JP2022173695A - Junction structure of small beam end - Google Patents

Abstract

To provide a junction structure of a small beam end, the junction structure capable of opposing a bending moment in a junction portion of a large beam and a small beam without increasing a cross section of the small beam.SOLUTION: Small beam ends are bonded to both sides of a web of a large beam by a gusset plate. A splice plate is bonded to bottom flanges of the small beams on both the sides with a high strength bolt. A plurality of shear connectors is erected on upper flanges of the small beams on both the sides, and extends across the large beam to provide a floor slab. Reinforcement means is provided in the shear connectors erected on the small beam ends so as to contact with the shear connector.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a joining structure for ends of small beams of steel frame construction.

As shown in FIG. 6, the end joints of the steel beams are made by joining only the gusset plates 20 attached to the large beams and the webs 22 of the small beams 21 with high-strength bolts 23. A pin connection type is generally used. Pin-joint type joints have simple details and high workability, but the bending moment load on the ends is zero in calculation. Therefore, as shown in FIG. 7, the stress and deflection at the center of the span are increased, and the cross section of the small beam is increased, which often causes an increase in cost. In particular, in a distribution facility or the like with a large load, even if there is a margin in terms of stress, small beams may have a large cross section in order to suppress the amount of deflection.

Japanese Patent Application Laid-Open No. 2015-68001 Japanese Patent Application Laid-Open No. 2017-53102

In the joint structure of Patent Document 1, a large beam is sandwiched between two small beams, butted and joined together. Reinforcing members are placed on the slab across the small beams. Further, Patent Document 2 relates to a joint structure of a beam and a member to be joined, a slab is similarly provided on the upper surface of these members, and a locking member fixed to the beam is embedded in the slab. It is joined to the member to be joined through the joint. A gusset plate is welded to the joining member and bolted to the web of the beam. A splice plate separate from the gusset plate is butt-welded to the member to be joined, and bolted to the lower flange of the beam.

Both the invention described in Patent Document 1 and the invention described in Patent Document 2 are structures in which the ends of small beams are joined to large girders. In the latter, the splice plates are butt-welded to support the bending moment by transferring compressive forces to the webs of the joined members.

However, particularly in the invention described in Patent Document 1, a reinforcing member such as a reinforcing bar is provided inside the slab separately from the slab bar. Since it is not attached, it does not directly bear the bending moment of the joint between the large beam and the small beam.

The present invention provides a joint structure for the ends of small beams that can withstand the bending moment at the joints of large and small beams without increasing the cross section of the small beams by adopting a relatively simple structure. It is intended to provide

In order to achieve the above object, in the present invention, the ends of the small beams are joined to both sides of the web of the large beam with gusset plates, and the splice plates are joined to the lower flanges of the small beams on both sides with high-strength bolts. Furthermore, a plurality of shear connectors are erected on the upper flanges of the small beams on both sides, and a floor slab is provided across the large beams, and the shear connectors erected at the ends of the small beams are in contact with reinforcing means. The joint structure of the end of the small beam is provided. Since the splice plate is joined to the lower flange of the small beam to the large beam with high-strength bolts, the processing can be simpler than the rigid joint that penetrates and welds the end of the small beam. In addition, since the reinforcing means embedded in the floor slab directly transmits the stress to the upper flange of the small beam via the shear connector, the tensile force generated in the floor slab is borne by the small beam. , the small beam cross-section can be reduced.

Here, as a more specific configuration of the reinforcing means, a means of adopting U-shaped rebars, making two rebars into a pair and superimposing them so that their curved portions are positioned on the outside, or two rebars. A pair of books were arranged, and the curved portions of each U-shaped muscle were arranged to face each other. By bringing the U-shaped reinforcement into contact with the shear connector by means such as binding, the tensile force generated in the floor slab is transmitted from the U-shaped reinforcement to the floor slab via the shear connector. The tensile force of the floor slab is efficiently transmitted to the girders by adhesion force.

Also, as a reinforcing means, a perforated plate was used in place of the U-shaped bar. Here, a means of stacking two perforated plates as a pair or a means of placing two perforated plates as a pair facing each other in the extending direction of the small beam was selectively used. The perforated plate acts to transfer the pulling force of the floor slab to the girders through the shear connectors.

According to the joint structure of the small beam ends of the present invention, the tensile force generated in the floor slab is transmitted from the reinforcement means to the small beam through the shear connector, and the bending moment is borne, so that stress and deflection can be reduced. , it became possible to reduce the cross section of the small beam.

1a is a side view showing one embodiment of the joint structure of the small beam end portion of the present invention, and 1b is a plan view of the same. Graph showing the moment distribution and deflection distribution of the structure in Figure 1 3a is a side view showing a modification of FIG. 1, and 3b is a plan view of the same. 4a is a side view showing the third modification of FIG. 1, and 4b is a plan view of the same. 5a is a side view showing the fourth modification of FIG. 1, and 5b is a plan view of the same. Side view showing a conventional pin joint structure Graph showing the moment distribution and deflection distribution of the structure of Figure 6

Preferred embodiments of the present invention will now be described with reference to the drawings. 1A and 1B show a joint structure of a small beam end portion according to an embodiment of the present invention, FIG. 1A being a side view and FIG. 1B being a plan view. In the figure, 1 is a large beam, and 2 and 2 are small beams butted together from both sides of the web of the large beam 1. Gusset plates 3 and 3 are pin-joined with high-strength bolts 4 to connect the small beams 2 and 2 to the large beam 1 . Also, the lower flanges 5.5 of the small beams 2.2 are joined to the splice plate 6 with pins. 7 is a floor slab provided on the upper flanges 8,8 of the small beams 2,2 and joined by shear connectors 9..9. Reference numeral 10 denotes a U-shaped reinforcement that functions as a reinforcing means provided so as to contact the shear connector 9. In this embodiment, the U-shaped reinforcement 10 is arranged so as to overlap from both sides so that the curved portion of the U-shaped reinforcement 10 is on the outside. is doing. What is important here is that the U-shaped reinforcements 10 must be arranged so as to be in contact with the shear connectors 9 without fail. In order to ensure the contact, it is preferable to bind the U-shaped reinforcements 10 to the shear connectors 9 and position them securely before pouring concrete. Shear connectors 9 that contact the U-shaped reinforcements 10 are erected at the ends of the small beams so that the tensile force generated in the floor slab 7 is transferred from the U-shaped reinforcements 10 via the shear connectors 9 to the floor slabs 7. It is directly transmitted to the small beam 2. Therefore, although it is preferable that the erecting position of the shear connector 9 is located at the end of the small beam in terms of design, the shear connector is not erected at the preferable position of the end of the small beam due to the restriction due to the distance from the other shear connectors 9. In some cases, a shear connector 9 for contacting the U-shaped bar 10 may be provided independently. The reinforcing bars 11...11 in FIG. 1b are anti-cracking bars of the floor slab 7. FIG. It should be noted that the U-shaped reinforcing bar 10 is preferably a deformed reinforcing bar in order to provide resistance to the tensile force.

FIG. 2 is a moment distribution diagram and a deflection distribution diagram of the structure shown in FIG. Since the deflection is also reduced, the small beam cross-section can be made smaller than the conventional structure if the same stress is secured.

FIG. 3 shows a modified example of this embodiment, FIG. 3a being a side view and FIG. 3b being a plan view. In the figure, the parts assigned the same numbers as in FIG. 1 show the same structures as in FIG. The structure different from the structure of FIG. 1 is the reinforcement structure of the U-shaped reinforcement 10 . That is, in the modified example of FIG. 3, the curved portions of the pair of U-shaped reinforcements 10 are arranged so as to face each other. Even in this case, the U-shaped reinforcement 10 is arranged so as to contact the shear connector 9 on the side of the small beam end. Therefore, the function as a whole is basically the same as the structure of FIG.

FIG. 4 shows a third modification, in which two pairs of perforated plates 12 functioning as reinforcing means are arranged in place of the U-shaped ribs. Although the material of the perforated plate 12 is not particularly limited, such as a steel plate or a stainless steel plate, it is required to have a strength capable of efficiently transmitting stress. The interval between the holes is also not particularly limited, but as shown in FIG. Since the shear connector 9 is caught in the space, stress transmission can be ensured. The perforated plate 12 is provided with not only holes for securing the shear connectors 9, but also a plurality of holes, so that the adhesion of the floor slab 7 to the concrete can be enhanced, and the pulling force can be further resisted. can be done.

FIG. 5 shows a fourth modified example, in which the perforated plates 12 used in the third modified example are not superimposed and installed, but two plates are installed independently in the direction of the small beam. In the modification, two sets of this mode are provided in parallel. In this embodiment, two pairs are provided in parallel as shown in the figure, but only one pair may be installed at the central portion of the upper flange of the small beam if the stress can be sufficiently resisted.

As shown in each of the above embodiments, in the joint structure of the small beam end of the present invention, the joint bears the bending moment and reduces the stress and deflection, so the small beam is more flexible than the conventional pin joint. A cross section can be made small. In addition, since the joint consists only of high-strength bolts, the processing is simpler than general rigid joints in which the ends of the small beams are completely penetrated and welded, and quality control is easier. In addition, compared to conventional pin joints, high-strength bolt joints on the lower flanges require only U-shaped reinforcing bars on the floor slab and perforated plates, making construction easier on site. become.

1 Large beam 2 Small beam 3 Gusset plate 4 High strength bolt 5 Lower flange of small beam 6 Splice plate 7 Floor slab 8 Upper flange of small beam 9 Shear connector 10 U-bar 11 Crack prevention bar 12 Perforated plate

In order to achieve the above object, in the present invention, the ends of the small beams are joined to both sides of the web of the large beam with gusset plates, and the splice plates are attached to the lower flanges of the small beams on both sides of the suspension with high-strength bolts. Further, a plurality of shear connectors are erected on the upper flanges of the small beams on both sides to direct the floor slab across the large beams, and the shear connectors erected at the ends of the small beams are reinforcing means. are provided in contact with each other, and the tensile force generated in the floor slab is transmitted to the small beam through the shear connector to bear the bending moment . Since the splice plate is joined to the lower flange of the small beam to the large beam with high-strength bolts, the processing can be simpler than the rigid joint that penetrates and welds the end of the small beam. In addition, since the reinforcing means embedded in the floor slab directly transmits the stress to the upper flange of the small beam via the shear connector, the tensile force generated in the floor slab is borne by the small beam. , the small beam cross-section can be reduced.

Claims (7)

A structure for joining small beam ends to a large beam, wherein the small beam ends are joined to both sides of the web of the large beam with gusset plates, and splice plates are attached to the lower flanges of the small beams on both sides. are joined with high-strength bolts, and a plurality of shear connectors are erected on the upper flanges of the small beams on both sides to provide a floor slab across the large beams, and the shears erected at the ends of the small beams A joint structure for the end of a small beam, characterized in that a reinforcing means is provided in contact with the connector. 2. The joining structure of the ends of the small beams according to claim 1, wherein the reinforcing means is a U-shaped bar. 3. The joining structure of the ends of the small beams according to claim 2, wherein two U-shaped rebars are arranged as a pair, and the rebars are superimposed so that the respective curved portions are located on the outside. 3. The joining structure of the ends of the small beams according to claim 2, wherein two U-shaped rebars are paired and arranged so that curved portions of the respective U-shaped rebars face each other. 2. The joining structure of the ends of the small beams according to claim 1, wherein the reinforcing means is a plate with holes, and the shear connectors are brought into contact with the holes. 6. The joining structure for the ends of small beams according to claim 5, wherein two perforated plates are superimposed as a pair. 6. The joining structure for the ends of the small beams according to claim 5, wherein two perforated plates are paired and arranged facing each other in the extending direction of the small beams.

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