JP3931635B2 - Composite box girder and its construction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a composite box girder using a compression slant and a tensile slant for the web part of the box girder and a construction method thereof, and is applied to, for example, a bridge superstructure.
[0002]
[Prior art]
Some bridge girder types use box girder structures such as PC box girder bridges and steel box girder bridges.
[0003]
In the case of a PC box girder bridge, a bridge can be constructed with a relatively simple construction facility in a short construction period by constructing a precast block made of reinforced concrete or prestressed concrete with a box-shaped cross section by overhanging or the like.
[0004]
Further, in order to reduce the weight of the box girder and to rationalize the structure and improve the workability, the web of the PC box girder bridge is replaced with a corrugated steel sheet (see, for example, JP-A-2001-81720), web There are steel-concrete composite truss bridges with a truss structure (see, for example, JP-A-11-222816 and JP-A-2000-104219).
[0005]
[Problems to be solved by the invention]
As a disadvantage of the conventional PC box girder bridge, in order to resist the shearing force, the web becomes thick and the weight of the bridge superstructure becomes heavy, so that the scale of the substructure has to be large.
[0006]
Further, when the web becomes thick, the tension force in the PC steel material or the like is dispersed, and a large tension force is required to introduce a predetermined introduction force. For this reason, the amount of PC steel etc. also increases.
[0007]
Furthermore, there is a limit to the size of a single precast block in order to perform overhanging construction.
[0008]
Regarding the composite truss bridge, the truss structure theoretically bears only the axial force because the point part is a pin structure, but the composite truss is bent or sheared because the point part is rigidly connected or close to it. . In addition, a large grading part is required to make the structure resistant to that. In addition, there is a problem that on-site work becomes complicated due to the on-site assembly and concrete placing work.
[0009]
The present invention is intended to solve the problems of the conventional box girder structure as described above, and can be reduced in weight by reducing the cross section of the girder, and each member constituting the box girder can be easily precast. The purpose of the present invention is to provide a composite box girder excellent in workability and economy and its construction method.
[0010]
[Means for Solving the Problems]
The composite box girder according to claim 1 of the present application is arranged so that a plurality of pre-cast upper floor block blocks and lower floor block blocks are crossed in an X shape in an elevational view on the web portion of the box girder. A plurality of compression diagonal members and tensile diagonal members are connected together, and the upper floor slab blocks and lower floor slab blocks are connected in the direction of the box girder axis, so that the tensile diagonal members substantially resist only tensile force. PC steel rods, PC cables, or thin steel plates are used.
[0011]
As the compression diagonal material, one made of a material such as high-strength concrete, short fiber reinforced concrete, concrete-filled steel pipe, or FRP can be considered. In addition, precasting can shorten the work period in on-site construction.
[0012]
The compression diagonal material is mainly expected to have a compressive resistance, but it is also conceivable to use a material having a high tensile strength under a design condition in which an alternating load acts.
[0013]
Tensile diagonal members are those who expect a mainly tensile resistance force, miniaturization of the member, PC steel bars from the goodness of handling in the case of precast reduction, but such as a PC cable can be considered, not good even thin plate of steel.
[0014]
In addition, the compression diagonal material and the tensile diagonal material can be efficiently arranged to function as a compression diagonal material and a tensile diagonal material by crossing them in an elevational view. In terms of design conditions, it may be possible to arrange the compression diagonal and the tensile diagonal with the same cross section.
[0015]
More specifically, for example, a tensile diagonal member is arranged in the same direction so that the compression diagonal member is sandwiched, or a PC steel rod as a tensile diagonal member is passed through a steel pipe as a compressive diagonal member. An arrangement in which a tensile diagonal is passed through the diagonal is also conceivable. In this case, depending on the direction of the alternating load, one of the compression diagonal material and the tensile diagonal material functions substantially from time to time.
[0016]
In addition, the compression diagonal and tensile diagonal are basically equivalent to a structure in which the PC box girder web is replaced, and are arranged in a form extending in the box girder axis direction at the PC box girder web position. In order to ensure the above, it can also be arranged in a direction orthogonal to the box girder axis direction.
[0017]
The upper floor block and the lower floor block are basically equivalent to the upper floor plate and the lower floor plate of the PC box girder, but plate-shaped precast members made of high-strength concrete or short fiber reinforced concrete should be used. Thus, the cross-sectional area can be reduced, the weight can be reduced while maintaining high strength, and the assembly and erection work at the site can be facilitated.
[0020]
In the composite box girder of the present invention, since the compressed diagonals and tensile diagonal members are arranged to cross in an X shape in elevation view, compression and tension diagonal member to exert a compressive resistance resistor Efficient stress transmission can be achieved by balancing the tensile diagonal material that exerts the force.
[0021]
Claim 2 is the composite box girder according to claim 1, is obtained by limiting the case where there with the top floor plate block or lower deck block, the junction between the compression diagonal members or tensile diagonal member as a pin junction .
[0022]
In the present invention, the compression diagonal member and the tensile diagonal member are combined to reduce the cross section of the diagonal member, so that the joint between the upper and lower floor slab and the compression diagonal member or the tensile diagonal member is relatively pin-bonded. It is easy, and it is only necessary to resist the force in the axial direction without substantially bending or shearing the compression slant or tensile slant. As a more rational structure, the cross section of the member is reduced and the weight is reduced. be able to.
[0023]
In particular, on-site work can be greatly simplified by precasting the upper and lower floor slabs, the compression diagonal material, and the tensile diagonal material, respectively, and making the joint part a pin joint.
[0024]
The invention according to claim 3 of the present application is the construction method of the composite box girder according to claim 1 or 2 , wherein the newly installed lower floor slab block is connected to the front of the existing lower floor slab block in the box girder axial direction. A step of connecting the existing upper floor slab block and the newly installed lower floor slab block with a tensile diagonal member, and subsequently connecting the new upper floor slab block to the front of the existing upper floor slab block in the box girder axial direction. The lower floor slab block and the newly installed upper floor slab block are connected to each other with a compression slant to repeat the overhanging construction.
[0025]
First, in the work of connecting and extending the lower floor slab block to the existing lower floor slab block, it is possible to support it diagonally from the existing upper floor slab block by using a tensile diagonal material, and in a stable state the upper floor slab block Work such as connecting and compressing diagonal materials. By repeating these operations, the composite box girder can be efficiently erected.
[0026]
In addition, in the state which connected the lower floor block blocks and the upper floor block blocks, the existing part in overhang construction can be stabilized by performing tension | tensile_strength by PC steel etc. suitably.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the basic structure of the composite box girder of the present invention. In this example, as shown in FIG. 1 (a), the upper floor block 1 and the lower floor block 2 are respectively in the box girder axis direction. The upper and lower floor slab blocks 1 and 2 are connected by a compression diagonal member 3 and a tensile diagonal member 4 that intersect in an X shape in an elevational view.
[0028]
FIG. 1 (b) is a view as seen from the box girder axis direction. In this example, in addition to the web positions on both sides of the box girder, the compression diagonal material 3 and the tensile diagonal material 4 are also arranged at the center. Further, the tensile diagonal material 4 is arranged on both sides of each compression diagonal material 3. However, various arrangements of the compression diagonal member 3 and the tensile diagonal member 4 are conceivable, and there is no particular limitation as long as the upper and lower floor slab blocks 1 and 2 of the composite box girder can be stably connected.
[0029]
The upper and lower floor slab blocks 1 and 2 are made of plate-shaped precast members, and connect the upper floor slab block 1 and the lower floor slab block 2 to each other in the bridge axis direction. Introducing prestress in the direction of the bridge axis can also be performed at the construction stage, but generally the amount of prestress introduced differs between construction and completion.
[0030]
The compression diagonal member 3 is considered to have a high compressive strength such as high-strength concrete, short fiber reinforced concrete, concrete-filled steel pipe, etc. On the other hand, the tensile diagonal member 4 has a high tensile resistance such as a PC steel rod or PC cable. It is possible to reduce the weight by reducing the cross section as small as possible.
[0031]
Further, by precasting the compression diagonal material 3 and the tensile diagonal material 4 as well, the work at the site is simplified and the construction period can be shortened.
[0032]
FIG. 2 shows an example of a pin joint portion to the upper floor block 1 of the compression diagonal material 3. In addition, although not shown in figure, it can consider similarly about a junction part with a lower floor block.
[0033]
In this example, the end cross section of the compression diagonal member 3 is formed in an arc shape, while a groove (compression diagonal member 3) having an arc cross section corresponding to the end cross section of the compression diagonal member 3 is formed on the bottom surface of the upper floor block 1. Is formed in a circular arc shape only in the direction of the bridge axis) or a spherical recess (when the end of the compression slant 3 is spherical), and a cushioning material such as synthetic rubber is formed in the groove or recess. The pin joint portion 11 is formed so as to receive the end portion of the compression diagonal member 3 through 14.
[0034]
Further, as a fixing means, a bolt hole 12 is formed in advance at the end portion of the compression diagonal member 3, and a tension steel material 13 having a bolt-like tip from the upper surface side of the upper floor slab block 1 is screwed into the bolt hole 12. It is supposed to be.
[0035]
In addition, it can be made to resist with respect to a small tensile force by using what has the necessary tensile strength as the steel material 13 for tension | tensile_strength.
[0036]
The bolt hole 12 can be formed by embedding anchor metal fittings having bolt holes on the inner surface, and a reinforcing short fiber or the like is partially used to reinforce the end of the compression diagonal member 3. Mixed concrete can also be used.
[0037]
FIG. 3 shows an example of a pin joint portion of one to the upper floor slab block of the tensile diagonal member 4. In addition, although not shown in figure, it can consider similarly about a junction part with a lower floor block.
[0038]
In this example, the anchor end of the anchoring device 22 in which the fixing end of the tensile diagonal member 4 made of a PC cable or the like is positioned in the cross section of the upper floor slab block 1 and the fixing end is embedded in the upper floor slab block 1. The pin joint portion 21 is formed by being able to rotate in an arc-shaped groove or a spherical recess.
[0039]
FIG. 4 shows another example of a pin joint portion to the upper floor block 1 of the tensile diagonal member 4. Although not shown, the joint portion with the lower floor slab block can be similarly considered.
[0040]
In this example, a thin steel plate material is used as the tensile diagonal member 4, and an end portion thereof is attached to the pin 33 of the anchor device 32 embedded in the upper floor slab 1 to form the pin joint portion 31.
[0041]
FIG. 5 shows still another example of the joining structure of the compression diagonal member 3 and the tensile diagonal member 4 to the upper floor block 1. FIGS. 6 and 7 show an overall view and an overview of the girder when the joint structure is applied to a composite box girder bridge.
[0042]
In this example, a compression diagonal material receiving portion 41 is provided on the lower surface of the upper floor slab block 1 (upper surface in the case of the lower floor slab block 2), and the arc shape of the compression diagonal material 3 made of steel or the like having an arc-shaped cross section at the end. The cross-sectional portion is received by the corresponding groove portion 43 to be pin-joined.
[0043]
In addition, for the tensile diagonal member 4, a PC steel rod or a PC cable is used, and a groove-like recess is formed on the upper surface of the upper floor block 1 (lower surface in the case of the lower floor block 2) as the tensile diagonal material receiving portion 42. The end of the tensile diagonal member 4 is fixed by a fixing plate 44 and a nut 45 in the groove.
[0044]
FIG. 8 shows an embodiment in which the composite box girder construction method of the present invention is applied to the construction of the composite box girder bridge, and the composite box girder can be extended by the following procedure. .
[0045]
The new lower floor block 2 is connected to the front part of the existing lower floor block 2 installed by overhanging in the box girder axial direction, and these are tensioned with PC steel or the like (see FIG. 8 (a)). In addition, although not shown in figure, you may construct in the state which attached the end of the tension diagonal material 4 to the newly installed lower floor block 2 previously.
[0046]
Next, the existing upper floor slab block 1 and the newly installed lower floor slab block 2 are connected by a tensile diagonal member 4 made of a PC cable or the like (see FIG. 8B).
[0047]
Subsequently, the compression diagonal material 3 is set obliquely on the lower floor block 2 (see FIG. 8 (c)). Although not shown, the compression diagonal member 3 can be supported by an appropriate support or support device.
[0048]
The new upper floor slab block 1 is connected to the front of the existing upper floor slab block 1 in the box girder axis direction, and is connected to the end of the compression diagonal member 3 set on the lower floor slab block 2 (FIG. 8 (d)). reference). In that state, the upper floor slab block 1 is tensioned with PC steel or the like.
[0049]
By the above work, the overhanging construction corresponding to one block is completed, and by repeating this work the required number of times, it is possible to perform the construction by overhanging the composite box girder bridge.
[0050]
【The invention's effect】
A position corresponding to a box girder web, compression diagonal members to resist compressive forces, PC steel bars as tensile diagonal member to resist tensile forces, by arranging the PC cable or thin plate steel, digit lightweight Can be achieved.
[0051]
In addition, prestress introduced into the floor slab is not dispersed to the diagonal by connecting the compression diagonal and tensile diagonal to the upper and lower floor slab blocks with pin joints that do not transmit bending moment. In addition, the structure of the joint can be reduced.
[0052]
By precasting all the members, the work on site is reduced, and overhanging can be performed only by combining delivered parts.
[Brief description of the drawings]
FIG. 1 shows the basic structure of a composite box girder according to the present invention, in which (a) is an elevation view as seen from a direction orthogonal to the axial direction of the box girder, and (b) is as seen from the axial direction of the box girder. FIG.
FIG. 2 is a vertical cross-sectional view showing an example of a structure for joining a compression diagonal material to an upper floor slab block.
FIG. 3 is a vertical sectional view showing an example of a structure for joining a tensile diagonal material to an upper floor slab block.
FIG. 4 shows another example of a structure for joining an upper floor slab block of a tensile diagonal material, where (a) is a vertical sectional view in the box girder axis direction, and (b) is a direction orthogonal to the box girder axis direction. (C) is the figure which looked up the upper floor slab block from the lower part.
[Fig. 5] Fig. 5 shows still another example of the joining structure of the compression and tensile diagonal materials to the upper floor block. (A) is a vertical sectional view in the box girder axis direction, and (b) is the box girder axis. (C) is a view of the upper floor block viewed from above.
6 is a perspective view showing an overview when the composite box girder having the joint structure of FIG. 5 is applied to a composite box girder bridge. FIG.
7 is a perspective view showing an overview in a beam corresponding to FIG. 6. FIG.
FIG. 8 is a conceptual diagram showing a construction procedure in one embodiment of the construction method of the composite box girder according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Upper floor slab block, 2 ... Lower floor slab block, 3 ... Compression diagonal, 4 ... Tensile diagonal, 5 ... Bridge pier, 11 ... Pin joint, 12 ... Bolt hole, 13 ... Steel for tension, 14 ... Buffer 21 ... Pin joint part, 22 ... Anchor device, 31 ... Pin joint part, 32 ... Anchor device, 33 ... Pin, 41 ... Compression diagonal material receiving part (pin joint part), 42 ... Tensile diagonal material receiving part, 43 ... groove, 44 ... fixing plate, 45 ... nut

Claims (3)

A plurality of precast upper floor block blocks and lower floor block blocks are connected with a plurality of compression and tension slant members arranged so as to intersect the web part of the box girder in an X shape in an elevational view. And a PC steel bar, a PC cable, or a thin plate-shaped steel material in which the upper floor slab blocks and the lower floor slab blocks are connected to each other in the box girder axial direction and substantially resist only tensile force as the tensile diagonal member. A composite box girder characterized by using.  The composite box girder according to claim 1, wherein a joint portion between the upper floor block or the lower floor block and the compression diagonal member or the tensile diagonal member is a pin joint.   The construction method for a composite box girder according to claim 1 or 2, wherein a new lower floor slab block is connected in front of the existing lower floor slab block in the box girder direction, and the existing upper floor slab block and the newly installed lower girder block are The step of connecting the floor slab block with a tensile diagonal member, and then connecting the new upper floor slab block to the front of the existing upper floor slab block in the box girder axial direction, and the new lower floor slab block and the new upper floor slab A method for constructing a composite box girder characterized in that an overhanging construction is performed by repeating the step of connecting blocks with compression diagonal materials.

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