JP4430267B2 - How to install arch ribs - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for constructing arch ribs in a concrete arch bridge.
[0002]
[Prior art]
Conventionally, an overhanging construction method is known as one of the methods for constructing arch ribs in a concrete arch bridge.
[0003]
In this overhanging construction method, as shown in FIG. 10, a plurality of arch rib constituting blocks A1 ′, A2 ′, A3 ′,... It is supposed to be. That is, the wagegen 110 is advanced to the tip end along the arch axis Ax ′ of the overhanging portion 102A, and a new arch rib constituting block is constructed on the small edge (tip surface) 102Aa of the overhanging portion 102A using this wageen 110. It is like that. This construction is performed by the steps of formwork installation, rebar PC assembly, and concrete placement curing.
[0004]
When performing this overhanging construction, an end post 104 is constructed in the vicinity of the end of the arch rib 102 in advance, and a backstay is provided on the back side (the anti-arch rib side) of the end post 104 (or a pyrone installed thereon). 106 is constructed, and then the base end portions 108a of the plurality of forestays 108 that obliquely suspend the overhanging portion 102A are fixed to the end posts 104 (or pyrone), respectively. In this overhanging construction method, the end post 104 is used as a compression member, and the fore stay 108 and the backstay 106 are used as tension members to resist the overturning moment during overhanging construction.
[0005]
[Problems to be solved by the invention]
In the above-described conventional overhanging construction method, the purpose of arranging the fore stay 108 is to reduce the negative bending moment (moment in the direction of the arrow shown in the figure) acting on the end (sprinkling part) of the arch rib 102 that accumulates as the overhanging progresses. Since it is limited to keep the soundness of the member in the middle of the construction by doing so, there are the following problems.
[0006]
That is, in the above-described conventional overhanging construction method, the tip 108b of the fore stay 108 is located a few blocks away from the small edge 102Aa of the overhanging section 102A in order to prevent interference with the wage 110 performing overhanging construction. In this way, it is fixed to the overhanging portion 102A.
[0007]
In this case, a negative bending moment acts on the distal end portion of the overhanging construction portion 102A due to the weight of the wagen 110 and the weight of the concrete placed by the construction of the new arch rib constituting block. Therefore, in order to properly support the distal end portion of the overhanging portion 102A even after the concrete mold is removed, it is necessary to apply a positive bending or axial compression force that cancels the tension at the upper edge of the distal end portion.
[0008]
Therefore, in the conventional overhanging construction method, in order to cancel the pulling of the upper edge of the tip of the overhanging construction part 102A, an axial compression force is applied by arranging a PC steel rod in the upper floor slab of the arch rib 102. .
[0009]
However, when PC steel bars are arranged in this way, there is a problem that workability is very poor because a PC steel bar joining operation is required for each arch rib constituting block. Further, it is difficult to remove the PC steel bar arranged in this way later, and it is also difficult to release the axial compression force. However, after the arch rib 102 is installed, the axial compression force of the PC steel bar is low. If it is not released, there is also a problem that pre-secondary cross-sectional force which is structurally disadvantageous remains. Therefore, it is desirable to reduce as much as possible the amount of PC steel rods arranged in the upper floor slab of the arch rib 102.
[0010]
The present invention has been made in view of such circumstances, and when extending an arch rib in a concrete arch bridge, it is possible to greatly reduce the amount of PC steel rods arranged in the upper slab of the arch rib. An object of the present invention is to provide a method for installing an arch rib that can be used.
[0011]
[Means for Solving the Problems]
In the present invention, the object is achieved by devising the fixing position of the forestay tip to the overhanging portion.
[0012]
That is, the construction method of the arch rib according to the present invention is as follows:
In the arch rib erection method, constructing at least a part of the arch rib in the concrete arch bridge as an erection erection part by adding a plurality of arch rib constituent blocks by erection erection from the end of the arch rib,
The base end portions of the plurality of forestays that obliquely suspend the overhanging construction portion are fixed to the forestay support structure constructed in the vicinity of the end portion of the arch rib, and the front end portions of the plurality of forestays are each arch rib constituting block There line of the above overhanging erection so as to fixation of the small,
In that case, the fore stay support structure is composed of an end post and a pair of blade walls extending from the end post to the back side, and the base ends of the fore stays are fixed to the back portions of the blade walls. It is characterized by.
[0013]
The above-mentioned “arch rib” may be constructed entirely by overhanging from the end of the arch rib, or only part of it may be constructed by overhanging from the end of the arch rib. There may be.
[0014]
The above-mentioned “multiple foray stays” means that a plurality of fore stays are used throughout the overhanging construction process. During the overhanging construction, a plurality of forestays are always fixed to each blade wall at the same time. However, it is not always necessary to change the number of fixings according to the stage of overhanging construction, and only one forestay may be temporarily fixed.
[0015]
[Effects of the invention]
As shown in the above configuration, the arch rib erection method according to the present invention is a projecting erection part in which at least a part of an arch rib in a concrete arch bridge is extended from an end part of the arch rib and a plurality of arch rib constituting blocks are added. The base ends of the multiple stay stays that slantly hang the overhanging construction part are fixed to the fore stay support structure built near the end of the arch rib, and the distal ends of the multiple stay stays are configured as arch ribs. Since the overhanging construction is carried out so as to be fixed at the small edge of the block, not only the negative bending moment acting on the end of the arch rib accumulated as the overhanging construction progresses can be reduced, but also Advantageous effects can be obtained.
[0016]
That is, at the time of overhanging construction, a negative bending moment acts on the tip of the overhanging construction part due to the weight of the wagen and the weight of the concrete placed by construction of a new arch rib component block. By fixing at the edge of each arch rib building block, it is possible to ensure positive bending at the tip of the overhanging construction part, so that the tip of the overhanging construction part can be properly supported even after the concrete mold is removed. it can. As a result, it is possible to greatly reduce the amount of PC steel bars that have conventionally been arranged in the upper floor slab of the arch rib.
[0017]
As described above, according to the present invention, when the arch rib is extended and installed in the concrete arch bridge, the amount of the PC steel rod disposed in the upper floor slab of the arch rib can be greatly reduced.
[0018]
And since the amount of this PC steel rod can be greatly reduced, unnecessary residual secondary force can be reduced and the sectional force state can be improved, so the amount of reinforcing bars used in the overhanging portion can also be reduced.
[0019]
In the above configuration, the angle at which each foray stay is arranged is not particularly limited, but it is preferable to arrange the fore stay at an angle close to the tangential direction of the arch axis from the viewpoint of preventing interference with the wageen.
[0020]
Further, in the above configuration, the fixing position of each foray stay on the fore stay support structure may be set at the same position, but if these are set at positions shifted in the vertical direction, the fore stay fixing work can be easily performed. In addition, each forestay can be easily arranged at an angle close to the tangential direction of the arch axis.
[0021]
Further, in the present invention, the forestay support structure is composed of an end post and a pair of blade walls extending from the end post to the back surface side, and the base end portion of each foray stay is fixed to the back surface portion of each blade wall. Therefore , it is possible to effectively resist the overturning moment at the time of overhanging construction. Moreover, in this case, the end post and the pair of blade walls can be raised in a U-shape at the same time, so that the lateral rigidity (stability) during the overhanging can be increased.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 is a side view showing a concrete arch bridge 10 that is a target of an arch rib erection method according to an embodiment of the present invention in a state immediately after completion of arch rib erection.
[0024]
As shown in the figure, the arch bridge 10 is an upper arch bridge having an arch span length of about 100 m, and is formed between a pair of arch abutments 12 constructed on the ground 2 on both sides in the bridge axis direction at the arch bridge construction position. The arch ribs 14 are erected, and the upper floor slab 20 is constructed above the arch ribs 14 and a pair of end posts 16 constructed on both sides in the bridge axis direction, whereby the erection is performed. In this arch bridge 10, a pair of blade walls (wings) 18 extending from the end posts 16 to the back side (anti-arch rib side) are constructed on both sides of each end post 16 in the direction perpendicular to the bridge axis. These pairs of blade walls 18 support both side edges of the upper floor slab 20.
[0025]
The arch rib 14 is constructed by closing a pair of overhanging portions 14A and 14B constructed by overhanging from both arch abuts 12 at the center portion of the span.
[0026]
2 to 9 are diagrams illustrating the overhanging process of the arch rib 14. Since this overhanging construction is performed in the same manner on both sides of the arch rib 14 in the bridge axis direction, the process of overhanging the overhanging construction portion 14A on one side will be described with reference to these drawings.
[0027]
First, as shown in FIG. 2, the arch abut 12 is applied to the ground 2 located at the end of the arch rib 14, and the end post 16 (forestay support structure) is constructed at the upper end of the arch abut 12. At that time, a pair of blade walls 18 (forestay support structure) is also constructed together with the end posts 16.
[0028]
Then, the base end portions 22 a of the plurality of ground anchors 22 are fixed to the ground 2 on the back side of the end post 16, and the tip end portions 22 b of the ground anchors 22 are fixed to the upper surface portion 18 a of the blade wall 18. At this time, the plurality of ground anchors 22 are arranged so as to spread radially from the distal end portion 22b to the proximal end portion 22a, and the fixing positions of the ground anchors 22 on the blade wall 18 are mutually in the front-rear direction. Set to a shifted position.
[0029]
Further, a springing support 30 is constructed on the front side (arch rib side) of the arch abut 12 and the arch rib constituting block A1 constituting the springing portion of the arch rib 14 is constructed. This construction is performed by the steps of mold installation, rebar PC assembly, and concrete placement curing.
[0030]
Next, as shown in FIG. 3, the front end 24b of the oblique stay forestay 24 is fixed to the fore edge (front end face) A1a of the arch rib constituting block A1, and the base end 24a of the forestay 24 is fixed to the blade wall 18. It is fixed to the back surface portion 18b. At that time, the fixing position of the fore stay 24 to the blade wall 18 is set to a lower position of the back surface portion 18b. After this fixing, the forestay 24 is tensioned to maintain the arch rib constituting block A1 in a slanting state so that it can resist the overturning moment. The fore stay 24 may be tensioned on either the base end portion 24a or the front end portion 24b (the same applies to the following). Thereafter, the wage 40 is assembled and installed on the arch rib building block A1.
[0031]
Next, as shown in FIG. 4, the arch rib constituting block A2 adjacent to the arch rib constituting block A1 is constructed so as to be cantilevered along the arch axis Ax by using the wage 40. This construction is performed by the steps of mold installation, rebar PC assembly, and concrete placement curing.
[0032]
Then, the front end portion 24b of the fore stay 24 is fixed to the fore edge A2a of the newly constructed arch rib constituting block A2, and the base end portion 24a is fixed to the back surface portion 18b of the blade wall 18. At that time, the fixing position of the fore stay 24 to the blade wall 18 is set to a position slightly shifted upward from the fore stay 24 used for obliquely hanging the arch rib constituting block A1. After this fixing, the forestay 24 is tensioned to maintain the arch rib constituent blocks A1 and A2 (the overhanging portion 14A) in a slanting state so that they can resist the overturning moment.
[0033]
Then, as shown in FIG. 5, the wage 40 is advanced along the arch axis Ax onto the arch rib constituting block A2 to prepare for the construction of the next arch rib constituting block A3.
[0034]
In the same manner, the arch rib constituent blocks A3, A4, A5,... Adjacent to the arch rib constituent block A2 are sequentially constructed, and these are overhanged by sequentially obliquely suspending them by the arrangement and tension of the fore stay 24. The construction part 14A is extended and constructed.
[0035]
FIG. 6 is a view showing a state immediately before the extension construction of the overhanging construction part 14A is completed up to the arch rib construction block A6 and the next construction of the arch rib construction block A7. FIG. Furthermore, it is a figure which shows the mode just before constructing the next arch rib structural block A11 after completing to the arch rib structural block A10. Moreover, FIG. 8 is a figure which shows a mode that the arch rib structural block A13 in front of an arch crown is constructed.
[0036]
As shown in these drawings, the forestay 24 is fixed to each of the arch rib constituting blocks A3, A4, A5,..., And the small ends A3a, A4a, A5a, etc. of the arch rib constituting blocks A3, A4, A5,. Further, the fixing positions of the fore stays 24 on the blade wall 18 are set at positions that are sequentially shifted upward at substantially equal intervals. Of the forestays 24 that have already been arranged, the forestay 24 arranged at a position closer to the arch abut 12 does not contribute much to the resistance of the overturning moment, so that the extension construction of the overhanging portion 14A is progressing. It will be removed sequentially.
[0037]
As shown in FIG. 8, when the extending construction of the overhanging construction part 14A has progressed to the arch rib constituting block A13 just before the arch crown, the overhanging construction has been carried out simultaneously with the overhanging construction part 14A from the opposite side in the bridge axis direction. The overhanging construction part 14B is also in a state where the extension construction has progressed to the arch rib constituting block B13.
[0038]
Then, as shown in FIG. 9, the construction of the last arch rib constituting block A14 (B14) located in the arch crown closes the pair of overhanging portions 14A and 14B on both sides in the bridge axis direction, and the arch rib 14 is installed. After completion, the wage 40 is removed, and the fore stay 24 is also removed.
[0039]
As described above in detail, the arch rib erection method according to the present embodiment is configured such that the arch rib 14 in the concrete arch bridge 10 is extended from the end portion of the arch rib 14 and a plurality of arch rib constituting blocks A1, A2, A3, Are constructed as an overhanging construction part 14A (or 14B), a pair of base ends 24a of a plurality of forestays 24 that obliquely hang the overhanging construction part 14A is constructed in the vicinity of the end of the arch rib 14. Are fixed to each of the blade walls 18 and the tips 24b of the plurality of forestays 24 are fixed to the small ends A1a, A2a, A3a,... Of the arch rib constituting blocks A1, A2, A3,. Therefore, it acts on the end portion of the arch rib 14A that accumulates as the overhanging progresses. Bending moment can not only reduce, it is possible to obtain the following effects of.
[0040]
That is, at the time of overhanging construction, a negative bending moment acts on the tip of the overhanging construction portion 14A due to the weight of the wage 40 and the weight of the concrete placed by construction of a new arch rib component block. By fixing the distal end portion 24b to the small ends A1a, A2a, A3a,... Of each arch rib constituting block A1, A2, A3,. Therefore, the end portion of the overhanging portion 14A can be properly supported even after the concrete mold is removed. As a result, it is possible to greatly reduce the amount of PC steel bars that have conventionally been arranged in the upper floor slab of the arch rib.
[0041]
Thus, according to this embodiment, when extending the arch rib 14 in the concrete arch bridge 10, the amount of the PC steel bars arranged in the upper floor slab of the arch rib 14A can be greatly reduced.
[0042]
And since the amount of this PC steel bar can be significantly reduced, unnecessary residual secondary force can be reduced and the sectional force state can be improved, so that the amount of reinforcing bars used in the overhanging portion 14A can also be reduced.
[0043]
In addition, in the present embodiment, each fore stay 24 is arranged at an angle close to the tangential direction of the arch axis Ax, so that the front end 24b of the fore stay 24 is not interfered with the wage 40. It can fix to small edge A1a, A2a, A3a, ... of each arch rib structural block A1, A2, A3, ....
[0044]
Further, in the present embodiment, the fixing positions of the fore stays 24 on the blade wall 18 are set at positions shifted from each other in the vertical direction, so that the fixing work of the fore stays 24 can be easily performed, It becomes possible to arrange each fore stay 24 at an angle close to the tangential direction of the arch axis Ax.
[0045]
Further, in the present embodiment, a forestay support structure is constituted by the end post 16 and a pair of blade walls 18 extending from the end post 16 to the back side, and the base ends of the forestays 24 are provided on the back surface of each blade wall 18. Since the portion 24a is fixed, it is possible to effectively resist the overturning moment during the overhanging construction. Moreover, since the end post 16 and the pair of blade walls 18 can be raised in a U-shape at the same time, the lateral rigidity (stability) during the overhanging can be increased.
[0046]
Instead of doing this, it is also possible to fix the base end portion 24a of each fore stay 24 to the end post 16 or fix it to a pyrone installed on the end post 16.
[0047]
By the way, in the above-described embodiment, among the forestays 24 that have already been arranged, the forestays 24 that are arranged near the arch abut 12 are sequentially removed as the extension construction of the overhanging portion 14A progresses. However, the forestays 24 may not be removed until the arch rib 14 has been installed.
[0048]
Moreover, in embodiment, although demonstrated as what constructs each arch rib structural block which comprises overhanging construction part 14A, 14B by the cast-in-place construction method, it constructs by the precast segment construction method which assembles the arch rib structural block manufactured beforehand in the factory etc. Even in this case, the same effects as those in the above embodiment can be obtained by employing the same construction method as in the above embodiment.
[0049]
Furthermore, in the above-described embodiment, the case where the arch rib 14 is installed over the entire length by extending the bridge erection position from both sides in the bridge axial direction has been described. However, the bridge erection position has a predetermined length by extending from the both sides in the bridge axis direction. Even when the arch rib 14 is constructed by closing the central portion of the arch rib 14 with a melane material after the construction of the overhang construction portion, the construction method of the above embodiment can be adopted at the time of the overhang construction. Is possible. Even in this case, the same effect as that of the above embodiment can be obtained.
[0050]
Moreover, in the said embodiment, although the concrete arch bridge 10 used as the object of the construction method of the arch rib 14 was demonstrated as an upper arch bridge, when it is a middle arch bridge or a lower arch bridge However, by adopting the same construction method as in the above embodiment, the same effects as in the above embodiment can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view showing a concrete arch bridge subject to an arch rib laying method according to an embodiment of the present invention in a state immediately after completion of arch rib laying. FIG. 2 shows an arch rib overhanging step in the embodiment. Side view (Part 1)
FIG. 3 is a main part side view showing the arch rib overhanging step (part 2).
FIG. 4 is a side view of an essential part showing an overhanging step of the arch rib (No. 3).
FIG. 5 is a side view of the main part showing the arch rib overhanging step (No. 4).
FIG. 6 is a side view of the main part showing the arch rib overhanging step (No. 5).
FIG. 7 is a side view of the main part showing the arch rib overhanging step (No. 6).
FIG. 8 is a main part side view showing the arch rib overhanging step (No. 7);
9 is a side view of an essential part showing a state immediately after the arch rib overhanging step is completed. FIG. 10 is a view similar to FIG. 6 showing a conventional example.
2 Ground 10 Concrete arch bridge 12 Archabat 14 Arch ribs 14A, 14B Overhang construction part 16 End post (forestay support structure)
18 Wing Wall (Forestay Support Structure)
18a Upper surface portion 18b Back surface portion 20 Upper floor slab 22 Ground anchor 22a Base end portion 22b Tip end portion 24 Fore stay 24a Base end portion 24b Tip end portion 30 Springing support 40 Wagen A1 to A13, A14 (B14), B11 to B13 Arch rib configuration Block A1a-A6a, A10a, A13a, B13a Small-mouth Ax Arch axis

Claims (2)

In the arch rib erection method, constructing at least a part of the arch rib in the concrete arch bridge as an erection erection part by adding a plurality of arch rib constituent blocks by erection erection from the end of the arch rib,
The base end portions of the plurality of forestays that obliquely suspend the overhanging construction portion are fixed to the forestay support structure constructed in the vicinity of the end portion of the arch rib, and the front end portions of the plurality of forestays are each arch rib constituting block There line of the above overhanging erection so as to fixation of the small,
In that case, the fore stay support structure is composed of an end post and a pair of blade walls extending from the end post to the back side, and the base ends of the fore stays are fixed to the back portions of the blade walls. An arch rib installation method characterized by the above.   2. The arch rib installation method according to claim 1, wherein a fixing position of each of the fore stays to the fore stay support structure is set to a position shifted from each other in the vertical direction.

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