Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles

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Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles Powered By Docstoc
					Horizontal Loading Tests
 on Model Foundations
Retrofitted by Micropiles

  Masahiro NISHITANI
  Jiro FUKUI
  Takeshi UMEBARA
     IAI, PWRI
     Structures Research Group
     Foundation Engineering Team
 Retrofitting of Existing Foundation by Micropiles


Limited                             Widening of Footing
Headroom
                                         Existing Pile


                                          Micropile




                    Bearing Layer
          Presentation Outline

• Outline of horizontal loading tests on
  group piles
• Results of horizontal loading tests
• Results of simulation analyses for the
  loading tests
• Summaries
          Presentation Outline

• Outline of horizontal loading tests on
  group piles
• Results of horizontal loading tests
• Results of simulation analyses for the
  loading tests
• Summaries
       To Clarify the Effects of Group Piles….
Existing Footing
                                              Existing Pile



                                             Micropile




      Plane of Existing Foundation with Micropiles
→ Horizontal Loading Tests on Model Foundations
            Cases of Horizontal Loading Tests
                                           Spacing between Existing
                                              Piles Center and      Inclination Angle of
Case           Number of Piles
                                              Micropiles Center      Micropiles (°)
                                                  (mm)
 1     Single Existing Pile                           -                      -
 2     Single Micropile                               -                      -
 3     4 Existing Piles                               -                      -
 4     4 Existing Piles and 6 Micropiles             200                     0
 5     4 Existing Piles and 6 Micropiles             400                     0
 6     4 Existing Piles and 6 Micropiles             200                     10
 7     4 Existing Piles and 6 Micropiles             200                     20
Case 1   Case 2
Case 3
            Cases of Horizontal Loading Tests
                                           Spacing between Existing
                                              Piles Center and      Inclination Angle of
Case           Number of Piles
                                              Micropiles Center      Micropiles (°)
                                                  (mm)
 1     Single Existing Pile                           -                      -
 2     Single Micropile                               -                      -
 3     4 Existing Piles                               -                      -
 4     4 Existing Piles and 6 Micropiles             200                     0
 5     4 Existing Piles and 6 Micropiles             400                     0
 6     4 Existing Piles and 6 Micropiles             200                     10
 7     4 Existing Piles and 6 Micropiles             200                     20
       Models of Case 4 to Case 7

Rear                                  Front




                    Existing Pile   Micropile

                          Loading Direction
Case 4   Case 5
Case 6   Case 7
                Specifications of Model Piles

                Diameter Thickness Sectional Area Moment of Inertia
                (mm) (mm)              (cm2)         (cm4)
Existing Pile       114.3       3.5          12.18      187.0
Micropile            34.0       2.3          2.291       2.89
    Loading Test for Case 3



   Jack




Steel Bar
                         Footing
          Presentation Outline

• Outline of horizontal loading tests on
  group piles
• Results of horizontal loading tests
• Results of simulation analyses for the
  loading tests
• Summaries
               Curve of Load and Displacement
             210

             180

             150
     i kN
Load  j




             120                                  Case1
                                                  Case2
              90                                  Case3
              60                                  Case4
                                                  Case5
              30                                  Case6
                                                  Case7
               0
                   0   20      40       60        80   100
                                               i mm
                       Displacement of Footing  j
Bending Moment on Existing Piles in Case 3 and Case 4
                                                   ng         kN
                                              B endi M om ent ( ・m )
                                        -10      -5    0     5      10
                                   30


                                 -30


                                 -90
             Ground Level (cm)



                                 -150


                                 -210

                                                              C ase3
                                 -270                         Front P iel
                                                              C ase3
                                                                       l
                                                              R ear P ie
                                 -330                         C ase4
                                                              Front P iel
                                                              C ase4
                                 -390                                  l
                                                              R ear P ie
Bending Moment on Existing Piles in Case 4 and Case 6
                                                   ng         kN
                                              B endi M om ent ( ・m )
                                        -10      -5    0      5      10
                                  30


                                 -30

             Ground Level (cm)
                                 -90


                                 -150


                                 -210

                                                              C ase4
                                 -270                         Front P iel
                                                              C ase4
                                                                       l
                                                              R ear P ie
                                 -330                         C ase6
                                                              Front P iel
                                                              C ase6
                                                                       l
                                                              R ear P ie
                                 -390
Bending Moment on Micropiles in Case 4 and Case 6
                                                 ng          kN
                                            B endi M om ent ( ・m )
                                        6
                                      -0.       4
                                              -0.    -0.
                                                       2       0
                                                              0.    2
                                                                   0.
                                30


                                -30


                                -90
           Ground Level (cm)



                               -150


                               -210

                                                 C ase4
                               -270                       l
                                                 Front P ie
                                                 C ase4
                                                         l
                                                 R ear P ie
                               -330              C ase6
                                                          l
                                                 Front P ie
                                                 C ase6
                                                         l
                                                 R ear P ie
                               -390
Shearing Force on Existing Piles in Case 3 and Case 4
                                                 ng       kN
                                           S heari Force ( )

                                        -30 -20   -10       0   10
                                   30


                                  -30


                                  -90
             Ground Level (cm)



                                 -150


                                 -210

                                              C ase3
                                 -270         Front P iel
                                              C ase3
                                                       l
                                              R ear P ie
                                 -330         C ase4
                                              Front P iel
                                              C ase4
                                                       l
                                              R ear P ie
                                 -390
Shearing Force on Existing Piles in Case 4 and Case 6
                                                ng       kN
                                           Sheari Force ( )
                                        -30 -20 -10         0   10
                                   30


                                  -30


             Ground Level (cm)    -90


                                 -150


                                 -210

                                              C ase4
                                 -270
                                              Front P iel
                                              C ase4
                                                       l
                                              R ear P ie
                                 -330         C ase6
                                              Front P iel
                                              C ase6
                                                       l
                                              R ear P ie
                                 -390
Axial Force on Existing Piles in Case 3, Case 4 and Case 6
                                                   al       kN
                                                A xi Force ( )
                                           -60 -30 0 30 60 90
                                      30


                                     -30


                Ground Level (cm)    -90


                                    -150


                                    -210


                                    -270
                                                      C ase3   Front P iel
                                                      C ase3            l
                                                               R ear P ie
                                    -330              C ase4   Front P iel
                                                      C ase4            l
                                                               R ear P ie
                                                      C ase6   Front P iel
                                    -390              C ase6            l
                                                               R ear P ie
Axial Force on Existing Piles in Case 4 and Case 6
                                                al       kN
                                             A xi Force ( )
                                       -20   -10    0     10    20
                                 30


                                 -30


            Ground Level (cm)    -90


                                -150


                                -210


                                -270                     C ase4
                                                         Front P iel
                                                         C ase4
                                -330                              l
                                                         R ear P ie
                                                         C ase6
                                                         Front P iel
                                                         C ase6
                                -390                              l
                                                         R ear P ie
Curve of Horizontal Ground Reaction and Displacement
 Horizontal Ground Reaction (KN/m
                               2
                                 )   400                G L. 27m
                                                C ase3 ( . -0. )
                                                        G L. 57m
                                                C ase3 ( . -0. )
                                                        G L. 87m
                                                C ase3 ( . -0. )
                                                        G L. 27m
                                                C ase4 ( . -0. )
                                     300                G L. 57m
                                                C ase4 ( . -0. )
                                                        G L. 87m
                                                C ase4 ( . -0. )

                                     200


                                     100


                                       0
                                            0
                                           0.       5
                                                   0.          0
                                                              1.       1.
                                                                        5           0
                                                                                   2.          5
                                                                                              2.
                                                    0.0       0.5     1.0     1.5       2.0
                                                              0.0     0.5      1.0      1.5
                                                          spl              l cm
                                                        D i acem ent of P ie ( )
          Presentation Outline

• Outline of horizontal loading tests on
  group piles
• Results of horizontal loading tests
• Results of simulation analyses for the
  loading tests
• Summaries
To Study the Design Method of
 Group Piles with Different Diameter Piles….
→ Simulation Analyses for Loading Tests by
    Ductility Design Method
                                            P




                                                      100 200



                                                                    300
                                                200
                                  400




                                                300
                                  200




                                                200
                                  200




                                                200
                                  200




                                                200
                                  200




                                                200
                                  200 200




                                                200
    Non-Linear Model




                                                                          4,400
                                                200
                                  200




                                                                3,900
                                                200
                                  200
    ・Ground Properties




                                                200
                                  200




                                                200
                                  200




                                                200
                                  200
    ・Flexural Rigidity of Piles




                                                200
                                  200




                                                200
                                  200




                                                200
                                  200




                                                200
                                  200




                                                350
                                  500




                                                250
                  Model of Transverse Resistance of Pile
                  (N/m2)



                            Upper Limit of Ground Reaction
Ground Reaction




                  PHU




                           Tan-1kHE

                      0                   Displacement   (m)
Transverse Resistance Characteristics of Pile
kHE = akbk kH
pHU = apbp pU
  ak, ap: Correction Factors of a Single Pile
  bk, bp: Correction Factors of Group Piles
To consider the group effects…
     ak b k = 1
     ap (Cray Ground) = 1.0
     apbp (Sandy Ground) = S/D (≦3)
To consider the group effects of trailing piles…
                                 Loading Direction


Rear                                        Front




         Trailing Piles       Front Pile

   pHU         ½          :       1
            Simulation Procedure

1) Study new correction factors for a single pile,
   fitting with Case 1 test results

2) Study new correction factors for group piles,
   fitting with Case 3 test results

3) Analyze Case 4 to Case 6,
   using new correction factors
           New Correction Factors on Analyses

              Ductility Design Method          New Correction Factors
  Case
            ak     bk       ap   ap・bp     ak      bk       ap     ap・bp
                                           3.0              6.0
  1, 2     1.5     -      3.0      -               -                  -
                                          (×2)           (×2)
                                           3.0     4/3
   3       1.5     2/3    -        *1                       -         *2
                                          (×2) (×2)
                                           3.0     4/3
 4, 5, 6   1.5     2/3    -        *1                       -         *2
                                          (×2) (×2)
*1: S/D in Transvers Direction of Loading (Less Than and Equal 3)
*2: S/D in Transvers Direction of Loading (without Upper Limit)
                 Model of Flexural Rigidity of Steel Pile
                  (Nm)
Bending Moment




                                Fully Plastic Moment
                 Mp
                         Y
                 My
                              Y: Yield State



                    0    φy                Curvature   (1/m)
                  Curve of Load and Displacement
            210

            180

            150
Load (kN)




            120                                           C ase3 Test
                                                                     ysi
                                                          C ase3 A nal s
                                                          C ase4 Test
             90
                                                                     ysi
                                                          C ase4 A nal s
                                                          C ase5 Test
             60                                                      ysi
                                                          C ase5 A nal s
                                                          C ase6 Test
             30                                                      ysi
                                                          C ase6 A nal s

              0
                  0   20   40        60     80     100     120    140      160
                      0    20        40     60      80     100    120      140
                           0         20     40      60     80     100      120
                                      0       20      40    60     80      100
                                  spl               ng m
                                D i acem ent of Footi ( m )
    Bending Moment on Existing Piles in Case 3 and Case 4
                             B endi M om ent ( ・m )
                                  ng         kN                                                ng         kN
                                                                                          B endi M om ent ( ・m )
                           -15 -10     -5       0   5   10                              -15 -10 -5     0   5 10
                      30                                                          30


                     -30                                                         -30


                     -90                                                         -90




                                                             Ground Level (cm)
Ground Level (cm)




                    -150                                                         -150


                    -210                                                         -210
                                Test R esult
                                            l
                                on Front P ie
                    -270        Test R esul t                                    -270
                                                                                             Test R esul t
                                            l
                                on R ear P ie
                                                                                             on Front P iel
                                    ysi
                                A nal s R esult                                              Test R esul t
                    -330                    l
                                on Front P ie                                    -330                    l
                                                                                             on R ear P ie
                                    ysi
                                A nal s R esult
                                on R ear P ie
                                            l       Case 3                                       ysi
                                                                                             A nal s
                                                                                             R esult
                                                                                                              Case 4
                    -390                                                         -390
Bending Moment on Micropiles in Case 4
                                         ng          kN
                                    B endi M om ent ( ・m )
                                    0
                                  -1.       5
                                          -0.          0
                                                      0.    5
                                                           0.
                             30


                            -30


                            -90
       Ground Level (cm)


                           -150


                           -210
                                        Test R esul t
                                        on Front P iel
                           -270         Test R esul t
                                                    l
                                        on R ear P ie
                                            ysi
                                        A nal s R esul t
                           -330         on Front P iel
                                            ysi
                                        A nal s R esul t
                                                    l
                                        on R ear P ie
                           -390
Curve of Horizontal Ground Reaction and Displacement
                                       400
                                                  Case 3                    Test R esul t
    Horizontal Ground Reaction (kN/m                                        on Front P iel
                                       350
                                 )
                                                                            Test R esul t
   2



                                                                                        l
                                                                            on R ear P ie
                                       300                                  M odelon Front P ie l
                                                                                  n
                                                                            U sed i A nal sysi
                                       250                                  M odelon R ear P iel
                                                                                  n
                                                                            U sed i A nal sysi
                                       200
                                                                                G L. 57m
                                                                         D epth; . -0.
                                       150

                                       100

                                        50

                                         0
                                              0
                                             0.    5
                                                  0.         0
                                                            1.        1. 5       0
                                                                                2.            5
                                                                                             2.
                                                         spl             l cm
                                                       D i acem ent of P ie ( )
Curve of Horizontal Ground Reaction and Displacement
                                     300
                                                                           Test R esul t
                                                Case 4                     on Front P iel
  Horizontal Ground Reaction (kN/m
                                                                           Test R esul t
                                )

                                     250
                                                                                       l
                                                                           on R ear P ie
                              2




                                                                           M odelU sed
                                     200                                   n      ysi
                                                                           i A nal s


                                                                              G L. 57m
                                                                       D epth; . -0.
                                     150


                                     100


                                      50


                                      0
                                            0
                                           0.        0.5                 0
                                                                        1.                   5
                                                                                            1.
                                                      spl              l cm
                                                    D i acem ent of P ie ( )
                   Summaries
• Results of horizontal loading tests
  → Existing foundations with micropiles have a
     large retrofitting effects.
  → Spacing has little effect on retrofitting.
  → Retrofitting effects are counted by installing
     micropiles incliningly.
• Results of simulation analyses
  → It is possible to use the ductility design method
     to perform retrofitting design.

				
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posted:8/7/2012
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