Strut connection structure

Abstract

To provide a strut connection structure which is easy to construct and whose construction period can be shortened.SOLUTION: A strut connection structure is a structure for connecting the lower part of the outer surface of a main girder with a strut, which diagonally connects the lower part of the outer surface of the main girder and an overhanging deck of a box girder bridge. The connection structure includes a first joint surface provided at the lower part of the outer surface of the main girder, a second joint surface provided on the strut to be joined to the first joint surface, a steel pipe insertion hole opening on the first joint surface, a recess part provided in the second joint surface to form a space between the first joint surface and the second joint surface, a steel shear key fitted into the space, a steel pipe that penetrates the steel shear key in the axial direction of the strut and is inserted into the steel pipe insertion hole with one end protruding from the lower surface of the steel shear key, and an anchor bar attached to the strut so that the tip protrudes from the second joint surface. Inserting the anchor bar into the steel pipe of the steel shear key fitted into the space causes the strut to be connected to the lower part of the outer surface of the main girder.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present invention relates to a connection structure between the lower part of the main girder of a strut that supports a cantilever floor slab in a concrete bridge.

Background Art

[0002] In the upper structure of a concrete bridge, the side ends of the floor slab that constitutes the road surface are often constructed so as to project from the main girder body. Particularly in a large box girder bridge, the width of the cantilever floor slab becomes large, and the floor slab thickness tends to increase in order to safely support the vehicle load to be carried. In order to avoid this, a structure in which the lower part of the main girder and the tip of the cantilever floor slab are connected by a strut (rod-shaped bracing member) is often adopted. Also, when extending the cantilever floor slab toward the outside of the main girder in order to widen the floor slab, a strut may be adopted to support the extended cantilever floor slab.

[0003] Examples of the conventional structure for connecting the lower part of the main girder and the tip of the cantilever floor slab with a strut are as follows. For example, Patent Document 1 discloses a bridge superstructure including a cantilever floor slab projecting laterally from the main girder part, a receiving member fixed to the lower part of the main girder part, and a strut rising obliquely upward from the receiving member, and the cantilever floor slab is supported by the strut. An engaging convex part is formed on the back surface of the receiving member, and an engaging concave part having a depth equal to or less than the cover thickness of the reinforcing bar is formed on the lower surface of the lower part of the main girder part, and the receiving member is fixed to the main girder part in a state where the engaging convex part is fitted into the engaging concave part.

Prior Art Documents

Non-Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0006] Furthermore, the receiving member has an engaging projection formed on its back surface, and is fixed by fitting the engaging projection of the receiving member into an engaging recess formed on the lower outer surface of the main girder. The engaging recess on the lower outer surface of the main girder is formed by creating an incision with a concrete cutter and removing the concrete remaining in the incision. However, with this structure, the shear force acting on the receiving member is transmitted to the main girder by the interlocking of the engaging projection of the receiving member and the engaging recess of the main girder. Therefore, precision is required in forming the engaging recess of the main girder, and construction is time-consuming. This may increase costs and prolong the construction period.

[0007] This invention was made to solve these problems, and its objective is to provide a strut connection structure that is easy to install and can shorten the construction period. [Means for solving the problem]

[0008] In order to achieve the above objective, the strut connection structure according to the present invention provides a connection structure for a strut that diagonally connects the lower outer surface of the main girder of a box girder bridge to the cantilevered deck, with respect to the lower outer surface of the main girder. A first joint surface provided on the lower part of the outer surface of the main girder, a second joint surface provided on the strut so as to be joined to the first joint surface, and a steel pipe insertion hole opening to the first joint surface, The strut is configured to be connected to the lower part of the outer surface of the main girder by inserting the anchor bar into the steel pipe of the steel shear key which is fitted into the space between the first and second joining surfaces, a recess provided on the second joining surface which is fitted into the space, a steel shear key which is fitted into the space, a steel pipe which is inserted into the steel pipe insertion hole which is fitted into the space, and an anchor bar which is attached to the strut such that its tip protrudes from the second joining surface, and the strut is connected to the lower part of the outer surface of the main girder by inserting the anchor bar into the steel pipe of the steel shear key which is fitted into the space.

[0009] Furthermore, in the strut connection structure described above, a torsion-preventing plate may be provided on the steel shear key, and a plate fitting portion may be formed on the first joint surface in which the torsion-preventing plate is fitted in the axial direction of the strut to restrict the movement of the strut in the axial direction. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view of a box girder bridge structure as seen from the direction of the road lanes. [Figure 2] This is a cross-sectional view showing the strut connection structure of this embodiment. [Figure 3] This is a three-view drawing of a steel shear key 104. [Figure 4] This diagram shows the construction procedure for the strut joint structure of this embodiment. [Figure 5] This is a cross-sectional view showing a modified example of the strut connection structure of the above embodiment. [Figure 6] These are three-view drawings of the steel shear key 104 used in the strut connection structure of the above modified example. [Figure 7] This diagram shows the construction procedure for the strut connection structure of the above embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described based on the drawings. Figure 1 is a side view of a box girder bridge structure employing the strut connection structure according to the present invention, as seen in the direction of the road lane. As shown in the figure, the box girder bridge structure of this embodiment comprises a pair of left and right web sections (main girder sections) 11a and 11b, an upper deck slab 12 installed between the upper ends of the pair of left and right web sections 11a and 11b, an overhanging deck slab 13 extending laterally from the upper deck slab 12 beyond the web section 11b, a lower deck slab 14 provided to connect the lower ends of the pair of left and right web sections 11a and 11b, and a strut 20 that diagonally connects the overhanging deck slab 13 to the lower part of one of the web sections 11b (the lower part of the outer surface of the main girder).

[0012] The web sections 11a, 11b, the upper deck 12, the cantilevered deck 13, and the lower deck 14 can be made of, for example, cast-in-place reinforced concrete, precast concrete, or prestressed concrete. The web sections 11a, 11b, the upper deck 12, the cantilevered deck 13, and the lower deck 14 are all constructed as continuous wall-like structures in the direction of the bridge axis, forming a box girder with a cavity inside. The struts 20 are made of, for example, columnar cast-in-place reinforced concrete, precast concrete, prestressed concrete, or steel pipes. The upper end of the strut 20 is connected to a connection part 15 provided on the lower surface of the cantilevered deck 13, and the lower end of the strut 20 is connected to a base part 16 (lower part of the outer surface of the main girder) provided at the bottom of the web section 11b.

[0013] Next, the connection structure between the strut 20 and the base portion 16 of the web portion 11b (strut connection structure) will be described. Figure 2 is a cross-sectional view showing a strut connection structure. As shown in the figure, this strut connection structure includes a web-side joining surface 101 (first joining surface) provided on the base portion 16 (lower part of the outer surface of the main girder) of the web portion 11b, a strut-side joining surface 107 (second joining surface) provided at the end of the strut 20 so as to abut and join with the web-side joining surface 101, a steel pipe insertion hole 102 opening in the web-side joining surface 101, a recess 103 formed in the strut-side joining surface 107, and a steel shear key 104 fitted into the space of the recess 103 between the web-side joining surface 101 and the strut-side joining surface 107.

[0014] Here, the details of the steel shear key 104 will be explained using Figure 3. Figure 3 is a three-view drawing of the steel shear key 104. As shown in the figure, the steel shear key 104 has a truncated pyramidal shape. The steel shear key 104 has an upper surface 104a, a lower surface 104b, and four inclined sides 104c, 104d, 104e, and 104f. The upper surface 104a and the lower surface 104b are parallel to each other, and the area of ​​the upper surface 104a is smaller than the area of ​​the lower surface 104b. The material for the steel shear key 104 can be general structural rolled steel such as SS400.

[0015] A steel pipe 105 is fixed to the steel shear key 104 by welding or screwing, so as to pass through it vertically. The steel pipe 105 can be a general carbon steel pipe for piping, such as an SGP pipe or STKM pipe. One upper end of the steel pipe 105 is aligned with the upper surface 104a of the steel shear key 104, and the other end of the steel pipe 105 protrudes from the lower surface 104b of the steel shear key 104. One upper end of the steel pipe 105 is open so that the anchor bar 106 of the strut 20 can be inserted. The anchor bar 106 has a circular cross-sectional shape, and its outer diameter is slightly smaller than the inner diameter of the steel pipe 105. For example, if the diameter of the anchor bar 106 is φ20 mm, the inner diameter of the steel pipe 105 is about φ30 mm. The gap between the inner wall surface of the steel pipe 105 and the anchor bar 106 is filled with a filler such as epoxy resin. The anchor bar 106 is made of a non-corrosive material and may be composed of, for example, carbon fiber reinforced plastic or stainless steel rebar.

[0016] Returning to Figure 2, the web-side joining surface 101 and the strut-side joining surface 107 are in contact with each other. The web-side joining surface 101 is a surface (inclined surface) perpendicular to the axial direction of the strut 20. More specifically, a pedestal portion 16 that bulges laterally is provided at the lower end of the web portion 11b, and the web-side joining surface 101 is provided on this pedestal portion 16. A steel pipe insertion hole 102 that opens to the web-side joining surface 101 is drilled into the pedestal portion 16.

[0017] On the other hand, the strut-side joint surface 107 is a surface that abuts against the web-side joint surface 101 and is perpendicular to the axial direction of the strut 20. The above-mentioned recessed portion 103 is provided on this strut-side joint surface 107. The recessed portion 103 is formed at the center of the strut-side joint surface 107 and forms a space for fitting the steel shear key 104 between the web-side joint surface 101. In this space, the above-mentioned steel shear key 104 is disposed with a steel pipe 105 protruding from the lower surface 104b of the steel shear key 104 inserted into the steel pipe insertion hole 102 that opens to the web-side joint surface 101 of the pedestal portion 16. The outer diameter of the steel pipe 105 is slightly smaller than the inner diameter of the steel pipe insertion hole 102. For example, when the outer diameter of the steel pipe 105 is φ38 mm, the inner diameter of the steel pipe insertion hole 102 is about φ50 mm. The gap between the inner wall surface of the steel pipe insertion hole 102 and the outer peripheral surface of the steel pipe 105 is filled with a filler such as epoxy resin to prevent the intrusion of water or the like into the steel pipe insertion hole 102.

[0018] The aforementioned anchor bar 106 is fixed to the lower end portion of the strut 20. The anchor bar 106 is provided with one end protruding in the axial direction of the strut 20 from the recessed portion 103 of the strut 20. The protruding portion of this anchor bar 106 is inserted into the steel pipe 105 of the steel shear key 104 fitted into the space between the web-side joint surface 101 and the recessed portion 103. Here, the steel pipe 105 protruding from the lower surface 104b of the steel shear key 104 is inserted into the steel pipe insertion hole 102 provided on the web-side joint surface 101 of the pedestal portion 16 and held here. As a result, a connection structure of the strut 20 with required shear rigidity is obtained.

[0019] Next, the construction procedure of the strut connection structure of the present embodiment will be described with reference to FIG. 4. FIG. 4 is a diagram showing the construction procedure of the strut joint structure. First, as shown in (A), a steel pipe insertion hole 102 is drilled in the web-side joint surface 101 in a direction along the axial direction of the strut 20, and a filler such as epoxy resin is injected into the steel pipe insertion hole 102. Next, as shown in (B), the protruding portion of the steel pipe 105 of the steel shear key 104 is inserted into the steel pipe insertion hole 102. At this time, the steel shear key 104 is inserted until its lower surface 104b abuts against the web-side joining surface 101. Next, a filler such as epoxy resin is injected into the steel pipe 105 of the steel shear key 104, and as shown in (C), the portion protruding from the lower end of the anchor bar 106 provided on the strut 20 is inserted into the steel pipe 105 which opens to the upper surface 104a of the steel shear key 104. This fills the space between the inner wall surface of the steel pipe 105 and the surface of the anchor bar 106 with the filler. When the strut-side joint surface 107 comes into contact with the web-side joint surface 101, the steel shear key 104 is fitted into the space between the web-side joint surface 101 and the recess 103 of the strut-side joint surface 107, thereby completing the connection between the strut 20 and the web 11b.

[0020] The joining structure of the strut 20 having the above configuration provides the following advantages compared to the technology described in Patent Document 1, which is cited as a conventional technology. According to the technology described in Patent Document 1, in order to form an engagement recess in the main girder, a concrete cutter was used to cut into the main girder and remove the concrete in the area to be formed as the engagement recess. In this technology described in Patent Document 1, the shear force acting on the receiving member is transmitted to the main girder by the interlocking of the engagement projection of the receiving member and the engagement recess of the main girder. Therefore, the formation of the engagement recess in the main girder requires high precision, making construction time-consuming, which is considered to be one of the obstacles to shortening the construction period. In contrast, in the strut connection structure of this embodiment, the construction on the web portion 11b side only requires drilling the steel pipe insertion holes 102 with a drill, thus reducing the time and effort required for construction and enabling a shortened construction period. Furthermore, since only one steel pipe insertion hole 102 is needed for each connection point of the strut 20, it is easy to avoid interference with the reinforcing bars placed in the web portion 11b.

[0021] Furthermore, in the technology described in Patent Document 1, the anchor bar of the strut is directly inserted into the insertion hole of the engagement recess in the main girder, so there is a risk of damaging the insertion hole or the surrounding area of ​​the main girder when connecting the strut. On the other hand, according to this embodiment, the anchor bar 106 is inserted into and held within the steel pipe 105, thus reducing the risk of damaging the web portion 11b.

[0022] Furthermore, the strut connection structure of this embodiment eliminates the need for special material components such as receiving members made of ultra-high-strength fiber-reinforced concrete, thus simplifying the component manufacturing process and reducing costs.

[0023] Next, a modified example of the strut joint structure of this embodiment will be described. Figure 5 is a cross-sectional view showing the strut connection structure of this modified example, and Figure 6 is a three-view drawing of the steel shear key 104 used in the strut connection structure of this modified example. In these figures, the same reference numerals are used for the same parts as in the above embodiment. Here, only the parts that differ from the structure of the above embodiment will be described.

[0024] As shown in Figures 5 and 6, a torsion prevention plate 110 is added to the steel shear key 104 used in this modified strut connection structure. The torsion prevention plate 110 is fixed to the lower surface 104 of the steel shear key 104 on the side facing the first joint surface 101, for example, by welding or screwing. The torsion prevention plate 110 has a steel pipe insertion hole 112 for inserting a steel pipe 105 that penetrates the steel shear key 104 vertically.

[0025] On the other hand, as shown in Figure 7(A), a plate fitting portion 111 is provided at the open end of the steel pipe insertion hole 102 drilled in the web-side joint surface 101, into which the anti-torsion plate 110 is fitted in the axial direction of the strut 20. The plate fitting portion 111 is a recess corresponding to the outer shape of the anti-torsion plate 110 and has a depth equal to the thickness of the plate fitting portion 111. By fitting the anti-torsion plate 110 three-dimensionally into the plate fitting portion 111, it is possible to prevent the steel pipe 105, steel shear key 104, and strut 20, which are structural elements on the strut 20 side, from rotating in response to rotational forces applied to the strut 20. Furthermore, it is possible to prevent construction problems such as the steel shear key rotating from a predetermined position during installation and not fitting correctly into the recess when connecting the strut.

[0026] In this modified example, a rectangular anti-torsion plate 110 is used, but any shape is acceptable as long as it can suppress the rotation of the structure on the strut 20 side.

[0027] It goes without saying that the strut connection structures of the embodiments and their modified forms described above can be used in the construction of new road bridges with cantilevered decks using struts, and in the construction of existing road bridges where cantilevered decks and the struts for them are added. In particular, when adding cantilevered decks and the struts for them, the fact that the construction work on the existing main girder section 11 only requires drilling steel pipe insertion holes 102 is a major advantage in reducing construction costs and shortening construction time. [Explanation of symbols]

[0028] 11a, 11b...Web Department 12…Main floor slab 13...Extruded floor plate 14…Bottom plate 15…Connection part 16…Base 20... Strut 101... Web side joint surface 102... Steel pipe insertion hole 103... recessed area 106... Anchor bar 107... Strut side joint surface 110...Anti-twist plate 111...Plate fitting section

Claims

1. In the connection structure of a strut that diagonally connects the lower outer surface of the main girder of a box girder bridge to the cantilevered deck, A first joint surface is provided on the lower part of the outer surface of the main girder and is a surface perpendicular to the axial direction of the strut, A second joining surface is provided on the strut so as to be joined to the first joining surface, and the second joining surface is a surface perpendicular to the axial direction of the strut, A steel pipe insertion hole opening into the first joint surface, A recess is provided on the second joining surface so as to form a space between the first joining surface and the second joining surface, A steel shear key fitted into the aforementioned space, A steel pipe is inserted into the steel shear key in the axial direction of the strut, with one end protruding from the lower surface of the steel shear key and inserted into the steel pipe insertion hole. The assembly comprises an anchor bar attached to the strut such that its tip protrudes from the second joint surface, The anchor bar is inserted into the steel pipe of the steel shear key fitted into the space, thereby connecting the strut to the lower part of the outer surface of the main girder. Strut connection structure.

2. A strut connection structure according to claim 1, A torsion-preventing plate is provided on the steel shear key, and a plate fitting portion is formed on the first joint surface that allows the torsion-preventing plate to be fitted in the axial direction of the strut to restrict the movement of the strut in the axial direction. Strut connection structure.

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