JP7692807B2 - Joint structure between steel girder and precast deck - Google Patents

Description

The present invention relates to a joint structure between a steel girder and a precast deck.

Conventionally, steel girders and precast decks are joined by welding stud dowels to the upper flange of the steel girder as a slip stopper, placing a precast deck with a box-punched hole that penetrates from top to bottom on the upper flange of the steel girder, and fitting the welded stud dowels into the box-punched hole. The box-punched hole is then filled with a filler such as non-shrink mortar and allowed to harden, integrating the steel girder with the precast deck to form a composite girder.

However, near the supports where large shear forces act, a large number of studs are required to prevent slippage, which not only limits the reinforcement of the precast deck, but also weakens its durability because it requires post-cast construction. There is also the problem that the filling material requires time to harden, which lengthens the construction period. For this reason, there was a strong demand for a method to join the precast deck to the steel girders as a single unit without creating box-punched holes.

To solve these problems, for example, Patent Document 1 discloses a joint structure between a steel girder and a precast deck in which an insert that screws into a bolt is embedded in the precast deck, a through hole is drilled in the upper flange of the steel girder, and the upper flange of the steel girder and the insert in the precast deck are joined by screwing the bolt together (see paragraphs [0012] to [0027] of the specification of Patent Document 1 and Figure 1 of the drawings, etc.).

However, the joint structure between the steel girder and the precast deck described in Patent Document 1 can be constructed in a short period of time because no time is required for the filler to harden, but there is a problem in that through holes must be provided in the upper flange of the steel girder, resulting in cross-sectional defects and structural weaknesses.

Patent Document 2 also discloses a joint structure between a steel girder and a precast deck, which includes a slip prevention section having a stud dowel 11, an insert nut 7 embedded in the underside 3a of the precast deck 3, a bolt 9 attached to the insert nut 7, and a filler 15 that hardens to embed the stud dowel 11 and the bolt 9 (see paragraphs [0017] to [0032] of the specification of Patent Document 2, Figure 5 of the drawings, etc.).

However, the joint structure between the steel girder and the precast deck described in Patent Document 2 had the problem that although it could withstand shear forces, it could not withstand bending moments perpendicular to the bridge axis.

JP 2015-86595 A JP 2021-1457 A

The present invention was devised in consideration of the above-mentioned problems, and its purpose is to provide a joint structure between a steel girder and a precast deck that can be constructed in a short period of time, has no cross-sectional defects in the steel girder, and can withstand both shear forces in the bridge axis direction and bending moments perpendicular to the bridge axis.

The joint structure between a steel girder and a precast deck according to claim 1 is a joint structure between a steel girder and a precast deck placed on the steel girder, characterized in that a pair of steel jigs with an L-shaped cross section having a bottom part and a rising part are attached to both edges of the upper surface of the upper flange of the steel girder by stud bolts fused to the upper flange, a shear-stop steel material having an enclosing part surrounding at least three sides, the left and right and the bottom, is protruded from the underside of the precast deck, a connecting bolt is inserted between the pair of steel jigs and fastened to the rising part, and the connecting bolt is inserted into the enclosing part of the shear-stop steel material to join the steel girder and the precast deck.

The joint structure between a steel girder and a precast deck according to claim 2 is the joint structure between a steel girder and a precast deck according to claim 1, characterized in that the surrounding portion is made of a U-shaped steel bar or a perforated steel plate when viewed from the side.

The joint structure between a steel girder and a precast deck according to claim 3 is the joint structure between a steel girder and a precast deck according to claim 1 or 2, characterized in that the pair of steel jigs are attached to both edges of the upper flange of the steel girder so that the rising portion is on the outside, and a filler material is filled between the pair of steel jigs.

The joint structure between a steel girder and a precast deck according to claim 4 is characterized in that in the joint structure between a steel girder and a precast deck according to claim 1 or 2, the pair of steel jigs are attached to both edges of the upper flange of the steel girder so that the rising portion is on the inside, and the connecting bolt and the stud bolt are embedded inside the filling material.

According to the inventions of claims 1 to 4, since there are no through holes that penetrate vertically in the precast deck, not only can the precast deck have no structural weak points, but also work can be done on the precast deck while the filling material is hardening, resulting in a short construction time. In addition, according to the inventions of claims 1 to 4, since there is no need to provide through holes in the steel girders, cross-sectional defects in the steel girders can be eliminated, resulting in a safe structure. Furthermore, according to the inventions of claims 1 to 4, the steel girders and the precast deck are joined by inserting the connecting bolts into the shear-stop steel material that is U-shaped in side view, so that it can withstand not only shear forces perpendicular to the bridge axis, but also shear forces in the bridge axis direction and bending moments perpendicular to the bridge axis, resulting in a joint structure that is strong in terms of earthquake resistance.

In particular, according to the invention of claim 2, the surrounding portion is made of a U-shaped steel bar or a perforated steel plate when viewed from the side, so that the connecting bolt is securely surrounded by the surrounding portion, transmitting shear forces and bending moments and resisting these stresses.

In particular, according to the invention of claim 3, the steel jig can partially serve as a formwork for the filling material, so that the installation work for the formwork can be partially omitted, making it possible to complete construction in an even shorter time.

In particular, according to the invention of claim 4, the connecting bolts and stud bolts are embedded inside the filler, so there is no need to apply anti-rust treatment to the stud bolts and steel jigs or to use stainless steel for these components, which reduces the unit price of the components and makes it possible to carry out the work inexpensively.

FIG. 1 is a vertical cross-sectional view of a bridge cut perpendicular to the bridge axis, showing the configuration of a joint structure between a steel girder and a precast deck according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, showing the joint structure between the steel girder and the precast deck. FIG. 3 is a cross-sectional view taken along line B-B in FIG. 1, showing the joint structure between the steel girder and the precast deck. FIG. 4 is a vertical cross-sectional view of a bridge cut along a direction perpendicular to the bridge axis, showing the configuration of a joint structure between a steel girder and a precast deck according to a second embodiment of the present invention. FIG. 5 is a diagram showing a joint structure between a steel girder and a precast deck in accordance with a third embodiment of the present invention, in which the left half corresponds to the cross-sectional view along line A-A in FIG. 1, and the right half corresponds to the cross-sectional view along line B-B in FIG. 1.

Below, we will explain in detail one embodiment of the joint structure between a steel girder that serves as a continuous girder and a precast deck slab according to the present invention, with reference to the drawings.

[First embodiment]
The joint structure between a steel girder and a precast deck according to the first embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 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 a steel girder and a precast deck according to the first embodiment of the present invention. Figure 2 is a cross-sectional view of line A-A in Figure 1 showing the joint structure 1 between a steel girder and a precast deck, and Figure 3 is a cross-sectional view of line B-B in Figure 1 showing the joint structure 1 between a steel girder and a precast deck. Note that X in the figures 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 up-down direction Z. However, the filler material in Figures 2 and 3 is omitted for ease of viewing.

The joint structure 1 between a steel girder and a precast deck in the first embodiment (hereinafter also simply referred to as joint structure 1) is a joint structure between a steel girder and a precast deck that joins a steel girder 2 and a precast deck 3 placed on the steel girder 2.

(steel girder)
The steel girder 2 is made of an I-beam and has an upper flange 20, a lower flange 21 and a web 22 connecting them.

(Stud bolt)
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 bolts 4 are made of rod-shaped steel material, and are so-called threaded studs, with a threaded portion 40 formed at one end (upper end) of the rod so that a nut 41 can be screwed onto them, and a base end 42 at the other end (lower end) being 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 bolts 4.

(Precast floor slab)
The precast deck 3 is a rectangular precast deck made of reinforced concrete that has been manufactured in advance by pouring concrete in a factory or the like, and has a U-shaped anti-slip steel member 30 made of deformed steel bars that protrudes downward from the bottom surface 3a. Of course, the part of the anti-slip steel member 30 that protrudes from the bottom surface 3a is U-shaped when viewed from the side when viewed along the direction Y perpendicular to the bridge axis, and is effectively fixed inside the concrete of the precast deck 3. The U-shaped part of the anti-slip steel member 30 when viewed from the side serves as a surrounding part that surrounds the connecting bolt 6 described below.

(Steel jig)
The steel jig 5 is a steel material having an L-shaped cross section, and includes a bottom surface portion 50 that is installed on the upper surface 2a of the upper flange 20 of the steel girder 2, and a rising portion 51 that rises perpendicular to the bottom surface portion 50. The rising portion 51 is provided with a bolt hole (not shown) through which a connecting bolt 6 is inserted. As shown in FIG. 1, in the joint structure 1 according to this embodiment, the bottom surface portions 50 of the pair of steel jigs 5, 5 are attached along both edges of the upper flange 20 of the steel girder 2 so that 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, facing inward and facing each other.

(Connecting bolt)
1, the connecting bolt 6 is a fully threaded bolt made of steel, with nuts 60 screwed onto both ends, and is bolted and fixed into the respective bolt holes of the pair of steel jigs 5. 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 steel bar having threads formed at both ends. However, since the nuts 60 and bolt ends of the connecting bolt 6 according to this embodiment are exposed from the filler, it is preferable that the connecting bolt 6 be made of stainless steel from the viewpoint of rust prevention.

The connecting bolts 6 are bolted and installed between the rising parts 51 of a pair of steel jigs 5 whose bottom parts 50 are fixed by stud bolts 4 to the upper surface 2a of the upper flange 20 of the steel girder 2. As a result, the connecting bolts 6 are inserted into the U-shaped anti-slip steel material in side view, and the gaps are filled and solidified with the filler material 7 described below, effectively joining the steel girder 2 and the precast deck 3.

As a result, the joint structure 1 can withstand bending moments along the direction perpendicular to the bridge axis Y, as indicated by the arrows in Figure 1, and can also withstand shear forces along the bridge axis direction X, as indicated by the arrows in Figures 2 and 3.

(filling material)
As shown in FIG. 1 , a filler 7 made of a time-hardening material such as non-shrink mortar is filled between a pair of steel jigs 5 in the upper and lower gaps between the steel girder 2 and the precast deck 3, filling and hardening the gaps between the stud bolts 4, the steel jigs 5, and the connecting bolts 6.

In other words, as described above, the stud bolts 4 are welded to the upper surface 2a of the upper flange 20 of the steel girder 2, the steel jig 5 is installed, and then a temporary wooden or plastic formwork (not shown) is installed between the steel jigs 5 shown in FIG. 3 and filled with the filler 7. After that, the connecting bolts 6 are inserted through the steel jig 5 and the anti-slip steel material 30 of the precast deck 3, effectively joining the steel girder 2 and the precast deck 3. This filler 7 has the function of filling the gaps between the various members and evenly transferring the load of the precast deck 3 to the steel girder 2.

According to the joint structure 1 of the first embodiment described above, since there are no through holes that penetrate vertically through the precast deck 3, not only can structural weak points in the precast deck 3 be eliminated, but work can be done on the precast deck 3 even while the filling material 7 is hardening, resulting in construction being completed in a short time. In addition, since there is no need to provide through holes in the steel girders 2 according to the joint structure 1, cross-sectional defects in the steel girders 2 can be eliminated, resulting in a structurally safe structure.

Furthermore, according to the joint structure 1, the steel girder 2 and the precast deck 3 are joined by inserting the connecting bolt 6 into the U-shaped anti-slip steel material 30 that is shaped in a side view, so that it 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 as shown by the arrows in Figures 2 and 3, and the bending moment along the direction perpendicular to the bridge axis Y as shown by the arrow in Figure 1, resulting in a joint structure that is strong in terms of earthquake resistance.

In addition, with the joint structure 1, the steel jig 5 can partially serve as the formwork for the filling material 7, so some of the work of setting up the formwork can be omitted, making it possible to complete the construction in an even shorter time.

[Second embodiment]
Next, a joint structure 1' between a steel girder and a precast deck according to a second embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a vertical cross-sectional view of a bridge cut along the direction perpendicular to the bridge axis Y, showing the configuration of the joint structure 1' between a steel girder and a precast deck according to the second embodiment of the present invention.

The second embodiment of the joint structure 1' between a steel girder and a precast deck (hereinafter also referred to as joint structure 1') differs from the previously described joint structure 1 mainly in that the rising portions 51 of a pair of steel jigs 5, 5 are attached so as to face inward. The same components are given the same reference numerals and detailed descriptions are omitted.

(Steel jig)
The steel jig 5 is a steel material with the same L-shaped cross section as the previously described joint structure 1, but as shown in Figure 4, in the joint structure 1 according to this embodiment, the steel jig 5 is attached along both edges of the upper flange 20 of the steel girder 2 so that the rising portion 51 is on the inside (the side closer to the center line of the web 22 of the steel girder 2, which is the bridge axis), i.e., the bottom portions 50 of the pair of steel jigs 5, 5 are attached facing outward and opposite each other.

(Connecting bolt)
As shown in Fig. 4, the connecting bolt 6' is a fully threaded bolt made of steel like the connecting bolt 6, and has the aforementioned nuts 60 screwed to both ends and is bolted to the respective bolt holes of the pair of steel jigs 5. However, in the joint structure 1', the mounting orientation of the pair of steel jigs 5, 5 is different from that of the above-mentioned joint structure 1, and the bottom surface parts 50 are mounted facing outward along the edge of the steel girder 2 of the same width, so that the distance between the rising parts 51 is shorter than that of the joint structure 1. For this reason, the length of the connecting bolt 6' is shorter than that 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 steel bar having threads formed at both ends.

On the other hand, in the connecting bolt 6' according to this embodiment, the nut 60 and the bolt end are not exposed from the filler 7, but are embedded inside the filler 7. Therefore, there is less need for the connecting bolt 6' to be made of stainless steel for rust prevention purposes.

(filling material)
The filler 7 of the joint structure 1' is also a filler made of a time-hardening material such as non-shrink mortar, similar to the joint structure 1. However, in the joint structure 1', the steel jigs 5 are attached so that the bottom parts 50 face outward, so that it is necessary to install a formwork and fill the filler 7 as usual.

In addition to the above-described effects, the joint structure 1' between the steel girder and the precast deck according to the second embodiment has the following advantages: the connecting bolts 6' and the stud bolts 4 are embedded inside the filling material 7, so there is no need to apply rust-proofing treatment to the stud bolts 4 and the steel jigs 5 or to use stainless steel for these components, which reduces the unit price of the components and makes it possible to carry out construction at low cost.

[Third embodiment]
Next, using Figure 5, we will explain the joint structure 1" between a steel girder and a precast deck in accordance with the third embodiment of the present invention. Figure 5 is a diagram showing the joint structure 1" between a steel girder and a precast deck in accordance with the third embodiment of the present invention, where the left half corresponds to the cross-sectional view along line A-A in Figure 1, and the right half corresponds to the cross-sectional view along line B-B in Figure 1. Note that since the symbols overlap, only the shear-stop steel material is shown within the dotted circle.

The third embodiment of the joint structure 1" between a steel girder and a precast deck (hereinafter also referred to as joint structure 1") differs from the previously described joint structure 1 mainly in the shape of the anti-slip steel material. The same components are given the same reference numerals and detailed descriptions are omitted.

As shown in FIG. 5, the anti-slip steel material 30" of the joint structure 1" according to this embodiment is a rectangular perforated steel plate protruding from the underside 3a of the precast deck 3, and corresponds to the steel jig 5 described above. This anti-slip steel material 30" has a pair of left and right side portions 30a" and a bottom portion 30b" and top portion 30c" and is configured with surrounding portions that surround the connecting bolt 6 on all four sides, left and right and above and below. By surrounding the connecting bolt 6, it transmits shear forces and bending moments and has the function of resisting these stresses.

However, the anti-slip 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 FIG. 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 anti-slip steel material 30" shown by the dashed line. This is because the upper edge portion 30c" abuts against the underside 3a of the precast deck 3 via the surrounding filler 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".

Although a steel plate with a rectangular hole has been described as the anti-slip steel material 30" of the joint structure 1" according to the third embodiment, the anti-slip steel material according to the present invention may be a steel plate with a circular hole. In short, the anti-slip steel material according to the present invention may have a surrounding portion that surrounds the connecting bolt 6 on at least three sides (left, right, and bottom) using a steel plate or material so that tensile force, etc. can be transmitted.

The joint structure 1" according to 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 the surrounding portion consisting of a pair of left and right side edges 30a" and a lower edge 30b" and an upper edge 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 shown by the arrow in Figure 5 and the bending moment along the direction perpendicular to the bridge axis Y shown by the arrow in Figure 1, making it a strong earthquake-resistant structure.

The above provides a detailed explanation of the joint structure 1-1" between a steel girder and a precast deck according to an embodiment of the present invention. However, the above-mentioned and illustrated embodiments are merely examples of embodiments that are embodied in the practice of the present invention. Therefore, the technical scope of the present invention should not be interpreted in a limiting manner based on these.

1, 1': Joint structure between steel girder and precast deck 2: Steel girder 2a: Top surface 20: Top flange 21: Bottom flange 22: Web 3: Precast deck 3a: Bottom surface 30, 30": Anti-slip steel material 30a": Side edge portion 30b": Bottom edge portion 30c": Top edge portion 30d": Embedded portion 4: Stud bolt 40: Threaded portion 41: Nut 42: Base end portion 5: Steel jig 51: Bottom surface portion 52: Rising portion 6, 6: Connecting bolt 60: Nut 7: Filler

Claims (4)

A joint structure between a steel girder and a precast deck placed on the steel girder,
A pair of steel jigs having an L-shaped cross section and a bottom portion and a rising portion are attached to both edges of the upper surface of the upper flange of the steel girder by stud bolts fused to the upper flange,
A shear-stop steel member having a surrounding portion surrounding at least the left, right, and bottom three sides is protruded from the underside of the precast floor slab,
A connecting bolt is inserted between the pair of steel jigs and fastened to the rising portion,
A joint structure between a steel girder and a precast deck, characterized in that the steel girder and the precast deck are joined by inserting the connecting bolt into the surrounding portion of the anti-slip steel material. The joint structure between a steel girder and a precast deck according to claim 1, characterized in that the surrounding portion is made of a U-shaped steel bar or a perforated steel plate when viewed from the side. The pair of steel jigs are attached to both edges of the upper flange of the steel girder so that the rising portion is on the outside,
3. The joint structure between a steel girder and a precast deck according to claim 1 or 2, characterized in that a filler is filled between the pair of steel jigs. The pair of steel jigs are attached to both edges of the upper flange of the steel girder so that the rising portion is on the inside,
3. The joint structure between a steel girder and a precast deck according to claim 1 or 2, wherein the connecting bolts and the stud bolts are embedded inside a filler material.

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