Faar Field Manual

INTRODUCTIONIntroduction to FAARFIELD Previous Next FAARFIELD is a computer program for airport pavement thickness design. It implements both layered elastic based and three-dimensional finite element-based design procedures developed by the Federal Aviation Administration (FAA) for new and overlay design of flexible and rigid pavements. The thickness design procedures implemented in the program are the FAA airport pavement thickness design standards referenced in Advisory Circular (AC) 150/5320-6E. The core of the program is a structural response module consisting of two programs, LEAF and NIKE3D (version 3.3.2.FAA.1.0). LEAF is a layered elastic computational program implemented, in this case, as a Microsoft Windows™ dynamic link library (DLL) written in Visual Basic 2005™. NIKE3D (version 3.3.2.FAA.1.0, as modified by the FAA) is a threedimensional finite element (3D-FE) analysis program, written in Intel™ Visual Fortran™ and linked to the main program through a dynamic-link library. A second Fortran program, INGRID, is also linked to the main program and generates input files for the 3D-FE analysis. The remainder of the program is written in Visual Basic 2005™ and operates under Microsoft Windows™. Both LEAF and NIKE3D are loaded and executed by FAARFIELD when needed and are not visible to the user. The versions of NIKE3D and INGRID implemented in FAARFIELD are FAA modifications of software programs originally developed by the Lawrence Livermore National Laboratory (LLNL) of the US Department of Energy, and are distributed in compiled form under terms of a software sharing agreement between the FAA and LLNL. Design information is entered by means of two graphical screens, one for the structure and one for the traffic. Default values and ranges for the various input parameters have been set so that the designs produced by FAARFIELD are compatible with designs produced by the previous FAA design procedures in AC 150/5320-6D (Chapters 3 and 4) for airplanes up to and including the B747 (i.e., S, D, 2D and 2D/2D2 gears). Designs for new generation airplanes having 3D landing gears, such as the Boeing B777 and Airbus A380 series, were not covered by the previous design procedures. AC 150/5320-6E, in conjunction with FAARFIELD, provides the necessary information for thickness design when 3D and complex airplane gears are included in the airplane mix. FAARFIELD represents a significant departure from previous FAA standards. Apart from the procedures being implemented as a computer program instead of as nomographs, the main change in pavement design from the user‟s perspective is that the “design airplane” concept has been replaced by design for fatigue failure expressed in terms of a “cumulative damage factor” (CDF) using Miner‟s rule. Also, the major material property of the pavement layers is now uniformly expressed as an elastic modulus instead of the previous CBR (California Bearing Ratio) for flexible pavements or k value for rigid pavements. Formulas for transforming CBR and k values to modulus values are provided where appropriate in the documentation. Automatic conversion is provided in the program. It should also be borne in mind that, although layered elastic based procedures, and threedimensional finite element models, are normally considered to be mechanistic, and more rational than the previous procedures, a considerable amount of engineering judgment is still required. Designs produced by FAARFIELD should comply with the detailed requirements and recommendations of AC 150/5320-6E. The program does not automatically satisfy all of these requirements and the recommendations in the AC should be followed in the selection of input parameters. It is the designer‟s responsibility to use the program and the advisory circular in conjunction with each other. A complete description of the design procedures and program structure is not possible within the confines of a user‟s manual, and these descriptions can be found in other publications. The main intent of the user‟s manual is to provide sufficient information for operating the program, selecting input data values, and interpreting the output data. Installation of the program is described first, followed by descriptions of the various parts of the program and its operation. Information is then given on the structure data input requirements and how they relate to the design procedures. Final sections provide a short discussion on program running times, with possible strategies for decreasing design time for a given design case, a description of the structure of external data files so that interested users can access the files and incorporate the data in other applications if desired, and a selection of design examples. The relationship between the layered elastic and three-dimensional finite element based thickness design procedures and the previous nomograph-based thickness design procedures in AC 150/5320-6D is not discussed in the manual. However, it should be pointed out that the traffic and failure models are fundamentally different and comparisons between the two sets of procedures are only valid when considering multiple airplane traffic mixes. Single airplane comparisons misleadingly indicate a degree of conservatism with the LED procedures which is not present for typical multiple airplane mixes. The program is also primarily intended for use in designing airport pavements according to a standard procedure. It is not intended to be used to compare the damaging effects of different airplane by running single airplane designs or CDF computations, i.e., ACN type calculations. INSTALLATION Installation of FAARFIELD Previous Next Installation of FAARFIELD can be done from either a distribution disk or from a hard drive directory in which the distribution files have been saved. After placing the disk in a drive or copying the files to the hard drive, click the Windows Start button in the toolbar, followed by Settings and Control Panel. Click Add/Remove Programs and then click the Add New Programs icon. Click the CD button and follow the instructions to locate the correct disk drive. If installing from a hard drive, click Browse and find and select the directory containing the installation files. Open the file setup.exe and click Finish. The installation process starts automatically. The default installation directory is C:\Program Files\FAA\FAARFIELD\. Click Change Directory if you want to install in a different directory. Click the large button on the left to complete the installation. The installation directory is created if it does not already exist. A new program group is created called FAARFIELD. Start the program by clicking the Windows Start button followed by Programs. Locate FAARFIELD on the Programs Menu and click the FAARFIELD menu item. The following files are installed by setup: FAARFIELD Installation Directory FAARFIELD.exe LEAFClassLib.dll AMClassLib.dll ACClassLib.dll Visual Basic 2005 I/O and design program. Leaf compiled as an VB 2005 dynamic link library. Automesh compiled as an VB 2005 dynamic link library. Airplane library compiled as an VB 2005 dynamic link library. NIKE3D.dll 3-dimensional FEM analysis program compiled as dynamic link library. Ingrid3.dll Preprocessor for NIKE3D, compiled as dynamic link library. FAARFIELD.chm Help file. Readme.txt Information on program function. LEDFAAacLibrary.Ext External airplane library. FAARFIELD1.xml Working directory information. DFORMD.DLL File needed to run Ingrid3.dll and NIKE3D.dll. DFORRT.DLL File needed to run Ingrid3.dll and NIKE3D.dll. msvcrt.dll File needed to run Ingrid3.dll and NIKE3D.dll. stdole.dll File needed to run FAARFIELD.exe. Microsoft.Visual.Basic.Compability.dll File needed to run FAARFIELD.exe. Interop.Scripting.dll File needed to run FAARFIELD.exe. The files are stored in one zip file „FAARFIELD.zip‟ before installation. „Setup.Exe‟ in „FAARFIELD.zip‟ installs the FAARFIELD program. OVERVIEW Program Windows Previous Next The program consists of five main windows rigidly linked together as shown in the figure. The essential windows for pavement design are STARTUP, STRUCTURE, and AIRPLANE. The NOTES and AIRPLANE DATA windows are for convenience in entering additional data describing the structure and traffic, and for viewing data. Details of the required information are given in the section of this document where the data entry windows are discussed. as described under File Management. All job files have the extension *. The directory in which the job files are stored can also be changed. The name of the working directory.job. The operations associated with each of the command buttons on the STARTUP window are briefly described under separate headings.Operations within a window are executed by clicking the mouse cursor on a “command button. Jobs are listed in the list box on the left of the window.” Program Windows and Linkage STARTUP WINDOW Introduction Previous Next The startup window has two functions. The second is to organize the basic data storage units.” The sections are provided only for starting new designs. airplane names and gross loads. Startup Window Section data consists of pavement structure properties. and annual departures and growth for each airplane. The first is to allow selection of either the STRUCTURE or the NOTES window. deletion. Scroll bars will appear if there are too many jobs or sections to fit in the boxes. can be done using Windows Explorer. where necessary. Startup Window STARTUP WINDOW .” Jobs are stored as ASCII text files containing up to 100 sections. It is always available to create new section data. This is necessary if no other job files are present because new structures cannot be created from scratch. The Samples structures are also typical of current pavement design practice and are a convenient starting point for design. “click the command button called Structure” is abbreviated by “click Structure. Note: The normal Windows menu / file dialog box system is not supported. File backup and. in which all job files listed in the left hand list box are stored. This was done to simplify the user interface. The data in the Samples sections cannot be changed and the structures cannot be “designed.” Command buttons are referred to by showing the button name in bold type. Individual job files can be saved using the Save As function described later under DATA FILES – File Management. consisting of “Sections” embedded in “Jobs. is displayed below the right hand (sections) list box. For example. All sections in the selected job are listed in the right hand list box. A special job file called Samples is initialized within the system and does not exist as an external file. All job files existing in the working directory are listed on the left of the window. Command Buttons Previous Next More: New Job Delete Job Copy Section Dup. Section Delete Section Help Demonstration About Structure Notes Options Exit STARTUP WINDOW > Command Buttons New Job Previous Next . together with space. Unbonded on Rigid (unbonded concrete overlay on an existing rigid pavement). New Regid. STARTUP WINDOW > Command Buttons Delete Job Previous Next To delete a job file. When first created. Normal letters and numbers are allowed. 2. New sections cannot be created from scratch. The delete operation can also be started by highlighting the job file to be deleted and pressing the Delete key on the keyboard. Then click Delete Job. A message box will be displayed asking if you want to continue. AC on Flexible (asphalt overlay on an existing flexible pavement). hyphen (-) and underscore (_). a message box with a No or Cancel option is displayed to reduce the risk of accidentally destroying the information. Note: Whenever. Deleting a job will cause all of the information in a job file to be deleted from the disk. Six types of structure are included: 1.New jobs are created by clicking New Job. STARTUP WINDOW > Command Buttons Copy Section Previous Next New pavement structures cannot be created from scratch in the STRUCTURE window. New Flexible. old sections are moved and renamed using Dup. Instead. Section or Copy Section. and close the dialog box. Clicking OK or pressing Enter on the keyboard will accept the name. The section list box shows the type of structure for each listed section so that the desired type of structure can be selected before copying without having to check the STRUCTURE window. . job files are completely empty. The name can have up to 36 characters. AC on Rigid (asphalt overlay on an existing rigid pavement). A dialog box will then appear requesting that a name be entered for the new job. create the file. Click Yes to delete the file and close the message box. 4. first select the job to be deleted by clicking the job’s name in the left hand list box. Instead. as in this case. existing structures in one job are copied to another job (or duplicated and renamed within a single job as described below). Clicking Cancel will close the dialog box without creating a new file. information can be destroyed by an action. 5. 3. Click No to close the message box without deleting the job. STARTUP WINDOW > Command Buttons Delete Section Previous Next To delete a section. Enter the new name in the displayed dialog box. Section Previous Next A section can be duplicated within any job and given a new name. STARTUP WINDOW > Command Buttons Dup.6. With the mouse button still down. The caption on the button will change to End Copy. Click on the section to be copied with the left mouse button and hold the mouse button down. 3. A dialog box will be displayed asking you to enter the name of the new section. Repeat to copy more sections or click End Copy to end copying. The sequence for copying a section is: 1. The old name can be kept provided it does not already exist in the job the section is being copied to. first select the job. Select the job to be copied from by clicking the job name. consisting of alphanumeric. Click Copy Section. The copy section dialog box will then appear. Section. Select the section to be copied by clicking the section name in the right hand list box Select the job to be copied to by clicking the job name. The delete operation can also be started by highlighting the section to be deleted and pressing the Delete key on the keyboard. Only one file can be copied in this way at a time. or underscore. The name can have up to 12 characters. 2. Then select the section and click Delete Section. First select the job. STARTUP WINDOW > Command Buttons . Copying can be stopped at any time by clicking End Copy. Steps 1 through 3 above can be replaced by a drag and drop operation. drag the cursor across the screen and drop it onto the target job name. hyphen. Part Bonded on Rigid (partially bonded concrete overlay on an existing rigid pavement). The section data is completely deleted from the job file and cannot be recovered. Then select the section and click Dup. The demonstration can also be terminated from any of the demonstration specific message boxes by clicking Cancel. The delay setting can be changed any time a demonstration specific message box is displayed by clicking Change Delay. A time delay is inserted between each distinct operation in the demonstration so that the functions occurring can be observed. The demonstration can be run through all three windows in succession.Help Previous Next The Help file is loaded by clicking Help in any of the windows except the AIRPLANE DATA window. and AIRPLANE windows is started by clicking Demonstration. STARTUP WINDOW > Command Buttons About Previous Next Displays the application “About” box giving a brief description of the application and information on the configuration of the computer system. STARTUP WINDOW > Command Buttons Structure Previous Next Transfers control to the STRUCTURE window. The default delay setting is 2 seconds. STARTUP WINDOW > Command Buttons Notes Previous Next . STARTUP WINDOW > Command Buttons Demonstration Previous Next An interactive demonstration of the major functions in the STARTUP. STRUCTURE. or by pressing the F1 key on the keyboard. or individual windows can be selected. This allows incidental section information to be entered and attached to the job file and a summary of the section data to be viewed. STARTUP WINDOW > Command Buttons Options Previous Next Transfers control to the OPTIONS window. Clicking a new section name in the list changes the displayed structure to that of the new name. The NOTES window is described last. Structure Window STRUCTURE WINDOW Command Buttons Previous Next More: Modify Structure . STARTUP WINDOW > Command Buttons Exit Previous Next Closes all files and exits to Windows.Transfers control to the NOTES window. On the right of the window is a table showing the structure with all layers illustrated and the values of all changeable parameter values displayed. STRUCTURE WINDOW Introduction Previous Next The STRUCTURE window allows a pavement structure to be modified and “designed” to carry the load applied by the selected traffic. On the left of the window is a list of the sections in the current job. Modify Structure then changes to End Modify and Design Structure changes to Add/Delete. The only operations allowed until End Modify is clicked are modifications to the structure.Add/Delete End Modify Design Structure Interrupt Design Save Structure Life Airplane Back STRUCTURE WINDOW > Command Buttons Modify Structure Previous Next A structure is modified from the modify mode. 3. Modifications which can be made to a structure are: 1. Change the composition of a layer (change layer type). Change the flexural strength of a PCC layer. generally entered by clicking Modify Structure. Change the thickness of a layer. Alternative ways of entering modify mode are double clicking a section name (also changes the displayed structure) and double clicking the picture of the structure (also starts an associated modification sequence). Change the modulus value of a layer (except asphalt and PCC). 4. . 2. The purpose of this section is simply to outline the operation of the program. 6. The reason for disallowing the structure is given in the message. is displayed at the top of the picture of the structure and can be given any value within the range 1 to 50 years. the use of an undefined layer results in a nonstandard structure. Certain combinations of layers are not allowed in a structure (aggregate on the top. The conversion factors used are given in the section Layer Types. Structure properties are changed by clicking on the picture of the structure over the displayed value or setting. CBR for flexible pavements and k value for rigid pavements. the value in the other column changes automatically. Instructions are then given for changing the value or setting. Change the iteration layer for flexible pavement design. Detailed guidelines for selection are given in a later section. Design life. The thickness display column in the bottom layer is therefore used to display either the CBR or the k value corresponding to the modulus value of the bottom layer. in years. Layer types and modulus values must be selected for compatibility with the layered elastic design procedures and with FAA pavement design standards and recommendations. A warning message is also printed in the Design Info text box in the NOTES window. When the displayed value of a layer thickness or layer modulus is clicked. In particular. an input box is displayed giving instructions on changing the value. the structure is not checked during selection and layers can be changed to anything until End Modify is clicked. the standard design life is 20 years. If the value in either of the two columns is changed. A complete check of the structure is then made and a message displayed if the structure is not valid for design. In some cases.5. for example). Delete an existing layer. However. To change the layer type. If the design life of a section is different than 20 years the message “Non-Standard Life” is displayed. Layer Types Clicking on the picture in the layer type column displays the selection box shown. These must be read before using the program to design pavements to FAA standards. 7. . Note: The thickness of the bottom layer is assumed to be infinite and cannot be assigned a value. You cannot leave modify mode until the structure is valid for design. Clicking on the message displays a longer message explaining why the life is non-standard. the modulus value cannot be changed manually and a description is given of how the program assigns the value automatically. However. click the type you want to select followed by OK. Duplicate (add) an existing layer. The iteration layer is indicated by the small arrow in the left margin of the picture of the structure. The structure type is automatically determined from the top two layers and the correct design procedure executed. Except for new flexible pavements. After clicking the button you must select a layer in the picture of the structure. (CDFU is related to the remaining life of the existing pavement. the iteration layer cannot be changed. In some cases. During design the iteration layer is highlighted by changing its display color. Clicking in the margin to the left of any layer except for the top or bottom layers will select that layer as the adjustment layer for design.) Recommendations for selecting appropriate values of SCI and CDFU are given in the discussion of concrete layers in the Layer Types section. The small arrow in the left margin of the picture of the structure indicates the layer which will be adjusted during design (see below under Design Structure). STRUCTURE WINDOW > Command Buttons Add/Delete Previous Next Layers can be added or deleted using Add/Delete. No functions other than structure modifications can be executed while the modify mode is active. STRUCTURE WINDOW > Command Buttons Design Structure Previous Next Clicking this button adjusts the thickness of one of the layers (the “iteration layer”) of the structure so that the design criteria for the particular type of structure are satisfied.Input data for overlay structures also includes the structural condition index (SCI) of the existing pavement before overlay and. under some conditions. the Cumulative Damage Factor Used (CDFU) of the existing pavement. This is only included to prevent unreasonable layer thicknesses and is not intended . the thickness of an adjacent layer is changed. STRUCTURE WINDOW > Command Buttons End Modify Previous Next Terminates the modify mode. A box is displayed requesting the selection of Add or Delete. if a new computed layer thickness is unreasonable (such as negative). The position of the arrow can only be changed when the structure is a new flexible pavement. Selecting Delete completely removes the selected layer from the structure. Selecting Add duplicates the selected layer. The properties of the layer can then be changed as desired. Information on the state of the design is displayed at the bottom of the picture of the structure. STRUCTURE WINDOW > Command Buttons Interrupt Design Previous Next When a design is started by clicking Design Structure. Saving the structure after a design has run to completion marks the section in the data record as being a completed design. Save Structure changes to Interrupt Design. Modifications made to a pavement structure do not become permanent until the data is saved using Save Structure. STRUCTURE WINDOW > Command Buttons Life Previous Next .to try to optimize the design. the structure does not become permanent in the job until the structure is saved (see Save Structure). Returning to the STRUCTURE window restores the original structure and all changes will have been lost. During design. This transfers control to the STARTUP window. This cannot be done in modify mode or during design. Or the structure can be changed and a new design started from the changed condition. Clicking this button during design stops the design calculations and leaves the thickness of the layer being adjusted at its value at the time of stopping the design. You can therefore try different designs and return to the original structure by canceling the save with the following sequence: click Back followed by clicking NO in the displayed message box. The design can be restarted with the structure as it existed at the time of interruption by clicking Design Structure again. If it occurs. the structure should be inspected and changed if necessary. STRUCTURE WINDOW > Command Buttons Save Structure Previous Next The structure is saved in the current section data record by clicking Save Structure. followed by a redesign. Details of the design procedures executed by Design Structure for the different pavement structures are given in the Pavement Thickness Design section. Clicking Back without having saved the structure causes a message box to be displayed which prompts for the structure to be saved. STRUCTURE WINDOW > Command Buttons Airplane Previous Next Transfers control to the AIRPLANE window. return to the STARTUP window. the life computed using Life will equal the design life. return to the STRUCTURE window. Airplane are transferred from the library list to the design list by . CDF and percent CDFU are computed for new pavement design based on the current setting of design life. annual departures. and percent annual growth (defined below). Except for gross load. Airplane are selected from a library and placed in a list of design airplane. At the top left of the window is a list of library airplane groups.Computes the life of the current section in years. with associated data. If design for the section has been run to completion. If you want to change to another job. but is provided for convenience in computing CDFU and CDF. Other sections or jobs cannot be selected from the AIRPLANE window. This function is not required for design. all necessary airplane information for design is stored internally as part of the library and cannot be changed. Airplane Window At the top right of the window is a table which lists the design airplane for the currently selected section. If you want to change to another section. STRUCTURE WINDOW > Command Buttons Back Previous Next Returns control to the STARTUP window. Selecting one of these groups will display all of the airplane in that group in the list box located below the airplane group box. AIRPLANE WINDOW Introduction Previous Next The AIRPLANE window allows for the creation and modification of an airplane list for the currently selected section in the currently selected job. or by double clicking the airplane name in the library list.changing the data for one changes the data for the other automatically. Annual departures is defined as the airplane departure rate in departures per year. Percent annual growth is defined as the percent change in annual departures per year over the design life of the pavement. The tire contact lengths and widths are those used in the calculation of pass-tocoverage ratio for the airplane. and percent annual growth) can be changed by clicking on the value to be changed.) Certain airplanes with D or 2D belly gear (DC10-30/40.selecting an airplane in the library list (by clicking the name once) and clicking Add. An elliptical contact patch is assumed. or by double clicking the airplane name in the design list. The library list contains airplane representative of the most common commercial and military airplane. the fraction of the gross load carried by the main gear has been set at 95 percent to make the FAARFIELD design procedures compatible with the requirements of AC 150/5320-6E. (In contrast. Scrolling the table columns to the left shows columns for: total lifetime departures. Data for the Generic group are based on the generic airplane types used to generate the design nomographs in previous FAA ACs. circular tire contact patches are used in LEAF because the layered elastic model is axisymmetric. tandem-wheel spacing. tire pressure. percent gross load on the design gear. annual departures. with its area equal to the tire load divided by the tire pressure. An input box is displayed which gives instructions and the allowed ranges for data entry. and A340 series) are treated as two separate airplanes for design. either by a similar airplane or from the “Generic” group list. and tire contact length. Substitutions can be made for airplane not in the list. Values in the first three data columns of the design airplane list table (gross load. MD11ER. The total number of departures for the selected airplane over the design life of the pavement is given by the equation: where: N L a b = total departures = pavement design life = initial annual departures = percent annual growth . a two-gear 2D airplane (wing gear) and a single-gear D or 2D airplane (body gear). dual-wheel spacing. Airplane are removed from the design list by selecting an airplane in the design list (by clicking the name once) and clicking Remove. For all airplane in the library. and removing one of the two airplane from the design list removes the other automatically. The displayed value is the number of annual departures for the selected airplane at the start of the pavement‟s design life. A maximum of 40 airplane can be included in the design list. adding a DC10-30/40 to the design list places the two airplane for design in the list automatically. None of these can be changed. Negative values represent a decrease in annual departures. The data for the two airplane are also tied . tire contact width. For example. the actual traffic mix (departures of each airplane type) should be entered in the airplane window. and assumes zero departures for the airplane from the time at which the departure rate becomes zero to the end of the design life.3) displayed a message “Non-Standard Airplane List” in cases where the airplane list contained only one airplane. it is emphasized that in cases where the pavement will be trafficked by a mixture of airplane. Do not first convert airplane to “equivalent” departures of a design airplane (as was done in previous FAA design procedures). AIRPLANE WINDOW Airplane Lists Containing a Single Airplane Type Previous Next Previous FAA thickness design programs (LEDFAA 1. AIRPLANE WINDOW Command Buttons Previous Next More: Add Remove Clear List Save List Save to Float Add Float . This is no longer true in FAARFIELD. It is recognized that in some cases a single airplane best represents the actual traffic on a given pavement feature.Large negative percent annual growth can result in negative airplane departures before the end of the design life has been reached. The program automatically detects this condition if it occurs. However. before returning to the STRUCTURE window. AIRPLANE WINDOW > Command Buttons Save List Previous Next Saves the data for all of the airplane in the design list into the data record for the currently selected section in the currently selected job.CDF Graph View Gear Back AIRPLANE WINDOW > Command Buttons Add Previous Next An airplane is transferred from the library list to the design list by selecting an airplane name in the library list and clicking Add. AIRPLANE WINDOW > Command Buttons Remove Previous Next An airplane is removed from the design list by selecting the airplane name and clicking Remove. . AIRPLANE WINDOW > Command Buttons Clear List Previous Next Deletes all airplane from the design list. or discarded. or by double clicking the airplane name in the design list. All changes made to a design list must be saved. The same operation can also be performed by double clicking an airplane name in the library list. The Save operation permanently changes the airplane data stored in the section data record. If changes have been made to the design list and the list has not been saved. Clicking Save to Float transfers the current design list and airplane data to the floating list. AIRPLANE WINDOW > Command Buttons View Gear Previous Next Transfers control to the AIRPLANE DATA window (discussed under separate heading). The floating list is displayed in the list box at the bottom right of the window and is always empty when the program starts. AIRPLANE WINDOW > Command Buttons CDF Graph Previous Next Displays airplane CDF graph.” list of airplane is provided to allow an existing list to be transferred easily to a different section. The new floating list will remain available until the next Save to Float operation or the program is terminated. a message box is displayed requesting that the changes be saved .AIRPLANE WINDOW > Command Buttons Save to Float Previous Next An independent. Button is enabled after running Life or Design in the STRUCTURE window. “floating. AIRPLANE WINDOW > Command Buttons Back Previous Next Returns control to the STRUCTURE window. replacing the existing floating list. AIRPLANE WINDOW > Command Buttons Add Float Previous Next Adds the airplane in the floating list to the current design list up to the maximum of 20 airplane. Control cannot return to the STRUCTURE window until the changes have been saved or discarded. or that the Back operation be canceled. Upon closing and reopening FAARFIELD. OPTIONS WINDOW Introduction Previous Next An OPTIONS window is provided to give the user the ability to modify many pavement structure and general options from a single location.or discarded. It is possible to restore all original (default) settings by clicking “Restore Default” at the lower right corner of the OPTIONS window. Options Window OPTIONS WINDOW Pavement Structure Options Previous Next More: CDF Tolerance Life Tolerance No AC CDF Alternate Subgrade Automatic Base Design NSection Parameter Partially Bonded Overlay on Rigid . the default options settings are restored. modified options are in effect only as long as the session is open. Also. This option is most effective during initial design of pavement sections with thick aggregate layers and many airplane in the design list. new rigid pavements. This applies to: HMA on rigid overlays. the faster the convergence. The default value is 0.005 (maximum accuracy).OPTIONS WINDOW > Pavement Structure Options CDF Tolerance Previous Next Design of certain pavement types is an iterative process accomplished when CDF equals 1. OPTIONS WINDOW > Pavement Structure Options Alternate Subgrade Previous Next .02 to 0. but the less accurate the solution will be. This applies to: new flexible pavements. the faster the convergence. OPTIONS WINDOW > Pavement Structure Options No AC CDF Previous Next An option called “No AC CDF” is included to disable the computation of asphalt surface CDF at the end of a flexible pavement design.005 to 0.tolerance). HMA on flexible overlays. Life tolerance defines the convergence tolerance on the computed life in years. unbonded PCC on rigid overlays. To switch on the AC CDF computation (recommended for a final design check). OPTIONS WINDOW > Pavement Structure Options Life Tolerance Previous Next Design of certain pavement overlay types is an iterative process accomplished when the computed life equals the design life of 20 years (or a value specified by the user). The default is set for the AC CDF computation to be turned off.05.40 years. The user can specify CDF tolerance in a range from 0.5 years. and partially bonded PCC on rigid overlays. The larger the specified tolerance. uncheck the box.0 +/. The default value is 0. but the less accurate the solution will be. CDF tolerance defines the convergence tolerance on the computed CDF (CDF = 1. and PCC on flexible overlays. The user can define Life tolerance in a range from 0. The larger the specified tolerance. An option called “Alternate SG” is included to allow one of the upper layers to be set as the subgrade for design. It defines the number of traffic intervals for which the elastic modulus of the PCC base layer is recalculated. As long as Alternate SG is checked. but less accuracy. For the same design inputs. “Design of Overlays for Rigid Airport Pavements. The default setting is to enable automation base design.. The default value of NSection is 16. This represents the strength properties of a standard subbase material meeting the requirements of Item P-154. More information on this topic can be found in Rollings. pages 103-107. stiff bottom layers in the structure. the thickness of a standard crushed aggregate base layer (Item P-209) is designed to protect a subbase layer with an assumed CBR of 20. As described in AC 150/5320-6E. Partially bonded PCC on rigid overlays are no . Used in conjunction with relocation of the iteration layer (see subsection Design Structure). OPTIONS WINDOW > Pavement Structure Options NSection Parameter Previous Next This parameter applies only to unbonded PCC on rigid and partially bonded PCC on rigid overlay structures. Lower values of NSection will lead to faster convergence.” April 1988.S. For a stabilized base later. however the required thickness of stabilized base material (P-401) is reduced by an equivalency factor of 1. paragraph 314d. R. the thickness of a partially bonded PCC overlay falls between bonded and fully unbonded overlays. for example. FAA Technical Report DOT/FAA/PM-87/19. the same computation is performed. OPTIONS WINDOW > Pavement Structure Options Automatic Base Design Previous Next This option invokes an automatic design procedure for base layer thickness in new flexible pavements. this allows for the inclusion of. The procedure is to check the Alternate SG check box and select as the iteration layer the layer above the alternate subgrade.6. This option only applies to flexible pavement design. OPTIONS WINDOW > Pavement Structure Options Partially Bonded Overlay on Rigid Previous Next A partially bonded overlay is defined as a PCC on rigid overlay where no particular attempt is made to either eliminate or achieve bond between the concrete overlay and the existing rigid pavement. the design will always be based on the vertical strain at the top of the layer below the iteration layer. This option applies only to flexible pavements. by default. These additional output files are saved to the working directory. Therefore. OPTIONS WINDOW > General Options . The default setting is checked (files are not created). The additional output files created by FAARFIELD are: LeafSG. If a partially bonded PCC on rigid overlay is selected by checking this option. The default setting is English.” OPTIONS WINDOW General Options Previous Next More: Units No Out File Batch Mode OPTIONS WINDOW > General Options Units Previous Next Throughout the FAARFIELD program. the option to design partially bonded PCC on rigid overlays is disabled.longer considered standard FAA designs in AC 150/5320-6E. units can be displayed in either Metric or English by selecting the appropriate radio button.out for rigid pavements. OPTIONS WINDOW > General Options No Out File Previous Next Unchecking this option causes FAARFIELD to create certain additional output files. a message will be displayed: “Non-Standard Structure. The contents of these files is discussed in the section of this document on Output Data Files.out for flexible pavements and NikePCC. the batch job will halt until the message is cleared. The first section to be designed is selected in the list box and Batch clicked. maintenance history. However. The design information is fixed and is taken from the section data record. location. The notes are entered by the user and can contain up to 30. such as “minimum thickness for a layer. The option is activated by double clicking anywhere on the gray background of the structure window.000 characters for each section (5 to 20 pages).Batch Mode Previous Next A batch option has been included in the program so that a number of time consuming designs can be executed unattended. when clicked. Each section in the list starting at the one selected to the last will then. if any other message. in turn. A check box appears which.” is displayed. On the right of the window is a text box which contains either the design information or the notes for the currently selected section. changes the caption of the Life button to Batch. The “already designed” and “saving structure” messages are suppressed. On the left of the window is a list of the sections in the currently selected job. such as size. NOTES WINDOW Introduction Previous Next The NOTES window is provided for viewing a summary of the design information for the currently selected section and for entering and saving notes on the currently selected section. Text is entered and edited as it would be in the Windows Notepad text editor. Notes Window NOTES WINDOW Command Buttons Previous Next More: Design Info Notes . be designed and the results stored in the job file. etc. NOTES WINDOW > Command Buttons . such as a text editor or word processor. NOTES WINDOW > Command Buttons Copy Previous Next Copies the design information and the notes from the NOTES window to the Windows clipboard. NOTES WINDOW > Command Buttons Notes Previous Next Displays in the NOTES window text box the notes for the currently selected section. NOTES WINDOW > Command Buttons Print Previous Next Prints the design information and the notes from the NOTES window to the currently selected default Windows printer.Copy Print Save Save XML NOTES WINDOW > Command Buttons Design Info Previous Next Displays in the NOTES window text box the design information for the currently selected section. The text can then be pasted into another application. ) NOTES WINDOW > Command Buttons Save XML Previous Next Saves the design data for the currently selected section in the Extensible Markup Language (XML) file format. The horizontal locations of the points at which the pavement responses are computed (the evaluation points) are shown in the picture as small black dots. An image of the window is printed by clicking Print. the notes for a section contain only the section name unless the section was created using Copy Section in the STARTUP window. The XML data file can also be imported directly into FAA Form 5100-1. The XML data file can be imported to any application supporting the XML format. The generated file has a filename with the extension . (Each job file has a corresponding nts file. An XML schema file (FAARFIELD sample xml schema. AIRPLANE DATA WINDOW Viewing the Gear Layout Previous Next The AIRPLANE DATA window primarily shows the main gear layout for the airplane currently selected in the design list. When initialized. Airplane Landing Gear Data CUMULATIVE DAMAGE FACTOR CDF .xml and contains the same data displayed in the “Design Information” pane. Gross load can also be changed by clicking the Gross Load data display box. Precise locations of the evaluation points are listed in the output data files (see later under Data Files).Save Previous Next Saves the notes for the currently selected section in the nts file for the currently selected job. The gear layout and the tire contact patches are drawn to scale. “Airport Pavement Design” (electronic version) for inclusion in the Engineer’s Report. in which case the old notes are copied into the new section.xml) is provided as part of the FAARFIELD package. An image of the picture can be copied to the clipboard by clicking the right mouse button on the picture. The CDF for design is taken to be the maximum over all 82 strips. CDF is calculated for each 10 inch wide strip along the pavement over a total width of 820 inches. therefore.. but that it will have failed according to the definition of failure used in the design procedure. the pavement will have used up all of its fatigue life. This is because a different pavement load will be applied by each gross load. airplane with different main gear track widths will have different pass-tocoverage ratios in each of the 10 inch strips and may show little cumulative effect on the . A value of CDF greater than one does not necessarily mean that the pavement will no longer support traffic. the thickness is adjusted to make the CDF for subgrade failure equal to 1. all of the fatigue life will have been used up and the pavement will have failed. Each failure mode included in the design procedure will have a separate CDF. and the value of CDF will give the frac tion of the life used. or. Multiple airplane types are accounted for by using Miner's Rule instead of the "design airplane" concept as in the current procedures. Note: In these definitions. the thickness design is based on the assumption that failure occurs when CDF = 1. and within the constraints of uncertainties in material property assumptions.Previous Next Cumulative damage factor (CDF) is the amount of the structural fatigue life of a pavement which has been used up. etc. failure means failure in a particular structural failure mode according to the assumptions and definitions on which the design procedures are based. for one airplane and constant annual departures: When CDF = 1. It is expressed as the ratio of applied load repetitions to allowable load repetitions to failure. the asphalt is predicted to fail before the subgrade. or: CDF = CDF1 + CDF2 + . When CDF > 1. When CDF < 1. For example. and adjustments should be made to base and subbase layers so that asphalt CDF is less than 1 in the final design.5 inches (equivalent to airplane operation on a taxiway) and used in the above equation for Miner‟s rule. Nevertheless. Even with the same gear geometry. CDFN Where CDFI is the CDF for each airplane type in the mix and N is the number of airplane types in the mix. in flexible pavement design. An additional computation is then made to find the CDF for asphalt surface cracking. Note: The same airplane model with two different gross loads represents two different airplane types. Pass-to-coverage ratio is computed for each strip based on a normally distributed airplane wander pattern with standard deviation of 30. the asphalt is predicted not to fail in cracking before the subgrade fails. But if the asphalt CDF is greater than 1.. In the program implementation. the pavement will have some life remaining. If the asphalt CDF is less than 1. . is that the design procedure executed by the program is automatically determined by the layer types of the top two surface layers. Rollings.7781. For example.. Gonzalez.000 to 4. Jr. R. and C.R. Development of a Structural Design Procedure for Flexible Pavements.N. Barker.C. Brabston. minimum allowable thicknesses for layers have been built into FAARFIELD to conform to the applicable requirements of AC 150/5320-6E. and specifying types. Design of Overlays for Rigid Airport Pavements. Report No. April 1988. 3. Report No.35 and modulus must be in the range 1. R. minimum thicknesses from FAARFIELD should always be checked against the requirements of the advisory circular for the particular pavement type under design to ensure that the design meets the current standard. Some of the types can be placed at any position in a structure..000 psi. References for specific details of the FAARFIELD design procedures are: 1. and E. Development of a Structural Design Procedure for Rigid Airport Pavements. FAA-RD-74-199. Pavement Design by Elastic Layer Theory. September 1975. The reason for specifying placement. F. W..R.R.maximum CDF. LAYER TYPES Introduction and LED References Previous Next Eighteen layer types are included for building pavement structures. 2. Kansas City. while others can only be placed in specified positions. 4. All layer types except undefined are related in some way to layer types identified or specified in AC 150/5320-6E. Report No..) However.. DOT/FAA/PM-87/19. However. Proceedings. W. Some flexibility is allowed by the inclusion of an “undefined” layer type. undefined layer types do not meet FAA standards for airport pavement design. depending on how close the gear tracks are to each other. ASCE Conference on Airplane/Pavement Interaction. Barker. Removing the airplane with the lowest stress or strain may then have little effect on the design thickness. W. 1991. The requirements and guidelines of AC 150/5320-6E should be followed whenever there is a discrepancy between FAARFIELD and the advisory circular.S.000. Control of default parameter values is also easier when placement is controlled. FAA. This section provides information on the relationship between the FAARFIELD and AC 150/5320-6E layer types and provides additional guidance on selecting appropriate layer properties as input data for FAARFIELD. and W.RD.R. April 1977. Barker. and the presence of aggregate layers. Odom. Parker.C. Gunkel. (Default values and ranges for all layer types are displayed in the Modify Structure data entry dialog boxes. The only restrictions on this type are that Poisson‟s ratio is fixed at 0. where: ESG k = Resilient modulus of the subgrade. direct input of CBR values is also acceptable. psi = Foundation modulus of the subgrade. For existing pavements the E modulus can be determined in the field from non-destructive testing (NDT) such as falling-weight deflectometer (FWD) tests and this may be necessary if direct testing of the subgrade is impractical. However. all structural computations are performed using the elastic modulus E. 5285 Port Royal Road. the failure models represent the relationship between . for rigid pavement design.Copies of the FAA reports may be obtained from the National Technical Information Service. If the k-modulus can be determined by plate load testing. As given in the following section (Pavement Thickness Design). the conversion from CBR to k-value for the subgrade can be achieved using the following formula: (k in pci) The equations for converting CBR and k to E modulus are based on empirical data and were used in the development of the flexible and rigid pavement failure models. Although FAARFIELD performs computations based on elastic modulus. the foundation modulus can be expressed as the modulus of subgrade reaction k or as the elastic (Young‟s) modulus E and can be input into the program directly in either form. Similarly. pci . The procedure which will be applicable in most cases is to use available CBR values and substitute in the relationship: E = 1.500 CBR (E in psi). In cases where CBR data are available. or is otherwise available. If the foundation modulus is input as a k-value it is automatically converted to the equivalent E value using the following equations (which are equivalent): or. If the subgrade is accessible then the k-value can be determined directly by plate-load testing. Springfield. This method will provide designs compatible with the earlier flexible design procedure based on subgrade CBR. VA 22161 LAYER TYPES Subgrade Layers Previous Next Subgrade modulus values for flexible pavement design can be determined in a number of ways. then the k-value should be input directly into the FAARFIELD program without first converting to E modulus. For overlays on existing PCC with SCI=100. see the section on Stabilized Layers. with modulus fixed at 200.computed pavement response (strain or stress) and coverages to failure measured in full-scale tests. most of which were run before 1974. Therefore. LAYER TYPES Concrete Layers Previous Next Four types of concrete layers are included: PCC surface. The modulus of all PCC types is fixed at 4. CBR was used for flexible pavements and k value for rigid pavements. or under an asphalt or PCC overlay. Flexural strength can be varied in the range 500 to 800 psi. conversions were required to estimate resilient modulus for use in the layered elastic computations of strain and stress. LAYER TYPES Asphalt Layers Previous Next Two types of hot mix asphalt (HMA) layers are included: asphalt surface and asphalt overlay. (For HMA used as a stabilized base layer. The conversion equations are therefore an integral part of the design procedures when measured values of CBR or k are used for design. The asphalt surface type can only be placed on the top of a structure. The asphalt overlay type can also be placed over a Rubblized PCC Base type.000 psi and Poisson‟s ratio fixed at 0.15 in all cases.) Both types have the same properties. Poisson‟s ratio is fixed at 0. The asphalt overlay type can be placed over asphalt surface or PCC surface types. it is assumed that the existing pavement may have suffered serious deterioration before the overlay and SCI can be given values in the range 100 (none to negligible structural cracking) to 40. Details of the development of the conversion equations are given in references 1 and 2. PCC partially bonded overlay on a PCC pavement. . (PCC modulus is considered to be independent of flexural strength. For unbonded overlays. The overlay types can only be placed on the top of the structure. PCC unbonded overlay on a rigid pavement. The PCC surface type can be placed on the top of the structure for new designs or next to the top for overlays. Resilient modulus of the subgrade was not typically measured during the full-scale tests. see Cumulative Damage Factor Used (CDFU).000.) Overlaid rigid pavement designs require the SCI of the existing pavement as an input. and PCC overlay on a flexible pavement.35. PCC overlay on flexible pavement can be placed on an asphalt or undefined layer.000 psi except for PCC surface when it is part of an overlay structure (see below). The procedure for computing percent CDFU for a rigid pavement with SCI = 100 is as follows: . and assuming that traffic on the pavement has been constant over time. it can be activated from the Options window. For aggregate base layers. an additional input is required to define the amount of life that has been used by the existing pavement up to the time of the overlay. a good estimate of CDFU can be obtained from: where: LU LD = number of years of operation of the existing pavement until overlay = design life of the existing pavement in years This equation was derived from the empirical relationship between traffic coverages and SCI given in reference 3 and applies to pavements on conventional (aggregate) base. the simple relationship given above is not valid for such structures. FAARFIELD implements a modification of this empirical relationship for higher quality base materials to account for the observed performance of rigid pavements on stabilized bases. By default. This modification essentially increases the percent of design life remaining after the SCI starts to drop from 100 if the base and subbase layers are of higher quality than an 8-inch (203 mm) aggregate subbase (aggregate base thicker than 8 inches (203 mm) or stabilized base thicker than 4 inches (102 mm)). Note that partially bonded overlays are no longer considered a standard FAA design in AC 150/5320-6E. a message will appear: “Non-Standard Structure. if a partially bonded overlay is selected. it is assumed that the existing pavement is in sound to barely failed condition before the overlay and SCI can be given values in the range 100 (none to negligible cracking) to 77 (slightly worse than the FAARFIELD definition of end-of-design-life of SCI = 80). The input is in terms of “CDF used to first crack” (CDFU) and is equivalent to equation 42. In FAARFIELD. However.” More: Cumulative Damage Factor Used (CDFU) Structural Condition Index (SCI) LAYER TYPES > Concrete Layers Cumulative Damage Factor Used (CDFU) Previous Next When SCI = 100 for overlay design of an existing rigid pavement. this option is inactive in FAARFIELD. However. the percent CDFU is computed and displayed when the Life button is clicked in the STRUCTURE window. p 98. in reference 3.For partially bonded overlays. Hence. 3. For a concrete overlay on rigid pavement the following. The computation is automatic and transparent to the user. taken from reference 3. 2. The following. The range is 100 to 67. Estimate the traffic which has been applied to the pavement and enter into the airplane design list. can be used to relate the c factor in the previous FAA procedure with SCI required for input in FAARFIELD: . Set design life to the amount of time the pavement will have been in operation up to the time of overlay. Setup the structure based on the original design assumptions. Values of percent CDFU greater than 100 indicate that the procedure predicts that the SCI of the pavement should be less than 100. However. Then repeat the steps given above and use the new value of percent CDFU. An alternative procedure is to run Design Structure for the original structure with design life set to the actual design life. Percent CDFU will be displayed when the computation is completed. If it is suspected that the pavement has been subjected to more. can be used to relate the c factor in the previous FAA procedure with SCI required for input in FAARFIELD: Asphalt overlays on rigid pavements also require the input of a value for SCI of the existing pavement.1. taken from reference 3. percent CDFU should be increased from the computed value. Run Life. A value of 100 should then be entered for percent CDFU as input data for the overlay design. 4. but not SCI. since the computation of percent CDFU will be based on estimated structure properties and traffic. it is possible to obtain an estimate of SCI from this information. the modulus of the base pavement is varied as a function of SCI of the base pavement when SCI is less than 100 according to the relationships given in reference 3. For both partially bonded and fully unbonded concrete overlays. Setting percent CDFU to 100 will give the most conservative design. or heavier. If the c factor is available for a particular pavement. the value is likely to be unreliable. LAYER TYPES > Concrete Layers Structural Condition Index (SCI) Previous Next The ranges of the SCI inputs correspond to specific ranges of the factors cb and cr used in the earlier method of overlay design based on the thickness deficiency approach (refer to AC 150/5320-6D). traffic than assumed in the Life computation. (27. Crushed Aggregate Base Course or Item P-208.000 lbs. The modulus of crushed aggregate layers is computed automatically and cannot be changed manually. Aggregate Base Course. Subbase Course. AC 150/5320-6D (FAA. .000 kg) or less. The modulus of uncrushed aggregate layers is computed automatically and cannot be changed manually.The range for c is specified in an earlier version of the advisory circular. Accordingly. paragraph 309.000 lbs. “Non-Standard Structure. 1995).” Item P208 can be used as a subbase layer without restriction. LAYER TYPES Aggregate Layers Previous Next More: Crushed Aggregate Uncrushed Aggregate Modulus Values of Aggregate Layers LAYER TYPES > Aggregate Layers Crushed Aggregate Previous Next Crushed Aggregate in FAARFIELD corresponds to Item P-209. The use of Item P-208 as a base material is limited by AC 150/5320-6E.. Note that the relationship is not valid when SCI is between 75 and 100. if P-208 is used as a base material and airplane in the airplane list exceed 60. to pavements designed for gross loads of 60. a message will be displayed. LAYER TYPES > Aggregate Layers Uncrushed Aggregate Previous Next Uncrushed Aggregate in FAARFIELD corresponds to Item P-154. This can result in a condition in . (Sublayering by the Modulus procedure accounts for thick layers. For efficiency in iterating to a valid thickness design. One consequence of this is that the CDF can increase when sublayering first occurs.0. The modulus value displayed in the structure table for an aggregate layer is the average value of the sublayer modulus values. and multiple layers of a single aggregate type are not necessary.) The maximum number of aggregate layers which may be present in a structure is therefore two.5 to 2.000 are displayed for crushed and uncrushed respectively. but are treated as a single layer with modulus equal to the average modulus of what would be the sublayers. The following additional restrictions also apply: 1. in which case the “defaults” of 75.000 and 40.0. full sublayering is used according to the Modulus procedure. which was a predecessor of FAARFIELD. (Maximum sublayer thicknesses are 8 inches for uncrushed aggregate and 10 inches for crushed aggregate. If crushed and uncrushed layers are adjacent. In the “Modulus” procedure. Aggregate layers can be placed anywhere in the pavement structure except at the top or bottom. the crushed layer must be above the uncrushed layer (to be compatible with the modulus procedure). These defaults are never used in calculations.LAYER TYPES > Aggregate Layers Modulus Values of Aggregate Layers Previous Next The modulus values of aggregate layers are calculated automatically. and are also dependent on the modulus of the layer below the aggregate layer. if the thickness of an uncrushed aggregate layer increases from 15. Note: Sublayering of aggregate layers is not performed in rigid pavement designs.99 inches to 16. Sublayering by the Modulus procedure also causes a discontinuity in computed CDF when the number of sublayers changes as the total thickness of an aggregate layer crosses over the threshold during design. and the CDF may jump from a value above 1 to a value below 1. This is for compatibility with the Modulus procedure. The “Modulus” procedure used to compute the modulus values was developed by the US Army Corps Waterways Experiment Station (WES) for the LEDNEW program. For example. sublayering is performed automatically. one of each type. When CDF is outside the range 0. The only exception is for newly created layers. When CDF is within the range 0.5 to 2. apparently indicating an error in the procedure.01 inches the number of sublayers increases from 2 to 3. Only one crushed layer and one uncrushed layer may be present in a structure. a two-stage process is used during design with thick aggregate layers. the aggregate layers are not sublayered for Leaf. 2.) The modulus values of the sublayers decrease with increasing depth of a sublayer within the aggregate layer. 000 0. and the thickness of the iteration layer changes back and forth across the threshold continuously. The variable stabilized layers can be assigned modulus values within a range. LAYER TYPES Stabilized Layers Previous Next Two categories of stabilized layers are included.000 700. and sudden changes in AC layer CDF may occur for flexible pavements. The fixed modulus types correspond to standard material items. Within each category. both fixed-modulus and variable-modulus layer types are available.20 250. then the condition exists. the number of sublayers in a structure is fixed when CDF is within the range 0.7 to 1.000 700.000 500. the upper and lower limits of the modulus range were established by comparison with the equivalency factors used in the previous FAA (CBR –based) design procedure. Property values are: Type Modulus. The condition can be detected by running Design Structure again after a design has been completed. whatever the thickness of the iteration layer may be.which a given combination of structure and traffic does not have a CDF of 1. A further consequence is that pavement life computed using Life will not agree with the design life. To stop the continuous iteration. If the second design gives a different thickness than the first. classified as stabilized (flexible) and stabilized (rigid).000 400.000 250.35 150. For stabilized layers in flexible pavements. psi Poisson‟s Ratio 0.4.000 400.000 Stabilized (flexible) Variable Minimum Variable Maximum P-401/P-403 Asphalt Stabilized (rigid) Variable Minimum Variable Maximum P-301 Soil Cement Base P-304 Cement Treated Base P-306 Econocrete Subbase . If it is necessary to establish a modulus value for a variable stabilized base layer. M.000 psi = 0. including a variable stabilized layer in a pavement structure will cause a message to display: “Non-Standard Structure. University of Maryland. materials. Rearranging gives: . this allows for computing estimated asphalt CDF values with asphalt modulus different than the fixed value of 200.000 psi will result in nonconservative designs compared with the current FAA design procedure. Since variable stabilized layers do not correspond to standard FAA materials. Report II. typical laboratory test data for stabilized materials should not be used in preparing input data for FAARFIELD designs. It is very important to recognize that flexible pavement thickness designs made with the top layer modulus value greater than 200.000 psi. If an undefined layer is the topmost layer of a pavement structure. and using the Life option. paragraph 314d (flexible pavements). Asphalt Mixture Material Characterization. depending on the composition of the second layer. either the new flexible or an asphalt overlay pavement design procedure is automatically selected.000 psi = 4.W.000. the user should refer to the guidance contained in AC 150/5320-6E. For flexible pavements. May 1989): where E and T = asphalt modulus with units of 105 psi = asphalt temperature in degrees Fahrenheit.. Properties of the layer type are: minimum modulus maximum modulus Poisson‟s ratio minimum thickness = 1.Because the modulus values were determined on the basis of producing thickness designs comparable with the CBR design procedure. or otherwise nonstandard.” LAYER TYPES Undefined Layer Previous Next This layer type is included to allow the use of layers not covered by the most common structural materials and to investigate the effects of using new. The modulus value for asphalt layers as a function of temperature can be estimated using the relationship (Witczak.35 (fixed) = 2 inches There are no restrictions on placement of the undefined layer. Clicking on the message displays a longer message explaining why the structure is non-standard.The design procedures executed when an undefined layer is present in one of the top two layers of a pavement structure are summarized below. Portland Cement Concrete (PCC) overlay on existing flexible. HMA overlay on flexible. Partially bonded concrete overlay on existing rigid*. Top Layer Undefined Undefined Undefined Undefined Asphalt Surface PCC Surface Asphalt Overlay PCC Overlay Second Layer Asphalt Surface PCC Surface Any Overlay Any except the above Undefined Undefined Undefined Undefined Design Procedure Asphalt Overlay on Flexible Asphalt Overlay on Rigid Not valid for design New Flexible New Flexible New Rigid Asphalt Overlay on Flexible PCC on Flexible (New Rigid) If a structure contains one or more undefined layers. 2. and new rigid pavements are designed with the following general procedure: . 4. New flexible. 5. * Non-Standard Structure in AC 150/5320-6E New flexible. The long message is also displayed in the Design Info text box in the NOTES window. PAVEMENT THICKNESS DESIGN General Design Procedure Previous Next Thickness designs can be made for seven different types of pavement structure: 1. HMA overlay on existing rigid. 3. 6. 7. HMA overlay on existing flexible. New rigid. the message “Non-Standard Structure” is displayed. Unbonded concrete overlay on existing rigid. 4. Repeat until the thickness design is satisfactory. Click Save Structure. and set the design life. the opposite of the trend for subgrade strain. Add the airplane CDFs together to find the CDF for the structure. Click Design Structure in the STRUCTURE window. 3. Calculate the maximum stress or strain at a layer interface in the structure for each airplane in the design list. (Increasing thickness decreases CDF. 2. airplane list selection. 3. With the fixed default asphalt modulus value of 200. if necessary. Calculate the allowable number of airplane departures to failure for each airplane based on a defined relationship between allowable departures and stress or strain. 4. For these reasons.1. 5. More details are given below for design of each of the different types of pavement structure. the subgrade strain is . Overlap of the CDFs can therefore occur and a proper design never realized. 2. but the design procedures require more steps because deterioration of the existing pavement is included. and to save run time.000 psi. This is the CDF for each airplane. Under these conditions the horizontal strain also has a tendency to increase as the pavement depth increases. horizontal strain only becomes the dominant criterion when the structure is very deep and is heavily loaded. manually adjust the thickness of other layers in the structure and click Design Structure again. Adjust the thickness of the prescribed layer until structure CDF = 1. This causes the thickness of a prescribed layer to be automatically adjusted by the program until the design criteria are satisfied.) Design for overlays on rigid pavements is generally similar in terms of structure definition. Create a structure. This permanently saves all the information for the new structure in the job file and makes the section as being a completed design. Find the ratio of actual departures to allowable departures for each airplane. The automatic adjustment of the prescribed layer in step 2 is done by FAARFIELD as follows: 1. PAVEMENT THICKNESS DESIGN New Flexible and HMA Overlay on Flexible Previous Next Subgrade vertical strain and horizontal strain at the bottom of the top layer are the design criteria for both pavement types. Inspect the structure when the design program has stopped running and. a design airplane list. and program execution. Table 3-9.6. When the subgrade criterion has been satisfied. or set at its minimum thickness. For overlay design. In AC 150/5320-6E. indicated by the small arrow to the left of the structure) is adjusted to make the subgrade CDF approximately equal to one. This tolerance can be temporarily changed from the Options window. The default error control is that the design will terminate when CDF is in the range 0.used to iterate to a subgrade CDF of one. For new flexible design. The thickness of the top layer is automatically adjusted to make the subgrade strain CDF equal to one. many layered. for a new flexible pavement structure with a standard crushed aggregate base layer (P-209 or P-208) and standard subbase layer (P-154). the top layer is always the design layer. In FAARFIELD. One consequence of delaying asphalt CDF calculation until after satisfying the subgrade criterion is that the design continues to run after the displayed (subgrade) CDF has reached its terminal value. This computed thickness is compared with the minimum thickness requirements listed in AC 150/5320-6E.005. The larger of the two thicknesses is used in the final thickness design. It is intended only to protect from inappropriate input data. and the structural thickness thus obtained is compared to the 5 inch minimum stabilized base thickness. For stabilized base courses. the base course thickness is computed as the thickness required to protect a subgrade of CBR 20. The failure model used to find the number of coverages to failure for a given vertical strain at the top of the subgrade is: where: C = number of coverages to failure = vertical strain at the top of the subgrade . This procedure is not intended to “optimize” a design. If the CDF is less than one with both of the adjusted layers at their minimum thicknesses. the minimum thickness is 5 inches. the CDF is displayed and the design terminated. The procedure is terminated. the thickness of the layer above is halved. the thickness of the layer next to the subgrade (the design layer. If the structure is saved after design without making any modifications. the section data is marked as being a completed design and the asphalt CDF stored in the job file section data record. structures (compared to computing subgrade and asphalt strain each time). For a standard stabilized base course (P-401 or P-403). The value of asphalt CDF is displayed when the computation is complete. a similar procedure is used. If the layer next to the subgrade becomes thinner than its specified minimum thickness. Only one evaluation depth needs to be sent to LEAF and the run time is approximately halved for deep. The value of the asphalt CDF can be viewed in the Design Info text box in the NOTES window. Table 3-9 lists the minimum aggregate base course thickness requirements. A message is displayed stating that asphalt CDF is being computed. and the procedure continued.995 to 1. except that the required structural thickness of base course to protect a CBR 20 subbase is reduced by an equivalency factor of 1. if the top layer becomes thinner than its minimum thickness. with a message. a final calculation is made to find the asphalt CDF (again using only one evaluation depth). 2523.75 of the Westergaard edge stress for design). The general procedure is to compute 75 percent of the free edge stress with the gear oriented parallel to the slab edge. The .5878. where R is the concrete flexural strength is the computed concrete tensile strengthand FCAL = stress calibration factor. and then select the higher of the two cases as the working stress for design. d = 0. FCAL = 1. free edge stress is computed for the gear load and reduced by 25%. Failure for a rigid pavement in FAARFIELD is defined as SCI= 80.7409. for the majority of gear configurations it can be predicted which orientation will yield the critical stress. However. b = 0. so it is not necessary to FAARFIELD to do more than one computation per gear. For a new rigid pavement.The failure model used to find the number of coverages to failure for a given horizontal strain at the bottom of the surface asphalt layer is: where: C = number of coverages to failure = asphalt modulus.2465. Edge stresses and interior stresses for rigid pavements are computed using the three-dimensional finite element model. psi = horizontal strain at the bottom of the surface asphalt layer PAVEMENT THICKNESS DESIGN New Rigid Pavement Previous Next For new rigid design CDF is calculated using the horizontal edge stress at the bottom of the PCC layer. The slab dimensions are fixed by the program and cannot be changed by the user. To make the FAARFIELD design procedure compatible with the historical FAA thickness procedure (which uses 0. The rigid pavement failure model used in FAARFIELD has the general form: where: SCI = Structural Condition Index DF = design factor defined as R/.13 F′s = stabilized base compensation factor (see below) Parameters: a = 0. c = 0. and 75 percent of the edge stress with the gear oriented perpendicular to the slab edge. the program iterates on the thickness of the PCC layer (the design layer) until the failure model predicts a value of SCI=80 at the end of the design life (20 years for standard designs). In this way. the new rigid pavement design procedure is automatically executed. should be treated as a new rigid pavement with the thickness of the PCC layer equal to the sum of the overlay and existing PCC thicknesses.number of coverages to failure (C) is therefore the number of coverages for SCI = 80 at any given value of R/ (reference 2). . or on a 4-inch thick stabilized layer (500. The factor F′s is used to adjust the slope of the line when the structure includes a higher quality (stabilized) base. PAVEMENT THICKNESS DESIGN Concrete Overlay on Flexible Pavement Previous Next When the PCC overlay on flexible layer is placed over an asphalt surface or undefined layer. bonded concrete overlay. A third type of overlay. according to the applicable provisions of AC 150/5320-6E (405d.000 psi). a message will be displayed: “Non-Standard Structure. But if the thickness or quality of of the base/subbase structure is greater than either of these two conditions. the value of F′s is one and the basic (uncompensated) failure model is recovered. by default. The option may be enabled from the Options window. if a partially bonded PCC on rigid overlay is selected. When the concrete slab is placed on an 8-inch thick crushed aggregate layer. CDF is calculated for the concrete overlay layer using the same model as that used in new rigid pavement design. the maximum tensile stress at the bottom of the overlay is used as the critical response in the calculation of CDF. The failure model above assumes that the SCI deteriorates under traffic as a linear function of the logarithm of coverages (after first reaching the first structural crack). based on the overlay type selected. But the . Within the three-dimensional finite element model. an appropriate value of horizontal interface stiffness is assigned internally. Partially bonded PCC overlays are longer considered standard designs in AC 150/5320-6E. the sensitivity of the FAARFIELD design thickness to base/subbase material quality is adjusted to be compatible with that of the previous FAA design procedure given in AC 150/53206D (1995). This is analogous to the use of the new PCC design curves in AC 150/5320-6D as described in paragraph 71 of the AC.(2)). However.” The design starts with a trial overlay thickness selected by the user. For both unbonded and partially bonded overlays. F′s decreases. Therefore. design of partially bonded PCC on rigid overlays is disabled. PAVEMENT THICKNESS DESIGN Concrete Overlay on Rigid Pavement Previous Next Two types of PCC overlay on rigid pavement are considered in the program: fully unbonded and partially bonded. and the number of coverages to failure increases. the deterioration of the SCI of the existing PCC is considered. and the difference between the calculated and desired design life is less than a given tolerance. After the CDF has been calculated. including the processor speed and available RAM.elastic modulus of the existing pavement is assumed to decrease during the period of time when the SCI of the existing pavement is less than 100. FAARFIELD no longer considers the contribution of reflection crack propagation through the HMA overlay thickness to the computed life of the overlay. (The inner loop in LEAF consumes almost all of the solution time. which by default is 0. depending on the base/subbase structure. This results in solution times which are typically much longer than those for the other pavement types. the number of airplane in the design mix. The design is terminated when the calculated value of CDF is in the range 0. The value of the terminal SCI in the life computation is either 40 or 57.995 and 1. In general. and .005 and the difference between the calculated and desired design life is less than a given tolerance. which by default is 0. RUNNING THE PROGRAM Solution Times Previous Next For flexible pavements. but this mainly affects the response of Windows when performing other tasks while a design is in progress and not the total solution time.4 years. rigid pavement designs take longer to execute than flexible pavement designs. the execution time required to design a structure is almost completely dependent on the floating point performance of the computer when performing the layered elastic strain and stress calculations. This is because the 3-dimensional finite element models used in the rigid pavement procedure are computationally intense. PAVEMENT THICKNESS DESIGN HMA Overlay on Rigid Pavement Previous Next The design of HMA overlay on rigid pavement is similar to that of PCC overlay on rigid pavement. The tensile stress of the overlay layer therefore varies during the life of the overlaid pavement and the CDF of the structure must be computed by numerical integration.4 years. Execution time is roughly proportional to the total number of “design” wheels for all of the airplane in the design list. The run time for finite element based designs depends on many factors. the thickness of the overlay is adjusted to bring the next calculated CDF closer to a value of 1 for the correct design life.) The next most important factor is disk access time. and is proportional to a small power of the number of layers in the structure. In both cases. The design terminates when the terminal SCI is reached. this allows for the inclusion of. An option called “Alternate SG” is included to allow one of the upper layers to be set as the subgrade for design. The option is activated by double clicking anywhere on the gray background of the structure window.) Thick aggregate layers increase the solution time more than would be expected because of the sublayering used to represent variation of modulus with depth.005) to the CDF to be removed from the analysis during finite element processing. This eliminates time-consuming and unnecessary finite element computations and also allows airplane makinig a negligible contribution (<0. for example. the batch job will halt until the message is cleared. Alternatively. when clicked. If a lengthy design computation is underway. Design computation is only allowed from the first instance of the program. The criterion for the design of new flexible pavements is to limit the vertical strain at the top of the subgrade to a specified value. any other application can be run from Windows while a design is in progress. An additional option called “No AC CDF” is included to disable the computation of asphalt surface CDF at the end of a flexible pavement design. (These airplane will still appear in the airplane list in all program output. changes the caption of the Life button to Batch.the size of the largest gears in the mix (multiple axle gears take longer than single axle gears due to a larger mesh). This option is most effective during initial design of pavement sections with thick aggregate layers and many airplane in the design list. Thin concrete overlays on rigid pavements have the longest solution times of all the structure types. Used in conjunction with relocation of the iteration layer (see subsection Design Structure). in turn. The results can be viewed in the NOTES window after the batch job has finished. Each section in the list starting at the one selected to the last will then. A check box appears which. a second instance of FAARFIELD can be started and section data edited. Rigid overlay designs take significantly longer to execute than new rigid designs. The “already designed” and “saving structure” messages are suppressed. if any other message. RUNNING THE PROGRAM Options Previous Next A batch option has been included in the program so that a number of time consuming designs can be executed unattended. be designed and the results stored in the job file. but their CDF contribution is reported as 0. stiff bottom layers in the structure. The first section to be designed is selected in the list box and Batch clicked. such as “minimum thickness for a layer. However.” is displayed. The procedure is to check the Alternate SG check box and . FAARFIELD implements a number of computational strategies designed to minimize computation time. Among these is the use of a preliminary design running LEAF prior to performing the final design iterations based on the three-dimensional finite element model. such as “minimum thickness for a layer. This option is most effective during initial design of pavement sections with thick aggregate layers and many airplane in the design list. If a lengthy design computation is underway. As long as Alternate SG is checked. As long as Alternate SG is checked. stiff bottom layers in the structure. Design computation is only allowed from the first instance of the program. The criterion for the design of new flexible pavements is to limit the vertical strain at the top of the subgrade to a specified value. a second instance of FAARFIELD can be started and section data edited. Each section in the list starting at the one selected to the last will then. any other application can be run from Windows while a design is in progress. the design will always be based on the vertical strain at the top of the layer below the iteration layer. RUNNING THE PROGRAM Copying to the Clipboard Previous Next . the batch job will halt until the message is cleared. An additional option called “No AC CDF” is included to disable the computation of asphalt surface CDF at the end of a flexible pavement design. in turn. if any other message. the design will always be based on the vertical strain at the top of the layer below the iteration layer. An option called “Alternate SG” is included to allow one of the upper layers to be set as the subgrade for design.” is displayed. this allows for the inclusion of. Used in conjunction with relocation of the iteration layer (see subsection Design Structure). The option is activated by double clicking anywhere on the gray background of the structure window. Alternatively. be designed and the results stored in the job file. RUNNING THE PROGRAM Options Previous Next A batch option has been included in the program so that a number of time consuming designs can be executed unattended. A check box appears which. However.select as the iteration layer the layer above the alternate subgrade. The procedure is to check the Alternate SG check box and select as the iteration layer the layer above the alternate subgrade. The “already designed” and “saving structure” messages are suppressed. for example. when clicked. changes the caption of the Life button to Batch. The results can be viewed in the NOTES window after the batch job has finished. The first section to be designed is selected in the list box and Batch clicked. should be done with Windows Explorer. The first extra function allows job files to be saved in a selected directory other than the working directory. airplane loads. Similarly. However. Right click in the box displaying the name of the working directory. Only one file can be saved at a time. right click on the job file to be saved. details of the structure. DATA FILES File Management Previous Next In general. The new name is displayed in the box in the STARTUP window and the names of any job files existing in the new working directory are displayed in the left hand list box. check your computer documentation for the equivalent function. The second function is to create a new working directory or to change the current working directory. Then hold down the Alt key and press the PrintScreen key. First make sure that the window to be copied is the active window by clicking the mouse within the window area. and pavement responses are stored in an ASCII text output file and placed in the current working . If the window is not copied to the clipboard. A standard Windows Save As dialog box will appear. two extra functions have been added to FAARFIELD to simplify working within the program. The job file can then be saved anywhere within the computer‟s resources. In the STARTUP window. such as backup and deletion. Navigate to the directory you want to be the current working directory and press Save. the picture of the gear layout in the AIRPLANE DATA window can be copied by right clicking on the picture. file management. No action is taken other than returning the name of the new directory to FAARFIELD. DATA FILES Output Data Files Previous Next At the end of the structural design or life computation. The picture of the structure in the STRUCTURE window can also be copied to the clipboard by placing the mouse pointer within the area of the picture and clicking the right mouse button. Navigate to the correct directory and press the createa-new-folder icon to create a new directory.In addition to copying the design and notes information to the clipboard from the NOTES window. with or without changing the name. any of the program windows can be copied to the clipboard as a bitmap using the Windows Alt-PrintScreen function. replacing the ones already there. A standard Windows Save As dialog box will appear. The bitmap can then be pasted into another application and printed or saved. and overwrite the files generated by the previous computation. The output files always have the same names.out (subgrade responses for a flexible pavement) 2. In addition. The filenames are: 1. DATA FILES Storage Files Previous Next Permanent information for layered elastic design is stored in *. This will cause four option check boxes to appear. stresses.job and *. More: . Clicking on the gray background a second time will hide the option boxes. depending on the pavement type.out (PCC surface layer responses for a rigid pavement) For flexible pavements. etc. LeafSG. *. N3dhsp (3-dimensional finite element detailed output file – Note: this file can be lengthy) 3.directory.nts files. *. Principal and octahedral stresses are included. For rigid pavements.dat (generated 3-dimentional mesh data that can be imported to a postprocessor program for viewing) Note: Output files will NOT be created if the “No Out File” option is checked. LeafSG. the 3-dimensional finite element stress computation model produces a number of output files: 1.out (asphalt surface layer responses for a flexible pavement) 3.txt (3-dimensional finite element summary output file) 2. NikePCC. Pltdata. strains. and displacements are given for each evaluation point for each airplane in the traffic mix. double click anywhere on the gray background of the Structure window. Unchecking the box marked “No Out File” will cause output files to be created on subsequent runs. Both files can be read by other applications if necessary. and LeafAC.out contains the maximum computed horizontal stress on the bottom of the slab for each airplane in the traffic mix. tracking design history.out contains the responses computed at the top of the subgrade. LeafAC. To activate the output files.job files contain all of the data required by FAARFIELD for all of the sections in one job. Nike3d. NikePCC.out contains the data for responses computed at the bottom of the asphalt surface layer.nts files contain user entered information not needed by FAARFIELD but which may be useful in identifying features of the pavement sections. xml Files Previous Next FAARFIELD stores job data using the Extensible Markup Language (XML) format.xml Files LEDFAA *.w3. Information on the XML format may be found in several publications or online at: http://www.job File with 2 Sections Layer Codes *.JOB.JOB. The following XML schema describes the structure of the *.job File Format Example of a *. such as MicrosoftTM ExcelTM. A description of the XML elements follows.JOB.xml file. <?xml version="1. This allows for easy import of job and section data to applications supporting XML.w3.nts File Format DATA FILES > Storage Files *.0" encoding="UTF-8" standalone="no" ?> <xsd:schema xmlns:xsd="http://www.org/2001/XMLSchema"> <xsd:element name="JobInfo"> <xsd:complexType> <xsd:sequence> <xsd:element minOccurs="0" maxOccurs="unbounded" <xsd:complexType> <xsd:sequence> <xsd:element name="SectionName" type="xsd:string" /> name="SectionInfo"> .*.org/XML/. <xsd:element name="jobDesigned" type="xsd:string" /> <xsd:element name="S" type="xsd:string" /> <xsd:element name="jobCDFAsp" type="xsd:decimal" /> <xsd:element name="jobLife" type="xsd:integer" /> <xsd:element name="jobSCIB" type="xsd:decimal" /> <xsd:element name="jobLifeExistPCC" type="xsd:decimal" /> <xsd:element name="jobNPLayers" type="xsd:integer" /> <xsd:element name="jobNAC" type="xsd:integer" /> <xsd:element minOccurs="0" maxOccurs="unbounded" name="LayerInfo"> <xsd:complexType> <xsd:sequence> <xsd:element name="jobThick" type="xsd:decimal" /> <xsd:element name="jobModulus" type="xsd:decimal" /> <xsd:element name="jobLCode" type="xsd:decimal" /> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element minOccurs="0" maxOccurs="unbounded" name="AircraftInfo"> <xsd:complexType> <xsd:sequence> <xsd:element name="jobACName" type="xsd:string" /> <xsd:element name="jobGL" type="xsd:decimal" /> <xsd:element name="jobRepsAnnual" type="xsd:integer" /> . or Flexural Strength (psi) when the layer is PCC Layer Code Airplane Name Gross Taxi Weight (lbs) Annual Departures of Airplane % Annual Growth for Airplane For each section. even if the screen display is set to Metric. Likewise. Note that the above values are stored in English (US Customary) units.<xsd:element name="jobRepsInc" type="xsd:integer" /> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:schema> XML Element:Subelement jobCDFAsp jobLife jobSCIB jobLifeExistPCC jobNPLayers JobNAC LayerInfo:jobThick LayerInfo:jobModulus LayerInfo:jobLCode AircraftInfo:jobACName AircraftInfo:jobGL AircraftInfo:jobRepsAnnual AircraftInfo:jobRepsInc Description Asphalt Layer CDF Design Life (years) Structural Condition Index Percent CDFU Number of Layers Number of Airplanes Layer Thickness (inches) Layer Modulus (psi). element LayerInfo is repeated up to the number of pavement layers in the section. element AircraftInfo is repeated up to the number of airplanes in the traffic mix. DATA FILES > Storage Files . job File Format Previous Next Note: The following information pertains to the old *.job files in the working directory.xml files.job format. The format of the old *. When this is done. Subsequent changes will be saved only to the *. It is provided for reference.job files is as follows: 0 1 2 3 4 5 6 0123456789012345678901234567890123456789012345678901234567890 Format# SectionName Date Life Time SCI Thick(1) Thick(2) Thick(3) Thick(I) Thick(NL) ACName(1) ACName(2) ACName(J) ACName(NA) %CDFU NL Modulus(1) Modulus(2) Modulus(3) Modulus(I) DateTime NA LC(1) LC(2) LC(3) LC(I) ACCDF Modulus(NL) LC(NL) GL(1) Rps(1) GL(2) Rps(2) GL(J) Rps(J) GL(NA)Rps(NA) %Growth(1) %Growth(2) %Growth(J) %Growth(NA) .job files will not be affected. When FAARFIELD encounters *.LEDFAA *.xml format.job format that was used by LEDFAA. FAARFIELD saves new job data in the Extensible Markup Language (XML) format. the original *. However. FAARFIELD will read older job files created in the *.JOB.job files are moved to a subdirectory of the working directory called old_job_files.JOB. the original *. it will automatically read them and convert them to the new *. Blank Line (for expansion) Blank Line (for expansion) Next set of section data, starting with the name Explanation of *.job File Field Names Format# = File format identifier; “Format3” SectionName = section name; Type = string; current = Type = string Type = string; Format = Type = string; Format = Date = date of completed design; XX/XX/XX Time = time of completed design; XX:XX:XX DateTime = date and time of completed design in VB format; Type = double precision real Field Width = 20 Note: When a design has not been completed for the section, Date = 11/01/71, Time = 00:00:00, DateTime = 26238 Name ACCDF Life SCI %CDFU NL NA Thick(I) Modulus(I) LC(I) ACName(J) GL(J) RPS(J) Description Asphalt Layer CDF Design Life Structure Condition Index Percent CDFU Number of Layers Number of Airplane Thickness of Layer I Modulus of Layer I * Layer Code for Layer I Airplane Name for Airplane J Gross Load for Airplane J Annual Repetitions for Airplane J Type Real Integer Real Real Integer Integer Real Integer Integer String Integer Integer Field Width 12 4 8 8 4 4 12 12 8 21 9 8 %Growth(J) Percent Annual Growth for Airplane J Real * Flexural strength when the layer is PCC. DATA FILES > Storage Files Example of a *.job File with 2 Sections 12 Previous Next Format3 NewFlexible 11/01/71 00:00:00 0.000000 20 0.00 5.0000 8.0000 10.0000 0.0000 DC10-10 0.000000 B747-200B Combi Mixd 0.000000 B777-200 ER 0.000000 NewRigid 11/01/71 00:00:00 0.178967 20 0.00 14.0000 6.0000 0.00 4 700 700000 3 5 17 11/01/71 100.00 4 3 1 14 6 4 2263 11/01/71 200000 400000 75000 15000 458000 873000 832 634500 425 6.0000 0.0000 DC10-10 0.000000 75000 15000 458000 6 4 2263 B747-200B Combi Mixd 0.000000 B777-200 ER 0.000000 DATA FILES > Storage Files Layer Codes 833000 832 634500 425 Previous Next = = = = = = = = = = = = = = = = = = = = Undefined P-401/P-403 Asphalt Surface Not Used Not Used Subgrade P-501 PCC Surface P-209 Crushed Aggregate Base Course Variable Stabilized Base (rigid) P-154 Subbase Course (uncrushed aggregate) Variable Stabilized Base (flexible) P-401/P-403 Asphalt Overlay P-501 PCC overlay fully unbonded P-501 PCC overlay partially bonded P-501 PCC overlay on flexible P-401/P-403 Stabilized Base (flexible) P-301 Soil Cement Base Course P-304 Cement Treated Base Course P-306 Econocrete Subbase Course P-208 Aggregate Base Course Rubblized PCC Base Course 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 DATA FILES > Storage Files *.nts File Format Previous Next concrete overlay on rigid. and asphalt overlay on rigid.000 256.nts files contain user entered information about sections in a job stored as strings.200 360 720 720 . The format consists of a sequential list of each section name. #NFNo) Input #NFNo. Introduction Previous Next Four design examples are given: new flexible.*. NotesString$ = Input$(SLen.500 877.nts file is as follows: NFNo = FreeFile Open FileName$ For Input As #NFNo For I = 1 To ISect Line Input #NFNo. it is assumed that external job files have not been created and the designs are started from the internal Samples job.000 396. Examples are also given to illustrate overlay design on composite pavements and the effects of sublayering in aggregate layers. ' Length of NotesString. SS$ Next I Close NFNo All data in the notes for section ISect is left in the string NotesString$. followed by the notes string. SLen ' Section name.000 Annual Departures 360 4.000 537. representing a very heavily loaded pavement as would be found at a major port: Airplane B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline Gross Weight. lbs 150. new rigid. A Visual Basic 2005 routine to read the data for a specified section (ISECT) in a *. In the first 2 examples. All of the design examples have the same traffic mix. DESIGN EXAMPLES ' Get CRLF. S$ Input #NFNo. the length of the notes string for that section. 3.000 633. DESIGN EXAMPLES New Flexible Design Example Previous Next The pavement in the new flexible pavement design example is to service airplane of greater than 100. 5.000 583. Copy the selected section to the new job by clicking on the new job file name in the left hand list box and entering. Item P-401.000 lbs gross weight. complying with AC 150/5320-6E. Enter a name for the new job in the displayed dialog box and click OK. in the displayed dialog box. paragraph 314c. if there are no external job files. The design life is 20 years. 4. Clear the message by clicking OK and press the New Job command button.MD83 DC10-30/40 MD11ER L-1011 161. a message is displayed stating that there are no job files in the working directory. 1.000 600 360 700 320 Percent annual growth is assumed to be zero in all of the examples. Reselect the Samples job by clicking on its name in the left hand list box. The determination and selection of suitable base and subbase thicknesses is discussed below after describing the initial setup of the example. 2. layer thickness results are all given to 1 decimal place. is selected for the subbase. Rounding would be done before writing the final design specifications. which exceeds the minimum thickness of 4 inches required by AC 150/5320-6E. 6.000 498. End the copy procedure by clicking End Copy. The thickness of the HMA surface layer is 5 inches. Crushed Aggregate Base Course. Select the new flexible sample section in the right hand list box by clicking on the NewFlexible section name. The ubgrade CBR for the example is 8. the section name to be used in the new job. Also. the STARTUP window is displayed and. . Plant Mix Bituminous Pavement. When FAARFIELD is first started. and must therefore have a stabilized base and subbase as specified in AC 150/5320-6E. Click Copy Section to start the procedure for copying from the Samples job to the new job. 7. is selected for the base course and Item P-209. . 4. Click Clear List and answer Yes in the displayed message box. 9. Select the first airplane in the group to be added to the table of design airplane by clicking on its name in the library list.8. Initially. Any of these values can be changed within a specified range by clicking on the number in the table. click on the CBR box in the Subgrade layer. 6. information for the traffic mix listed in the introduction to the design examples must be entered in the AIRPLANE window.) 5. 7. If a mistake is made and the wrong airplane added to the table. “Default” values of gross weight. Note that the L-1011 in this example is contained in the Other Commercial group. the only change that needs to made is to change the subgrade CBR from the default value of 15 to the actual value of 8. and percent annual growth will be displayed in the table. Select one of the airplane groups in the top left hand list box to display the airplane contained in that group in the lower left hand Library list box. Select the rest of the airplane to be added to the design airplane table from the group one at a time and change the default data values as required. Repeat the process for each group until all airplane in the traffic mix have been added to the table. The new flexible pavement structure from the Samples job will be displayed after transfer to the STRUCTURE window. 3. 8. modify the structure in the STRUCTURE window. An input box is displayed which also gives the default value and the range within which a new value can be entered. Next. Click Airplane to transfer control to the AIRPLANE window. But before starting design of the structure. enter the correct value. To do this: 1. and click OK. (Double clicking the name will also transfer the airplane. Enter the new value and click OK. All airplane stored in the new flexible section of the Samples job will be deleted from the table of design airplane. Click Back to return to the STRUCTURE window. Transfer the airplane to the table by clicking Add. Click Save List and answer OK to the displayed message. annual departures. 2. Click Modify Structure. Then click End Modify. Select the new job file in the left hand list box and double click on the section name in the right hand list box (or click Structure) to transfer to the STRUCTURE window. the airplane can be removed by selecting its name and clicking Remove (or by double clicking its name). Click Options to open the OPTIONS window.The thickness of 8 inches for the P-401/P403 base layer will be used as a starting point.” Also. In this case. and uncheck the box labeled “Enable Automatic Base Design.00 . which satisfies the design requirement. and click OK. From the NOTES window. the design information for the final design is: The structure is New Flexible. The program will now keep the base thickness unchanged at 11 inches.23 0.000 537. uncheck the box labeled “No AC CDF.23 in Airplane Information No.” Click OK. . Asphalt CDF = 0. but will compute a new subbase thickness.00 0. Next. the computed base thickness is 10.00 11. Click Save Structure to save these changes.00 0. For this example. select a base thickness of 11 inches. The program will automatically compute base and subbase thicknesses.2 inches gives a total pavement thickness of 30.35 0. To perform the final design run. Top First No.000 400.0 inches was finally selected. Design Life = 20 years.00 0. Based on the initial run. enter the new base thickness of 11 inches. click on Design Structure. Click End Modify. FAARFIELD will automatically compute the required base layer thickness to comply with the structural requirements and minimum thickness required by AC 150/5320-6E.2 inches.000 256. Again. Design Info button.64 inches and the subbase thickness is 14. click the Back button to return to the STARTUP window. Click Modify Structure.500 877.35 0. The procedure followed by FAARFIELD is described in the section on Pavement Thickness Design (New Flexible and HMA Overlay on Flexible).418 12. lbs 150. the computed subbase thickness is 14. the subbase thickness of 14. 1 2 3 4 5 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline Gross Wt. In this example. Pavement Structure Information by Layer.00 Modulus psi 200.35 Strength R. Click on Design Structure.00 14.95 inches.000 46. After the final design run.0046. 1 2 3 4 Type P-401/ P-403 HMA Surface P-401/ P-403 St (flex) P-209 Cr Ag Subgrade Thickness in 5. a base thickness of 11.000 Annual Departures 360 4.35 0.200 360 720 720 % Annual Growth 0. Click Structure to return to the STRUCTURE window.psi 0 0 0 0 Total thickness to the top of the subgrade = 30.2 inches. first modify the structure in the STRUCTURE window. click on the thickness box in the P-401/P-403 base layer.000 Poisson's Ratio 0. By default.000 396.00 0. 05 0. The subgrade k value is 120 pci and the surface is Item P-501. A 2-layer subbase has been selected with Item P304.03 P/C Ratio 1.33 0.33 0.00 CDF Max for Airplane 0.000 633. some time can be saved by using the floating airplane list: 1.00 0.03 0.68 0.63 1.650 3. Design life is 20 years.20 Note that the wing gear and the belly gear for the MD11 and A340-200 are treated as separate airplane in the design procedure.08 0.64 1.6 7 8 9 10 MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly 161. Since the airplane mix is the same as in the flexible example.01 0.00 0. and the pavement for the new rigid design example must therefore have a stabilized subbase course to satisfy the requirements of AC 150/5320-6E.00 0.55 0. Select the NewFlexible design example while in the STRUCTURE window and transfer to the AIRPLANE window by clicking Airplane.00 0.00 0. DESIGN EXAMPLES New Rigid Design Example Previous Next The new rigid design example uses the same traffic mix as the new flexible design example.00 0.00 inches.000 568. 2.00 0. This is not an error.00 Additional Airplane Information No. the thickness of the subgrade is given as 0.01 0. The design can be started by copying the NewRigid section in the Samples job to the same job file as used in the new flexible example.03 0.08 0.00 0. Portland Cement Concrete Pavement.200 1. .200 3.563 600 1.000 633. Crushed Aggregate Base Course below.30 0. at the top and Item P-209. 1 2 3 4 5 6 7 8 9 10 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly CDF Contribution 0. Click Save to Float to copy all of the airplane in the design airplane list to the Float Airplane list.21 0.650 0. but reflects the assumption in the layered elastic representation of the structure is that the subgrade is infinitely thick.00 0. Also.00 0.59 0.00 0.45 1.563 568.33 0.55 0. with a design flexural strength of 725 psi.59 0. Cement Treated Base. a lower subbase thickness of 6 inches. Various design options for subbase thicknesses can be tried. and a surface thickness of 16. Top First No. the subbase layer thicknesses (the Samples job values are 6 inches for each layer). The Layer Type Selection box will be displayed. Thicknesses of structural layers above the subgrade can be changed by clicking the respective Thickness boxes and entering the new values. followed by Design Structure causes the thickness of the top layer to be changed until the CDF for tensile stress at the bottom of the surface layer has a value of 1. Start the design by changing the subbase material: 1. Clicking End Modify. Click Back to return to the STRUCTURE window and select the NewRigid section.psi . All of the information for the Samples job structure is correct for this example except for the upper subbase layer. Save the newly created airplane list and return to the STRUCTURE window with the Back button. 5. The design in this case was finalized with a Cement Treated Base (CTB) layer thickness of 8 inches. The thickness of P-304 CTB is changed from 6 inches to 8 inches in this example. Design Life = 20 years. Design Info button. is given below for the structure only (Note that while the airplane information is the same as in the new flexible example. 6. and. The information in the Design Information pane of the NOTES window can be copied to the clipboard for pasting into an application or written to an XML data file using the “Save XML” function from the NOTES window. Type Thickness in Modulus psi Poisson's Ratio Strength R. 2.3. Click Modify Structure. In this case the computed surface thickness is 16. Go to the AIRPLANE window and clear the design airplane list with the Clear List command button.7 inches for a CDF of 1. Click on P-304 Cement Treated Base under the heading Stabilized (rigid) and click OK.7 inches. 4. the subgrade modulus value. The box will close and the layer in the pavement structure will change to P-304. The structure is New Rigid. the PCC flexural strength. The final design information from the NOTES window. depending on the design engineers judgment. Pavement Structure Information by Layer. Click Add Float to copy the airplane in the float list to the design airplane list. Click the box containing the name of the material for the upper subbase layer (P-306 Econocrete in this case). the computed P/C ratios and CDF contributions for the airplane are not the same in the two examples). The subgrade k value and the PCC flexural strength are both changed by clicking in their respective boxes and entering the new values in the input boxes. with the Design Structure function executed after each change. 00 0.00 0.563 568.000 568.00 4.000 396. lbs 150.00 0.00 0.000 256.650 % Annual Growth 0.200 360 720 720 600 1.25 CDF Max for Airplane 0.000 161.15 0.650 3.02 0. 1 2 3 4 5 6 7 8 9 10 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly CDF Contribution 0.46 3.518 12.00 0.563 Annual Departures 360 4.500 877.200 1.00 0.56 0.00 0. In the design example.000 30.56 0.43 3.00 0.61 0.00 0.00 0. The properties of the existing structure are: .1 2 3 4 PCC Surface P-304 CTB P-209 Cr Ag Subgrade 16. 1 2 3 4 5 6 7 8 9 10 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly Gross Wt.01 1.00 0.89 2.00 0.90 3.000 537.66 in Airplane Information No.35 0.000.00 0.00 6.40 725 0 0 0 Total thickness to the top of the subgrade = 30.00 0.00 0.60 4.200 3.20 0.99 DESIGN EXAMPLES Concrete Overlay on Rigid Design Example Previous Next Design of an overlay on a rigid pavement normally starts with an existing pavement structure having a known SCI. The same traffic mix as used in the new pavement design examples is to be applied for 20 years after overlaying.000 633.66 8. an unbonded overlay is to be applied over an existing rigid pavement which has an SCI of 70.18 0.10 0.00 0.000 633.25 P/C Ratio 3.68 3.25 3.01 0. a concrete strength of 700 psi will be used. For the PCC overlay.00 0.22 0.152 0.51 3.00 0.000 500.00 0.00 Additional Airplane Information No.00 0. FAARFIELD computes a thickness of 12. Click Add/Delete Layer. 7. as described in the new pavement design examples. SCI and %CDFU (percent cumulative damage factor used). If Life is not already set to 20. and select Overlay fully unbonded from the Layer Type Selection box under the heading PCC: All P-501. 2. SCI of the existing pavement = 70.00 6. %CDFU cannot be changed in this example because SCI is less than 100.000 30. the final structure with airplane information is: The structure is Unbonded PCC Overlay on Rigid.152 Poisson's Ratio 0.00 8. After clicking OK to close the Layer Type Selection box. From the NOTES window. Run the design by clicking Design Structure.00 0.15 0. Design Info. This process will take considerably longer than in the new pavement designs.000. click in the Des.40 Strength R. This will give the pavement a life of 20 years after overlaying.00 Modulus psi 4.20 0. A duplicate of the surface layer will be added to the structure adjacent to the original surface layer. Initially. 3. . 5. %CDFU will default to a value of 100. 1 2 3 4 Type PCC Surface P-304 CTB P-209 Cr Ag Subgrade Thickness in 14.35 0. 4. Click Modify Structure.80 inches. or 13 inches. this will be rounded to the nearest 0. Click End Modify to leave the modify mode. Click anywhere within the PCC surface layer in the picture of the structure. while still in modify mode. the thickness of the overlay layer will iterate to the correct thickness. Click on the SCI box and change the value to 70. Normally.psi 725 0 0 0 After setting up the structure to match the information above and setting the traffic information. Life box and enter a value of 20. Top First No. the thickness of the overlay layer will change in increments of 2 inches. For the PCC overlay.5 inch.518 12.Pavement Structure Information by Layer. an overlay layer is added in the STRUCTURE window as follows: 1.000 500. After 2 successive thicknesses have bracketed the correct design thickness. following AC 150/5320-6E. the new surface layer will change to an overlay and two additional data entry boxes will appear to the right of the design life box. 6. Click on the layer material box in the new surface layer. 650 % Annual Growth 0.15 0.61 0. Pavement Structure Information by Layer.000 537.Design Life = 20 years.00 0.00 0.14 0.00 0.000 500.25 3.01 0.25 0.00 0.14 0. But this is not the value used during design when the SCI of the layer is less than 100.00 0.40 Strength R.43 3.200 3.563 568. 1 2 3 4 5 6 7 8 9 10 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly CDF Contribution 0.99 In the output from the NOTES window.00 0.00 0.000 161.46 3.00 0.00 0.00 Additional Airplane Information No.00 0.00 0.200 360 720 720 600 1.000 396.00 0.000. 1 2 3 4 5 6 7 8 9 10 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly Gross Wt.00 CDF Max for Airplane 0. lbs 150.000 256.89 2.518 12.00 0.000 psi.000 633.000.35 0.00 0.000.01 1. 1 2 3 4 5 Type PCC Overlay Unbond PCC Surface P-304 CTB P-209 Cr Ag Subgrade Thickness in 12.80 in Airplane Information No.563 Annual Departures 360 4.48 0.psi 700 725 0 0 0 Total thickness to the top of the subgrade = 40.51 3.650 3. The value used is calculated from the relationship (given in reference 3): where: SCIExist = SCI of the existing PCC layer as it deteriorates during the life of the overlaid structure .000 4.20 0.25 0.500 877.15 0.02 0.01 0.000 633.000 568.00 6.00 0.00 0.00 0.000 30.60 4.00 8.68 3.20 P/C Ratio 3.61 0.00 Modulus psi 4.00 0.152 Poisson's Ratio 0.90 3. the modulus of the PCC surface layer of the existing structure is given as 4. Top First No.80 14.200 1. 000 psi. DESIGN EXAMPLES HMA Overlay on Rigid Design Example Previous Next HMAoverlays on existing rigid pavements are designed in exactly the same way as concrete overlays except that the HMA Overlay layer type is selected from the Layer Type Selection box.00 Modulus psi 200.psi 0 725 0 0 0 Total thickness to the top of the subgrade = 36. SCI of the existing pavement = 70. For the same existing pavement and airplane traffic as used in the concrete overlay design example.000.00 8.00 .EExist E100 = modulus of the existing PCC layer at SCIExist = modulus of the existing PCC layer when its SCI is 100 (4.6 inches. The final structure with airplane information from the NOTES window.15 0. lbs 150.6 inches.518 12. is: The structure is AC Overlay on Rigid.00 0.152 Poisson's Ratio 0.000 30. so the value of 4.64 14. 1 Name B737-400 Gross Wt.35 0. FAARFIELD computes a required HMA overlay thickness of 8. But if. the layer is known to be seriously deteriorated. from field surveys. which is appropriate for design of new structures.40 Strength R. 1 2 3 4 5 Type P-401/ P-403 HMA Overlay PCC Surface P-304 CTB P-209 Cr Ag Subgrade Thickness in 8.000 psi in this case) The modulus of the CTB layer is also set at its default value of 500.000. The total structure thickness is 36.20 0. Top First No.500 Annual Departures 360 % Annual Growth 0. Subbase material substitutions are appropriate where there is evidence of serious deterioration from field surveys.000 4. it can be replaced in the representation of the structure by a lower quality layer type or by the variable stabilized layer type with its modulus value set to less than 500.35 0. Design Life = 20 years.64 in Airplane Information No. The modulus of the existing PCC surface layer is adjusted during the design. Pavement Structure Information by Layer. Design Info.00 6.000 500.000 psi reported in the design information from the NOTES window is an upper limit for the modulus values used in the life computations.000.000 psi. 563 4.000 568.99 DESIGN EXAMPLES Overlays on Composite Pavements Previous Next Design of overlays on existing rigid pavements which already have an asphalt overlay cannot be done directly using FAARFIELD because a PCC surface layer cannot be placed further down than the second layer in a structure.00 0.07 0.00 0.06 0.01 1.00 0.00 Additional Airplane Information No.90 3.000 633.000 537.00 0. The example .00 0.00 0.00 0.29 P/C Ratio 3.00 0.00 0.00 0.01 0.00 0.00 0.2 3 4 5 6 7 8 9 10 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly 877.24 0.46 3.65 0.000 161. The maximum sublayer thicknesses are 8 inches for uncrushed aggregate and 10 inches for crushed aggregate (except when the number of layers is fixed to avoid continuous iteration).00 0.29 CDF Max for Airplane 0.43 3.00 0.000 633.65 0.60 4. The modulus of the substitute layer can be selected based on the design engineers judgment of the SCI of the existing PCC layer and application of the equation for PCC layer modulus given in the concrete overlay design example.68 3. sublayering of aggregate layers is included in the design procedures.650 0.000 396.200 1.00 0.25 3.00 0.563 568. The following example illustrates the effects of the sublayering caused by changes in effective stiffness of an aggregate layer when the number of sublayers changes. DESIGN EXAMPLES Effects of Sublayering in Aggregate Layers Previous Next As discussed in the section on aggregate layers.650 3.00 0.200 3.01 0. One method of representing such a structure is to replace the PCC layer in the existing pavement with an undefined layer or a variable stabilized layer.89 2. 1 2 3 4 5 6 7 8 9 10 Name B737-400 B747-400 B757-200 B767-200 ER B777-200 Baseline MD83 MD11ER MD11ER Belly A340-200 std A340-200 std Belly CDF Contribution 0.51 3.000 256.200 360 720 720 600 1.00 0.01 0. Airplane in the mix are B-747-400. resulting in the following structure: The structure is New Flexible.466 13. lbs 873.93. and B777200 Baseline.00 15. it is used in this example for illustrative purposes.000 68. The modulus values of . Top First No.00 16.structure has a 6 inch thick asphalt surface layer over aggregate base and subbase layers and a 9 CBR subgrade (modulus of 13.6022.000 500 % Annual Growth 0. Automatic base layer thickness design was disabled. 1 2 3 4 Type P-401/ P-403 HMA Surface P-209 Cr Ag P-154 UnCr Ag Subgrade Thickness in 6.35 0. and an asphalt CDF of 0.500 Poisson's Ratio 0.791 26. Then. But running Life after the design was completed gave a life of 21.500 537. Pavement Structure Information by Layer. Asphalt CDF = 0.000 150. 1 2 3 4 Type P-401/ P-403 HMA Surface P-209 Cr Ag P-154 UnCr Ag Subgrade Thickness in 6.00 0.00 0.00 The design was run by setting the subbase as the iteration layer and starting from an arbitrary subbase thickness. Design was run again.35 0.35 0. the thickness of the subbase decreased from 16.500 psi). The structure is New Flexible.35 0. since AC 150/5320-6E would require a stabilized base for the given airplane mix.00 Modulus psi 200.5 years.00 Modulus psi 200.00 11. Design Life = 20 years.35 0. without changing any of the properties of the structure or the airplane mix. Note that the structure as shown is a non-standard structure.psi 0 0 0 0 Total thickness to the top of the subgrade = 32.6926.500 Poisson's Ratio 0. However.88 in From the first to the second design.865 13.88 0.88 inches and crossed the threshold for sublayering from 2 sublayers to 3.psi 0 0 0 0 Total thickness to the top of the subgrade = 33.04 in Airplane Information No.04 to 15.000 Annual Departures 2. Design Life = 20 years. which do not agree with the design information.00 11.04 0.60.35 0.35 Strength R.500 16.802 26. Top First No. Asphalt CDF = 0. 1 2 3 Name B747-400 MD83 B777-200 Baseline Gross Wt. Pavement Structure Information by Layer.35 Strength R. a subgrade CDF of 0.000 66. MD83. Then. Two other interesting aspects of this example are: 1.69 Asphalt CDF after Life 0. but decreases the asphalt CDF by a much larger relative amount. the structure started with the number of 3 sublayers.88 79. as did the asphalt CDF. and the design completed with 3 sublayers and a thickness of less than 16 inches. the design would have cycled back and forth across the threshold thickness of 16 inches with CDF values of 0.000 psi on the second design decreases the subgrade CDF to 0. Changing the base material to variable stabilized at 150.60 0. For the first design the subbase has 2 sublayers instead of the 3 required by its thickness of more than 16 inches.492 Modulus of subbase sublayer 3 no sublayer Average modulus of the subbase 26. This is because.str file). when Life was run. Property Design 1 Subbase thickness 16.5 Subgrade CDF after Life 0.802 Modulus of subbase sublayer 1 30.04 Modulus of base sublayer 1 78.497 27.05 (a negligible amount). the number of sublayers was fixed when the thickness of the subbase was greater than 16 inches.865 18. . the number of sublayers was fixed at 3.60 Design 2 15.7 percent). 2. with the sublayer modulus values included (read from the Leaf.337 Average modulus of the base 66.939 57.398 20.699 26.791 32.07 to 1.267 Modulus of base sublayer 2 55.02 (4. the correct number of 3 sublayers was created and the life computations made for a slightly different structure. during the final stages of design. The changes in the structure are summarized in the table below. from 0. when the second design was run. Removing the MD83 from the airplane list and running Life on the second design decreases the subgrade CDF from 1. Also.93 and 1. If the number of layers had not been fixed at some stage.07 repeated endlessly.both aggregate layers also changed.24 (60 percent).643 68.07 0.25 and decreases the asphalt CDF to 0.6 1.466 Design life after Life 21.60 to 0.440 Modulus of subbase sublayer 2 22.93 Asphalt CDF 0.70 All of the values given are for the structure at the end of design except where noted that they were obtained after running Life.