Method of constructing the main tower

Abstract

To provide a construction method for a main tower capable of reducing work at a construction site and shortening a construction period in the main tower of an extradosed bridge or a cable-stayed bridge.SOLUTION: A main tower includes a steel shell member 12, an inner concrete part 13 provided inside the steel shell member 12, and an outer concrete part 14 provided outside the steel shell member 12. A diagonal member fixing steel shell member 12b to which a diagonal member is fixed is manufactured in a factory or the like in a state in which an outer pipe 25b through which the diagonal member is inserted is attached. When the diagonal member fixing steel shell member 12b is installed at a predetermined position, a part of the outer pipe 25b passes through the outer concrete part 14 one step lower than the diagonal member fixing steel shell member 12b. Therefore, the outer concrete part 14 of each stage is formed in parallel with or in front of or behind the inner concrete part 13 of the next higher stage after the diagonal member fixing steel shell member 12b of the stage is installed.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for constructing a main tower in a bridge including a main tower, a main girder, and a plurality of diagonal members fixed to the main tower and the main girder.

Background Art

[0002] In an extradosed bridge or a cable-stayed bridge, a plurality of diagonal members are fixed to a main tower and a main girder. The plurality of diagonal members include those fixed to one side in the bridge axis direction of the main tower and those fixed to the other side. In order to support the horizontal component of the force transmitted from the plurality of diagonal members to the main tower, a plurality of steel shell members having a cylindrical shape are arranged in the main tower, and a pair of diagonal members are fixed to both ends in the bridge axis direction of each steel shell member (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the fields of civil engineering and architecture, it is required to reduce the work at the construction site and shorten the construction period. The same is also required when constructing a main tower having the above structure. In view of such problems, an object of the present invention is to provide a method for constructing a main tower that can reduce the work at the construction site and shorten the construction period in the construction of a main tower having the above structure.

Means for Solving the Problems

[0005] To solve the above problems, one aspect of the present invention provides a method for constructing a main tower in a bridge (1) comprising a main tower (2), a main girder (3), and a plurality of diagonal members (4) including one end fixed to the main tower and the other end fixed to the main girder, wherein the main tower comprises a plurality of steel shell members (12) stacked on top of each other, each including a steel cylindrical part (11) that opens at the top and bottom, an internal concrete part (13) formed inside the cylindrical part of the plurality of steel shell members, and an external concrete part formed outside the cylindrical part of the plurality of steel shell members (14) (a) a step of manufacturing a plurality of the steel shell members in a factory and / or on-site yard, wherein the plurality of steel shell members comprises a lower steel shell member (12a) to be positioned at the lowest level and a plurality of diagonal member anchoring steel shell members (12b) to be positioned above the lower steel shell member, the diagonal member anchoring steel shell members further comprising an outer cylindrical tube (25b) that penetrates the walls at both ends of the cylindrical portion (11b) in the bridge axis direction to accommodate one end of the diagonal member; and (b) a step of constructing the base (6) of the main tower. (c) a step of fixing the lowest steel shell member to the base; (d) a step of pouring concrete into at least both ends in the bridge axis direction within the cylindrical portion (11a) of the lowest steel shell member in order to form the internal concrete portion within the cylindrical portion; and (e) setting up a first formwork (46,48) (n steps) that accommodates at least both ends in the bridge axis direction of the steel shell member (n steps of steel shell member, n is a positive integer) that is located at the uppermost position at that time, and placing the diagonal brace anchoring steel shell member (n+1 steps) on top of the steel shell member (n steps). The step is to house a part of the outer cylindrical pipe extending from the diagonal member anchoring steel shell member (n+1 stages) within the first formwork (n stages); (f) to pour concrete to embed the outer cylindrical pipe in at least both ends in the bridge axis direction within the diagonal member anchoring steel shell member (n+1 stages) in order to form a part of the internal concrete portion, and to pour concrete within the first formwork (n stages) in order to form a part of the external concrete portion; and (g) to repeat steps (e) and (f). Here, "the X" (where X is a component) refers to a specific X among a plurality of Xs that was described immediately before.For example, in step (e), "the steel shell member" refers to "the steel shell member located at the uppermost position at that time," as described immediately before.

[0006] According to this embodiment, since steel shell members with the outer casing already attached are used in the factory or site yard, there is no need to attach the outer casing to the steel shell members at the installation location at the construction site, reducing work at the installation location and shortening the construction period. Furthermore, since the outer concrete section of each stage is formed in parallel with or ahead of the inner concrete section of the stage above, rather than in parallel with the inner concrete section of the same stage, the outer concrete section of each stage that partially accommodates the outer casing contained in the steel shell member of the stage above can be formed efficiently.

[0007] In the above embodiment, step (a) may include attaching internal reinforcing bars (17) to be placed in the cylindrical portion (11) of the steel shell member (12) to the cylindrical portion, and attaching connecting reinforcing bars (18) to the cylindrical portion of the steel shell member, the lower part of which is placed in the cylindrical portion of the steel shell member and the upper part which protrudes into the cylindrical portion of another steel shell member to be placed on top of the steel shell member.

[0008] According to this embodiment, since the internal reinforcement and connecting reinforcement are installed in a factory or the like, the work of installing them at the installation site of the steel shell member can be omitted, and the construction period is shortened.

[0009] In the above embodiment, step (b) may include installing a plurality of main reinforcing bars (10) in the base (6) that extend upward and are to be embedded in the outer concrete portion (14).

[0010] According to this embodiment, since it is not necessary to place main reinforcement in the internal concrete portion, when placing the steel shell member, including the internal reinforcement, at the installation site, the main reinforcement does not interfere with the internal reinforcement, making it easier to place the steel shell member.

[0011] In the above embodiment, step (a) includes holding a sheath (10) which is disposed within the cylindrical portion (11) and extends in the direction of extension of the main tower (2) within the cylindrical portion; step (e) includes connecting the sheath contained in the mounted diagonal member anchoring steel shell member (12b) to another sheath located below it; the construction method may further include (h) inserting tension members (15) into the interconnected sheaths; and (i) after steps (g) and (h), tensioning the tension members.

[0012] In this configuration, the internal concrete sections, which are cast at each stage and do not contain main reinforcement, are integrated by tensioning members.

[0013] In the above embodiment, the main tower (2) includes hollow portions (9) within the cylindrical portions (11) of a plurality of steel shell members (12) that separate the internal concrete portions (13) into two in the direction of the bridge axis, and step (a) includes attaching a second formwork (16) to the cylindrical portion of each of the steel shell members in a removable manner to define the interface between the two internal concrete portions and the hollow portions, and steps (d) and (f) may include not pouring concrete into the hollow portions and removing the second formwork after pouring concrete into the cylindrical portions.

[0014] According to this embodiment, since the steel shell member 12 is placed at the installation site with the second formwork already attached, the installation work of the second formwork at the installation site can be omitted, and the construction period is shortened.

[0015] In the above embodiment, the first formwork (46, 48) may include a precast concrete formwork (46).

[0016] According to this embodiment, since the precast concrete formwork constitutes part of the main tower, the removal work can be omitted, and the construction period can be shortened.

[0017] In the above embodiment, the external concrete portion (14) may be spaced apart in the bridge axis direction so as to be connected to each other via a plurality of steel shell members (2).

[0018] According to this embodiment, even if the steel shell member deforms due to tensile force from the diagonal members after the construction of the main tower, the deformation mainly occurs in the center of the steel shell member in the bridge axis direction, thus preventing cracks from forming in the outer concrete portion. Furthermore, if the outer concrete portion were to be provided around the entire perimeter of the steel shell member, it would be necessary to form the central part of the outer concrete portion in the bridge axis direction after the installation of the diagonal members to prevent cracking. However, in this embodiment, this work is not required, and the construction period can be shortened.

[0019] In the above embodiment, the diagonal brace anchoring steel shell member (12b) is placed on another steel shell member (12) via a height adjustment structure (22), and two steel shell members (12) that are adjacent to each other vertically are adjacent to each other via the height adjustment structure such that the cylindrical portions (11) are spaced apart from each other, and the height adjustment structure may include a first support portion (29) provided on one of the two steel shell members, a height adjustment bolt (30) that is screwed into the first support portion and has an axis parallel to the vertical direction, and a second support portion (31) provided on the other of the two steel shell members, to which the tip of the height adjustment bolt abuts or into which the height adjustment bolt is screwed.

[0020] According to this embodiment, the height adjustment of a steel shell member placed on top of another steel shell member becomes easier. Furthermore, since the cylindrical portions of adjacent steel shell members do not come into contact with each other, unevenness of the upper and lower edges of the cylindrical portions is tolerated, and high precision is not required in the manufacturing of the cylindrical portions, allowing them to be manufactured at low cost.

[0021] In the above aspect, a horizontal position adjustment structure (23) for adjusting the horizontal position of the steel shell member arranged above is provided between two adjacent steel shell members (12) vertically. The horizontal position adjustment structure may include a third support portion (39) fixed to one of the two steel shell members, a horizontal position adjustment bolt (40) screwed into the third support portion and having an axis parallel to the horizontal direction, and a abutting piece (41) fixed to the other of the two steel shell members and against which the tip of the horizontal position adjustment bolt abuts.

[0022] According to this aspect, it becomes easy to adjust the horizontal position of the steel shell member placed on top of another steel shell member.

[0023] In an aspect including both the above height adjustment structure (22) and horizontal position adjustment structure (23), the first support portion (29) is fixed to the outer peripheral surface of the cylindrical portion (11) of one of the two steel shell members (12) and includes a first steel plate (32) having a horizontal main surface, a first through hole (33) through which the height adjustment bolt (30) is inserted through the first steel plate, and a first nut (34) screwed onto the height adjustment bolt and locked to the first steel plate. The second support portion (31) is fixed to the outer peripheral surface of the cylindrical portion of the other of the two steel shell members and includes a second steel plate (35) having a horizontal main surface, a second through hole (36) through which the height adjustment bolt is inserted through the second steel plate, and a second nut (37) screwed onto the height adjustment bolt and locked to the second steel plate. The third support portion (39) is fixed to the outer peripheral surface of the cylindrical portion of one of the two steel shell members and the first steel plate and includes a third steel plate (42) having a main surface parallel to the vertical direction, and a third nut (43) fixed to the third steel plate and to which the horizontal position adjustment bolt (40) is screwed. The height adjustment structure and the horizontal position adjustment structure may be configured such that the upper end of the third steel plate can be located above the second steel plate, or the lower end of the third steel plate can be located below the second steel plate.

[0024] According to this aspect, since the third steel plate reinforces the bending rigidity of the first steel plate, the amount of steel used can be reduced.

Effect of the Invention

[0025] According to the above aspect, there is provided a method for constructing a main tower including a steel shell member with diagonal members fixed to both ends in the bridge axis direction, which can reduce the work load at the construction site and shorten the construction period.

Brief Description of the Drawings

[0026] [Figure 1] Perspective view of the upper part of the main tower according to the embodiment [Figure 2] Front view of the main tower according to the embodiment [Figure 3] Explanatory drawing showing the construction method of the main tower according to the embodiment (A: Cross-sectional view perpendicular to the bridge width direction (A-A cross-sectional view in FIG. B), B: Horizontal cross-sectional view (B-B cross-sectional view in FIG. A)) [Figure 4] Explanatory drawing showing the construction method of the main tower according to the embodiment (A: Cross-sectional view perpendicular to the bridge width direction (A-A cross-sectional view in FIG. B), B: Horizontal cross-sectional view (B-B cross-sectional view in FIG. A)) [Figure 5] Explanatory drawing showing the construction method of the main tower according to the embodiment (A: Cross-sectional view perpendicular to the bridge width direction (A-A cross-sectional view in FIG. B), B: Horizontal cross-sectional view (B-B cross-sectional view in FIG. A)) [Figure 6] Explanatory drawing showing the construction method of the main tower according to the embodiment (A: Cross-sectional view perpendicular to the bridge width direction (A-A cross-sectional view in FIG. B), B: Horizontal cross-sectional view (B-B cross-sectional view in FIG. A)) [Figure 7] Explanatory drawing showing the construction method of the main tower according to the embodiment (A: Cross-sectional view perpendicular to the bridge width direction (A-A cross-sectional view in FIG. B), B: Horizontal cross-sectional view (the left side is the B1-B1 cross-sectional view in FIG. A, and the right side is the B2-B2 cross-sectional view in FIG. A)) [Figure 8] Explanatory drawing showing the construction method of the main tower according to the embodiment (A: Cross-sectional view perpendicular to the bridge width direction (A-A cross-sectional view in FIG. B), B: Horizontal cross-sectional view (the left side is the B1-B1 cross-sectional view in FIG. A, and the right side is the B2-B2 cross-sectional view in FIG. A)) [Figure 9] Plan view of the cylindrical part (including other members to be confirmed by welding, etc.) according to the embodiment [Figure 10] Front view of the height adjustment structure and horizontal position adjustment structure of the steel shell member according to the embodiment. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a perspective view of the main tower 2 of the bridge 1 according to the embodiment (the upper left is partially omitted to show the interior), and Figure 2 is a partial cross-sectional front view of the bridge 1 according to the embodiment.

[0028] As shown in Figures 1 and 2, the bridge 1 is an extradosed bridge comprising a main tower 2, a main girder 3, and a plurality of diagonal members 4 (in Figure 2, the diagonal members 4 other than the one located at the very bottom are not shown).

[0029] The main tower 2 includes a base 6 extending upward from the pier 5, an anchoring section 7 extending upward from the base 6 to which a plurality of diagonal members 4 are fixed, and a top section 8 extending upward from the anchoring section 7 (the top section 8 is not shown in Figure 1). In this embodiment, a pair of main towers 2 are provided that extend diagonally upward from both ends of the pier 5 in the bridge width direction so as to be inclined outward in the bridge width direction. However, the main towers 2 may extend vertically, or one main tower 2 may be provided so as to extend upward from the center of the main girder 3 connected to the pier 5 in the bridge width direction, or the main towers 2 may be inclined in the bridge axis direction. The main tower 2 includes a hollow section 9 extending in the direction of the main tower 2's extension, and the hollow section 9 is configured so that workers can pass through it for inspection and other maintenance after the bridge 1 is completed.

[0030] The base 6 and the top 8 are made of reinforced concrete and include main reinforcement bars 10 (see Figure 3) that extend in the direction of extension of the main tower 2 and distribution reinforcement bars (not shown) that extend in the horizontal direction.

[0031] The anchorage section 7 includes a plurality of steel shell members 12 stacked on top of each other along the extension direction of the main tower 2, including a cylindrical section 11 with openings at the top and bottom; two internal concrete sections 13 formed at both ends in the bridge axis direction within the cylindrical section 11; an external concrete section 14 formed outside the cylindrical section 11 and spaced apart in the bridge axis direction; and a plurality of tensioning members 15 that introduce tension in the extension direction of the main tower 2. In the anchorage section 7, the hollow section 9 is provided in the central part in the bridge axis direction within the cylindrical section 11, and the internal concrete section 13 is spaced apart in the bridge axis direction by the hollow section 9. The external concrete section 14 has main reinforcement bars 10 (see Figure 3) and distribution reinforcement bars (not shown) embedded in it.

[0032] The multiple steel shell members 12 include one bottom-level steel shell member 12a positioned at the lowest level, and multiple diagonal member anchoring steel shell members 12b positioned above the bottom-level steel shell member 12a to which the diagonal members 4 are fixed. Hereinafter, for members included in the steel shell members 12, the subscript "a" will be added to the members included in the bottom-level steel shell member 12a, and the subscript "b" will be added to the members included in the diagonal member anchoring steel shell members 12b. When there is no need to distinguish between them, the subscripts "a" and "b" will be omitted.

[0033] As shown in Figures 1, 4, 7, 9, and 10, each steel shell member 12 has a formwork 16 used to form the internal concrete section 13, which is removably attached inside the cylindrical section 11. Each steel shell member 12 includes a cylindrical section 11, internal reinforcing bars 17 and connecting bars 18 embedded in the internal concrete section 13, anti-slip members 19 protruding from the inner and outer circumferential surfaces of the cylindrical section 11 and embedded in the internal concrete section 13 and the external concrete section 14, a sheath 20 embedded in the internal concrete section 13 through which a tensioning member 15 is inserted, a suspension fitting 21 fixed to the cylindrical section 11, a height adjustment structure 22 for adjusting the vertical position of two vertically adjacent steel shell members, and a horizontal position adjustment structure 23 for adjusting the horizontal position of two vertically adjacent steel shell members. The lowest steel shell member 12a further includes a fixing bracket 24a for fixing to the base 6. The diagonal brace anchoring steel shell member 12b further includes an outer cylindrical tube 25b through which the diagonal brace 4 is inserted. Each steel shell member 12 is assembled in the factory with these members included, and the formwork 16 is attached.

[0034] The cylindrical portion 11, in plan view, has the shape of an athletics track (oval), that is, a shape in which the shorter side of a rectangle is replaced by a semicircle that is convex outwards. The cylindrical portion 11 may be manufactured by curving a single steel plate into a cylindrical shape and joining both ends in the circumferential direction to each other by welding or fasteners, or by arranging multiple steel plates to form a cylindrical shape and joining them to each other by welding or fasteners. Furthermore, the shape of the cylindrical portion 11 in plan view may be a semi-ellipse or arc for the semicircular portion, or the overall shape may be an ellipse or a rectangle.

[0035] The formwork 16 is used to define the interface between the internal concrete section 13 and the hollow section 9, and is attached to the cylindrical section 11 by fasteners such as bolts (not shown) so that it can be removed after the internal concrete section 13 is formed. Both ends of the formwork 16 in the bridge width direction abut against the inner circumferential surface of the cylindrical section 11. The formwork 16 is preferably made of steel. The formwork 16a of the lowest steel shell member 12a has a flat plate shape. The formwork 16b of the diagonal brace anchoring steel shell member 12b abuts against the opening surface on the upper end side of the outer cylindrical pipe 25b. The formwork 16b of the diagonal brace anchoring steel shell member 12b has a plate shape that is bent inward in the bridge axis direction of the cylindrical section 11b in the middle of the vertical direction. By having such a bent shape, the part of the formwork 16b that abuts against the outer cylindrical pipe 25b is perpendicular to the extending direction of the outer cylindrical pipe 25b.

[0036] The internal reinforcement bars 17 include bars extending in the direction of the bridge axis, bars extending in the direction of the bridge width, and bars extending in the direction of the extension of the main tower 2, and are attached to the cylindrical portion 11 such that the entire structure is located within the space enclosed by the bridge axis end of the cylindrical portion 11 and the formwork 16.

[0037] The connecting reinforcement bars 18 are attached to the cylindrical portion 11 via internal reinforcement bars 17 such that their lower ends are located within the space enclosed by the end of the cylindrical portion 11 in the bridge axis direction and the formwork 16, and their upper ends protrude above the upper ends of the cylindrical portion 11 and the formwork 16. The upper part of the connecting reinforcement bars 18 protrudes into the space enclosed by the end of the cylindrical portion 11 in the bridge axis direction of another steel shell member 12, which is placed on top of the steel shell member 12 to which the connecting reinforcement bars 18 are attached, and the formwork 16. The lower end of the connecting reinforcement bars 18a attached to the lowest steel shell member 12a is located near the lower end of the cylindrical portion 11a. Among the connecting reinforcement bars 18b attached to the diagonal member anchoring steel shell member 12b, the lower end of the connecting reinforcement bars 18b that are arranged to overlap the outer cylindrical pipe 25b when viewed from above is located above the outer cylindrical pipe 25b so as not to obstruct the arrangement of the outer cylindrical pipe 25b. Of the connecting reinforcement bars 18, the upper end of the connecting reinforcement bar 18b, which is positioned to overlap the outer cylindrical pipe 25b when viewed from below, is located below the outer cylindrical pipe 25b of the other steel shell member 12 placed above it. It is preferable that the connecting reinforcement bars 18 have hooks at their lower and upper ends. In particular, it is preferable that the ends of the connecting reinforcement bars 18, which are set to be short so as not to obstruct the arrangement of the outer cylindrical pipe 25b, have hooks with a bending angle of 180°. The connecting reinforcement bars 18 reinforce the vertical tensile strength of the internal concrete portion 13.

[0038] The shear prevention member 19 includes a headed stud fixed to the inner circumferential surface of the cylindrical portion 11 by welding or the like and embedded in the internal concrete portion 13, and a headed stud fixed to the outer circumferential surface of the cylindrical portion 11 by welding or the like and embedded in the external concrete portion 14. The shear prevention member 19 may use angle material or perforated steel plate dowels instead of headed studs, or these may be used in combination.

[0039] The sheath 20 is temporarily fixed to the internal reinforcement 17 at the factory so that its upper end is at the same height as or above the upper end of the cylindrical section 11. At the construction site, after the steel shell member 12 containing the sheath 20 is placed on top of other steel shell members 12, the sheath 20 of the other steel shell member 12 is joined to the sheath 20 of the other steel shell member 12 by a coupler sheath joint or the like. In a plan view, the sheath 20 is placed in a total of four locations, two in each of the two internal concrete sections 13. In each internal concrete section 13, the two sheaths 20 are spaced apart from each other in the bridge width direction.

[0040] As shown in Figure 9, the lifting fitting 21 includes a fixing part 26 fixed to the outer surface of the cylindrical part 11 by welding or fasteners, a U-shaped fitting 27, and a shaft part 28 that connects both ends of the U-shape of the fitting 27 to the fixing part 26 so as to be rotatable around the circumferential direction of the cylindrical part 11 as its axis. The lifting fitting 21 is used to lift the steel shell member 12 with a lifting machine such as a crane (not shown).

[0041] As shown in Figure 10, the height adjustment structure 22 includes a first support portion 29 provided on the upper part of the outer surface of the cylindrical portion 11 of the lower steel shell member 12, a height adjustment bolt 30 that is screwed into the first support portion 29 and has an axis parallel to the vertical direction, and a second support portion 31 provided on the lower part of the outer surface of the cylindrical portion 11 of the upper steel shell member 12, into which the height adjustment bolt 30 is screwed.

[0042] The first support portion 29 includes a first steel plate 32 having a horizontal main surface, fixed to the outer circumferential surface of the cylindrical portion 11 of the steel shell member 12 located below by welding or the like, a first through hole 33 through the first steel plate 32 for inserting a height adjustment bolt 30, and a first nut 34 that screws onto the height adjustment bolt 30 and cooperates with the head of the height adjustment bolt 30 to clamp the first steel plate 32. The second support portion 31 includes a second steel plate 35 having a horizontal main surface, fixed to the outer circumferential surface of the cylindrical portion 11 of the steel shell member 12 located above by welding or the like, a second through hole 36 through the second steel plate 35 for inserting a height adjustment bolt 30, and a pair of second nuts 37 that screws onto the height adjustment bolt 30 and clamp the second steel plate 35. To increase the bending rigidity of the second steel plate 35, the height adjustment structure 22 may further include an auxiliary steel plate 38 fixed by welding or the like to the upper surface of the second steel plate 35 and the outer peripheral surface of the cylindrical portion 11 of the steel shell member 12 positioned above, so as viewed from the direction of protrusion from the cylindrical portion 11, it abuts the second steel plate 35 at a right angle. By changing the position of the second nut 37 relative to the height adjustment bolt 30, the distance between the first steel plate 32 and the second steel plate 35 changes. This makes it possible to adjust the height (vertical position) of the steel shell member 12 positioned above relative to the steel shell member 12 positioned below. Note that instead of providing a pair of second nuts 37, one may be provided to lock the second steel plate 35 from below. Alternatively, the second nut 37 may be omitted, the tip of the height adjustment bolt 30 may strike the second steel plate 35, the first nut 34 may be supported from below by the first steel plate 32, and the height of the upper steel shell member 12 may be adjusted by changing the position of the first nut 34 relative to the height adjustment bolt 30.

[0043] The horizontal position adjustment structure 23 includes a third support portion 39 provided on the upper part of the outer circumferential surface of the lower steel shell member 12, a horizontal position adjustment bolt 40 screwed into the third support portion 39 and having an axis parallel to the horizontal direction, and a strike piece 41 provided on the lower part of the outer circumferential surface of the upper steel shell member 12, against which the tip of the horizontal position adjustment bolt 40 strikes.

[0044] The third support portion includes a third steel plate 42 having a main surface parallel to the vertical direction, fixed to the side end of the first steel plate 32 by welding or the like so as to abut the first steel plate 32 at a right angle when viewed from the direction of protrusion from the cylindrical portion 11, and fixed to the outer circumferential surface of the cylindrical portion 11 of the steel shell member 12 located below by welding or the like, and fixed to the main surface of the third steel plate 42 and a third nut 43 into which a horizontal position adjustment bolt 40 is screwed. The third nut 43 is fixed to the main surface of the third steel plate 42 by welding or the like at a part of its outer circumferential surface. The upper end of the third steel plate 42 and the third nut 43 are located above the lower end of the cylindrical portion 11 of the steel shell member 12 located above. The third steel plate 42 increases the bending rigidity of the first steel plate 32 by abutting the first steel plate 32 at a right angle. The horizontal position adjustment structure 23 and the height adjustment structure 22 are provided in pairs on opposite sides in the bridge axis direction and in pairs on opposite sides in the bridge width direction. By changing the position of the horizontal position adjustment bolt 40 relative to the third nut 43, the horizontal position of the upper-positioned steel shell member 12 relative to the lower-positioned steel shell member 12 can be adjusted.

[0045] As shown in Figure 4, the fixing bracket 24a is an angle material including a vertical piece fixed to the lower end of the outer surface of the cylindrical portion 11a by welding or fasteners, and a horizontal piece extending outward from the lower end of the vertical piece relative to the cylindrical portion 11a. The lower surface of the horizontal piece of the fixing bracket 24a is flush with the lower edge of the cylindrical portion 11a. The horizontal piece of the fixing bracket 24a is fixed to the upper surface of the base 6 by anchor bolts (not shown), etc. In a plan view, the fixing brackets 24a are provided at four locations near the point where the cylindrical portion 11a changes from a straight section to a semicircular section.

[0046] As shown in Figure 7, the outer tube 25b is a cylindrical member made of steel or resin into which one end of the diagonal member 4 (see Figure 1) is inserted. The peripheral wall of the cylindrical portion 11b of the diagonal member anchoring steel shell member 12b is provided with a through hole 44b through which the outer tube 25b is inserted. In this embodiment, the pair of outer tubes 25b attached to one diagonal member anchoring steel shell member 12b are not symmetrical (left and right refer to left and right in the plane of Figure 7), because the lengths of the main girders 3 extending from the main tower 2 to the left and right are different. This embodiment can be applied regardless of whether or not it is symmetrical.

[0047] In Figure 2, the main girder 3, shown in cross-section, extends in the direction of the bridge axis and forms a rigid frame structure with the main tower 2 and pier 5. The main girder 3 is a box girder made of prestressed concrete, but it may be a different type of concrete girder or a steel girder. The pier 5 and the main girder 3 are provided with a passage 45 that communicates with the hollow section 9 provided in the main tower 2 and extends parallel to the bridge width direction.

[0048] As shown in Figures 1 and 2, the diagonal member 4 includes a cable that is anchored to the main tower 2 at one end and to the main girder 3 at the other end to receive tensile force, and extends diagonally such that one end is higher than the other when viewed from the bridge width direction.

[0049] Next, the construction method of the main tower 2 will be explained with reference to Figures 2 to 8. Note that the main reinforcement bars 10 are not shown in Figure A of Figures 4 to 8.

[0050] At the factory, workers manufacture the steel shell members 12 and attach the formwork 16 to the steel shell members 12. The steel shell members 12 are then transported from the factory to the construction site. However, all or part of the assembly of the steel shell members 12, or the attachment of the formwork 16 to the steel shell members 12, may be carried out not at the factory, but at a site yard such as a workspace or material storage area located near the place where the steel shell members 12 are to be installed.

[0051] At the construction site, first, as shown in Figure 3, workers construct the base 6 using cast-in-place concrete. From the upper surface of the constructed base 6, the main reinforcing bars 10, which are to be embedded in the external concrete section 14 (see Figure 1), extend outwards. The main reinforcing bars 10 are spliced ​​and extended as needed before their upper ends are embedded in the concrete. Precast concrete formwork (not shown) may be used as the formwork for constructing the base 6.

[0052] Next, as shown in Figure 4, the worker places the lowest steel shell member 12a on the upper surface of the base 6 using a lifting machine such as a crane (not shown). Then, the worker fastens the fixing bracket 24a to the base 6 with anchor bolts or the like (not shown), thereby fixing the lowest steel shell member 12a to the upper surface of the base 6.

[0053] Next, as shown in Figure 5, the worker pours concrete into the area enclosed by the peripheral walls on both ends of the cylindrical portion 11a of the lowest steel shell member 12a in the bridge axis direction and the formwork 16a, thereby forming internal concrete portions 13 at both ends of the cylindrical portion 11a in the bridge axis direction. The worker then removes the formwork 16a.

[0054] Next, as shown in Figure 6, the workers install precast concrete formwork 46 (hereinafter referred to as "PCa formwork 46") to accommodate both ends of the lowest steel shell member 12a in the bridge axis direction, that is, the parts where the internal concrete section 13 is formed. The PCa formwork 46 has a U-shape in plan view and two pieces together accommodate one end of the lowest steel shell member 12a in the bridge axis direction. The pair of PCa formwork 46 are arranged so that the ends of the U-shape face each other in plan view, that is, they form a rectangle with a break in the middle in plan view. In plan view, one end of the U-shape of each PCa formwork 46 abuts against the outer surface of the cylindrical section 11, and a gap 47 is created between the other ends.

[0055] Next, as shown in Figure 7, the worker places the other diagonal brace anchoring steel shell member 12b on top of the lowest steel shell member 12a using a lifting machine such as a crane (not shown), and adjusts the height and horizontal position of the placed diagonal brace anchoring steel shell member 12b using the height adjustment structure 22 and the horizontal position adjustment structure 23 (see Figure 10). At this time, the cylindrical parts 11 of the two steel shell members 12 stacked vertically are spaced apart, and the distance between them is smaller than the maximum size of the coarse aggregate of the concrete used to form the internal concrete part 13, which is about 20 mm. In addition, the outer cylindrical tube 25b of the placed diagonal brace anchoring steel shell member 12b is inserted into the gap 47 between two pairs of PCa formwork 46 located one level below it.

[0056] Next, as shown in Figure 8, the worker installs formwork 48 to fill the gap 47. The outer cylindrical tube 25b of the diagonal brace anchoring steel shell member 12b one level above penetrates the formwork 48. The formwork 48 works in cooperation with the PCa formwork 46 to function as formwork for forming the outer concrete section 14. The worker pours concrete into the area surrounded by the cylindrical section 11a of the lowest steel shell member 12a, the PCa formwork 46, and the formwork 48 to form the outer concrete section 14 of that level, and also pours concrete into the area surrounded by the inner circumferential surfaces on both ends of the cylindrical section 11b of the diagonal brace anchoring steel shell member 12b one level above, in the bridge axis direction, and the formwork 16b, to form the inner concrete section 13 at both ends of the cylindrical section 11b in the bridge axis direction. Once the poured concrete is ready for demolding, the worker removes the formwork 16b and 48. The PCa formwork 46 integrates with the external concrete section 14 to form part of the anchorage section 7 of the main tower 2. Although the gap between the two stacked steel shell members 12 is not sealed, the gap is about 20 mm, which is smaller than the maximum size of the coarse aggregate in the concrete. Therefore, there is only a small amount of concrete leakage from the gap to form the internal concrete section 13, and this does not pose a problem.

[0057] Subsequently, the workers repeat the work described in Figures 6 to 8. When repeating, "lowest steel shell member 12a" in the descriptions of Figures 6 and 7 should be read as the steel shell member 12 located at the top at that time, and "lowest steel shell member 12a" in the description of Figure 8 should be read as the steel shell member 12 one level below the newly placed diagonal brace anchoring steel shell member 12b. The order of the work described in Figures 6 to 8 may be changed if the formation of the lower outer concrete section 14 occurs after the installation of the upper steel shell member 12 and the PCa formwork 46 and formwork 48, and the formation of the upper inner concrete section 13 occurs after the installation of the upper steel shell member 12.

[0058] At the top of the anchorage section 7 (see Figure 2), the workers form an internal concrete section 13 inside the cylindrical section 11b of the diagonal brace anchoring steel shell member 12b, and after installing the top PCa formwork 46, they do not place the steel shell member 12 on top of it, but instead close the gap 47 with formwork 48 to form the top external concrete section 14. Then, as shown in Figure 2, the workers insert a tensioning member 15 into the sheath 20 and tension the tensioning member 15 to introduce tension in the direction of extension of the main tower 2. In this way, the anchorage section 7 of the main tower 2 is constructed.

[0059] After the anchoring section 7 is constructed, the workers will construct the top section 8 with cast-in-place concrete. Precast concrete formwork (not shown) may be used as the formwork for constructing the top section 8.

[0060] As shown in Figure 1, in the portion of the steel shell member 12 that is exposed from the external concrete portion 14, the gap between two steel shell members 12 that are stacked on top of each other is sealed with a coating material 49.

[0061] As shown in Figures 1 and 2, after the construction of the main tower 2, the workers construct the main girder 3 using the cantilever erection method, etc., and erect the diagonal members 4 from the lower section of the main tower 2. The workers insert one end of the diagonal member 4 into the outer cylindrical pipe 25b and fix the other end of the diagonal member 4 to the surface defined by the formwork 16 in the internal concrete section 13 using the anchoring device 50.

[0062] The effects and advantages of the main tower 2 and its construction method according to this embodiment will be described.

[0063] As shown in Figures 4 and 7, the steel shell member 12 is placed at the installation site in a factory or other facility with the cylindrical part 11, anti-slip member 19, suspension fittings 21, height adjustment structure 22, horizontal position adjustment structure 23, and fixing bracket 24a, as well as the internal reinforcing bars 17, connecting bars 18, sheath 20, and outer cylindrical pipe 25b, and with the formwork 16 attached. Therefore, the work of installing the internal reinforcing bars 17 and formwork 16 at the installation site is unnecessary, reducing the amount of work at the installation site and shortening the construction period.

[0064] As shown in Figures 7 and 8, the diagonal brace anchoring steel shell member 12b is placed at the installation site including the outer cylindrical pipe 25b. The outer cylindrical pipe 25b, which extends diagonally downward from the cylindrical portion 11b, passes not only through the portion of the external concrete portion 14 at the same height as the diagonal brace anchoring steel shell member 12b, but also through the portion at the same height as the steel shell member 12 of the lower level. By forming the external concrete portion 14 of each level not in parallel with the formation of the internal concrete portion 13 within the steel shell member 12 of that level, but in parallel with or before / after the formation of the internal concrete portion 13 of the diagonal brace anchoring steel shell member 12b of the level above, the outer cylindrical pipe 25b attached to the diagonal brace anchoring steel shell member 12b can be positioned at the desired location.

[0065] As shown in Figures 3 and 4, by arranging the main reinforcement bars 10 in the outer concrete section 14, even if the reinforcement bars to be placed in the inner concrete section 13 are pre-placed in the cylindrical section 11 at a factory or the like, the main reinforcement bars 10 will not interfere with the internal reinforcement bars 17 etc. placed inside the steel shell member 12 when it is placed at the installation location of the steel shell member 12, making it easier to place the steel shell member 12. The inner concrete sections 13 of each stage are connected by connecting bars 18 and integrated with each other by tensioning members 15 arranged along the extending direction of the main tower 2.

[0066] As shown in Figures 6 to 8, by using PCa formwork 46 to form the external concrete section 14, the removal of formwork in that section becomes unnecessary, reducing work at the construction site and shortening the construction period.

[0067] As shown in Figure 1, when the diagonal members 4 are erected, the cylindrical section 11 is subjected to tensile force in the bridge axis direction due to the tensile force from the diagonal members 4 and deforms. If the outer concrete section 14 is installed to cover the entire outer surface of the steel shell member 12, cracks will occur in the outer concrete section 14 due to the deformation of the cylindrical section caused by the tensile force from the diagonal members 4. If a part of the outer concrete section 14 is formed after the erection of the diagonal members 4 to prevent cracking, this work will extend the construction period. In this embodiment, since the two outer concrete sections 14 are spaced apart in the bridge axis direction, the deformation of the cylindrical section 11 due to the tensile force from the diagonal members 4 mainly occurs in the portion of the cylindrical section 11 that is exposed from the outer concrete section 14, so cracks in the outer concrete section 14 due to the tensile force from the diagonal members 4 are unlikely to occur. In addition, since the entire outer concrete section 14 is formed before the erection of the diagonal members 4, the extension of the construction period can be suppressed.

[0068] As shown in Figure 10, the height adjustment structure 22 and the horizontal position adjustment structure 23 make it easy to adjust the position of the diagonal brace anchoring steel shell member 12b that is newly placed on top of the other steel shell member 12. In addition, the third steel plate 42 of the horizontal position adjustment structure 23 not only supports the third nut 43 and the horizontal position adjustment bolt 40, but also increases the bending rigidity of the first steel plate 32 of the height adjustment structure 22, thereby suppressing an increase in the amount of steel used.

[0069] If the steel cylindrical parts 11 were to come into contact with each other, that is, to make metal-to-metal contact, then high precision would be required in the manufacturing of the cylindrical parts 11, such as ensuring that there are no unevennesses on the upper and lower edges of the cylindrical parts 11. However, in this embodiment, the steel shell members 12 that are adjacent to each other vertically come into contact with each other via the height adjustment structure 22, and the cylindrical parts 11 do not come into contact with each other. Therefore, high precision is not required in the manufacturing of the cylindrical parts 11, and the cylindrical parts 11 can be manufactured at low cost.

[0070] As shown in Figures 1 and 8, the horizontal component of the force transmitted from the diagonal member 4 to the main tower 2 is mainly supported by the steel cylindrical section 11, while the vertical component is mainly supported by the internal concrete section 13 and the external concrete section 14 via the cylindrical section 11 and the shear-preventing member 19.

[0071] This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments or modifications and can be broadly modified and implemented. The present invention may be applied to the construction of the main tower of a cable-stayed bridge. The diagonal members may be fixed to the lowest steel shell member. With respect to the height adjustment structure and the horizontal position adjustment mechanism, in steel shell members adjacent to each other vertically, the first and third support parts may be provided on the upper steel shell member, and the second support part may be provided on the lower steel shell member. [Explanation of Symbols]

[0072] 2: Main tower 4: Diagonal material 6: Base 7: Fixing section 9: Hollow part 10: Main reinforcing bars 11: Cylindrical part 12: Steel shell member 12a: Bottommost steel shell member 12b: Steel shell member for anchoring diagonal members 13: Interior concrete section 14: Exterior concrete section 15: Tensile material 16: Formwork (Second formwork) 17: Internal reinforcement 18: Connecting muscle 19: Anti-slip member 20: Sheath 22: Height adjustment structure 23:Horizontal position adjustment structure 25b: Outer tube 46: Precast concrete formwork (first formwork) 48: Formwork (First formwork)

Claims

1. A method for constructing a main tower in a bridge comprising a main tower, a main girder, and a plurality of diagonal members including one end fixed to the main tower and the other end fixed to the main girder, wherein the main tower comprises a plurality of steel shell members stacked on top of each other, each including a steel cylindrical portion with an opening at the top and bottom, an internal concrete portion formed inside the cylindrical portion of the plurality of steel shell members, and an external concrete portion formed outside the cylindrical portion of the plurality of steel shell members, (a) A step of manufacturing a plurality of the steel shell members in a factory and / or a field yard, wherein the plurality of steel shell members comprises a lowermost steel shell member to be positioned at the lowest level and a plurality of diagonal member anchoring steel shell members to be positioned above the lowermost steel shell member, and the diagonal member anchoring steel shell members further include an outer cylindrical tube that penetrates the walls at both ends of the cylindrical portion in the bridge axis direction to accommodate one end of the diagonal member, (b) The step of constructing the base of the main tower, (c) The step of fixing the lowest steel shell member to the base, (d) A step of pouring concrete into at least both ends in the bridge axis direction within the cylindrical portion of the lowermost steel shell member in order to form the internal concrete portion within the cylindrical portion, (e) A step of installing a first formwork that accommodates at least both ends of the steel shell member in the bridge axis direction with respect to the uppermost steel shell member at that time, and placing the diagonal brace anchoring steel shell member on top of the steel shell member, wherein a portion of the outer cylindrical pipe extending from the diagonal brace anchoring steel shell member is housed within the first formwork, (f) A step of pouring concrete to embed the outer cylindrical pipe in at least both ends in the bridge axis direction within the diagonal member anchoring steel shell member in order to form a part of the internal concrete portion, and pouring concrete into the first formwork in order to form a part of the external concrete portion, (g) A step of repeating steps (e) and (f) above A construction method that includes the following features.

2. The construction method according to claim 1, wherein step (a) includes attaching internal reinforcing bars to be placed in the cylindrical portion of the steel shell member to the cylindrical portion, and attaching connecting reinforcing bars to the cylindrical portion of the steel shell member, the lower part of which is placed in the cylindrical portion of the steel shell member and the upper part of which protrudes into the cylindrical portion of another steel shell member to be placed on top of the steel shell member.

3. The construction method according to claim 2, wherein step (b) includes installing a plurality of main reinforcing bars in the base that extend upward and are to be embedded in the external concrete portion.

4. Step (a) includes holding a sheath, which is disposed within the cylindrical portion and extends in the direction of extension of the main tower, within the cylindrical portion. Step (e) includes connecting the sheath included in the mounted diagonal brace anchoring steel shell member to another sheath located below it, The aforementioned construction method is, (h) The step of inserting tensioning material into the sheaths which are connected to each other, (i) The construction method according to claim 3, further comprising the step of tensioning the tensioning material after steps (g) and (h).

5. The main tower includes a hollow section within the cylindrical portion of the plurality of steel shell members, which separates the internal concrete portion into two in the direction of the bridge axis. Step (a) includes, within the cylindrical portion of each of the steel shell members, removably attaching a second formwork to the cylindrical portion for defining the interface between the two internal concrete portions and the hollow portions, The construction method according to claim 1, wherein in steps (d) and (f), concrete is not poured into the hollow portion, and the second formwork is removed after concrete is poured into the cylindrical portion.

6. The construction method according to claim 1, wherein the first formwork includes precast concrete formwork.

7. The construction method according to claim 1, wherein the external concrete section is spaced apart in the direction of the bridge axis so as to be connected to one another via a plurality of steel shell members.

8. The aforementioned diagonal brace anchoring steel shell member is placed on other steel shell members via a height adjustment structure. The two steel shell members, which are adjacent to each other vertically, are adjacent to each other via the height adjustment structure such that the cylindrical portions are spaced apart from each other. The construction method according to claim 1, wherein the height adjustment structure includes a first support portion provided on one of the two steel shell members, a height adjustment bolt screwed into the first support portion and having an axis parallel to the vertical direction, and a second support portion provided on the other of the two steel shell members, to which the tip of the height adjustment bolt abuts or into which the height adjustment bolt is screwed.

9. Between two steel shell members that are adjacent to each other vertically, a horizontal position adjustment structure is provided to adjust the horizontal position of the upper steel shell member. The construction method according to claim 1, wherein the horizontal position adjustment structure includes a third support portion fixed to one of the two steel shell members, a horizontal position adjustment bolt screwed into the third support portion and having an axis parallel to the horizontal direction, and a strike piece fixed to the other of the two steel shell members and striking against the tip of the horizontal position adjustment bolt.

10. Between two steel shell members that are adjacent to each other vertically, a horizontal position adjustment structure is provided to adjust the horizontal position of the upper steel shell member. The horizontal position adjustment structure includes a third support portion fixed to one of the two steel shell members, a horizontal position adjustment bolt screwed into the third support portion and having an axis parallel to the horizontal direction, and a strike piece fixed to the other of the two steel shell members, against which the tip of the horizontal position adjustment bolt strikes. The first support portion includes a first steel plate having a horizontal main surface, fixed to the outer circumferential surface of one of the two steel shell members, a first through hole through the first steel plate for inserting the height adjustment bolt, and a first nut that is screwed onto the height adjustment bolt and locked to the first steel plate. The second support portion is fixed to the outer circumferential surface of the other cylindrical portion of the two steel shell members and includes a second steel plate having a horizontal main surface, a second through-hole through the second steel plate for inserting the height adjustment bolt, and a second nut that is screwed onto the height adjustment bolt and locked to the second steel plate. The third support portion includes a third steel plate fixed to the outer circumferential surface of one of the two steel shell members and the first steel plate, having a main surface parallel to the vertical direction, and a third nut fixed to the third steel plate into which the horizontal position adjustment bolt is screwed. The construction method according to claim 8, wherein the height adjustment structure and the horizontal position adjustment structure are configured such that the upper end of the third steel plate may be located above the second steel plate, or the lower end of the third steel plate may be located below the second steel plate.

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