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					midas GTS 2D Tutorial                                                  MIDAS IT Co., Ltd.




                          midas GTS Tutorial

               Seismic Evaluation of Abutment using Time History Analysis




1                                                                     http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                    MIDAS IT Co., Ltd.


    1. Overview



    • Seismic design of abutment                                                Abutment
    • Elastic spring using sub-grade reaction               Embankment
      coefficient
    • Eigenvalue analysis
    • Point spring with calculated damping      Clay                                Piles
      constant                                                Weathered
                                                                Rock
    • Long/short/custom frequency
      Generation                                Soft Rock
    • Displacement and stability check
      using Time History Analysis about 3
      seismic waves


                                                                   Starting Files Required
                                                                • GTS 2D Tutorial.gtb




2                                                                                       http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                  MIDAS IT Co., Ltd.


    2. Material parameters

          Attribute


             Attribute                                       Property
                               Type    Material Name(ID)                      Mesh Set Name
             Name(ID)                                        Name(ID)

           Embankment (1)      Plane     Embankment (1)                        Embankment


               Clay (2)        Plane         Clay (2)                               Clay


          Weathered Rock (3)   Plane   Weathered Rock (3)                     Weathered Rock

             Soft Rock (4)     Plane      Soft Rock (4)                          Soft Rock

             Abutment(5)       Plane      Abutment (5)                          Abutment

             Steel Piles(6)    Line       Steel Piles (6)   Steel Piles (1)      Steel Piles




3                                                                                    http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                    MIDAS IT Co., Ltd.



           Material

                      ID                       1         2          3          4                  5

                                                                Weathered
                    Name                   Embankment   Clay                Soft Rock        Abutment
                                                                  Rock

                     Type                    Plane      Plane     Plane      Plane              Plane


       Modulus of Elasticity(E)[tonf/m2]      4000      850      15,000      30,000            232,000


              Poisson’s Ratio(ν)              0.35       0.3      0.35        0.27              0.19

           Unit Weight(Y) )[tonf/m3]          1.8        1.7        2          2.4               2.5


       Unit Weight(Saturated) )[tonf/m3]      1.9        1.8       2.1         2.5               2.5


             Cohesion(c)[tonf/m2]             1.5        5         20          45                300

               Friction Angle(Φ)               25        20       32.5         35                36

                      K0                       1         1          1          1                  1



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midas GTS 2D Tutorial                                                                  MIDAS IT Co., Ltd.




          Structure



                        Modulus of
         Material/                                           Unit Weight(Y)    D          Tw
                        Elasticity(E)   Poisson’s Ratio(ν)
         Property                                              [tonf/m3]      [m]         [m]
                         [tonf/m2]

           Steel         21000000              0.3                7.85        0.508      0.012




5                                                                                     http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                            MIDAS IT Co., Ltd.


    3. Opening file                                  4. Attribute Definition
    1        Open “GTS 2D Tutorial.gtb”              • This tutorial starts from the condition where Attribute
                                                     are already defined in the model.




        • Start midas GTS Program
        • Click on File>Open
        • Select to open “GTS 2D Tutorials 28.gtb”




6                                                                                               http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                         MIDAS IT Co., Ltd.


    5. Mesh Generation
     2   Auto Mesh Planar Area




                                 •Select Mesh > Auto Mesh > Planar Area…from the Main Menu
                                 •Select the highlighted edges from the picture
                                 •Mesh Type: Triangle
                                 •Mesh Size: Element Size : 1
                                 •Attribute ID: 5
                                 •Mesh Set: Abutment
                                 •Uncheck “Register Each Area Independently” Button
                                 •Click [Apply]Button




7                                                                                            http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                               MIDAS IT Co., Ltd.


     3   Auto Mesh Planar Area




                                 • Select the highlighted edges from the picture
                                 • Mesh Type: Triangle
                                 • Mesh Size: Element Size: 1
                                 • Attribute ID: “1: Embankment”
                                 • Mesh Set: Embankment 1
                                 • Click [Apply]Button




8                                                                                  http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                              MIDAS IT Co., Ltd.


     4   Auto Mesh Planar Area




                                 • Select the highlighted edges from the picture
                                 • Attribute ID: “1: Embankment”
                                 • Mesh Set: Embankment 2
                                 • Click [Apply]Button
                                 • Follow the same process to create layers of Clay, Weathered Rock, and Soft Rock.




9                                                                                                http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                             MIDAS IT Co., Ltd.


     5   Extract Element
                                                                       ! Quick Note
                                                                   ※ If you get an error message of “Fail to get
                                                                   information from shape,” the internal edges probably
                                                                   had not been selected during mesh generation.
                                                                   Please delete all Mesh Sets and regenerate them




                           • From Main Menu, select Model > Element > Extract Element…
                           • Select “Edge” from From Shape
                           • Select 20 edges as shown in the picture
                           • Attribute ID: “6: Steel Piles”
                           • Mesh Set: “Steel Piles”
                           • Click [OK]Button




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midas GTS 2D Tutorial                                                                         MIDAS IT Co., Ltd.


     Calculating Sub-grade Reaction Coefficients

                        Vertical Reaction Coefficient



                           Lateral Reaction Coefficient


                                 Here,



                                                 Cross Sectional area   Subgrade Reaction Coefficients
                                                        (cm2)                     (tonf/m3)
             Embankment(Left)                         110101.57                    4396.80

             Embankment(Right)                            8822.06                 11329.76

                    Clay                              35199.65                     1432.90

              Weathered Rock                          20100.68                    31198.72

               Soft Rock(Side)                        109470.01                   33047.24

             Soft Rock(Bottom)                        527483.86                   18324.93


11                                                                                           http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                                       MIDAS IT Co., Ltd.


     6     Create Surface Spring




                                                                   • From Main Menu, select Model > Element > Create Surface
                                                                   Spring…
                                                                   • Object >Type: Element Edge
                                                                   • Element Width: 1 m
                                                                   • Select element edges on the left side of Embankment 2
                                                                   • Modulus of Subgrade Reaction: Kx = 4396.8
                                                                   • Click [Apply]Button.
                                                                   • Select element edge on the right side of Embankment 2.
                                                                   •Modulus of Subgrade Reaction: Kx = 11329.76
                                                                   • Using the same procedure, assign Surface Springs to Clay,
                                                                   Weathered Rock, Soft Rock.
                                                                   • For the bottom of Soft Rock, make sure to assign with Kz.
         ! Quick Note
         ※ Since Embankment 2 has different area on each
         side, we assign Surface Spring separately. However,
         for the rest of soil layers, both sides can be assigned
         with the same modulus together.

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midas GTS 2D Tutorial                                                           MIDAS IT Co., Ltd.


     7   Support




                        • From Main Menu, select Model > Boundary > Support…
                        • BC Set: Bottom Support
                        • Select all bottom nodes as shown in the picture.
                        • Select “Fixed”
                        • Click [OK] Button




13                                                                             http://gts.midasit.co.kr
midas GTS 2D Tutorial                                       MIDAS IT Co., Ltd.


     8       Analysis Case



     Analysis > Analysis Case…




      • From Main Menu, select Analysis > Analysis Case…
      • Click on Add
      • Name: Eigenvalue Analysis
      • Analysis Type: Eigenvalue
      • Click on    to open Analysis Control
      • Number of Frequency:30
      • Click [OK] Button




14                                                         http://gts.midasit.co.kr
midas GTS 2D Tutorial                                          MIDAS IT Co., Ltd.


     9        Analysis

     Analysis > Solve…




         ! Quick Note
         ※ The analysis process information is displayed
         in the Output Window. When a warning messag
         e is displayed, the analysis result will become ab
         normal. In such a case, we should carefully revie
         w the model for error.


         ※The result file is stored in .TA formats of the
         extension. The analysis process information is
         stored in .OUT files.




15                                                            http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                      MIDAS IT Co., Ltd.


     10    Eigenvalue Analysis Result




     • From Main Menu select Results > Result Tables > Vibration Mode Shape…
     • Select all modes from Active Dialog box and click on OK.
     • Check the periods of 2nd and 14th modes where mass participation is the largest.
     • Keep the record of frequencies of 1.8328 Cycle/sec and 5.3787 Cycle/sec.




16                                                                                        http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                           MIDAS IT Co., Ltd.



     Damper Calculation

          About P-wave,
                                            λ: Volumetric Elastic Modulus (tonf/m2)
                                            G: Shear Elastic Modulus (tonf/m2)
          About S-wave,                     E: Elastic Modulus
                                            ν: Poisson’s Ratio
                                            A: Section Area
            Here,




                          cp(tonf·sec/m3)                    cs(tonf·sec/m3)

           Embankment         34.32                               16.48

               Clay           14.08                                7.52

         Weathered Rock       70.05                               33.65

            Soft Rock         95.76                               53.75




17                                                                             http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                      MIDAS IT Co., Ltd.



     11   Create Surface Spring




                                  • From Main Menu, select Model > Element > Create
                                  Surface Spring…
                                  • Object>Type: Element Edge
                                  • Element Width: 1 m
                                  • Select element edges on both sides of Embankment 2.
                                  • Check on Damping Constant/Area.
                                  • Insert Cx= 34.32
                                  • Insert Cx= 16.48
                                  • Click [Apply] Button
                                  • Using the same procedure, assign Surface Springs to Clay,
                                  Weathered Rock, Soft Rock.
                                  • For the bottom of Soft Rock, make sure to assign with
                                  correct Cx and Cz (Cx = Cs, Cz=Cp).




18                                                                       http://gts.midasit.co.kr
midas GTS 2D Tutorial                                            MIDAS IT Co., Ltd.


     11. Ground Acceleration
     12   Ground Acceleration

                                • From Main Menu, select Model > Load > Time
                                History Analysis Data > Ground Acceleration…
                                • Click on      button in Time History Load Set
                                •Click on Add
                                • Enter “Hachinohe” as Load Set Name
                                • Select on Direct Integration on Analysis Method
                                • End Time: 25 sec
                                • Time Increment: 0.01 sec
                                • Step Number Increment for Output: 1
                                • Check on Calculate from Modal Damping in
                                Damping
                                • Enter the frequencies for 1st and 2nd modes from
                                previous analysis.
                                • Enter Damping Ratio as 0.05
                                • Click [OK] Button.




19                                                              http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                 MIDAS IT Co., Ltd.


     13     Ground Acceleration




     • Create two more load sets, Ofunato and Artificial, as shown in the picture.




20                                                                                   http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                     MIDAS IT Co., Ltd.


     14     Ground Acceleration




     • Click on    button on Function Name in Time Forcing
     Function
     •Click on Add Time Function
     • Function Name: Hachinohe
     • Time Function Data Type: Normalized Accel.
     • The acceleration value is already stored in an excel sheet, and
     copy and past to the table.
     • Click [OK] Button
21                                                                       http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                         MIDAS IT Co., Ltd.


      15     Ground Acceleration




     • Create two more forcing functions, Ofunato and Artificial, as shown in the picture.




22                                                                                           http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                      MIDAS IT Co., Ltd.


     16     Ground Acceleration




     • In Time History Load Set, select “Hachinohe”.
     • Function Name: Hachinohe
     • Direction: X
     • Click [Add] Button
     • Using the same procedure, create Ground Acceleration for Ofunato and Artificial.




23                                                                                        http://gts.midasit.co.kr
midas GTS 2D Tutorial                                             MIDAS IT Co., Ltd.


     17       Analysis Case


     Analysis > Analysis Case…




      • From Main Menu select Analysis > Analysis Case…
      • Click [Add]Button
      • Name: Hachinohe
      • Analysis Type: Time History
      • Check Empty on Initial Element and Initial Boundary in
      Analysis Model
      • Drag and drop the corresponding boundary condition
      and load from Set Tree into Activated. (Abutment,
      Embankment 1, Embankment 2, Clay, Weathered Rock,
      Soft Rock, Steel Piles, Surface Spring 7-11)
      •Click [OK] Button




24                                                               http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                            MIDAS IT Co., Ltd.


      18       Analysis Case

     Analysis > Analysis Case…




     • Click on Add in Analysis Case and create an Analysis Case for Ofunato.
     • Follow the same procedure for Artificial.




25                                                                              http://gts.midasit.co.kr
midas GTS 2D Tutorial                                           MIDAS IT Co., Ltd.


     18        Analysis

     Analysis > Solve…




          • Check off Eigenvalue.


          ! Quick Note
          ※ The analysis process information is displayed
          in the Output Window. When a warning messag
          e is displayed, the analysis result will become ab
          normal. In such a case, we should carefully revie
          w the model for error.


          ※The result file is stored in .TA formats of the
          extension. The analysis process information is
          stored in .OUT files.




26                                                             http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                 MIDAS IT Co., Ltd.


     19    Displacement




                          •From Main Menu select Result > Time History Data > Time History Graph
                          • Click on Define/Modify Function
                          •Function Data>Name: X-Displacement
                          • Select a node on the top right corner of abutment
                          • Component: Dx
                          • Analysis Case: Hachinohe.
                          • Click [Add] Button
                          •Click [Close] Button
                          • Check on X-Displacement in Function List, and click [Add from List] Button.
                          • Check on X-Displacement in Y Axis and click [Apply] Button
                          • The nodal displacements and the maximum value of X over time can be found.

27                                                                                   http://gts.midasit.co.kr
midas GTS 2D Tutorial                                                                                    MIDAS IT Co., Ltd.


     20      Displacement




     • From Main Menu select Result > Time History Data > Time      ! Quick Note
     History Plot
     • Analysis Set: “Hachinohe”                                    ※ Other result components such as soil stress
                                                                    and structural member force can be also check
     • Result : Displacement > DX                                   over time using this function.
     • Corresponding Dx contour plots will be presented over Time
     Steps

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midas GTS 2D Tutorial                                                                                 MIDAS IT Co., Ltd.


     21       Beam Fx




      • Post Works Tree > TH:Hachinohe > Hachinohe(All) >   • Post Works Tree > TH:Hachinohe > Hachinohe(All) >
      1D Element force > Beam Fx                            1D Element Stresses > Beam Ssz
      • It displays axial force of piles.                   • It displayed shear stress of piles.




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