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Fabrication and Erection of Akinada Bridge

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Fabrication and Erection of Akinada Bridge Powered By Docstoc
					              Fabrication and Erection of “Akinada Bridge”

                                        SATOU Youichi : Overseas Project Department, Bridge & Road Construction
                                                        Division, Logistics Systems & Structures
                                      NAGASAKO Taiki : Construction Department, Bridge & Road Construction
                                                        Division, Logistics Systems & Structures
                                          OKADA Seiji : Planning & Engineering Department, Bridge & Road
                                                        Construction Division, Logistics Systems & Structures
                                          OKA Kiyoshi : Manager, Construction Department, Bridge & Road
                                                        Construction Division, Logistics Systems & Structures




           In the concept of bridges linking Akinada Islets, the Akinada Bridge is the most important bridge linking
      Kawajiri Town, Hiroshima Prefecture, and Shimokamagari Islet. The bridge is the two-hinge-type suspension
      bridge with three continuous spans. The total length is 1 175 m with the main span of 750 m. One of design
      features is that the bridge shows a very slender shape in the width when compared with its span length, and the
      span lengths of the both sides are different, showing asymmetry in the side view. IHI participated in construction
      of the 2P main tower, cable work, and stiffening girder of the bridge, demonstrating its superior technology required
      for construction of large steel bridges. Outline of construction is described.




                                                                                                 Konigata Kawajiri-town
1. Introduction
                                                                                                 Toyoda-district Hiroshima
In bridging to link Akinada Islets where IHI has been                                            Prefecture (1A side)
engaged in the construction of such bridges as “Kamagari              Bridge type                3-span continuous 2-hinge
Ohashi,” “Okamura Ohashi,” and “Nakanoseto Ohashi,”                                              suspension bridge
the “Akinada Bridge” connecting Kawajiri-town,                        Road standard              Category 3 Class 3 (collector
Hiroshima Prefecture, and Shimokamagari Islet, is                                                road D standard)
positioned as one of the most important bridges to                    Design speed               V = 40 km/h
improve the convenience of local residents and promote                Design load                B live load
the general development in this area. This long and                   Bridge length              1 175 m (255 + 750 + 170)
large bridge is a 3-span continuous 2-hinge suspension                Width                      Total width 12.7 m (carriageway
bridge with a center span of 750 m and a box girder of                                           6.0 m, sidewalk/inspection path
1 175 m in total. The third-largest such bridge in Japan,                                        2.0 m ¥ 2)
it seems very slender because the girder width is narrow              Main tower height          About 120 m (T.P. + 128 m)
for span length. The bridge’s side spans are short and                Cable                      PWS
asymmetrical in length on the left and right sides.                   Main girder                Flat hexagonal shape steel box
   Since construction work joint venture IHI has joined                                          girder (2 compartments)
received orders for 2P main tower work in 1995, we                    Longitudinal slope         Center span 1.75% parabolic
have participated in cable work and stiffening girder                                            Side span 3.5% linear
(Section 1) work and demonstrated our technical expertise             Traverse slope             1.5% linear
in constructing large bridges. In this paper, we summarize
and report these construction works.
                                                                    3. 2P main tower work
                                                                    3.1 Work outline
2. Specifications                                                   The 2P main tower work is outlined below.
Fig. 1 shows the general view of this bridge, which is                Work name             Bridge construction [Akinada
outlined below.                                                                             Bridge main tower work (2P)]
  Route name             Main local road,                                                   work
                         Shimokamagari Kawajiri-                      Type of order received
                         line                                                               Construction Work Joint
  Construction place     From Shirosaki Shimokamagari                                       Venture
                         -town Aki-district Hiroshima                 Construction period From October 6, 1995 to
                         Prefecture (4A side) to                                            March 20, 1998
                                                                                                                                                                           1 175 000
                                                                                     255 000                                                                               750 000                                                                                          170 000
                                                      10 000                         241 000           4 000 4 000                                                             742 000                                                                        4 000 4 000 158 000                                     8 000
                                                                                      T. P.+128.508                                                                                                                                                                     T. P.+128.508




                                                                                                                                                                                            1 596
                         Kawajiri-town                                                (Theoretical height                                                                                                                                                               (Theoretical height                                  Shimokamagari-town
                                                                                      of cable)                                                                                                                                                                         of cable)
                                                                                                                                                                                                                                                                                                                              Proposed height




                                                                                                    1 980
                    Proposed height




                                                                                                                                                                                                                                                                                             4 062
                                                                                     8 809
                                                                                                                                                                                                                                                                                                                              T. P.+38.006




                                                                                                                                                                                                       2 000
                    T. P.+35.425




                                                                                                                                                                                            74 000
            Application point of cable force                                                                                                       Proposed height T. P.+50.912                                                                                                                                              Application point of cable force
                                                                                                                                                                                                                                                                                                                             T. P.+37.468
            T. P.+35.404

                                                                                               T. P.+44.350                                                       T. P.+42.200                                                           T. P.+44.350
                                                                             T. P.+7.000                                                                 H. H. W. L. T. P.+2.200                                  T. P.+7.000                                                                                                                        T. P.+8.000
                  T. P.-3.000
                                                                                                                                                                                                                  T. P.-1.000




                                                                                                                            14 000




                                                                                                                                                                                                                                                                             8 000
                                                                                                                                                                                                                                                                                                                   49 000




                                                                                                                                                                                            40 000
                                                              48 000            T. P.-7.000          12 000
                                                                                                                                                                                                                                                             1 200                                                   4A
                                                                1A                                               2P
                                                                                                                                                                                                                                                                        3P
                                                                                                                        103 000                                                   560 000                                                                   87 000           Cast-in-place concrete pile
                                                                                                                                                                                                                                                                             f = 2 m L = 22.0 31.0 m
                                                                                                                                                                                                                                                                             n = 14




                                                                                                                           30 000




                                                                                                                                                                                                                                                                                                                                            30 000
                                 30 000




                                                                                                                                                                                                                                                               30 000
                                                                          48 000
                                                                                                      12 000                                                                                                                                                                  12 000
                                                                                                                                                                           .+                                                                                                                                               49 000


                                             Typical cross section                                                                            Main tower                                     1A          48 000                                         Anchorage                                         4A              49 000
                    Typical section                                   Section with short hanger in center span                                                     3 500                    14 000 7 206     9 794 17 000
                                                                                                                                                                                                                                                                                                         17 000       11 592     6 408 14 000
                                                                                                                                       16 000
                                                                                                                 2 000
                                                                                                                 1 908




                (Pin anchorage portion)                                (Bearing pressure anchorage portion)                                                                                              2 000 15 000
                                                                                                                                                                                            T. P.+35 425                                                                                                                                                T. P.+38.006
                                  16 000 (Cable center spacing)                                                                                   T. P.+128.508                                                                                                                                                      15000 2 000




                                                                                                                                                                                                                                  4


                                                                                                                                                                                                                                          6 900
   1 500                                                                                          1 500




                                                                                                                                                                                                                             13.52




                                                                                                                                                                                                                                                                                                 6 650
                                                                                                                                                  (Theoretical height                       T. P.+35 404                                                                                                                                                T. P.+37.468
                       1 650                              12 700                     1 650




                                                                                                                                                                                                                                                                                                          24.308
                                                                                                                                                  of cable)                                                                                                  T. P.+5.000




                                                                                                                                                                                                                  45




                                                                                                                                                                                                                                                                                                                                                           8 500
                                600          750                       750     600




                                                                                                                                                                                                                                                                                                                               40
                                                                                                                       40 800




                                                                                                                                                                                                                                           10 600




                                                                                                                                                                                                                                                                                                4 000
                                                                                                                                                                                                                                                                                     4 000 7 000 7 850
                      2 000                                   6 000                    2 000




                                                                                                                                                                                       14 000 15 000




                                                                                                                                                                                                                                                                                              29 500
                                                                                                                                                                                                                                       38 000




                                                                                                                                                                                                                                                                                                                                                                    19 500
                                                                                                                                                                                           29 000




                                                                                                                                                                                                                                      10 500
                                              Asphalt pavement
                                               t = 65                                                                                                                                                                                                                                                                                                                        T. P.+8.000




                                                                                                                                                                                                                                                                                                                                                           11 000
                                                                                                                                                                                                                                                             T. P.-3.000
                                                                                                              121 508
                                                                                                              119 450
                                                      2 500




                                                               Proposed




                                                                                                                                                                                                                                          10 000
                                                                                                            44 500




                                                               height                                                                                                                       10 000                38 000                                                                                                    39 000             9 000
                                                                                                                                                                                                                48 000                                                                                                       49 000 1 000
        800




                              1.5%               1.5%            1.5%           1.5%
                                                                                                                                                                                                                             2P                    Main tower foundation                                                       3P
2 380




                                                                                                                       32 150




                                                                                                                                                                                                               5 500       19 000           5 500                                                            5 500           19 000         5 500




                                                                                                                                                                                                                                                                                                                                                8 000
        1 500




                                                                Inspection                                                                                                                                                                                                                   T. P.+7.000
                                          Public                car rail                                                                             T. P.+7.000                               T. P.+7.000
                                          utililies                              Maintenance
                                                                                                                                                                                                                                                                        H. H. W. L. T. P.+2.200
                                                                                                                 150




                                                                                                                                                                                                                                                   14 000
                                                                                 way                                                                                               H. H. W. L. T. P.+2.200
                                          9 000 (Inspection car rail spacing)                                                                                4 500
                                                                                                                                       19 000
                               8 000 (Web spacing) 7 660 (Web spacing)                                                                                                                                  T. P.-7.000                                                                          T. P.-1.000                                      Cast-in-place concrete pile
                    3 000                       13 000                 3 000                                                                                                                                                                                                                                                                  f = 2 m L = 22.0 31.0 m
                                                19 000                                                                                                                                                                     30 000                                                                                                             n = 14
                                                                                                                                                                                                                                                                                                           30 000


                                                                                                                                                                                                                                                                                                                                      (Note) T.P.: Tokyo Peil m
                                                                                                                                     Fig. 1     General view of “Akinada Bridge” (unit : mm)
                                                                                                                                                                                                                                                     Intermediate drawing
                                                                              Side span spacing     Center span spacing                                   Tower top portion                                                       E tower shaft side                  W tower shaft side
                                                                                                  (Top plate upper surface)
                                                                                        3 500                                                                   3 300        100                                                           3 300                            3 300
                                                        16 000
                                                                                        2 640                                                         430       2 870                                                            430       2 870                           2 870         430
                                  (Tower shaft center spacing sole plate top surface)     430        430                                                  1 305 690 1 305                                                             5 × 660 = 3 300                  5 × 660 = 3 300
                                                          C
                                                          L                                                                                               660 645    645 660
                                                                                                                                                                                                                                                                                  Ladder M.H




                                                                                                                                                                                                                                                                                                          350
                                                                                                                                                                                                                                                                                                          600




                                                                                                                                                                                                                         350
                                                                                                                                                                                                                         600
                                                                                                                                                                                                                                                                                                                                      Work quantity




                                                                                                                                                                                                                                                                                                                660
                                                                                                                                                                                                                                                                                                                      430




                2 000
                                                                                                                                                                                                         430
                                                                                                                                                                                                                       660
                                T. P.+126.600




                                                                                                                                                875
                                                                                                                                                430
                                                        Upper




                                                                                                                                                                                                   410
                                                                                                                                                                                                   660


                                                                                                                                                                                                   4 500
                                                                                                                                                                                                   3 640
                                                                                                                                                                                                                                                                                                                      3 640
                                                                                                                                                                                                                                                                                                                      4 500




                                                                                                                                                                                                                                                                                                         410
                                                                                                                                                                                                                                                                                                         660
                                                      horizontal                                                                                                                                                                                   Stairs                                   Elevator




                                                                                                                                                                                                                           660




                                                                                                                                   3 500
                                                                                                                                   2 640
                                                                                                                                                                                                                                                                                                                660
                                                       member




                                                                                                                                  875 875
                                                                                                                                                                                                     410
                                                                                                                                                                                                     660
                                                                                                                                                                                                                                                                                                         410
                                                                                                                                                                                                                                                                                                         660




                                                                                                                                                                                                   3 500
                                                                                                                                                                                                   2 640
                                                                                                                                                                                                                                                                                                                      2 640
                                                                                                                                                                                                                                                                                                                      3 500




                                                                                                                                                430
                                                                                                                                                875
                                                                                                                                                                                                                       660



                                                                                                                                                                                                         430




                40 800
                                                                                                                                                                                                                       350
                                                                                                                                                                                                                       600
                                                                                                                                                                                                                                                                                                                660
                                                                                                                                                                                                                                                                                                                      430



                                                                                                                                                                                                                                                                                                          350
                                                                                                                                                                                                                                                                                                          600
                                                                                                                                                                                                                                                                                                                                      3.2 Characteristics of structure




                                                                                                                                                      Upper horizontal member                                             Intermediate horizontal member                                          Lower horizontal member
                                                                                                                                                          3 499    3 500                                                         3 842 3 843                                                          4 214 4 215
                                                                                                                                                  412                           412                                      421                                421                             607                               607
                                                                                                                                                  412.5   5 × 535 = 2 675       412.5                                    421.5     5 × 600 = 3 000          421.5                           607.5      5 × 600 = 3 000        607.5
                                 T. P.+83.800




                                                                                                                                   573
                                                                                                                                   615
                                                                                                                                                                                                                                                                              560
                                                                                                                                                                                                                                                                              626




                                                                                                                                                                                                          553
                                                                                                                                                                                                          605
                                                     Intermediate
                                                                                                                                                                                                                                                                                                                                                             Steel weight about 1 650 t




                                                      horizontal




                                                                                                                        4 396
                                                                                                                                                                                               4 319
                                                                                                                                                                                                                                                                    4 468



                                                       member




                                                                                                                                901 1 146 901
                                                                                                                                                                                                       869 1 106 869
                                                                                                                                                                                                                                                                            880 1 120 880




                                                                                                                                967 1 232 967
                                                                                                                                                                                                       950 1 209 950
                                                                                                                                                                                                                                                                            983 1 250 983




                                                                                                                        4 094
                                                                                                                                                                                               3 950
                                                                                                                                                                                                                                                                    4 000




          44 500
                                                                                                                                   573
                                                                                                                                                                                                          553




                                                                                                                                   615
                                                                                                                                                                                                          605
                                                                                                                                                                                                                                                                              560
                                                                                                                                                                                                                                                                              626




                                                                                                              T. P.+51.900                         429                          429                                      437.5                              437.5                           623.5                             623.5
                                                                                                                                                   431     5 × 535 = 2 675      431                                      439.5     5 × 600 = 3 000          439.5                           626        5 × 600 = 3 000        626
                                                                                                             (Pin center)
                                                                                                                                                           3 533    3 537                                                          3 875       3 879                                                   4 247    4 252




119 450 (Vertical dimension)
                                                                             T. P.+44.350
                                                                                                                                                                                                                                 (c) Main tower base
                                                                                                                                                                                                                                        4 600
                                                                                                                                                                                                                         650            3 300               650
                                 T. P.+39.300
                                                                                                                                                                                                                         250       200         200          250
                                                                                                                                                                                                                         400       5 × 580      2 900       400
                                                       Lower
                                                      horizontal                                                                                                                                                                   5 × 660      3 300
                                                                                                                                                                                         250
                                                                                                                                                                                                400
                                                                                                                                                                                                                   660




                                                       member
                                                                                                                                                                                   650
                                                                                                                                                                                         210




                32 150
                                                                                                                                                                                                                   600
                                                                                                                                                                                                       660
                                                                                                                                                                                                                   660
                                                                                                                                                                                                                                       2 700




                                                                                                                                                                             5 800
                                                                                                                                                                             4 500




                                                                                                                                                                                                                                           1 400
                                                                                                                                                                                                 660
                                                                                                                                                                                               8 × 510 4 080




                                 T. P.+7.150
                                                                                                                                                                                                                   600




                               (Sole plate
                                                                                                                                                                                         210




                               underside)
                                                                                                                                                                                   650




                                                                                        430 364 430
                                           E tower post         W tower post                       4 500        (Note) T.P. : Tokyo Peil m
                                                                                                                                                                                         250
                                                                                                                                                                                                                                                                                                                                      whose main characteristics are described below.




                                                        19 000
                                                                                                                                                                                                400
                                                                                                                                                                                                                   660




                                   (Tower shaft center spacing sole plate underside) (Sole plate underside)

                                                                                                               Fig. 2        General arrangement of 2P main tower (unit : mm)
                                                                                                                                                                                                                                                                                                                                      Fig. 2 shows a general drawing of the 2P main tower,




                                                                                                           Fig 2      General arrangement of 2P main tower ( nit : mm)
   (1) For the section of the main tower, the outside                                  erection, the tower corner portion was provided with a
     corner portions are cut. Since the transverse space                               metal touch section, and the top and bottom end faces
     of main cable is narrow at 16 m while the center                                  of the tower blocks were cut with the milling machine
     span length is 750 m, the main tower and the entire                               while controlling the deflection of the blocks through
     bridge have a flexible structure. This measure is                                 multi-point supporting. The cut end faces were checked
     taken to improve stability against wind in                                        on the metal touch when the members were temporarily
     accordance with the results of wind tunnel tests.                                 assembled. The axis of the main tower blocks and the
   (2) Inside the main tower, 4 tuned mass dampers                                     inclination of the end faces were carefully controlled.
     (TMD) are installed. To counter vortex excitation                                 3.4 Erection
     that cannot be prevented by measure (1) above,                                    For erection of the main tower, we adopted an erection
     TMDs were installed for structural damping.                                       using a 110 tf lifting jib climbing crane. There were
   (3) For all the field joints of the main tower, field                               28 blocks for the tower of the 2P main tower and 6
     welding was adopted in consideration of appearance.                               for the horizontal beam, and they were divided so that
   (4) The dimensions of the main tower are 119.450                                    one block did not exceed 70 t. Fig. 3 shows the erection
     m in height, 19 m to 16 m in spacing of posts,                                    steps.
     and 3.3 m × 4.5 m to 3.5 m in section (tower                                         The following factors were considered during erection
     base to tower top), and the bridge presents a                                     of the main tower.
     more slender shape than existing suspension                                          (1) Securing levelness for installing sole plate
     bridges.                                                                                  An important point during erection of the main
3.3 Fabrication                                                                             tower for a suspension bridge or cable stayed bridge
IHI fabricated the anchor frame of the 2P main tower,                                       is perpendicularity of the main tower. Accuracy
tower blocks of the 1st to the 8th (14 blocks in total)                                     when installing the sole plate is important for
from tower base to tower center, sole plate, and horizontal                                 reproducing the accuracy of the main tower blocks
beam blocks at the lower part (about 1 000 t).                                              that was strictly controlled during fabrication. For
The outside dimensions of the sole plate are 5.8 m ×                                        installing the sole plate in the 2P main tower work,
4.6 m, and the plate thickness is 140 mm. On paying                                         the grouting method was adopted: mortar was filled
deformation of the plate, and the accuracy was controlled                                   under the sole plate after the sole plate was
by planning with a milling machine.                                                         accurately installed on the substructure.
   The edges of the joints of the tower were prepared                                       Subsequently, the filling rate just under the sole
for field welding. To the verticality of the tower during                                   plate was checked and the levelness of the plate




                        Step 1                      Step 2                   Step 3                      Step 4                         Step 5
  Sequence   Step 1   Climbing crane is assembled.                                            Step 4   The third climbing crane is raised.
                      Sole plate/tower shafts 1 to 5 and lower horizontal member are erected.          Tower shafts 11 and 12 are erected.
                                                                                                       Tower shafts 13 and 14 and upper horizontal member are erected.
             Step 2   The first climbing crane is raised.
                      Tower shafts 6 and 7 are erected.                                      Step 5    Tower top saddle and tower top crane are erected.
                                                                                                       Climbing crane is removed.
             Step 3   The second climbing crane is raised.
                      Tower shafts 8 to 10 and intermediate horizontal member are erected.

                                                             Fig. 3   Tower erection procedure
  was measured, confirming that the sole plate was                             Table 1 Precision requirements for main tower
  accurately installed on the top surface of the                                                              West tower bridge 1 / 11 900
  substructure.                                                                      Axial perpendicularity
                                                                                                              East tower bridge 1 / 14 100
(2) Installing main tower blocks and securing
     perpendicularity of field welding
                                                                                         (a) 3P side                            (b) 2P side
     Since the welding-all-around was done for the
                                                                                  TMD-E2       TMD-E1, E2                               HMD-E1
  main tower blocks, it was necessary to consider                   TMD-E1                                          HMD-E1
                                                                                     TMD-E3        TMD-E3
  the inclination caused due to the difference in weld
  shrinkage. The blocks were installed as shown in
                                                                                                                  TMD-E2                             TMD-E2
  Fig. 3, and simultaneous face-to-face welding was                                                TMD-E2                           TMD-E1
                                                                                   TMD-E2                                            TMD-E2          TMD-E2
  done for both tower using two automatic welding
  machines for the 1 joint, and the control was made
  so as to prevent error when installing and shrinkage
  difference when welding. As a result, a sufficient
  perpendicularity was secured as Table 1 shows.
(3) Prestressing of anchor bolts
     For the 2P main tower, 60 anchor bolts of 125
  mm in diameter were installed. The main tower is
  so designed as not to allow it rising on the sole                                                                    (Note) TMD : Tuned Mass Damper
  plate. For the prestressing amount to be introduced,                                                                          HMD : Hybrid Mass Damper

  therefore, we conducted an investigation to ensure
                                                                   Fig. 4 Arrangement of sway-damping devices at erection work
  the prevention of rising in the free-standing state
  of the main tower, completed state
  of the suspension bridge, state after
  100 years of service, and loaded state                 Table 2 Specifications of sway damping devices for erection
  due to earthquake, etc. For this
                                                                                   HMD-E1                      TMD-E2                        TMD-E1
  decision, we considered concrete              2p mass damper system
                                                                                 1st bending        1st torsion        2nd bending           1st lateral
  creep, drying shrinkage, and anchor                                                                                                    Galloping control
                                                        Purpose                Vortex induced     Vortex induced Vortex induced
  bolt relaxation.                                                            vibration control vibration control vibration control
                                                                                                                                         + vortex induced
                                                                                                                                        vibration control
     As a result, we decided to
  introduce the axial force of 1 960 kN      Targeted wind velocity (m/s)              7                 29                 27                   16

  {200 tf} per piece as the initial          Required damping           (–)          0.06              0.13                0.12                 0.07
  prestress amount. For controlling the      Vibration control type           1-axis V shaped              1-axis pendulum              1-axis pendulum
                                                                              type active type               passive type                  passive type
  axial force, we measured the value
                                             Overall mass of device      (t)     less than 26                 less than 24                 less than 40
  of the strain gauges put to the 8          Moving mass                 (t)          10                           10                            22
  anchor bolts, removed the residual         Targeted amplitude      (mm)           ± 300                        ± 300                         ± 70
  strain, calibrated the jack pressure       Natural frequency        (Hz)           0.36                         1.23                          0.63
  gauge, and measured the anchorage
                                             Adjustable frequency range        0.20 0.468 Hz                     ± 10%                        ± 10%
  loss of the construction detail. Based
                                             Pendulum length         (mm)                                        1 000                         1 000
  on the measuring the values, the
                                             Logarithmic decrement (–)                                            0.25                          0.25
  prestress force for each bolt was
                                             Number of units
  controlled.                                installed               (unit)            1                            2                             1
(4) Measures against wind during
  erection
     The main tower is more unstable against wind                            of the dynamic design of the tower.
  before the suspension bridge is completed. It is
  therefore necessary to take damping measures in
                                                                      4. Cable work
  accordance with the erection steps and free-standing                4.1 Work details
  state when the climbing crane is removed. As a                      In October 1996, construction work joint venture IHI
  result of investigation, we installed one active mass               has joined contracted for the cable work by Kure Civil
  damper (HMD-E1) and three TMDs as shown in                          Engineering Construction Office, Hiroshima Prefecture.
  Fig. 4 and Table 2 to secure stability against wind                 The work was completed in October 1998. The main
  during erection.                                                    cable on one side measures about 1 270 m in total
     For the 2P main tower, we conducted damping                      length and about 470 mm in diameter. The cable is
  tests using HMD-E1 as the vibrator. We checked                      composed of 52 parallel strands (54 strands with 2
  the natural frequency of the tower and the                          extra strands added for 3P to 4A because of steep
  logarithmic decrement and confirmed the adequacy                    slope), bundling 127 high-tensile galvanized steel wires
of 5.11 mm in diameter (Fig. 5). All the strands were                           Table 3       Specifications of main cables
converged and attached to sockets at the factory, and
                                                                                Item                            Unit          1A - 3P             3P - 4A
each strand was provided with a gauge wire for a
                                                               Sectional composition                      Strand/cable     PWS-127 × 52 PWS-127 × 54
standard of length and a red wire to confirm twisting          Cable wire diameter                              mm              5.11               5.11
of the strands. The main cable was erected by the PS           Number of wires                             pcs./cable           6 604              6 858
method in which the strands were wound on reels and                                                           N/mm2                6.3                6.3
                                                               Allowable tensile stress
transported to the site. The specifications of the main                                                    {kgf/cm2}            {64}               {64}
cable are shown in Table 3.                                                                                   N/mm2          1.99 × 105          1.99 × 105
                                                               Modulus of elasticity
   The main technical characteristics of this work are                                                     {kgf/cm2}        {2.03 ×      106}   {2.03 × 106}
described below.                                               Main cable sectional area                   cm2/cable            1 354              1 406
   (1) Adoption of pin anchoring structure for both                                                           kN/cable         84 946             88 210
                                                               Allowable tensile force
                                                                                                           {tf/cable}         {8 668}             {9 001}
     ends of the hanger rope.
                                                                                                              kN/cable         81 438             85 985
   (2) Use of parallel cable of the hanger rope covered        Maximum tension
                                                                                                           {tf/cable}         {8 310}             {8 774}
     with polyethylene
                                                               Main cable diameter        Typical             mm (%)         464     20         473     20
   (3) Use of a helicopter to transport the pilot rope of      (percentage of void)       Band                mm (%)         459     18         467     18
     the center span over the sea
   (4) Adoption of storm-less structure for the catwalk
   (5) Adoption of stairs structure for the catwalk near       high-speed vessels so as not to impede their navigation,
     the tower top between 3P and 4A with a large              for 2P to 3P where the ships sail, and then completed
     inclination                                               the drawing work of two east and west pilot ropes in
   Table 4 shows the main work quantities of this work.        about half a day using a helicopter (Aero Special SA330J,
4.2 Erection of splay saddle                                   lifting capacity 2 200 kg, extending tension 10 kN)
There are 4 splay saddles in total, 2 units each for 1A        during the time zone free from sailing ships (Fig. 8).
and 4A abutments, and the 1A east saddle was erected              For transporting the pilot ropes over the sea with the
using a full-swing FC boat of 200 tf lifting class (Fig. 6).   helicopter, we used light and strong polyaramide fiber
Other saddles were erected using a truck crane (Fig. 7).       ropes. For transporting the side spans 1A to 2P over
Prior to the erection, we carried out chipping of the          an area of the sea where no ships sail, we used a tugboat,
blockout portion under the sole plate at the installation      and for the side spans of 3P to 4A above land, we drew
position, marked the installation position to reflect the      the ropes using manpower and connected them at the
results of survey from the opposite shore, installed           abutments and the tower top using wire connectors
liners for adjusting the installation height and arranged      (Table 5).
reinforcing bars to prevent concrete cracking. For             4.4 Assembly of hauling system
erection, the saddle was divided into upper and lower          After transporting and connecting the pilot ropes, we
portions. After the installation was completed, we             assembled the hauling system to erect the catwalk and
adjusted the installation position of the lower part,          main cables by simultaneously drawing and winding the
temporarily held the saddle until it became independent        rope from the two unreelers installed on the 4A abutment.
as the cable erection advanced, carried out mortar
concrete filling and set back the upper portion.                  Table 4       Number of work processes in cable erection
4.3 Installation of pilot rope
                                                                     Work content             Unit      Qty                   Remarks
After temporary equipment was installed on the
abutments of 1A to 4A and the main towers, we installed        Fabrication of cable strands       t    2 768 Strand, socket, shim plate
the pilot rope, the first rope to connect spans. We            Fabrication of cable bands         t     182
investigated the service schedules of ferryboats and           Fabrication of hanger ropes                     Hanger rope, stay rope, hanger rope socket,
                                                                                                  t     160
                                                               and stay ropes                                  stay rope socket

                                                               Fabrication of catwalk                          Iron structure, catwalk rope, catwalk rope
                                            Extra strand                                          t     492
    Red wire            Gauge wire                             equipment                                       socket, floor system
                                         (only for 3P to 4A)
                                                               Fabrication of abutments
                                                               and main tower temporary           t     508 Scaffolding, bent, etc.
                                                               equipment
                                                                                                             (1) Erection of splay saddle
                                                                                                             (2) Pilot rope spanning
                                                                                                             (3) Erection of hauling system
                                                               Cable erection                                (4) Erection of catwalk equipment
                                                                                                 Set       1
                                                                                                             (5) Erection of cable strands
                                                                                                             (6) Squeezing
                                                                                                             (7) Erection of cable bands
                                                                                                             (8) Erection of hanger ropes
                                                                                                             (9) Erection of temporary equipment and
                                                                                                                 partial removal
               Fig. 5    Main cable strand composition                                                       (10) Electric equipment
          (a) Step 1 : Erection of temporary equipment and splay saddles                                         (d) Step 4 : Erection of strands
                                                                                                                                           Drawing direction
Splay saddle                                                                                                                        Strands                 Catwalk floor
            200 tf lifting class                                                                                                                            system
            full-turn FC boat
                                                Tower top crane                                                      Hauling rope       Carrier
                                           Tower top scaffolding           Splay saddle       Drive                                                               Unreeler



          1A            2P                                         3P         4A                1A        2P                                           3P        4A
                                                                                                                           Catwalk floor system


                             (b) Step 2 : Pilot rope spanning                                                  (e) Step 5 : Erection of cable band
                                                                                                                                              Main cable
Side span pilot rope                Helicopter         Center span pilot rope                                              Cable band
       Tugboat




           1A               2P                                          3P         4A           1A        2P                                           3P        4A
                                                                                                                          Catwalk floor system



                             (c) Step 3 : Erection of catwalk                                                  ( f ) Step 6: Erection of hanger rope
            Setback amount                                                Side span catwalk
            adjusting rope                                                                                               Cable band            Main cable
                                                                          floor system
                                                     Floor system                                                     Hanger rope
                                 Center span catwalk
                                                     erection direction      Hauling rope
                                 floor system
                                                                                 Unreeler
  Drive
                                                                                                1A        2P                                           3P        4A
                                                                                                                           Catwalk floor system
      1A               2P                                           3P           4A
                                     Cross bridge

                                                                    Fig. 6       Cable installing procedure




               Fig. 7 Erection work of 1A east spray saddle


  For this work, we used a 1-loop hauling system (Fig.                                                Fig. 8    Pilot rope installing using helicopter
  9) to connect the hauling ropes of the east and west
  lines with a long splice and turned them with a driving
  gear.                                                                                        the ship route and then fixed the sockets on both ends
  4.5 Erection of catwalk                                                                      to the anchoring devices of the abutments and tower
  The catwalk was erected using the hauling system. For                                        top. The catwalk floor system is of triple structure with
  the catwalk ropes, we connected the ropes of the spans                                       synthetic fiber net laid double on a welded-wire mesh
  and drew them from the unreelers installed on the 4A                                         to prevent tools, etc. from dropping. It was assembled
  abutment toward the 1A abutment by the free-hang                                             to a proper length and wound into a roll in advance at
  method while controlling the sag so as not to impede                                         a nearby work yard and then erected by sliding it on
     Table 5 Specifications of pilot rope and hauling ropes

                                        Rope Sectional Breaking load            Unit
     Rope type          Rope used     diameter area                            weight
                                       (mm) ( mm2) (kN)        {tf}            (kg/m)
      1A - 2P
                      6 ×24 Class A       12.5        55.2       77    {7.9}    0.52
      Pilot rope
       2P - 3P         Polyaramide
                                          12.0        37.0       66    {6.7}    0.13
      Pilot rope        fiber rope
      3P - 4A
                      6 ×37 Class A       20.0       157.0      213 {21.7}      1.44
      Pilot rope
     Second rope      6 ×37 Class A       20.0       157.0      213 {21.7}      1.44

      Pilot rope      6 ×37 Class A       35.5       495.0      213 {21.7}      1.44




                                           Hauling rope
                                                                                                     Fig. 11 Drawing out of cable strand
                                                                      Horizontal takeup

                                Carrier                                                   the operator in the drive operation room. The strands
        Sheave
                                                                                          drawn-out were temporarily stretched, and dropped into
                                                                                Counter   the saddle portions after the portions to be anchored to
                                                 Tramway bent
                                                                                -weight   the saddles of the abutments/tower top portion were
1A        Drive
                           2P
                                                                                          shaped, and the sockets on both ends were fixed to the
                                      Catwalk                                             anchor frame. The strands were adjusted through absolute
                                                                                          sag adjustment by measuring the shape of the reference
                                                                               4A
                                                                 3P                       strands and through the relative sag adjustment by
                   Fig. 9 Configuration of hauling system                                 measuring the relative difference between the reference
                                                                                          strands and adjusting strands during the night when
                                                                                          they are not affected by the temperature. After the
the catwalk ropes from each tower top of 2P/3P (Fig.                                      adjustment was completed, the tension adjustment of
10). After the catwalk was erected, we adjusted the set-                                  the anchor span was made.
back amount of the main tower during cable erection                                       4.7 Cable squeezing
with the set-back adjusting ropes installed in the side                                   After all the strands were erected, the arrangement was
spans.                                                                                    corrected during the night when the temperature changes
4.6 Erection of cable strands                                                             less, and they were bound to prevent deforming. For
The cable strands were drawn out on rollers arranged                                      cable squeezing to finish the cross-sectional shape of
on the catwalk from the unreelers on the 4A abutment                                      the main cable into a round shape, the cable was pre-
toward the 1A abutment using the hauling system (Fig.                                     squeezed to a void content of about 25% to 30% by
11). In the drawing-out work, wireless communications                                     tightening with lever block, etc. while giving vibration
were made and monitoring cameras were set at main                                         with a wooden maul, and then the squeezing was done
points, and the work situation was always checked by                                      with a squeezing machine (Fig. 12) with 6 jacks of




                       Fig. 10 Erection of catwalk                                                    Fig. 12 Squeezing cable machine
1 960 kN {200 tf} × 200 strokes installed around the                                                                         Carrier for erection

cable.
4.8 Erection of cable band                                                                                                                                            Carrier for erection

The cable band fitting positions were decided by
                                                                                                                                                                 Electric chain block
measuring the main-cable shape with electro-optical                                          Electric chain
distance measuring equipment during the night when                                           block

the effect of temperature is less. The end bands and
end stay bands were erected using an abutment crane                                                 Hanger rope               Cable band                          Cable band

and crane at the top of tower and other cable bands                                                                                                                      Hanger rope

were transported to and erected at the fitting positions
using an erecting carrier installed in each span. For the                                                                                                               Catwalk
cable band bolts, the axial force was introduced with
                                                                                                         Catwalk
a hydraulic bolt tensioner, and the axial force was
measured with an ultrasonic axial force meter (Fig. 13).
4.9 Erection of hanger rope                                                                                 Fig. 14 Procedure to extend hanger rope
The hanger rope was brought to the site after the final
length was decided reflecting the measuring results of
the main-cable shape when the pre-squeezing was                                            girders for the entire bridge.
completed and the sockets were attached. We adopted                                        5.2 Structural characteristics
two methods for erecting the hanger rope: one to erect                                     Main characteristics of the stiffening girder structure
from the upper side of the catwalk using the same                                          are described below. Fig. 15 shows the cross section
erecting carrier as for the cable bands and the other to                                   of the stiffening girder.
erect from the lower side of the catwalk using an erecting                                   (1) Adoption of flat hexagon box girder section with
carrier designed/manufactured anew (Fig. 14).                                                   fairing wind resistant
                                                                                             (2) For the hanger anchorage structure of the ordinary
5. Stiffening girder (section 1) work                                                           portion, we adopted the pin anchorage structure
5.1 Outline of work                                                                             manufactured from one thick steel plate without
The stiffening girder (section 1) work is outlined below.                                       reinforcing plate so that no stress concentration
  Work name                 Toll Road Project: Akinada                                          would occur, in consideration of the stress transfer.
                            Bridge Stiffening Girder                                         (3) For the anchorage structure on the girder side
                            (Section 1) Work                                                    of the short hanger portion, we used the bearing
  Type of order received Construction Work Joint                                                pressure anchorage structure using brackets to check
                            Venture                                                             the increase in sectional area of the hanger due to
  Construction period       From October 28, 1997 to                                            the stiffening girder out-of-plane buckling, thus
                            December 10, 1999                                                   securing the length of the short hanger.
  Work quantity             Steel weight about 4 800 t
  The work of Section 1 by the joint venture including                                          Typical section                               Section with short hanger in center span
                                                                                            (pin anchorage portion)                            (bearing pressure anchorage portion)
IHI was from the 1A on Kawajiri side to the field joint
FJ38 at the center of the center span, of the stiffening                                    1 500                     16 000 (Cable center spacing)                             1 500
                                                                                                    1 650                       12 700                                  1 650
                                                                                                            2 000 600 750                6 000          750 600 2 000


                       Bolt tensioner                 Cable
                                                                                                                            Asphalt pavement
                                                      To hydraulic pump unit                                                  ( t = 65 ) Proposed
                                                                                                                                         height
                                                                                                                                 2 500




                                                                                                            1.5%             1.5%                1.5%          1.5%
        58




                                                                               1 500 800




                                         Temperature sensor
                                                                                 2 380




                                         Probe

                                                                                                                                              Inspection
 Clamping bolt                                                                                                      Public utililies           car rail        Maintenance
                                                                                                                   9 000 (Inspection car rail spacing)         way
         Cable band                     Temperature sensor cable

                      Probe cable                                                                             8 000 (Web spacing)                7 660 (Web spacing)
                                                  Ultrasonic
                                                  measuring                                    3 000                                     13 000                             3 000
                                                  instrument                                                                             19 000

  Fig. 13 Bolt tensioner and ultrasonic axial force meter                                      Fig. 15 Stiffening girder cross section (unit : mm)
5.3 Fabrication                                                                             point of this bridge, the erection was made by
Blocks fabricated with a standard panel length of 12 m                                      holding a self-propelling barge at a fixed point that
and divided in 3 portions in the sectional direction were                                   allows mooring without anchoring, by means of
assembled in the factory yard in erection block. The                                        omnidirectional control propulsion equipment and
direct lifting block was made 24 m by assembling 2                                          automatic tracking equipment. Fig. 17 shows the
panels also in the bridge axial direction. For the yard                                     direct lifting of the center span using the self-
joint portion, the steel deck, side web, and lower flange                                   propelling barge. For the side spans between 1A
were welded, and for other portions without an                                              and 2P, the water depth was shallow and the self-
appearance problem, the HTB joining was done.                                               propelling barge could not sail, but since it was
5.4 Erection                                                                                outside sailing routes, we used a barge equipped
5.4.1 Erection method                                                                       with anchor mooring equipment and held it at a
For erecting the stiffening girder, we used the direct                                      fixed point by means of a winch.
lifting method to lift it directly from a barge held just
under the normal erection position with a lifting beam
installed on the main cable. When the water depth was
too shallow to use the direct lifting method, we used
the swing erection method to erect the block at its
normal position by alternately lifting it with the lifting
beam and hanger rope. Fig. 16 shows the outline of the
swing erection method.
   Since the girder movement is large during erection,
we adopted the all-hinge method using erection hinges
for the joint between blocks during the erection, thus
reducing the stress on the stiffening girder.
5.4.2 Characteristics of erection work
While adopting the above methods, we reduced the cost
and shortened the erection period by taking the following
measures.
   (1) Since the tidal current is fast and many ships                                         Fig. 17 Erection of main span by hoisting down
      sail in Menekoseto channel, the center span erection

             Barge mooring     Self-propelled barge held at fixed point   Anchorage hanger rope curtain releasing

                    Balance beam lowering

                      Slinging equipment

                           Hoisting

        Vertical-taking hanger rope drawing/anchoring
                                                                                                                    LB moving
                     LB releasing/moving
                                                                                                      LB moving
                          LB hoisting

        Vertical-taking hanger rope installation/removal


                Hanger rope drawing/installing                                                                                  Temporary suspended
                                                                                                                                hanger rope lowering
                   Lowering/block drawing

                Erection hinge/shear key fitting
                                                                                                                          Lowering · Drawing
                          Completion                                                    Hanger rope
                                                                                  drawing/anchoring



                                                                                                      LB moving LB moving
                                                                                      Hoisting             LB releasing LB releasing




                                                                                                                                      (Note) LB : Lifting Beam
                                                        Fig. 16 Swing erection block diagram
   (2) Since the girder section was small, we used one
     lifting beam for lifting the blocks by the direct lifting
     method. As a measure against the inclination of
     the lifted girder due to the dislocation between the
     center of gravity of the lifted girder in the axial
     direction of the bridge and the lifting equipment
     (balance beam), we provided the balance beam
     with 3 lifting points in the axial direction of the
     bridge and connected both ends with hydraulic
     jacks. For slinging the lifted block and balance
     beam, we used several types of methods because
     such conditions as design center of gravity,
     dislocation amount of the balance beam, and weight
     of the lifted block differ from block to block.
   (3) To facilitate the movement of the lifting beam
     to the erection position, we moved it with wheels
     on the main cable by means of a winch-drive
     system. The wheel was equipped with a hydraulic
     jack for riding over the cable bands of the main
     cable. As the wheels to run on the main cable, we
     used wooden ones so as not to damage the wires
     of the main cable. During the erection or when they
     were not used, they were fixed to the main cable
     with cable clamps using high-strength bolts. As a
     safety measure during the erection, the winch for
     running and winch for girder lifting were not
     interlocked.                                                              Fig. 18 Side span swing erection
   (4) Conventionally, temporary hanger ropes have
     been installed for the swing erection. But we used
     the hanger ropes of this equipment. Fig. 18 shows           tower/cable/stiffening girder, w stability against wind
     the swing erection of the side spans.                       during erection, and e closing moment using three-
5.4.3 Actual erection of stiffening girder                       dimensional and plane finite deformation analyses. We
Fig. 19 shows the erection sequence of the stiffening            had predicted such problems as sliding of the main
girders. The erection sequence was so decided that the           cable within the 3P tower top saddle, violation of route
construction period would be shortened in cooperation            limits, and exceeding the axial force of the links and
with the stiffening girder (section 2) work on the 4A            hanger ropes, but our analytical investigation confirmed
side from the center span. Also the erection start time          that the erection could be made without such problems.
of each block erection day was decided based on a tidal             As to the stability against wind, we received a report
current survey conducted in advance and the water                that it would not be sufficient against flutter (divergent
conditions. For erecting within the sailing route, the           vibration) during erection and conducted wind velocity
operation of the self-propelling barge from entry to             survey near the erection point and analytical investigation
leaving after completing the lifting was restricted to 60        based on Typhoon No. 19 in 1991. As a result, we
minutes, and the erection work was done under a detailed         confirmed that it could be improved to a safe level by
schedule based on general erection training and training         fixing the erected girder from the ground and the tower
to hold the self-propelling barge at a fixed point.              with wires before a typhoon and by connecting the
   Using the same procedure as for the girder erection,          main cable and the erected girder with the rope in an
the girder inspection car and work platform were erected         X pattern. Actually no typhoon came during the erection,
under the girder. The work platform was used for                 and we did not need to use the prepared wires.
splicing and painting the flange surfaces under the              5.4.5 Camber control
girder and was dismantled using a truck crane from above         The camber control was made jointly by Section 1 and
the girder after the erection was completed. The weather         Section 2 to check the work execution accuracy in stages
was fine and the erection work was completed as                  during and after the stiffening girder erection by comparing
scheduled.                                                       design values and measured values. Table 6 shows the
5.4.4 Erection calculation of stiffening girder                  measuring steps for camber control and Table 7 shows
Before the stiffening girder was erected, we (section 1          the measuring items for camber control. As to the
and section 2 jointly) extracted representative erection         vertical work quality completed of the stiffening girder,
steps and calculated q displacement of main                      Fig. 20 shows the differences between design values
                                                                                                           (a) Step 1


                                                                                                                                                                     · LB assembling
                                                 LB assembling                                                                                         LB assembling · 4A-side block wing erection
                                                                                                       Section 1/Section 2                                           · Center block erection
                           LB moving                                                 LB moving                                  LB moving
                        LB                                                                                   LB LB
                                                                                                                                                                                          LB assembling
                                                                                                     (Course range 560 000)

                 1A                                       2P                                                                                                       3P                         4A

                                                                                                                                                          Assembling block
                                                                                                                                                                (2 panels)


                                                                                                           (b) Step 2
                                                                                                                                                                          · Center span direct lifting
                                                                                                       Section 1/Section 2                                              LB erection
                                          LB                                LB                                                              LB                            · Side span swing erection


                                                                                                     (Course range 560 000)                                              Transfer
                                                                                Erection direction                         Erection direction                            platform
                 1A                                       2P                                                                                                       3P                         4A
                        Erection direction

                                                                                                                                                                           Assembling block


                                                                                                           (c) Step 3

                                                                                                                                                                                · Center span swing
                                                                                                       Section 1/Section 2                                              LB        erection
                                                                            LB                                                              LB                                  · Side span direct lifting/
                                                                                                                                                                                  swing erection
                             LB
                                                                                                                                           45 tfR/C
                             Transfer                                            Transfer            (Course range 560 000)         Transfer
                             platform Erection                 Erection          platform                                           platform      Erection    Erection
                                      direction                direction                                                                          direction   direction
                 1A                                       2P                                                                                               3P                                 4A


                                                                                                                                                              Assembling block
                                                                                                           (d) Step 4

                                                                                                                                                                           · Erection of closing block
                                                                                                                                                                           · Inspection car erection
                                                                                                       Section 1/Section 2                                              LB · Block connecting/bridge
                                                                            LB                                                              LB                               deck work
                             LB                                      45 tfR/C                                                              45 tfR/C                 45 tfR/C
                           Inspection car Transfer platform Transfer platform    Transfer platform   (Course range 560 000) Transfer platform         Inspection        Inspection
                                                                                                                                                      car               car
                                                                                                                                                                          Transfer platform
                 1A                                        2P                                                                                                      3P                         4A
 Vertical-taking
erection 3 blocks                              Vertical-taking
                                               7 blocks
                                                                                                                                                           Vertical-taking erection
                          Direct lifting                    Vertical-taking                           Direct lifting erection            Vertical-taking   3-division section assembling
     Erection
     method             erection 6 blocks                   9 blocks                                        24 blocks                    erection 8 blocks 14 blocks

     Vessel used           Deck barge                                                                 Self-propelled barge


                                                            Fig. 19 Erection sequence of stiffening girders (unit : mm)


         Table 6 Shape control measurement procedure                                                                      Table 7 Shape control measurement items
          Shape measuring timing                      Erection step               Remarks                             Item                                               Description
       Center span direct lifting                         Step 15                                           Temperature measuring Outside air temperature and surface temperature of main tower,
       erection                                           Step 25                                                                 cables, and stiffening girder
                                                                            During stiffening
       Center span swing erection                         Step 37                                           Tower top displacement Tilt of 2P and 3P main tower top portions
                                                                            girder erection
       Before center span closing                         Step 48                                            Splay saddle movement Movement of 1A and 4A anchorage splay saddles
       Center span temporary connecting completion        Step 50                                                   Cable sag        Vertical displacement of main cable of center span center portion

       After completion of field welding All rigid                                                          Vertical displacement of Vertical displacement at points in accordance with the progress
       of steel floor slabs                                                                                     stiffening girder    of stiffening girder erection
                                         connection       After erection of
       Before bridge deck paving is started Before paving stiffening girder
       Before work completion                         At completion
                                                                                                                                                          Table 8 List of dynamic monitoring use equipment
                                                                                                                                                                      Instrument used                                             Remarks
Difference between design value and measured value (mm)




                                                                                                                                                    Girder anemoscope/anemometer                                 Wind direction/wind velocity 2CH output
                                                          400
                                                                                                                                                    Voltage/current converter
                                                          350                                                                                                                                                    Direction normal to bridge axis
                                                          300                                                                                                      1/2L girder center                            Bridge axis direction
                                                                                                                                                                                                                 Vertical direction
                                                          250                                                                                                                                                    3 components in total
                                                          200                                                                                                                                                    Vertical direction
                                                                                                                                                                   1/2L girder end portion
                                                                                                                                                    Girder                                                       1 component in total
                                                          150                                                                                       speedmeter                                                   Direction normal to bridge axis
                                                          100                                                                                                      1/4L girder center                            Bridge axis direction
                                                                                                                                                                                                                 2 components in total
                                                           50                                                                                                                                                    Vertical direction
                                                                                                                                                                   1/4L girder end portion
                                                            0                                                                                                                                                    1 component in total
                                                                                                                                                    Anemoscope/anemometer (tower top)                            4-blade propeller
                                                          -50
                                                                                                                                                                   Tower top east bridge right-angle direction
                                                          -100
                                                             1A          2P                                                    3P       4A                        Tower top east bridge axis direction
                                                                                          Bridge axial direction                                    Servo type
                                                                                                                                                                  Tower top west bridge axis direction
                                                                                                                                                    accelerometer
                                                                    Fig. 20 Vertical finish of stiffening girder                                                  Tower web east bridge axis direction
                                                                                                                                                                   Tower web west bridge axis direction
                                                                                                                                                    Signal conditioner for accelerometer                         6CH/1 unit
                                                                                                                                                    Displacement TMD east bridge axis direction
and measured values.                                                                                                                                meter        TMD center bridge axis direction
5.4.6 Field observation                                                                                                                             Amplifier for displacement meter
The field observation was made for the following                                                                                                                   3P main tower base X component
purposes during the erection period and under the bridge                                                                                            Seismometer 3P main tower base Y component
service after completion after installing monitoring                                                                                                               3P main tower base Z component
instruments.                                                                                                                                                       4A Shimokamagari soil X component
  (1) During erection                                                                                                                               Seismometer 3A Shimokamagari soil Y component
     · Grasping and checking accuracy of structural                                                                                                                3A Shimokamagari soil Z component
                                                                                                                                                    3-component vector converter
       vibration characteristics
                                                                                                                                                    Board on     Main
     · Observation of wind response                                                                                                                 transmitting
                                                                                                                                                    side         Slave                                           For the slave, two boards each for
     · Grasping of actual bridge situation by monitoring                                                                                            Board on     Main                                            transmitting and receiving are installed
       and danger prediction                                                                                                                        receiving
                                                                                                                                                    side         Slave


                                                                                                                                                                                                                           3P anemoscope/anemometer


                                                                                                     1/2L point anemoscope/anemometer                                                                                      Tower top accelerometer 3CH
                                                                                                                                                         Voltage/current
                                                                                                                                                           converter
                                                                                                                                                                                                                              TMD displacement meter 2CH


                                                                                   1/2L point speedometer 4CH           Z        X      Y       Z                                                                             Tower web accelerometer 2CH

                                                                                   3/4L point speedometer 3CH           Z        Y      Z

                                                                           24-channel optical transmission receiver


                                                                                                                      Optical attenuator
                                                          Conditioner                                                 SVA-S11500 ( 20 dB )                                                   Voltage-
                                                                                 Light-
                                                           SC - 800                                                                                                                            light
                                                                                voltage        D/A       O/E                                                            E/O        A/D
                                                           (16CH)                                                                                                                           conversion             Measurement control panel
                                                                                                                                        Optical cable                                         board                (3P lower horizontal strut)
                                                                               conversion                                                SM 10/125
                                                                                 mode




                      Field observation equipment                                             FB-                                                                                    3F lower horizontal strut
                                                                                              200
                         (8CH signal processor)


                                                                                                      9821



                                                                              Control building
                                                                                                                                                                                                                 3P seismometer     3P seismometer
                                                                                                                                             This operation control range
                                                                                                                                                                                                                  3 components       3 components
                                                                                                                      Fig. 21 Dynamic monitoring system
  (2) In service                                            against wind using in advance some portions of this
     · Bridge behavior observation under typhoon and        system.
       earthquake conditions
     · Data recording at occurrence of excitation such
                                                            6. Conclusion
       as typhoon and earthquake                            We have outlined the construction of the “Akinada
     · Diagnosis of bridge soundness                        Bridge.” From just after the order was received, IHI’s
  Table 8 shows a list of instruments used for field        Design, Factory, and Erection Department and Technical
observation after the bridge was completed. Fig. 21         Research Institute were united to execute this work. As
shows the final entire system. The hatched portions are     a result, we were able to meet the customer’s
the work execution range of the joint venture including     requirements and completed the work without incident.
IHI. During the erection, we observed the girder behavior

				
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