Joint structure between steel truss and precast floor slab

Abstract

To provide a joint structure between a steel girder and a precast floor slab capable of being constructed in a short period of time and resisting shearing force in a bridge axial direction and bending moment in a direction orthogonal to a bridge axis without causing sectional deficit of the steel girder.SOLUTION: In a joint structure 1 between a steel girder and a precast floor slab for joining the steel girder 2 and the precast floor slab 3 placed on the steel girder 2, the steel girder 2 and the precast floor slab 3 are joined by using a stud bolt 4 welded to an upper flange 20 of the steel girder 2 to attach a pair of steel jigs 5, 5 with an L-shaped cross section having a bottom part 50 and a rising part 51 to both edges of an upper surface 2a of the upper flange 20, projecting an anti-slip steel material 30 having a side view U-shaped part that surrounds at least three parts of left, right, and bottom parts on a lower surface 3a of the precast floor slab 3, inserting a connection bolt 6 between the pair of steel jigs 5, 5 and fastening the same to the rising part 51, and inserting the connection bolt 6 into the anti-slip steel material 30 having the side view U-shaped part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a joint structure between a steel girder and a precast floor slab.

Background Art

[0002] Conventionally, for the joint between a steel girder and a precast floor slab, stud dowels are welded to the upper flange of the steel girder as a displacement stopper, and a precast floor slab having a box-out hole penetrating vertically is placed on the upper flange of the steel girder, and the welded stud dowels are housed in the box-out hole. Then, a filler such as non-shrink mortar is filled in the box-out hole and cured to integrate the steel girder and the precast floor slab into a composite girder.

[0003] However, in the vicinity of the fulcrum where a large shear force acts, the number of studs required for displacement prevention increases, not only restricting the reinforcement of the precast floor slab but also becoming a weakness in terms of durability due to post-cast construction. Also, since a curing time for the filler is required, there is a problem that it becomes a factor in prolonging the construction period. For this reason, a method of integrally joining the steel girder and the precast floor slab without providing a box-out hole in the precast floor slab has been eagerly desired.

[0004] In order to solve such problems, for example, Patent Document 1 discloses a joint structure between a steel girder and a precast floor slab in which inserts that are screwed with bolts are embedded in the precast floor slab, through holes are drilled in the upper flange of the steel girder, and the upper flange of the steel girder and the inserts of the precast floor slab are screwed and joined with bolts (see paragraphs

[0012] to

[0027] of the specification of Patent Document 1, FIG. 1 of the drawings, etc.).

[0005] However, the joint structure between the steel girder and the precast floor slab described in Patent Document 1 can be constructed in a short period because no curing time for the filler is required. However, since through holes are provided in the upper flange of the steel girder, there is a problem of cross-sectional loss and it becomes a structural weakness.

[0006] In addition, Patent Document 2 discloses a joint structure between a steel girder and a precast floor slab, which includes a shear prevention part having a stud gib 11, an insert nut 7 embedded in the lower surface 3a of the precast floor slab 3, a bolt 9 attached to the insert nut 7, and a filler 15 that is cured so as to embed these stud gibs 11 and bolts 9 (see paragraphs

[0017] to

[0032] of the specification of Patent Document 2, FIG. 5 of the drawings, etc.).

[0007] However, the joint structure between the steel girder and the precast floor slab described in Patent Document 2 has a problem that although it can resist shear force, it cannot resist bending moment in the direction perpendicular to the bridge axis, such as in the direction perpendicular to the bridge axis.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, the present invention has been devised in view of the above-described problems, and an object thereof is to provide a joint structure between a steel girder and a precast floor slab that can be constructed in a short period of time, has no cross-sectional defect in the steel girder, and can resist both shear force in the bridge axis direction and bending moment in the direction perpendicular to the bridge axis.

Means for Solving the Problems

[0010] The joint structure between the steel girder and the precast floor slab according to claim 1 is a joint structure between a steel girder and a precast floor slab placed on the steel girder, wherein a pair of steel fixtures having a bottom portion and a rising portion in an L-shaped cross section with stud bolts welded to the upper flange of the steel girder are attached to both edges of the upper surface of the upper flange of the steel girder, a displacement-preventing steel material having a surrounding portion surrounding at least the left and right and downward sides is projected on the lower surface of the precast floor slab, a connecting bolt is inserted between the pair of steel fixtures and fastened to the rising portion, and the steel girder and the precast floor slab are joined by inserting the connecting bolt through the surrounding portion of the displacement-preventing steel material.

[0011] The joint structure between the steel girder and the precast floor slab according to claim 2 is the joint structure between the steel girder and the precast floor slab according to claim 1, wherein the surrounding portion is made of a bar steel or a perforated steel plate having a U-shaped cross section in side view.

[0012] The joint structure between the steel girder and the precast floor slab according to claim 3 is the joint structure between the steel girder and the precast floor slab according to claim 1 or 2, wherein the pair of steel fixtures are attached to both edges of the upper flange of the steel girder such that the rising portions are on the outer sides, and a filler is filled between the pair of steel fixtures.

[0013] The joint structure between the steel girder and the precast floor slab according to claim 4 is the joint structure between the steel girder and the precast floor slab according to claim 1 or 2, wherein the pair of steel fixtures are attached to both edges of the upper flange of the steel girder such that the rising portions are on the inner sides, and the connecting bolt and the stud bolt are embedded inside the filler.

Effect of the Invention

[0014] According to the invention according to claims 1 to 4, since there is no through-hole penetrating the precast floor slab vertically, not only can the structural weak points of the precast floor slab be eliminated, but also work on the precast floor slab can be carried out until the filler hardens. As a result, construction can be completed in a short time. Further, according to the invention according to claims 1 to 4, since there is no need to provide a through-hole in the steel girder, the cross-sectional loss of the steel girder can be eliminated, and a structurally safe structure can be achieved. Moreover, according to the invention according to claims 1 to 4, since the connecting bolt is inserted into the anti-displacement steel material having a U-shaped side view, the steel girder and the precast floor slab are joined, so that not only the shear force in the direction perpendicular to the bridge axis but also the shear force in the bridge axis direction and the bending moment in the direction perpendicular to the bridge axis can be resisted, and a joint structure that is strong against earthquakes can be achieved.

[0015] In particular, according to the invention according to claim 2, since the surrounding portion is made of a bar steel or a perforated steel plate having a U-shaped side view, the connecting bolt can be reliably surrounded by the surrounding portion to transmit the shear force and the bending moment and resist these stresses.

[0016] In particular, according to the invention according to claim 3, since the steel jig can be partially used as a formwork for the filler, the installation work of the formwork can be partially omitted, and thus construction can be completed in an even shorter time.

[0017] In particular, according to the invention according to claim 4, since the connecting bolt and the stud bolt are embedded in the filler, there is no need to perform rust prevention treatment on the stud bolt or the steel jig or to make these members of stainless steel material, and the construction can be carried out at a low cost by reducing the unit price of the members.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0019] Hereinafter, an embodiment of the joint structure between the steel truss serving as a continuous truss and the precast floor slab according to the present invention will be described in detail with reference to the drawings.

[0020] [First Embodiment] The joint structure 1 between the steel truss and the precast floor slab according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a vertical cross-sectional view of a bridge cut along the direction Y perpendicular to the bridge axis showing the configuration of the joint structure 1 between the steel truss and the precast floor slab according to the first embodiment of the present invention. Further, FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1 showing the joint structure 1 between the steel truss and the precast floor slab, and FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1 showing the joint structure 1 between the steel truss and the precast floor slab. In the figures, X is the bridge axis direction X, Y in the figures is the direction Y perpendicular to the bridge axis, and Z in the figures is the vertical direction Z. However, the filling materials in FIGS. 2 and 3 are omitted for easy viewing.

[0021] The joint structure 1 between the steel truss and the precast floor slab according to the first embodiment (hereinafter also simply referred to as the joint structure 1) is a joint structure between the steel truss and the precast floor slab that joins the steel truss 2 and the precast floor slab 3 placed on the steel truss 2.

[0022] (Steel Truss) The steel truss 2 is made of I-beam steel and includes an upper flange 20, a lower flange 21, and a web 22 connecting these.

[0023] (Stud bolt) Further, stud bolts 4 are welded along both edges of the upper surface 2a of the upper flange 20 of the steel girder 2. The stud bolt 4 is made of a rod-shaped steel material, and a threaded portion 40 is formed at one end (upper end) of the rod shape so that a nut 41 can be screwed, and the base end portion 42 at the other end (lower end) is arc stud welded. A pair of steel jigs 5, 5 are attached along both edges of the upper surface of the upper flange 20 via the stud bolt 4.

[0024] (Precast floor slab) The precast floor slab 3 is a rectangular plate-shaped precast floor slab made of reinforced concrete, which is manufactured by casting concrete in a factory or the like in advance. A displacement-preventing steel material 30 having a U-shaped side view made of deformed steel bars protrudes downward from the lower surface 3a. Of course, the protruding portion of the displacement-preventing steel material 30 from the lower surface 3a has a U-shaped side view when viewed along the direction Y perpendicular to the bridge axis, and is effectively fixed inside the concrete of the precast floor slab 3. The U-shaped portion of the displacement-preventing steel material 30 in side view serves as an enclosing portion surrounding a connecting bolt 6 described later.

[0025] (Steel jig) The steel jig 5 is a steel material having an L-shaped cross section, and includes a bottom surface portion 50 installed on the upper surface 2a of the upper flange 20 of the steel girder 2 and a rising portion 51 rising perpendicular to the bottom surface portion 50. Further, a bolt hole (not shown) through which the connecting bolt 6 is inserted is formed in the rising portion 51. As shown in FIG. 1, in the joining structure 1 according to the present embodiment, the rising portion 51 is on the outer side (the side away from the center line of the web 22 of the steel girder 2 which is the bridge axis), that is, the bottom surface portions 50 of the pair of steel jigs 5, 5 face each other inward, and are attached along both edges of the upper flange 20 of the steel girder 2.

[0026] (Connecting bolt) As shown in Fig. 1, the connecting bolt 6 is a fully threaded bolt made of steel, with nuts 60 screwed onto both ends, and bolt-joined and fixed to the bolt holes of each of the pair of steel fixtures 5. Of course, the connecting bolt 6 is not limited to a fully threaded bolt, and it may be a bolt type with a bolt head at one end or a threaded steel bar with threaded portions formed at both ends. However, since the nut 60 and the bolt end portion of the connecting bolt 6 according to the present embodiment will be exposed from the filling material, it is preferably made of stainless steel for rust prevention.

[0027] The connecting bolt 6 is bolt-joined and installed between the rising portions 51 of the pair of steel fixtures 5 whose bottom surfaces 50 are fixed to the upper surface 2a of the upper flange 20 of the steel girder 2 by stud bolts 4. Thereby, after the connecting bolt 6 is inserted into the displacement-preventing steel material having a U-shaped side view, the gaps between these members are filled and solidified with a filling material 7 described later, so that the steel girder 2 and the precast floor slab 3 can be effectively joined.

[0028] Therefore, the joint structure 1 can resist the bending moment along the bridge axis perpendicular direction Y indicated by the arrow in Fig. 1, and can also resist the shear force along the bridge axis direction X indicated by the arrows in Figs. 2 and 3.

[0029] (Filling material) Also, as shown in Fig. 1, between the pair of steel fixtures 5 in the upper and lower gaps between the steel girder 2 and the precast floor slab 3, a filling material 7 made of a time-hardening material such as non-shrinking mortar is filled, and the gaps between the stud bolts 4, the steel fixtures 5, and the connecting bolt 6 are filled and solidified.

[0030] That is, as described above, after the stud bolt 4 is welded to the upper surface 2a of the upper flange 20 of the steel girder 2 and the steel jig 5 is installed, a temporary formwork made of wood, resin, etc. (not shown) is installed between the steel jigs 5 shown in FIG. 3, and the filler 7 is filled. Thereafter, the connecting bolt 6 is inserted through the anti-shift steel material 30 of the steel jig 5 and the precast floor slab 3, and the steel girder 2 and the precast floor slab 3 are effectively joined. This filler 7 has a function of filling the gaps between the members and evenly transmitting the load of the precast floor slab 3 to the steel girder 2.

[0031] According to the joining structure 1 according to the first embodiment described above, since the precast floor slab 3 has no through-hole penetrating vertically, not only can the structural weak part of the precast floor slab 3 be eliminated, but also the work on the precast floor slab 3 can be carried out until the filler 7 hardens. As a result, the construction can be completed in a short time. Further, according to the joining structure 1, since it is not necessary to provide a through-hole in the steel girder 2, the cross-sectional loss of the steel girder 2 can be eliminated, and a structurally safe structure can be obtained.

[0032] Moreover, according to the joining structure 1, since the connecting bolt 6 is inserted through the anti-shift steel material 30 having a U-shaped side view, the steel girder 2 and the precast floor slab 3 are joined. Therefore, not only the shear force along the bridge axis perpendicular direction Y, but also the shear force along the bridge axis direction X shown by the arrows in FIGS. 2 and 3 and the bending moment in the bridge axis perpendicular direction Y shown by the arrow in FIG. 1 can be resisted, and a seismic-resistant and strong joining structure can be obtained.

[0033] In addition, according to the joining structure 1, since the steel jig 5 can be partially used as a formwork for the filler 7, the installation work of the formwork can be partially omitted, and thus the construction can be completed in an even shorter time.

[0034] [Second Embodiment] Next, with reference to FIG. 4, the joining structure 1' between the steel girder and the precast floor slab according to the second embodiment of the present invention will be described. FIG. 4 is a vertical sectional view of a bridge showing the configuration of the joining structure 1' between the steel girder and the precast floor slab according to the second embodiment of the present invention, cut along the bridge axis perpendicular direction Y.

[0035] The joining structure 1' between the steel girder and the precast floor slab according to the second embodiment (hereinafter also simply referred to as the joining structure 1') is different from the above-described joining structure 1 mainly in that the rising portions 51 of the pair of steel fixtures 5, 5 are attached so as to be on the inner side. The same components are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0036] (Steel fixture) The steel fixture 5 is a steel material having the same L-shaped cross section as that of the above-described joining structure 1. However, as shown in FIG. 4, in the joining structure 1 according to the present embodiment, the rising portion 51 is on the inner side (the side closer to the center line of the web 22 of the steel girder 2 which is the bridge axis), that is, the bottom portions 50 of the pair of steel fixtures 5, 5 face each other outward, and are attached along both edges of the upper flange 20 of the steel girder 2.

[0037] (Connecting bolt) As shown in FIG. 4, the connecting bolt 6' is a fully threaded bolt made of steel, similar to the connecting bolt 6. Nuts 60 are screwed onto both ends thereof, and the bolt is bolted and fixed to the bolt holes of each of the pair of steel fixtures 5. However, in the joining structure 1', the mounting directions of the pair of steel fixtures 5, 5 are different from those of the above-described joining structure 1, and the bottom portions 50 face each other outward along the edge of the steel girder 2 having the same width. Therefore, the distance between the rising portions 51 is shorter than that of the joining structure 1. For this reason, the length of the connecting bolt 6' is shorter than the length of the connecting bolt 6. Of course, the connecting bolt 6' is not limited to a fully threaded bolt, and may be a bolt type having a bolt head at one end or a threaded bar steel having threaded portions formed at both ends.

[0038] On the other hand, in the connecting bolt 6' according to the present embodiment, the nuts 60 and the bolt ends are not exposed from the filling material 7, but are embedded inside the filling material 7. For this reason, the necessity for the connecting bolt 6' to be made of stainless steel for rust prevention is reduced.

[0039] (Filling material) The filler 7 of the joining structure 1' is also a filler made of a time-dependent hardening material such as non-shrinking mortar, similar to the joining structure 1. However, in the joining structure 1', since the mounting direction of the steel jig 5 is such that the bottom surface portions 50 face each other outwardly, it is necessary to install a formwork and fill the filler 7 as usual.

[0040] According to the joining structure 1' between the steel girder and the precast floor slab according to the second embodiment described above, in addition to the above-described effects, since the connecting bolts 6' and the stud bolts 4 are embedded inside the filler 7, there is no need to perform rust prevention treatment on the stud bolts 4 and the steel jig 5 or to make these members of stainless steel material, and it becomes possible to reduce the member unit price and perform construction at low cost.

[0041] [Third Embodiment] Next, with reference to FIG. 5, a joining structure 1'' between a steel girder and a precast floor slab according to the third embodiment of the present invention will be described. FIG. 5 is a view showing the joining structure 1'' between a steel girder and a precast floor slab according to the third embodiment of the present invention. The left half is a view corresponding to the cross-sectional view taken along line A-A of FIG. 1, and the right half is a view corresponding to the cross-sectional view taken along line B-B of FIG. 1. Note that, since the reference signs overlap, only the anti-slip steel material is shown within the dashed circle.

[0042] The difference between the joining structure 1'' between the steel girder and the precast floor slab according to the third embodiment (hereinafter also simply referred to as the joining structure 1'') and the above-described joining structure 1 is mainly that the shape of the anti-slip steel material is different. The same components are denoted by the same reference signs, and detailed description thereof is omitted.

[0043] The anti-slip steel material 30'' of the joining structure 1'' according to the present embodiment is, as shown in FIG. 5, a rectangular perforated steel plate protruding from the lower surface 3a of the precast floor slab 3, corresponding to the above-described steel jig 5. This anti-slip steel material 30'' has a configuration having a surrounding portion that surrounds the left and right, upper and lower four sides of the connecting bolt 6 including a pair of left and right side portions 30a'', a lower side portion 30b'', and an upper side portion 30c'', and has a function of transmitting shear force and bending moment by surrounding the connecting bolt 6 and resisting these stresses.

[0044] However, the shear stop steel material according to the present invention only needs to have a surrounding portion that surrounds the connecting bolt 6 on at least three sides, the left, right and bottom. In other words, the upper edge portion 30c" shown in Figure 5 does not need to protrude from the underside 3a of the precast deck 3, and may be integrated with the embedded portion 30d" of the shear stop steel material 30" shown by the dashed line. This is because it abuts against the underside 3a of the precast deck 3 via the surrounding filling material 7, and therefore stress can be transmitted to the steel girder 2 via the connecting bolt 6 and the steel jig even without the upper edge portion 30c".

[0045] Furthermore, a steel plate with a rectangular hole formed therein has been used as an example of the shear-stopping steel material 30" of the joint structure 1" relating to the third embodiment, but the shear-stopping steel material according to the present invention may be a steel plate with a circular hole formed therein. In short, the shear-stopping steel material according to the present invention may have a surrounding portion made of steel plate or steel material that surrounds the connecting bolt 6 on at least three sides, the left and right and below, so as to be able to transmit tensile force, etc.

[0046] The joint structure 1" of the third embodiment has the same effect as the joint structure 1, and the steel girder 2 and the precast deck 3 are joined by inserting the connecting bolt 6 into an enclosing portion consisting of a pair of left and right side portions 30a" and a lower portion 30b" and an upper portion 30c" of the anti-slip steel material 30". Therefore, the joint structure 1" can withstand not only the shear force along the direction perpendicular to the bridge axis Y, but also the shear force along the bridge axis direction X indicated by the arrow in Figure 5 and the bending moment in the direction perpendicular to the bridge axis Y indicated by the arrow in Figure 1, making it a strong seismic structure.

[0047] The joint structures 1-1" between steel girders and precast decks according to the embodiments of the present invention have been described in detail above. However, the embodiments described above or shown in the drawings are merely examples of specific embodiments for carrying out the present invention. Therefore, the technical scope of the present invention should not be interpreted in a limited manner based on these. [Explanation of symbols]

[0048] 1,1': Joint structure between steel girder and precast deck 2: Steel girder 2a: Upper surface 20: Upper flange 21: Lower flange 22: Web 3: Precast floor slab 3a: Lower surface 30, 30”: Anti-shift steel material 30a”: Side part 30b”: Lower side part 30c”: Upper side part 30d”: Embedded part 4: Stud bolt 40: Threaded part 41: Nut 42: Base end part 5: Steel jig 51: Bottom surface part 52: Upright part 6, 6: Connecting bolt 60: Nut 7: Filling material

Claims

1. A joining structure between a steel truss and a precast floor slab for joining the steel truss and the precast floor slab placed on the steel truss, On both edges of the upper surface of the upper flange of the steel truss, a pair of steel fixtures having a bottom surface portion and a rising portion and having an L-shaped cross section are attached by stud bolts welded to the upper flange, On the lower surface of the precast floor slab, a displacement-preventing steel material having a surrounding portion surrounding at least three sides of left, right, and lower is protruded, A connecting bolt is inserted between the pair of steel fixtures and fastened to the rising portion, The steel truss and the precast floor slab are joined by inserting the connecting bolt through the surrounding portion of the displacement-preventing steel material. A joining structure between a steel truss and a precast floor slab, characterized by the above.

2. The surrounding portion is made of a bar steel or a perforated steel plate having a U-shaped cross section in side view. A joining structure between a steel truss and a precast floor slab according to Claim 1, characterized by the above.

3. The pair of steel fixtures are attached to both edges of the upper flange of the steel truss such that the rising portion is on the outside, A filler is filled between the pair of steel fixtures. A joining structure between a steel truss and a precast floor slab according to Claim 1 or 2, characterized by the above.

4. The pair of steel fixtures are attached to both edges of the upper flange of the steel truss such that the rising portion is on the inside, The connecting bolt and the stud bolt are embedded inside the filler. A joining structure between a steel truss and a precast floor slab according to Claim 1 or 2, characterized by the above.

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