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					Storage Tank Foundation Analysis and Design Guide

Storage Tank Foundation Analysis and Design Guide

PURPOSE
This practice establishes guidelines and recommended procedures for the design of Tank foundations using
AFES (Automatic Foundation Engineering System). AFES can design Tank foundations as either soil- or pile-
supported footings.


CONTENTS
This practice comprises the following:


          Create or Open New Project
          Setting Soil and Pile Parameters
          Creating New Structure
          Exporting Load Combination
          Assign Foundation Grouping
          Editing footing sizes and other parameters
          Pier and Footing Reinforcement
          Set Pile Layout for Pile Foundations
          Import Load Combination for various foundation groups
          Assigning Equipment Data
          Performing Design and Analysis functions
          Quantity BOM (Bill of Material) function
          Construction Drawing
          Export 3D Modeling Data (PDMS, PDS Frame Work Plus)




FOUNDATION TYPES
Types of foundations normally considered as are the following:
          Gravel ring walls supporting the tank shell.
          Concrete ring walls supporting the tank shell.
          Concrete mat on grade supporting the entire tank.
          Concrete mat on piles supporting the entire tank.
          Concrete rib beams and mat foundation for cold storage tanks.
          Concrete mat and heating coils for cold storage tanks.


Foundation type to be utilized depends on the design requirements, type of tank, tank dimensions, soil and site
conditions, environmental conditions, material availability, local codes, and Client requirements.
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Storage Tank Foundation Analysis and Design Guide
Design data sample for equipment is shown below based from actual projects. This equipment is a Exchanger
supported by rectangular shape foundation.


DESIGN CONSIDERATIONS

Assumptions:
The center to center diameter of ring wall is equal to the nominal tank diameter. If not applicable, an alternate
foundation type shall be used.


       Empty Load − Bottom Plate Weight
W=
              π x Tank Diameter

Bottom Plate Weight = γ steel x Bottom Plate Thickness x Bottom Plate Area


                   2 xW
t.cal =                                              t.min = 300 mm
          q x H − 2 x h x (γ c − γ s )


       γ s 1 x h1 + γ s 2 x h2
γs =
              h1 + h2

Where:
q = unit weight of Tank fluid
γ c = unitweight of concrete
h1, h2 : Filling material height of ring wall
γ s 1, γ s 2 : unitweight of soil under Tank
W = weight of Tank shell plus the tributary weight of a cone perimeter of circumference
N = thickness of Tank shell plate
H = height of Tank
h = height of Ring wall
D = tan k diameter




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Storage Tank Foundation Analysis and Design Guide




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Storage Tank Foundation Analysis and Design Guide




      Create or Open New Project

      The first step is to enter project specific items. These items include general data, client data and Job
      data about a project. General data includes project No. Project Name, Client Name, Site Name, any
      more. The client data includes your client manager name, e-mail, number of telephone and fax,
      address. Job data includes assigned engineer, supervisor, duration of project, project rate that values
      the program needs to use for the specific project.


      The Project Number and Structure Name entered in Project Information will display as a menu header


      Note: General Data should be input. This data needs to use for the specific project.


      To open the existing project, or create a new project, Click on the “New/Open Project” from Top
      toolbar menu




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Storage Tank Foundation Analysis and Design Guide

      Create New Project

          From File menu, select New/Open Project.


      A window dialogue will display as shown.




          Select New Project option then click OK button.


      A window dialogue will display as shown.




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Storage Tank Foundation Analysis and Design Guide


           Enter information then click OK button.


                                 Or


      Open Existing Project

           From File menu, select New/Open Project.


      A window will display as shown.




            Select Open Existing Project.
            Select a project then click OK button.




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Storage Tank Foundation Analysis and Design Guide


        Setting Soil and Pile Parameters

        Setting of constants options include design information that AFES needs in order to design a
        foundation. This includes a number of parameters such as design code, safety factor, bearing
        capacity of soil, capacity of pile, material and unit weight, clear cover, allowable increase of soil,
        allowable increase of pile, strength reduction factors, supports and anchor bolt options.


        In case of New project, set all design parameters from the “Setting of Constant” form.


        Set Bearing Capacity of Soil from the Setting of Constant command

           Click Setting of Constant button.
           Select Bearing Capacity of Soil tab.




           Enter name in the Soil Bearing Capacity Name text box.
           Enter Soil Bearing Capacity (Qa) value.
           Click Save button.




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Storage Tank Foundation Analysis and Design Guide

      Set Capacity of Pile from the Setting of Constant button.

           Select Capacity of Pile tab.




           Enter name in the Pile Name text box.
           Select Pile Type.
           Select Pile Shape.
           Enter values for Pile dimensions.
           Enter values for Allowable Capacities.
           Enter values for Elastic Modulus (Ep) and Pile Area.
           Click Save button.




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Storage Tank Foundation Analysis and Design Guide


         Creating New Structure

         Every input and output data can be saved in AFES Data Base according to projects, which
         provide work efficiency in control over project information. An engineer is able to create a file
         for a new project, reuse data from projects conducted previously, or eliminate old and useless
         data for the user’s own sake.


         Choose Create New Structure button.
         “Add: New Structure Name” dialog window will appear. Input structure name, and then click on
         the “New” button.




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Storage Tank Foundation Analysis and Design Guide

      Exporting Load Combination

      This function enables us to export load combination data that was saved in text file in AFES program.
      After exporting the file, it will be available for import in this program.


      Export Load Combination before assigning group otherwise they will be deleted.


          Click Load Case/Combination button.
          Click Load Combination button.


      A warning message will appear as shown.




          Click OK button.


      The Load Combination form will appear as shown.




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Storage Tank Foundation Analysis and Design Guide
             Click Export button.
             Choose directory to save file, assign file name then click Save button.




      Assign Foundation Grouping.

      The Assign Foundation Grouping command is used for assigning group for models with multi-
      foundations. This is very important because it eliminates repetitions of commands. Foundations with
      the same load combinations are recommended to join in one group.


      The available foundation types are as follows;




      The foundation modules in red box shown in above figure are normally used for Storage Tanks. At
      the end of this step, we will create the structure as shown below.




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Storage Tank Foundation Analysis and Design Guide




           Click Geometric Data button.
           Create 3 nodes by clicking Add button 3 times.
           Enter coordinates as shown in figure above.




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Storage Tank Foundation Analysis and Design Guide
            Click Assign Foundation Grouping button.




      Assign group for node 1.

         Click New button.
         Assign name from the Group name text box.
         Select Tank_1 from the Group type.
         Select Pile fdn. option.
         Select Same size.
         Select node 1 from the Using node list form.
         Click arrow pointing to the right.
         Click Save button.




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Storage Tank Foundation Analysis and Design Guide




      Assign group for node 2.
          Click New button.
          Assign name from the Group name text box.
          Select Tank_1 from the Group type.
          Select Block Foundation.
          Select Non Pile fdn. option.
          Select Different size.
          Select node 2 from the Using node list form.
          Click arrow pointing to the right.
          Click Save button.




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Storage Tank Foundation Analysis and Design Guide




      Assign group for node 3.
         Click New button.
         Assign name from the Group name text box.
         Select Tank_1 from the Group type.
         Select Non Pile fdn. option.
         Select Different Size.
         Select node 3 from the Using node list form.
         Click arrow pointing to the right.
         Click Save button.




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Storage Tank Foundation Analysis and Design Guide




The preliminary structure configuration is shown below.




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Storage Tank Foundation Analysis and Design Guide


      Editing footing size and other parameters

      The Feature Data (Dimension) command is used to define the dimensions and other parameters
      necessary for the foundation and piers.


      Plan footing dimensions should be in even 2 inch (50 mm) increments. The footing thickness shall be
      12 inches (300 mm) minimum and thickened in 4 inch(=100 mm) increments. Size for both footings
      should normally be the same.
      The footing thickness adequate for embedment of pier or column reinforcement should be checked in
      accordance with Building Code. If top tension exists, the footing thickness shall be checked in
      accordance with Building Code.
      For thin footings with a large concentrated pier moment, the possibility of the moment increasing the
      punching shear should be considered similar to the way it would be for slabs (refer to Building Code).
      Engineering judgment should be used in deciding when this might be applicable.


      Edit footing size of group TANK1.
           Select TANK1 from the Group selection in top menu.




           Click Feature Data/Dimension button.
           Choose SUPT-01 in the Soil Name selection.




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Storage Tank Foundation Analysis and Design Guide




<Footing tab>




<Pier tab>
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Storage Tank Foundation Analysis and Design Guide


                Enter values as shown in the Feature form for Footing and Pier.
                Click Save button.


         Edit footing size of group TANK1RING.

                Select TANK1RING from the Group selection in top menu.




                Click Feature Data/Dimension button.
                Choose SUPT-01 in the Soil Name selection.




<Footing tab>




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Storage Tank Foundation Analysis and Design Guide




<Pier tab>
                  Enter values as shown in the Feature form for Footing and Pier.
                  Click Save button.


             Edit footing size of group TANK1BLOCK.

                   Select TANK1BLOCK from the Group selection in top menu.


                   Click Feature Data/Dimension button.
                   Choose SUPT-01 in the Soil Name selection.




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Storage Tank Foundation Analysis and Design Guide




<Footing tab>




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Storage Tank Foundation Analysis and Design Guide




<Pier tab>
             Enter values as shown in the Feature form for Footing and Pier. Note that only Grout
             Thickness is activated.
             Click Save button.




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Storage Tank Foundation Analysis and Design Guide


      Pier and Footing Reinforcement

      The Reinforcement Data command is used to assign bar sizes and spacing for piers and footings.
      Reinforcement bar sizes depend on the design code designated in the Setting of Constant command.
      Set of bar array options are available in the Footing option. The arrangement of footing bars are
      parallel to the X and Y axis except for Tank1 and Tank2 Ring type modules which are in radial and
      longitudinal directions.


      Below are based from our company standards.


      Minimum Pier Reinforcement
      Piers should be designed as cantilever beams with two layers of reinforcement. When the required
      reinforcing approaches ρmax, investigate the pier as a column. Size and reinforcement for each pier
      should normally be the same. Dowel splices are not required if the vertical pier reinforcing projection
      is less than 6 feet in height, or the rebar size in feet above the top of the footing. For cases that exceed
      this limit, use dowels with minimum projections required for tension splices in accordance with
      Building Code. Minimum reinforcing for piers is #5 at 12 inches on each face with #4 ties at 12
      inches. Place double ties at top of piers to protect anchor bolts. All ties should encircle the vertical
      reinforcement. Pier ties are not normally detailed as column ties. If longitudinal reinforcing is not
      required to resist vertical loads, as is normally the case, through ties are not required.
      Size and reinforcement for both columns should normally be the same. Use dowels to transfer the
      column loads to the footings. Minimum dowel projection should be that required for a tension splice
      in accordance with Building Code.


      Minimum Footing Reinforcement
      The minimum amount of bottom reinforcing is #5 at 12 inches c/c. If top reinforcing is required,
      minimum reinforcing is #4 at 12 inches c/c.


      From the main tool bar, click the “Reinforcement data”             button. Reinforcement data form will
      appear as shown in below figure.




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Storage Tank Foundation Analysis and Design Guide
      Tank1 Foundation with Ring Wall Pier




          Set Array Type
      Select from the array types of footing reinforcement layout. Different forms for single and double
      layer arrangement are presented.




          Set Footing reinforcement arrangement.




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Storage Tank Foundation Analysis and Design Guide
          Select Save then Close button.
          Select Pier tab.


      Enter the values of footing re-bar as shown.




          Select Save then Close button.


      Tank1 Block Foundation




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Storage Tank Foundation Analysis and Design Guide


            Set Pier reinforcement arrangement using the Pier tab.
            Select Save then Close button.


      Tank1 Ring Foundation with Ring Wall Pier




            Set Array Type


      Select from the array types of footing reinforcement layout. Different forms for single and double
      layer arrangement are presented.




            Set Footing reinforcement arrangement.




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Storage Tank Foundation Analysis and Design Guide




            Select Save then Close button.
            Select Pier tab.


      Enter the values of footing re-bar as shown.




            Select Save then Close button.


      Fore further discussions, refer to Help documents.


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Storage Tank Foundation Analysis and Design Guide


      Set Pile Layout for Pile Foundations

      The Pile Data command is used to layout and assign piles in the foundation. Regular pile
      arrangements are available for circular or rectangular arrays.


      This function is activated only when the selected type is Pile fdn. in the Assign Foundation Grouping
      command. Define pile features first before proceeding to this function in the Setting of Constant
      command.


      Set Pile Arrangement for foundation group TANK1 (Circular Array)


          Select TANK1 from the Group selection in top menu.


          Click Pile Data command.
          Select Array Wizard tab.
          Select Origin Point.
          Select PHC-12 from the Pile Name selection.
          Set Circular option.
          Enter Star Angle, No. and Pile Circle Dia. (PCD).
          Click Regenerate button.
          Click OK button.




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Storage Tank Foundation Analysis and Design Guide




Repeat above steps in creating new circular pile array arrangement then click “Add Draw” to include to defined
pile arrangement.


          Import Load Combination for various foundation groups.

          The Load Case/Combination command is used to define, add, edit or delete load cases and
          combinations.


          Assigned load cases can be combined with factors in accordance with a few design methods and
          specifications. Mainly applied load combinations are Allowable Strength Load Combination and
          Ultimate Load Combination. Combinations by Allowable Strength Design are normally applied with
          1.0 factored value.


          The purpose of the combinations is to take into account soil bearing capacity, sliding, overturning,
          uplift check, and pile capacity check for a pile supported foundation.


          Combinations referring to Ultimate Strength Design are used for footing reinforcement, pier design,
          one way shear check, and taking different factors for various cases.


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Storage Tank Foundation Analysis and Design Guide
      Below are load cases and load combinations usually used for Horizontal Vessel and Exchanger
      footing based from Building code. Load cases definitions are also discussed for further information.
      These are also based from our actual projects.


        DESIGN LOADS
        The following design loads shall be considered for design of the foundations.


      Erection Weight (De1)
      The erection weight is defined as the fabricated weight of the vessel, including internals and
      attachments that are installed integrally with the vessel. This information is taken from the vessel
      drawings. Verify that all items which are to be erected with the vessel are included in the erection
      weight.


      Empty Weight (De2)

        The empty weight is defined as the in-place weight of the completed exchanger/vessel (De1) plus the
        weight of internals, piping, insulation, and ladders and platforms, but excluding the weights of fluids or
        products which will be placed in the exchanger/vessel during operation. This information is taken from
        the vessel/exchanger drawings/data sheets and planning study drawings.


      Operating Weight (Do)
      The operating weight (also called "wet weight") is defined as the empty weight of the exchanger/vessel
      (De2) plus the weight of operating fluids or products. Verification of the operating conditions may be
      required from the Process Engineering Discipline. This information is taken from the vessel/exchanger
      drawings/data sheets.


      Test Weight (Dt)
      The test weight is defined as the empty weight of the exchanger/vessel (De2) plus the weight of test fluid
      (usually water) and any attached piping and equipment required for the hydrostatic test.               This
      information is taken from the vessel/exchanger drawings/data sheets. Note that this load condition is
      considered only when the exchanger/vessel is to be field-hydrotested. Verify with the Mechanical
      Discipline for this condition.


       Wind Loads (W)
      Transverse and longitudinal wind loads shall be determined in accordance with Design Guide 3DG-C01-
      00001 unless project criteria dictates otherwise. No allowance shall be made for shielding of wind loads
      by nearby equipment. The calculated design moments and shears due to wind load should be compared
      to those shown on the exchanger/vessel drawings. In case of major discrepancies between calculated

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Storage Tank Foundation Analysis and Design Guide
      wind loads and the loads shown on the equipment drawings, coordinate with the Mechanical Discipline
      for resolution.


      Seismic Loads (E)
      Seismic loads shall be determined in accordance with procedures presented in Company Design Guide
      unless project criteria dictates otherwise. The longitudinal seismic force shall be resisted by the fixed end
      pier only unless the piers are tied together by tie beams below the base plates. Transverse seismic forces
      shall be resisted by both piers using saddle or base plate reactions as the basis for computing base shear.
      The horizontal seismic loads shall be applied 100% in one direction and 30% in the orthogonal direction,
      i.e., E = ±(1.0 EH1 ± 0.3 EH2) and E = ±(0.3 EH1 ± 1.0 EH2).


        LOAD COMBINATIONS


      Concrete Foundation Design
      The following factored load combinations should be used for design of the foundations

        (a) 1.4 (Do + T + Dp)


        (b) 0.75 [1.4 De2 (or 1.4 De1)] ± 1.6 W


        (c) 1.2 De2 ± 1.0 E


        (d) 0.75 (1.4 Do + 1.4 T + 1.4 Dp) ± 1.6 W


        (e) 1.2 (Do + T + Dp) ± 1.0 E


        (f) 1.4 De2 + 1.7 Lb (for exchanger foundations only)


        (g) 1.2 Dt
      The load factors shown above are based on ACI 318, except for load combinations (c) and (e), which are
      based on the slightly more conservative requirements of IBC 2000. Also, in load combination (g), the
      factor of 1.2 is used (instead of 1.4) due to the transient nature of hydrotesting conditions. The load
      combinations 0.9D ± (1.6W or 1.0E), as listed in ACI 318, do not need to be considered since they are
      covered by load combinations (b) and (c).




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Storage Tank Foundation Analysis and Design Guide


      Wind load is calculated in accordance with ASCE 7-98 (including the directionality factor) and seismic
      load is calculated in accordance with IBC 2000 (based on strength-level methods, rather than service-
      level). If wind load is calculated using another code which does not include the wind directionality
      factor, the load factors for wind in the various load combinations should be reduced appropriately.
      Similarly, for service-level seismic loads based on another code, the seismic load factors should be
      increased as appropriate. (See Section R9.2 of ACI 318 for guidance.)


      The weight of the foundation and of the soil on top of the foundation shall be included as dead load in all
      of these load combinations.


      You can actually create new load combinations through the Load Combination button but in this
      example, we will use Import command.


           Click Load Combination button.


      The Load Combination form will display as shown.




           Click Import button.
           Access the load combination file then click Open button.


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Storage Tank Foundation Analysis and Design Guide
      A warning message will appear as shown.




           Select appropriate button as explained in the warning message form.
           Click Save button.


      Repeat same procedure for the other foundation groups.




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Storage Tank Foundation Analysis and Design Guide

      Assigning Equipment Data

      Equipment data is essential for Storage Tank Foundations. Empty load is used to determine required
      ring wall thickness to be compared to the minimum allowed. Nevertheless, the input load values for
      the Empty, Operation and testing weights may need to be entered again in the load case tables as they
      have no direct links. Tank dimensions and soil parameters including of the backfill materials are also
      necessary.




      Figure 1: Sample equipment input data for a certain equipment type normally used for Storage Tanks.




      Figure 2: Tank foundation modules showing equipments.
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Storage Tank Foundation Analysis and Design Guide


      Performing Design and Analysis functions

      AFES executes Foundation Analysis and Design according to design standards widely accepted. It is
      assumed that all external forces are loaded at the center of the piers and the connection between the
      pier and the footing is considered to be rigid enough to carry those forces. Strength, stability and
      sectional design of components of footing, pier, corbels and tie girders are properly examined.


      The design codes of AFES support ACI318-99, 02, BS 8110, Korean, AIJ-WSD99, CP-65 and IS456
      (2000).


           Click on the Foundation Analysis/Design button to be able to start analysis and design.




           Select Analysis button.




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Storage Tank Foundation Analysis and Design Guide


          For through discussion on setting other functions such as General, Temperature and
          Shrinkage/Stability, Tank Design, Detail Report Option and Contents, you may refer to help menu.


                Click Analysis button.
                 Click Report button to view calculation report.


The calculation report will display as shown below.




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Storage Tank Foundation Analysis and Design Guide


      Quantity BOM (Bill of Materials) function

      BOM functions are used for estimate of earthworks including other related items such as excavation,
      backfill, disposal, concrete, lean concrete, crushed stone, grout, formworks, protection materials,
      anchor bolts and steel reinforcements.


      Options for BOM take off for active structure and all structures in a project is supported.


      For Active Foundation structure


             From Design menu, select Quantity (BOM) then Take off BOM 3D.




             Set parameters from the Afes – Bill of Material form.




           Click OK button.


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Storage Tank Foundation Analysis and Design Guide
The Bill of Material form will display as shown below.




                  From Design menu, select Quantity (BOM) then Take off BOM 3D (All Structure).




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Storage Tank Foundation Analysis and Design Guide
           Set parameters from the Afes – Bill of Material form.




          Click OK button.
          Check structures to include BOM Take off calculation from the form below.




          Click OK button.
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Storage Tank Foundation Analysis and Design Guide
The Bill of Material form will display as shown below.




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Storage Tank Foundation Analysis and Design Guide

      Construction Drawing

      AFES is a completely integrated software package for automatically producing drawings of
      reinforcing details for foundations that have been analyzed and designed using AFES. AFES
      interfaces with AutoCAD and MicroStation to create a construction drawing with bar-schedule.


      The Export DXF File command is used to export the drawing files made from AFES to other
      programs such as AutoCAD and MicroStation. Standard drawings are already set up for various
      design codes.


      The program will create the DWG or DXF file format and display a construction drawing through a
      viewer.


      The drawing report consists of the Standards, Layout and Drawing detail including plan and sections
      of foundation with reinforcement schedules. You can set from this command the drawing preferences
      to be utilized before exporting to AutoCAD.


          Click Export DXF File button.
      A form will display as shown below.




            Set options from this form.
            Click OK button.
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Storage Tank Foundation Analysis and Design Guide
      Drawing details will display as below.




      <Foundation Layout Plan>




      <Tank1>
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Storage Tank Foundation Analysis and Design Guide




      <Tank1Block>




      <Tank1 Ring>


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Storage Tank Foundation Analysis and Design Guide


      Export 3D Modeling Data (PDMS, PDS Frame Work Plus)

      Today, plant design works involve many design parts, modeling objects from each part allows other
      parts to assess those object on their work process helping streamlining the work process through
      project completion. A 3D foundation model of the objects designed by various design parts
      effectively communicates the geometric design data. Therefore automating the work process from
      design to 3D modeling forms an integral component of reducing overall project cost. With our design
      to modeling interface from AFES to Frameworks Plus, you will experience significant productivity.


      Export to PDS


          Click Export PDS Data button.
      A dialogue form will display as shown.




           Set Output unit and coordinate mapping options.
           Check Send Model Data to PDS option then click OK button.


      Export to PDMS


           Click Export PDMS Data button.
      A dialogue form will display as shown.




           Set various parameters accordingly and click OK button.
      For further discussions, you may refer to Help PDF manuals.
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