JP5973295B2 - Column head construction method - Google Patents

Description

  The present invention relates to a method for constructing the pier upper part, ie the column head, of a concrete bridge girder supported on the pier.

  Many so-called cantilever construction methods are used to construct large-scale concrete bridges. In this method, after the pier is started up, it is constructed so that the bridge girder is extended from the pier to both the direction along the axis of the bridge girder (the direction of the bridge axis) for each construction block set to a predetermined length. It is.

As a method of constructing the column head of the bridge girder, a support work is started from the ground surface, a formwork is assembled on this support work, concrete is placed, and a support supported by a bracket attached to the upper part of the pier. In general, a method of assembling a work and placing concrete on the support is adopted.
On the other hand, Patent Document 1 and Patent Document 2 describe a method of forming a column head using a precast concrete member in order to simplify the support work and rationalize the construction of the column head.

JP 2003-328320 A JP 2008-274586 A

  There are concrete bridges adopting the cantilever construction method, where the bridge girder is wider than the pier dimension and the bridge girder extends in the width direction on the pier. Such a bridge girder has a column head cross girder having a large cross-sectional area on the bridge pier, and this column head cross girder is formed to protrude from the bridge pier in the width direction. And it is constructed so that a bridge girder may be projected from both sides of this column head in the direction of the bridge axis. In this way, when the bridge girder extends in the width direction from the pier, a large amount of cost and amount of work are required to assemble a support for constructing the column head. In other words, the column head cross beams projecting in the width direction have a large weight, and it is necessary to construct a support that can support this weight. In particular, a large-scale temporary work is required to support the large weight of the column head girder that protrudes to the side by the support work provided so as to protrude from the upper part of the pier because the height of the pier is large. End up.

  On the other hand, even if the column head is constructed using the precast concrete member, the column head and the column head horizontal beam of the bridge girder have a large cross-sectional area, and the weight of the precast concrete member is increased. For this reason, in order to lift the precast concrete member and perform the operation | work which installs in a predetermined position, a big lifting equipment is needed and it becomes difficult to construct a pillar head efficiently.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to efficiently construct a column head of a bridge girder on a bridge pier in a bridge having a structure in which the bridge girder projects laterally from the width of the pier. It is to provide a method for constructing a column head.

In order to solve the above-mentioned problem, the invention according to claim 1 includes a concrete pier raised on a foundation, and a concrete bridge girder supported on the pier and having a width larger than the width of the pier. A method of constructing a column head which is a bridge pier upper part of the bridge girder of a bridge provided, wherein the central block of the column head, which is a central part in the width direction of the bridge girder, is placed on site A step of forming on the bridge pier, and supporting the precast concrete block so as to project in the width direction of the bridge girder from the lower part of the side surface of the central block, and a joint surface between the central block and the precast concrete block. together butted each other, a step of connecting by prestressing to the joint surface by the tensioning force is introduced tendon, the flop Is supported on cast concrete block, a method constructing stigmas portion, characterized by and a step of pouring the concrete so as to be in close contact with the side surface of the upper surface and the central portion blocks of the precast concrete blocks.

  In this method, the central block can be formed on the pier without overhanging the side surface of the pier, and it is not necessary to provide a large support in this process. And even in the process of connecting and supporting the precast concrete block so as to project from the lower part of the central block, a support having a large support force is not required. Further, the cross-sectional area of the portion projecting in the width direction by the precast concrete block is limited to the lower part of the column head, and the weight of the precast concrete block can be kept small and can be easily lifted and joined. Furthermore, the upper part of the part protruding from the central block of the column head can be formed by supporting the weight on the part formed by joining the precast concrete blocks and placing concrete on site. Therefore, it is possible to efficiently construct the column head without constructing a support that can support a large weight.

  The invention according to claim 2 is the construction method of the column head according to claim 1, wherein the precast concrete block sequentially connects a plurality of the precast concrete blocks in the width direction of the bridge girder, It is assumed that the shape of a vertical cross section parallel to the axial direction of the bridge girder is a box shape and has a hollow portion.

  In this method, the precast concrete block that projects from the central block in the width direction of the bridge girder is divided into a plurality of parts, and the weight of each is reduced. Moreover, since the cross-sectional shape of the part which joins a precast concrete block and protrudes in the width direction becomes a hollow box shape, while maintaining big rigidity, weight can be made still smaller. Therefore, it is possible to easily perform the work of lifting and joining.

  The invention according to claim 3 is the method for constructing a column head according to claim 1 or 2, wherein the precast concrete block is fixed with a formwork for placing concrete on the precast concrete block. In this state, it is connected to the central block or another precast concrete block already connected to the central block.

  In this method, it is possible to efficiently perform the work of assembling a formwork for placing concrete on the joined precast concrete block. In particular, the formwork to be provided on the front end surface of the column head projecting in the width direction of the bridge girder should be installed on the side edge of the bridge girder by fixing it to the precast concrete block in advance without providing work scaffolding. This enables efficient work.

  As described above, in the column head construction method according to the present invention, it is possible to efficiently construct a column head having a shape in which the width of the bridge girder is larger than the width of the pier and projecting in the width direction from the pier.

It is a schematic side view which shows the bridge which can employ | adopt suitably the construction method of the column head which is one Embodiment of this invention. It is a cross-sectional view of the bridge shown in FIG. It is a cross-sectional view in the pier position of the bridge shown in FIG. It is a longitudinal cross-sectional view in the pier position of the bridge shown in FIG. 1, Comprising: It is sectional drawing in the AA line shown in FIG. It is a longitudinal cross-sectional view in the pier position of the bridge shown in FIG. 1, Comprising: It is sectional drawing in the BB line shown in FIG. It is a schematic front view which shows a state when forming a center part block on a bridge pier. It is a schematic perspective view which shows the state in which the center part block was formed. It is a schematic perspective view which shows the process of joining a precast concrete block to a center part block sequentially. It is a schematic perspective view which shows the state which complete | finished the process of joining a precast concrete block to a center part block sequentially. It is a schematic perspective view which shows the state which put concrete on-site on the overhang | projection part which joined the precast concrete block. It is a schematic front view which shows the state which attaches and joins the formwork for placing concrete on-site to a precast concrete block.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side view showing a bridge that can suitably employ the column head construction method of the present invention.
This bridge is an extradosed type cable-stayed bridge, and includes a bridge girder 3 spanned on the abutment 1 and the pier 2, a main tower 4 raised on the pier 2, and the main tower 4 It has a plurality of diagonal cables 5 and 6 which are stretched obliquely downward from both the upper and lower sides of the bridge girder 3 and support the bridge girder 3 in an oblique direction.
The extradosed type cable-stayed bridge has a relatively large bending rigidity of the bridge girder 3 and a small height of the main tower 4, and the inclination angles of the oblique cables 5 and 6 are small.

The bridge girder 3 is made of concrete, and as shown in FIG. 2, two sections having a box-shaped cross section are connected. The bridge girder 3 has an upper floor slab 11 that is continuous with two box-shaped cross-sections, a lower floor slab 12 that is independent at each of the two box-shaped cross-sections, and the upper floor slab 11 and the lower floor slab 12 that are The web 13 is connected to the web 13. The upper floor slab 11 and the lower floor slab 12 are made of concrete cast on site, and a precast plate is used for the web 13. This precast plate has a butterfly shape in which the lateral shape is the middle in the vertical direction, the horizontal dimension is reduced, and the vertical shape is gradually enlarged. This precast board is arranged in the axial direction of the bridge girder to form a web 13. Thus, by using a precast board as the web 13, the weight of the bridge girder 3 is reduced.
In this embodiment, a precast plate is used for the web of the bridge girder 3, but the structure of the bridge girder 3 is not limited to such a structure, and is made of concrete or steel on which the web is cast on site. Other forms of bridge girders may be used.

  The bridge girder 3 is supported by the pier 2 in a state in which the width is larger than the dimension in the width direction of the pier 2 and projects laterally from the pier 2. The bridge girder 3 has a column head horizontal girder 14 immediately above the pier 2, and the bridge girder 3 and the pier 2 are integrally formed to form a rigid frame structure. And the said main tower 4 is integrally started up on the position in which the column head horizontal girder 14 of the bridge girder 3 was provided.

  As shown in FIG. 3, the pillar head of this bridge girder includes a central block 21 formed of cast-in-place concrete immediately above the pier 2, and an overhanging portion 22 projecting from the central block 21 to both sides in the width direction. It consists of The lower portion of the overhanging portion 22 is formed by connecting a plurality of precast concrete blocks 23 in the width direction, and the upper portion is formed by concrete 24 cast on the precast concrete blocks 23 in the field.

  As shown in FIGS. 3 and 4, the central block 21 has a solid cross section and is continuous with the pier 2. As shown in FIGS. 3 and 5, the upper portion of the overhang portion 22 has a solid cross section, and a plurality of ducts 25 are provided in this portion in the bridge axis direction. A tension member for introducing prestress into the bridge girder is inserted into the duct 25. The lower part of the overhanging portion formed by the precast concrete block 23 has a rectangular hollow portion 26 in a cross section parallel to the axis of the bridge girder 3, and this hollow portion 26 extends from the joint surface with the central block 21. The bridge girder 3 continues in the width direction up to the vicinity of the position where the outermost web 13a is provided. A manhole 27 penetrating in the axial direction of the bridge girder 3 is provided in the hollow position.

  As shown in FIGS. 4 and 5, the column head is provided with a duct 28 perpendicular to the axis of the bridge girder so as to penetrate the upper part of the central block 21 and the overhanging portion 22. Prestress is introduced by the tension material inserted into these ducts 28, and can support the load on the bridge girder extending in the axial direction of the bridge girder 3 from the overhang portion 22. Further, a tension material for sequentially joining the precast concrete blocks is inserted into a duct 29 provided so as to penetrate the central block 21 from the portion 22 formed by the precast concrete block 23.

Next, a method for constructing the above column head will be described.
Concrete is placed in order for each predetermined height, and the pier 2 is raised to a predetermined height. The construction of the pier 2 may be performed by assembling a scaffold from the ground surface, or a jumping form or a sliding form in which a formwork and a scaffold are integrated can be used. Then, when the pier 2 is formed to a predetermined height, as shown in FIG. 6, the bracket is fixed to the concrete on the upper portion of the pier 2 to form the scaffold 31. A part of this scaffold 31 functions also as a support work.

The center block 21 of the column head is formed on the pier 2 by the work on the scaffold 31. As shown in FIG. 6, the central block 21 is formed by assembling a mold (not shown) on a scaffold 31 via a column 32 and placing uncured concrete in the mold. At this time, a precast concrete reference block 33 is installed at a portion where the precast concrete block constituting the projecting portion of the column head is joined, that is, a lower portion of the side face in the width direction of the central block 21. Concrete is placed using as a formwork. In this way, the central block 21 is formed as shown in FIG. 7, and the reference block 33 made of precast concrete is formed on the side surface in the width direction of the central block 21, that is, the lower portion of the surface 21a on which the column head is projected. Exposed.
Although the scaffold is not shown in FIGS. 7 to 10, the scaffold is maintained in a state of being fixed to the concrete on the upper part of the pier at least until the construction of the column head is completed.

  Subsequently, as shown in FIG. 8, the precast concrete block 23 previously formed in the factory or the production yard is joined to the reference block 33, and the plurality of precast concrete blocks 23 are joined sequentially to the width direction of the bridge girder 3. Overhang. The reference block 33 and the precast concrete block 23 are manufactured by a so-called match cast method in a factory or a manufacturing yard. That is, the reference block 33 is first manufactured by placing concrete in the mold, and after the concrete of the reference block 33 is hardened, the precast concrete block 23-1 joined to the reference block is referred to as the reference block 33. The joint surface is made as a formwork. It is possible to separate the reference block 33 and the precast concrete block 23-1 by interposing a release agent on the joint surface and hardening the concrete placed later. And the precast concrete block which manufactured the precast concrete block 23 joined sequentially is manufactured as a formwork. Thereby, the joint surface of each precast concrete block 23 becomes a corresponding shape, and it adheres closely at the time of joining.

In addition, the precast concrete block 23 is joined by applying an adhesive such as an epoxy resin to the joint surface, butting the joint surfaces together, and tensioning the tension material inserted through the duct 29 formed in advance. The block 23 is fixed so as to be integrated. In this way, the precast concrete blocks 23 are sequentially joined, and project from the central block 21 to both sides in the width direction of the bridge girder 3 as shown in FIG.
In this embodiment, the web of the bridge girder 3 is an arrangement of butterfly-shaped precast plates, and in order to maintain the continuous appearance of the bridge girder 3, the butterfly-shaped precast plate is provided on the side of the column head. The convex portion 34 having the same shape as that is formed.

When the lower part of the projecting portion 22 of the column head is projected from the central block 21 by the precast concrete block 23, a formwork (not shown) is formed above the side surface 23a perpendicular to the bridge axis direction of the precast concrete block 23. Assemble. In addition, a formwork (not shown) corresponding to the shape of the upper part of the bridge girder 3 and the overhanging slab is assembled from the front end surface of the precast concrete block 23-2 joined last, that is, the outer surface of the web 13 of the bridge girder 3. In addition, a sheath for inserting a tension member arranged in the axial direction of the bridge girder at a predetermined position, a sheath for inserting a tension member arranged in a direction perpendicular to the axis of the bridge girder in the column head, and the like are arranged. Then, a reinforcing bar (not shown) is arranged on the part overhanging by the precast concrete block 23.
It is desirable that the precast concrete block 23 is arranged so that a reinforcing bar protrudes upward from the upper surface at the time of manufacture and is continuous with the reinforcing bar arranged on the precast concrete block 23 via a joint.

  After placing the reinforcing bars, concrete is placed in the above-mentioned formwork, and as shown in FIG. 10, the concrete is hardened and the lower part of the projecting portion 22 composed of the central block 21 and the precast concrete block 23, and the concrete 24 on the site. The upper part of the overhanging portion 22 that has been laid is made continuous continuously. Then, a tension member (not shown) arranged in a direction perpendicular to the axis of the bridge girder 3 is tensioned, and a prestress in a direction perpendicular to the axis of the bridge girder is introduced into the column head to support the load acting from the bridge girder. To do.

In the above embodiment, the formwork for placing the concrete 24 on the upper portion of the overhanging portion 22 is assembled after the lower portion of the overhanging portion 22 composed of the precast concrete block 23 is formed. As shown in FIG. 11, the formwork 35 at the tip of the can be attached in advance to the precast concrete block 23-2 to be joined last.
The mold 35 provided to form the tip of the overhanging portion 22 has a shape that is continuous with the side surface of the web 13 and a shape that is continuous with the overhanging floor slab 11a, and all the precast concrete blocks 23 are joined together. In order to assemble the above-mentioned formwork later, a scaffold that extends right under the tip of the overhanging slab 11a is required. On the other hand, as shown in FIG. 11, the scaffold 31 formed by projecting from the upper part of the pier 2 can be simplified by attaching the formwork 35 of the projecting floor slab 11a to the precast concrete block 23-2 in advance. It becomes possible.

  When the column head is constructed as described above, the bridge girder 3 is constructed so as to sequentially project from the column head to each construction block preset in both directions along the axis of the bridge girder 3. In this embodiment, the main tower 4 for extending the oblique cables 5 and 6 is raised on the column head of the bridge girder 3. Then, the bridge girder 3 is further extended and supported while the bridge girder 3 is supported by the oblique cables 5 and 6 that are sequentially stretched.

In addition, this invention is not limited to the said embodiment, It can implement in another aspect within the scope of the present invention.
For example, in the present embodiment, the present invention is applied to the head of a bridge girder in a cable-stayed bridge, but is not limited to a cable-stayed bridge, and the load on the bridge girder is supported only by the bridge girder and the bridge girder supported on the abutment. It can also be applied to so-called girder bridges. Further, in this embodiment, a precast plate is used for the web. However, the web may be made of concrete that is cast on site together with the upper floor slab and the lower floor slab, or a steel member may be used for the web. . Further, the upper floor slab and the lower floor slab may be manufactured together with a web as a precast segment in a manufacturing yard or the like, and these may be joined to form a bridge girder.
Furthermore, the cross-sectional shape of the bridge girder is the one in which the above-described embodiment is formed by connecting two box-shaped cross-section portions by an upper floor slab and a horizontal girder, but is partitioned by one or two or more intermediate webs and continuously in the width direction A bridge girder having a box-shaped cross section may be used.

On the other hand, the projecting portion of the column head has a cross-sectional shape in which the lower portion formed by the precast concrete block is hollow, but the lower portion of the projecting portion can also be formed by a solid cross section. Moreover, a hollow part can also be provided in the upper part of the overhang | projection part formed with the concrete cast on-site.
Furthermore, although the central block of the column head has a solid cross section in the above embodiment, a hollow portion may be provided here.
In addition, the ratio of the cross-sectional area between the lower part made of precast concrete block and the upper part made of concrete cast in the field at the projecting part of the column head, the ratio of the dimension in the height direction, etc. The bridge girder can be set as appropriate according to the length of the bridge girder protruding from the pier in the width direction.

1: abutment, 2: pier, 3: bridge girder, 4: main tower, 5, 6: diagonal cable,
11: Upper floor slab, 11a: Overhanging floor slab, 12: Lower floor slab, 13: Web, 14: Pillar head beam
21: Central block, 22: Overhanging part of the column head, 23: Precast concrete block, 24: Concrete placed on the top of the overhanging part, 25: Duct in the bridge axis direction, 26: Hollow part of the column head, 27: Manhole, 28, 29: Duct provided perpendicular to the bridge axis direction,
31: Scaffolding, 32: Support column, 33: Reference block, 34: Convex part on the side of the column head, 35: Formwork

Claims (3)

A pillar head, which is the upper part of the bridge pier of the bridge girder, comprising a concrete pier raised on a foundation and a concrete bridge girder supported on the pier and having a width larger than the width of the pier. A method of building,
Forming the central block of the column head, which is a central portion in the width direction of the bridge girder, on the pier by concrete that is cast on site;
The precast concrete block is supported so as to protrude in the width direction of the bridge girder from the lower part of the side surface of the central block, the joint surface of the central block and the precast concrete block is abutted with each other, and tension is introduced. A step of introducing prestress to the joint surface with a strained material and connecting the joint surface;
And a step of placing the concrete so that it is supported by the precast concrete block and in close contact with the upper surface of the precast concrete block and the side surface of the central block. The precast concrete block is for sequentially connecting a plurality in the width direction of the bridge girder,
2. The method for constructing a column head according to claim 1, wherein the precast concrete block has a hollow portion with a box-shaped cross section parallel to the axial direction of the bridge girder. The precast concrete block is connected to the central block or another precast concrete block already connected to the central block in a state where a formwork for placing concrete is fixed on the precast concrete block. The method for constructing a stigma according to claim 1 or claim 2, wherein

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