow covers or simulating concentrated live loads. Second, CANDE uses an average of pipe stiffness values around the pipe, which may change from load step to load step, as determined from the nonlinear pipe-type models. NINC times. Repeat this line for each l oad step NINC. A typical value for all soil is 0. Thus, we obtain a solution using one load step. NINC This line must be repeated until load factors for all load steps are defined. The purpose of the comment is to document the rationale for the load factor value including load modifiers, etc.
At the other extreme, if each load step is assigned a different load factor for whatever reason , then the C-3 would be repeated NINC times. Level 1 is only suited for load factors associated with earth loads. See Part E for a discussion on load factors. Pipe Control commands and ti tle Use if Comments A The type of soil construction is controlled by the choice for WORD. The in-situ soil surface is at pipes invert and backfill soil is placed in lifts around and above the pipe.
The fill soils lateral extent is assumed indefinitely wide. Any trench depth may be specified, measured from the in-situ soil surface to the pipe invert. Similarly, any trench width may be specified. Backfill soil is placed in lifts to fill the trench plus overfill. That is, the entire soil system is one homogenous material to be defined by the user. This produces an idealized system similar to Level 1. This feature allows for frictional slippage, separation and re-bonding of the pipe-soil interface during the loading schedule.
Comment: The Level 2 Pipe Mesh generates a half mesh, symmetric about the vertical centerline, implying that all geometry and loading is mirror symmetric on both sides of the centerline. The node numbering and element connectivity remains the same for all choices of soil mesh type WORD.
Pipe Major geometry and loadi ng parameters Use if Comments A The default minimum coincides with the meshs minimum uniform surface height. Comment: See Figure 5. When interface elements are added to the mesh see Table 5. Pipe Control variables Use if Comments A The first five load steps include the gravity loads from the components listed below.
In summary, the steps are: 1 Pipe structure, in-situ soil and bedding. Unit 10 contains all the finite-element mesh data plus all the structural responses for each load step; it is intended as the data source for plotting mesh configurations, deformed shapes and contours. Unit 30 contains the detailed pipe responses RESULT at each node for each load step; it is intended as the data source for pipe response plots. Default implies no backpacking will be used. The trench depth is automatically scaled up to the nearest quarter diameter depth.
Thus, the actual mesh trench depths are 0. For trench depths above 1. The minimum allowable width is1. Box Control commands and ti tle Use if Comments A The in- situ soil surface is at pipes invert and backfill soil is placed in lifts along side and above the culvert.
Any trench depth may be specified, measured from the in-situ soil surface to the box invert. Motivations for changing the basic mesh include: add live load s , simulate voids or rocks in the soil system, and to change shapes such as the bedding.
The default case no modifications applies to many basic problems. Comment: The Level 2 Box Mesh generates a half mesh, symmetric about the vertical centerline, implying that all geometry and loading is mirror symmetric on both sides of the centerline.
Proceed to Line C Any number load steps may be specified for execution in a given problem. In summary the load steps are: 1 Box structure, in-situ soil and bedding. One half of vertical rise R2 F Height of soil cover above box. TRWID is the distance in feet from mid-depth of the boxs sidewall to trench wall. The minimum allowable gap width is 0. Arch Control commands and ti tle Use if Comments A Shapes are defined with 2 or 3 curved or straight segments defining half of the symmetrical arch or box.
The in-situ soil surface is level with arch footing and backfill soil is placed in lifts around and above the arch. Any trench depth may be specified, measured from the in-situ soil surface to the arch footing. Comments: Like all Level 2 options, the arch mesh is assumed symmetrical about the vertical centerline so that only one half of the system is modeled with finite elements. The automated subroutine generates all nodal points and elements to define the arch, in-situ soil, footing, backfill soil and interface elements between the arch and backfill soil.
The number of elements used to define the soil over the arch is dependent on the specified soil cover height above the crown. A maximum number of elements total are used for soil cover heights greater or equal to the arch rise. For cover heights greater than 1. Interface elements are always generated with the arch mesh so that the user must define the interface properties in Part D. There are 19 interface elements starting at the crown node and proceeding clockwise around the arch to node 19, the second to the last node before the connection to the footing.
The last arch node, number 20, connected to the footing is not assigned an interface element since relative slippage is restrained by the footing.
To simulate a fully bonded condition between the arch and backfill soil, the user may prescribe arbitrarily large values for the coefficient of friction and tensile breaking force in Part D or assign frictional properties as desired.
Arch Plot and print control Use if Comments A Up to 20 load steps may be specified to simulate placement of soil around and above the arch. The first eleven load steps include the gravity loads from the elements listed below followed by load steps of equivalent overburden pressure if needed: 1 Arch structure, in-situ soil and bedding.
The trench depth, specified in feet, is the distance from the arch footing to the trench surface. The trench depth is automatically scaled up to the nearest horizontal mesh-grid line, approximately spaced at intervals the arch rise. The maximum trench depth allowed is the minimum of 2. The maximum allowable trench gap is 0. The maximum allowable slope is 1. Comment: Figure 5. Arch Arch and footing dimensi ons Use if Comments A This applies to all arch shapes including 2- and 3- segment arches with curved or straight line segments One-half of arch span at footing level HFSPAN F This applies to all arch shapes.
Range 1. This feature is problem dependent and should be used in a trial and error fashion with graphical output of mesh topology. Figure 5. Finally, Table 5. Arch Arch segments and angles Use if Comments A Radius of 2nd segment R2 F THETA4 is the base angle defined by the line perpendicular to the end of the 3 rd segment and the horizontal footing line.
THETA4 may be positive or negative wherein the positive direction is measured counter clockwise from the horizontal. Node 1 is located at the crown and node numbering proceeds clockwise around the arch with Node 20 assigned to the footing connection.
The Arch Mesh assigns 10 or 13 nodes default values to the first arc segment depending on whether it is a 3-segment or 2- segment arch, respectively. NTN allows the user to prescribe a better distribution of nodes to the top arch to fit the problem at hand. In general the goal is to define the distribution of the nodes between the segments to achieve equal uniform lengths between all nodes.
NCN allows the user to prescribe a better distribution of nodes to the corner arch segment in order to fit the problem at hand with uniform lengths between nodes. The remaining number of nodes assigned to the 3 rd segment is NCN beyond the common node. Identification of interface element nodal connectivity Number of Nodes from Crown Pipe-soil Interface Nodes 1 Number of Nodes from Crown Pipe-soil Interface Nodes 1 1 ,, 11 ,, 2 ,, 12 ,, 3 ,, 13 ,, 4 ,, 14 ,, 5 ,, 15 ,, 5 ,, 15 ,, Interface Element Numbers See Table 5.
Example reasons to change coordinates include modeling variations in the culvert shape perhaps an imperfection , changing the dimensions of the bedding or footing elements, or altering the location of a live load on the soil surface.
The standard Level 2 loading is limited to gravity loads and uniform surface pressure loads. A prime reason for the NEWBD parameter is to permit the user is to add live loads into the loading schedule at any desired location and load step.
The user should identify NP by referring to the figures and charts associated with particular Level 2 mesh configuration that is being revised. Note that the automatic mesh checking routines in CANDE are by-passed in extended level 2 operations.
Therefore, the user must exercise diligence in assigning new coordinates to avoid producing elements that are badly shaped or inside out. Comment: The altered node coordinates are recorded in the CANDE output report under the heading Level 2 Extended, after the unaltered canned mesh nodes are printed. Proceed to line CX Of the six property array integers, the first four are the nodal connectivity, which are rarely revised. The last two property array integers, the material ID number and the load step number are well suited for revision.
Nonetheless, the option is provided here for expert users wishing to use this option in special circumstances. In general leave this entry blank. To retain the material ID number assigned in Level 2, leave this entry blank. To retain the original load step, leave blank Comment: The altered element properties are recorded in the CANDE output report under the heading Level 2 Extended, after the unaltered canned mesh element properties are printed.
Note, since Level 2 is based on symmetry any load applied to the right-hand mesh is automatically applied to the mirror side of the mesh.
Thus when applying a vertical point load on the system centerline, the actual load is twice the value of the specified load. X-Value BV 1 F Or, BV 1 is the x-displacement that will be specified in load step IA.
Y-Value BV 2 F Or, BV 2 is the y-displacement that will be specified in load step IA. Note that positive values are in the upward direction. The x and y boundary conditions specified above are re-interpreted to a rotated coordinate system x and y. BV 3 is the counter- clockwise angle from the x-axis to the x axis. Displacement loading conditions are applied in load step number IA and remain in effect for all subsequent increments. Comment: The new boundary conditions are recorded in the CANDE output report under the heading Level 2 Extended, after the original canned mesh boundary conditions are printed.
L3 Element number and property array Level 3 is the traditional method of defining mesh data for input into a finite element program. Accordingly, the user must prepare finite element mesh data representative of the soil-structure system to be designed or analyzed. Input commands C-1 and C-2 are control variables that are easily determined and entered into the input stream.
Command C-3 is used repeatedly to define all nodal coordinates. Similarly, command C-4 is used repeatedly to define all element properties, and finally command C-5 is used as needed to define all displacement and force boundary conditions.
To assist the user, CANDE is equipped with many advanced mesh generation features that can greatly reduce the amount of labor in defining the input data. These features are discussed as they arise in commands C-3 and C Note the GUI automatically supplies this word without prompt by the user. TITLE is printed out with mesh data as an aid to the user. TITLE may be any phrasing up to 68 characters.
L3 Element number and property array Use if Comments A Typically, the value of NINC matches the highest load step number defined in the element or loading schedule.
However, NINC may be less than this number if desired. Some errors may be fatal such as an inside-out element other errors may just be a warning such as skinny elements. Note, it is permissible to skip node numbers so that not all sequential numbers correspond to a node used in the mesh.
Unlike nodes, the element count NELEM must exactly match the number of elements actually used in the mesh. NBPTC may be larger but not smaller than the actual number of conditions.
In all cases the output is displayed in the users node numbering scheme. L3 Level 3 node input Repeat as necessary to define all nodes. Please click here if you wish to share information or are aware of any research underway that addresses issues in this research needs statement.
The information may be helpful to the sponsoring committee in keeping the statement up-to-date. Annual Meeting. Hide e-mail form. All Rights Reserved. Terms of Use and Privacy Statement. About TRB. Potential improvements that would greatly benefit users include the following: Modernize the CANDE analysis engine and transition the programming from the existing FORTRAN coding language into a more user-friendly, modern, object-oriented language such as C. To meet the above research objectives, the task group developing this research statement envisions the following tasks for this project: Survey the CANDE user community to identify all existing issues with the latest version of CANDE, including the CTB, to determine additional needs not addressed above, and to prioritize all proposed improvements.
Brent J. Michael G. Katona; Mr.
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