Joining structure and joining method

Abstract

To provide a junction structure and a joining method in a junction structure between a precast slab and a steel girder that improve a degree of freedom in design and workability.SOLUTION: A junction structure 1 is a junction structure that joins a steel girder 103 and a precast slab 3 installed on an upper flange 105 of the steel girder 103, and includes an anti-misalignment portion 23 having a projection 21 that is provided on an upper surface 105a of the upper flange 105 and protruding upward, an insert nut 7 embedded in a lower surface 3a of the precast slab 3, a bolt 9 attached to the insert nut 7 and projecting downward from the lower surface 3a of the precast slab 3, and a filling material 15 that is filled between the upper surface 105a of the upper flange 105 and the lower surface 3a of the precast slab 3 so as to embed the projection 21 and the bolt 9. The upper end of the projection 21 of the anti-misalignment portion 23 is closer to the upper surface 105a of the upper flange 105 than the lower end of the bolt 9.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a joining structure and joining method for joining a steel girder to a precast deck installed on the upper flange of the steel girder. [Background technology]

[0002] Conventionally, the joining structure and joining method disclosed in the following Patent Document 1 are for joining a steel girder and a precast deck installed on the upper flange of the steel girder. In this joining structure and joining method, a stud dowel is provided on the upper surface of the flange of the steel girder. An insert nut is embedded in the lower surface of the precast deck, and a bolt is attached to this insert nut so as to protrude downward. When joining the precast deck to the steel girder, the precast deck is installed on the upper surface of the flange in a positional relationship such that the lower end of the bolt is located below the upper end of the stud dowel, and a filler is filled between the upper surface of the upper flange and the lower surface of the precast deck so as to embed the stud dowel and the bolt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-1457 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned joint structure had to be designed so that the bolts and the stud dowels did not interfere with each other, which resulted in many design constraints. In addition, when constructing the above-mentioned joint structure, the precast deck had to be installed on the flange while adjusting the position so that the bolts did not interfere with the stud dowels, which resulted in poor workability. The present invention aims to provide a joint structure and a joint method for a joint structure between a precast deck and a steel girder that improves design freedom and workability. [Means for solving the problem]

[0005] The joining structure of the present invention is a joining structure for joining a steel girder and a precast deck installed on the upper flange of the steel girder, and comprises a slip prevention portion having a protrusion provided on the upper surface of the upper flange and protruding upward, an insert nut embedded in the underside of the precast deck, a bolt attached to the insert nut and protruding downward from the underside of the precast deck, and filler filled between the upper surface of the upper flange and the underside of the precast deck so as to embed the protrusion and the bolt, and the upper end of the protrusion of the slip prevention portion is positioned closer to the upper surface of the upper flange than the lower end of the bolt.

[0006] The joint structure of the present invention may be a joint structure of a precast deck constructed by replacing a deck on an upper flange of a steel girder, and the projection of the shear stopper may have a remnant of a projection included in the shear stopper of the deck before replacement. Also, the filler may be an ultra-high performance fiber-reinforced cement-based composite material.

[0007] The joining method of the present invention is a joining method for joining a steel girder and a precast deck installed on the upper flange of the steel girder, and includes a deck installation process in which a precast deck having an insert nut embedded in its underside and a bolt attached to the insert nut is installed on the upper surface of an upper flange provided with a slip prevention part having a protrusion protruding upward, and a filling process in which filler material is filled between the upper surface of the upper flange and the underside of the precast deck so as to embed the protrusion and the bolt, and in the deck installation process, the precast deck is installed so that the upper end of the protrusion of the slip prevention part is positioned closer to the upper surface of the upper flange than the lower end of the bolt. Effect of the Invention

[0008] According to the present invention, it is possible to provide a joint structure and a joining method that improves design freedom and improves workability in a joint structure between a precast deck and a steel girder. [Brief description of the drawings]

[0009] [Figure 1] 1 is an exploded perspective view of a road bridge to which the joint structure and joining method of the present embodiment are applied. [Diagram 2] 14(a), (b), and (d) are enlarged side views of the upper part of the steel girder, and (c) is an enlarged side view of the lower part of the precast deck. [Diagram 3] A cross-sectional view of a precast deck. [Figure 4] 1(a) and 1(b) are cross-sectional views showing a precast deck and steel girders. [Diagram 5] 13(a) and 13(b) are cross-sectional views showing the precast deck installed on the steel girders. [Figure 6] 13(a) and 13(b) are cross-sectional views showing the state in which filler has been filled between the precast deck and the steel girder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a joining structure and a joining method according to the present invention will be described in detail with reference to the drawings.

[0011] 1 is an exploded perspective view of a road bridge 101 to which the joint structure and joining method according to this embodiment are applied. The precast deck 3 is made of a concrete-based material and may be used when constructing a road bridge or may be used to replace the deck of an existing road bridge. The precast deck 3 has a rectangular shape in plan view, for example, about 2 m in the bridge axis direction and about 11 m in the direction perpendicular to the bridge axis.

[0012] The road bridge 101 has a plurality of steel girders 103 (three in the example shown in the figure) extending in the bridge axis direction. The precast deck 3 is spanned over the three steel girders 103 and joined at three points at the joints 107 of the upper flanges 105 of each steel girder 103. A road structure is constructed by arranging and installing a plurality of precast decks 3 in the bridge axis direction. The precast decks 3 are connected to each other in the bridge axis direction by a predetermined joint structure. The road bridge 101 is a composite girder, and it is important to have a slip stop between the precast deck 3 and the steel girders 103 so that the steel girders 103 and the precast deck 3 are integrated to resist loads.

[0013] The following describes a joining structure and method for joining the steel girder 103 and the precast deck 3 in this road bridge 101. The joining structure and method described below are applied when replacing the old deck of the road bridge 101 with a new precast deck 3.

[0014] 2 to 6 are cross-sectional views sequentially showing each step of a joining method for one precast deck 3, showing cross-sectional views at a position corresponding to a joint 107. FIGS. 2(a), (b), and (d) are side views showing an enlarged view of the upper part of the steel girder 103. FIG. 2(c) is a side view showing an enlarged view of the lower part of the precast deck 3. FIG. 3 is a cross-sectional view of the precast deck 3 taken in a vertical section extending in the bridge axis direction. In each of FIGS. 4 to 6, (a) is a cross-sectional view of the precast deck 3 and the steel girder 103 taken in a vertical section extending in the bridge axis direction, and (b) is a cross-sectional view of the precast deck 3 and the steel girder 103 taken in a vertical section extending in a direction perpendicular to the bridge axis.

[0015] In the road bridge 101 before the deck replacement, a stud dowel is provided on the upper surface 105a (hereinafter referred to as the "flange upper surface 105a") of the upper flange 105 of the steel girder 103, and the deck is provided with concrete so that the stud dowel is embedded in the underside. This stud dowel functions as a slip stopper for the deck before replacement. When replacing the deck, a cutting tool is inserted between the underside of the old deck and the flange upper surface 105a to cut off the head of the stud dowel, and the old deck is removed. After the old deck is removed, as shown in FIG. 2(a), the remains 10 of many cut stud dowels remain on the flange upper surface 105a. The remains 10 are in a state where the heads of the stud dowels have been cut off and only the round bar-shaped trunks remain, and protrude upward from the flange upper surface 105a.

[0016] (Steel girder processing process) In the steel girder processing step, as shown in FIG. 2(b), some of the debris 10 on the flange upper surface 105a is further cut and removed, and the removed area is polished and smoothed. Meanwhile, the other debris 10 remaining on the flange upper surface 105a is left as is. Here, the number of debris 10 left is, for example, about 1 / 4 to 1 / 3 of the total debris 10. The arrangement of the debris 10 left may be irregular or may follow a predetermined rule.

[0017] (Precast deck preparation process) As shown in FIG. 3, a precast deck 3 is prepared. The precast deck 3 has a plate-shaped structural part 5 made of a concrete-based material, and a plurality of insert nuts 7 embedded in the structural part 5. The insert nuts 7 are embedded in the lower surface 3a of the precast deck 3 and exposed on the lower surface of the structural part 5. The "lower surface" refers to the surface that forms the lower surface when the precast deck 3 is finally installed on the road bridge 101. The lower end surface of the insert nuts 7 is located at a position that is approximately flush with the lower surface 3a of the precast deck 3.

[0018] In a plan view, the insert nuts 7 are two-dimensionally arranged in an area corresponding to the joint 107 with the upper flange 105. For example, about a hundred and several tens of insert nuts 7 are arranged for one joint 107. The number and arrangement of the insert nuts 7 as described above are merely an example, and the actual number and arrangement are appropriately set according to the slip prevention performance required between the precast deck 3 and the steel girder 103. Such a precast deck 3 is fabricated in advance in a factory or the like and transported to the construction site of the road bridge 101.

[0019] (Bolt installation process) Next, as shown in FIG. 4, the bolts 9 are screwed into each insert nut 7 of the precast floor slab 3. At this time, as shown in an enlarged view in FIG. 2(c), at least some of the bolts 9k among the bolts 9 have a threaded portion longer than the threaded portion of the insert nut 7, and are screwed in until the tip of the threaded portion abuts against the female thread bottom of the insert nut 7, and protrude downward from the lower surface 3a of the precast floor slab 3. A vertical gap is formed between the head of the bolt 9 and the lower surface 3a of the precast floor slab 3. The head side of each of these bolts 9k protrudes downward from the lower surface 3a of the precast floor slab 3 by approximately the same length. The remaining bolts 9j among the bolts 9 have a threaded portion shorter than the threaded portion of the insert nut 7, and are screwed in until the head abuts against the lower surface 3a, and protrude downward from the lower surface 3a by the thickness of the head. In this way, the arrangement of two types of bolts 9k, 9j having different protruding amounts may be irregular or may follow a predetermined rule. This bolt attachment process may be carried out in advance at a factory or the like before the precast deck 3 is transported to the construction site.

[0020] (Stud dowel installation process) As shown in FIG. 4, a plurality of stud dowels 11 protruding upward are installed on the flange upper surface 105a of the steel girder 103. As shown in an enlarged view in FIG. 2(d), the stud dowels 11 have a round bar-shaped body 11b extending upward from the flange upper surface 105a, and a head 11a provided at the upper end of the body 11b and formed with a larger diameter than the body 11b. Each stud dowel 11 protrudes vertically upward from the flange upper surface 105a by approximately the same length. Each stud dowel 11 is melt-planted on the flange upper surface 105a by a known method so as not to overlap with the installation position of the remnant 10 left on the flange upper surface 105a as described above. For example, the stud dowel 11 may be melt-planted at the position of the removal trace of the polished remnant 10. The stud dowel 11 melt-planted here may be the same as the old stud dowel of the deck before replacement, or may be different.

[0021] Hereinafter, the stud dowels 11 fused to the flange upper surface 105a and the remnants 10 left on the flange upper surface 105a are collectively referred to as "projections 21." A large number of such projections 21 form a slip prevention portion 23 on the flange upper surface 105a. The projections 21 are two-dimensionally arranged in an area corresponding to the joint portion 107 in a plan view, and the same number of projections 21 as the bolts 9 described above are provided. In the example of Figs. 4 to 6, the projections 21 and the bolts 9 are provided in positions facing each other vertically, but the arrangement is not limited to this, and the projections 21 and the bolts 9 may be positioned offset from each other in a plan view.

[0022] Note that the number and arrangement of the debris 10 left on the flange upper surface 105a, the stud dowels 11 welded into the flange upper surface 105a, and the bolts 9k and 9j of the precast deck 3 shown in each figure are just examples, and the actual number and arrangement will be set appropriately depending on the anti-slip performance required between the precast deck 3 and the steel girder 103.

[0023] (Floor slab installation process) Next, as shown in FIG. 5, the precast deck 3 is installed on the steel girder 103. In the installed state, the lower surface 3a of the precast deck 3 and the flange upper surface 105a of the steel girder 103 face each other with a predetermined gap therebetween. In order to form a gap between the lower surface 3a and the flange upper surface 105a as described above, a spacer (not shown) or the like is sandwiched between them. In addition, in this installed state, the upper end of the projection 21 of the anti-slip portion 23 is located closer to the flange upper surface 105a (i.e., lower) than the lower end of the bolt 9. In other words, the upper end of the projection 21 that protrudes most upward (the stud dowel 11) is located closer to the flange upper surface 105a than the lower end of the bolt 9k that protrudes most downward among the bolts 9. In other words, the gap between the lower surface 3a of the precast deck 3 and the flange upper surface 105a is larger than the sum of the protrusion amount of the bolt 9k and the protrusion amount of the stud dowel 11. According to this positional relationship, a vertical gap exists between the projection 21 and the bolt 9, and no interference occurs between the projection 21 and the bolt 9.

[0024] (filling process) 6, the formwork material 13 is inserted between the lower surface 3a and the flange upper surface 105a, and a hardening filler 15 is introduced into the space between the lower surface 3a and the flange upper surface 105a. In order to properly fill the above-mentioned space with the filler 15, a filler introduction hole (not shown) that penetrates the precast floor slab 3 in the vertical direction may be provided. The filled filler 15 hardens with the protruding parts of the bolts 9 and the protrusions 21 embedded in it. As the above-mentioned filler 15, for example, a hydraulic material, for example, non-shrink mortar, is used.

[0025] The filler 15 may be a high-strength fiber-reinforced mortar. A high-strength fiber-reinforced mortar is a mortar having a compressive strength of 120 N / mm 2 The tensile strength of the short fiber is now 1N / mm 2 The above is short fiber reinforced mortar.

[0026] The filler 15 may also be an ultra high performance fiber reinforced cement-based composite material. Ultra high performance fiber reinforced cement-based composite materials are sometimes commonly abbreviated as "UHPFRC."

[0027] UHPFRC is a mixture containing, for example, cement, inorganic powder, aggregate, mixing water, chemical admixtures for concrete, and reinforcing fibers. The cement may be, for example, ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, or low-heat Portland cement. The inorganic powder may be, for example, silica fume, ground granulated blast furnace slag, fly ash, ground silica, wollastonite, or an expansive agent.

[0028] As an example, the above-mentioned aggregate has a particle size of 5.0 mm or less and an absolute dry density of 2.5 g / cm 3 The aggregate has a water absorption rate of 3.0% or less, a clay mass content of 1.0% or less, a fine powder content of 2.0% or less, and a NaCl content of 0.02% or less. This aggregate has a test result of "light" for organic impurities in fine aggregate specified in JIS (Japanese Industrial Standards) A 1105. This aggregate also has a stability of 10% or less according to the aggregate stability test method specified in JIS A 1122 for sodium sulfate, and is classified as Class A in terms of alkali-silica reactivity specified in JIS A 5308 Appendix 1.

[0029] The mixing water is, for example, mixing water other than recycled water as specified in JSCE-B 101-2013. The chemical admixture for concrete is a high-performance water reducer as specified in JIS A 6204. The reinforcing fiber has a diameter of 0.1 to 0.25 mm, a length of 10 to 24 mm, and a tensile strength of 2×10 N. 3 / mm 2 The reinforcing fibers may be, for example, steel fibers, high strength aramid fibers, or carbon fibers.

[0030] The UHPFRC that constitutes the filler 15 is, for example, a matrix composed of Portland cement, pozzolana, a binder containing inorganic powder such as ettrin-guide generating material, aggregate with a particle size of 2.5 mm or less, water, and a water-reducing agent. The mix of the filler 15 is a standard formula mix. The reinforcing fibers have a diameter of 0.2 mm, a length of 15 mm (manufacturing error less than ±2 mm), and a tensile strength of 2×10 3 N / mm 2 The steel fibers may be mixed in at 1.75 vol.%. The strength characteristics of UHPFRC after hardening are compressive strength 150 N / mm 2 Above, crack initiation strength 4N / mm 2 , and tensile strength 5N / mm 2 It is preferable that:

[0031] The standard mix ratio of UHPFRC that constitutes filler 15 is: flow value 250±20mm, mixing water ratio to binder 15%, air content 2.0%, mixing water 195kg / m 3 , high-performance water reducing agent 32.2kg / m 3 , and reinforcing fiber 137.4 kg / m 3 (1.75 vol.%).

[0032] By the above-mentioned joining method, the joining structure 1 between the steel girder 103 and the precast deck 3 is constructed, and the steel girder 103 and the precast deck 3 are joined. In this joining structure 1, the bolt 9 and the projection 21 connected via the filler 15 function as a horizontal slip prevention between the precast deck 3 and the steel girder 103. In the bolt 9k included in the bolt 9, the head of the bolt 9k is engaged with the filler 15, and similarly, in the stud dowel 11 included in the projection 21, the head 11a of the stud dowel 11 is engaged with the filler 15. Therefore, in the joining structure 1, the bolt 9k and the stud dowel 11 are capable of resisting a force that tries to pull the precast deck 3 upwardly away from the steel girder 103.

[0033] The following describes the effects of the above-mentioned joint structure 1 and joining method. In the above-mentioned joint structure 1 and joining method, the bolts 9 on the underside 3a of the precast deck 3 and the protrusions 21 of the steel girders 103 are connected via the filler 15, and the precast deck 3 and the steel girders 103 are prevented from shifting in the horizontal direction.

[0034] As described above, in the deck installation process, the precast deck 3 is installed on the steel girder 103 so that the upper end of the projection 21 of the anti-slip portion 23 is closer to the flange upper surface 105a (i.e., lower) than the lower end of the bolt 9. According to this positional relationship, a vertical gap exists between the projection 21 and the bolt 9, and interference between the projection 21 and the bolt 9 does not occur. In this way, in the design of the joint structure 1, the constraint of avoiding interference between the projection 21 and the bolt 9 is reduced. In addition, when installing the precast deck 3 on the flange upper surface 105a in the deck installation process, it is not necessary to adjust the position of the precast deck 3 to avoid interference between the projection 21 and the bolt 9. In addition, there is no need to increase the accuracy of the installation position of the projection 21 on the flange upper surface 105a, and the workload of melting the stud dowel 11 in the stud dowel installation process is also reduced. Therefore, in the joint structure 1 between the precast deck 3 and the steel girder 103, the degree of design freedom is improved and the workability is also improved.

[0035] As described above, the joint structure 1 has a structure in which the protrusion 21 and the bolt 9 do not overlap in the vertical direction within the filler 15, and therefore is considered to have a slightly inferior slip prevention function compared to a structure in which the protrusion 21 and the bolt 9 overlap in the vertical direction (for example, the connection structure described in Patent Document 1). However, particularly when a high-strength material (for example, high-strength fiber-reinforced mortar, UHPFRC) is used as the filler 15 material, horizontal shear force is sufficiently transmitted between the precast deck 3 and the steel girder 103 via the filler 15, which has high shear resistance, so that sufficient slip prevention between the precast deck 3 and the steel girder 103 can be achieved.

[0036] Furthermore, in the anti-slip portion 23 on the flange upper surface 105a, not only the stud dowels 11 but also the debris 10 remaining on the flange upper surface 105a are reused as protrusions 21. With this configuration, in the steel girder processing step after the old deck is removed, it is not necessary to remove all of the debris 10 on the flange upper surface 105a, and as a result, the burden of cutting and removing the debris 10 and polishing the removed area is reduced.

[0037] The present invention can be embodied in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. It is also possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of each embodiment may be used in appropriate combination.

[0038] For example, in the embodiment, the joint structure 1 and the above-mentioned joining method are applied to the road bridge 101 which is a composite girder, but the joint structure 1 and the above-mentioned joining method can also be applied to a bridge of a non-composite girder type. Also, in the embodiment, the joint structure 1 and the above-mentioned joining method are applied to the road bridge 101 which is a steel girder type, but the joint structure 1 and the above-mentioned joining method can also be applied to a bridge of a box girder type.

[0039] Also, instead of the stud dowels 11 on the flange upper surface 105a in the embodiment, for example, bolts and nuts attached through holes provided in the upper flange 105 may be installed. The protrusions 21 on the flange upper surface 105a may be composed of newly installed stud dowels 11 without including the debris 10. That is, in the above-mentioned steel girder processing step, all the debris 10 on the flange upper surface 105a may be removed. Also, it is not essential that the bolts 9 of the precast deck 3 include bolts 9j with a small protrusion amount, and all the bolts 9 may be composed of bolts 9k.

[0040] Furthermore, the joint structure 1 and the joint method in the embodiment are applied when replacing the old deck of the road bridge 101 with a new precast deck 3, but the present invention is applicable not only when replacing the deck, but also when constructing a new road bridge 101. In this case, the protrusions 21 on the flange upper surface 105a are all composed of newly installed stud dowels 11, and no remnants 10 exist. [Explanation of symbols]

[0041] 1...joint structure, 3...precast deck, 3a...underside, 7...insert nut, 9...bolt, 10...debris, 15...filler, 21...protrusion, 23...slip prevention part, 103...steel girder, 105...upper flange, 105a...upper surface of flange.

Claims

1. A joint structure for joining a steel girder and a precast deck installed on the upper flange of the steel girder, A slip prevention portion having a protrusion provided on an upper surface of the upper flange and protruding upward; An insert nut embedded in the underside of the precast deck; A bolt attached to the insert nut and protruding downward from the underside of the precast deck; A filler is filled between the upper surface of the upper flange and the lower surface of the precast floor slab so as to embed the protrusion and the bolt, A joining structure, wherein the upper end of the protrusion of the anti-slip portion is located closer to the upper surface of the upper flange than the lower end of the bolt.

2. A joint structure of a precast deck constructed by replacing the deck on the upper flange of the steel girder, The projection of the anti-slip portion is The joint structure according to claim 1 , comprising remnants of a protrusion that was included in the deck slab's shear stop before it was replaced.

3. The joint structure according to any one of claims 1 to 2, wherein the filler is an ultra-high performance fiber reinforced cementitious composite material.

4. A joining method for joining a steel girder and a precast deck installed on an upper flange of the steel girder, comprising: A deck installation process in which the precast deck having an insert nut embedded in the underside and a bolt attached to the insert nut is installed on the upper surface of the upper flange provided with a slip prevention portion having a protrusion protruding upward; and a filling step of filling a filler between the upper surface of the upper flange and the lower surface of the precast floor slab so as to embed the protrusion and the bolt. In the deck installation process, A joining method in which the precast deck is installed so that the upper end of the protrusion of the anti-slip portion is located closer to the upper surface of the upper flange than the lower end of the bolt.

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