JP7380230B2 - Beam opening reinforcement method and beam structure - Google Patents

Description

The present invention relates to a method for reinforcing the opening of a beam in which a through hole is formed, and a structure of the beam.

For example, through holes are sometimes opened in beams that make up the framework of a building for the purpose of passing pipes through. A beam provided with a through hole has lower bending strength than a beam not provided with a through hole. Therefore, in order to compensate for the decreased bending strength, reinforcement was conventionally performed for each through hole. For example, a ring material is installed in each through-hole of the beam, or a plate material is provided surrounding each through-hole (see, for example, Patent Document 1). In the beam described in this document, the width and thickness of the bending reinforcement section and the shear reinforcement section provided in the web of the steel beam body are set. Based on this width and thickness, a bending shear strength curve representing the relationship between the bending strength and shear strength of the opening portion of the beam is determined. Then, the bending shear strength curve is compared with the design shear force and design bending moment obtained from the design load assumed for the beam.

JP2017-210785A

The diameter of the through-hole provided in the beam may be changed depending on the conditions of the piping and the like. In this case, conventional techniques such as the reinforcing method described in Patent Document 1 require a ring-shaped reinforcing material depending on the diameter of the through-hole or a plate-shaped reinforcing material disposed around the through-hole. Furthermore, each time the diameter of the pipe changes, it is necessary to manufacture a reinforcing material according to the diameter of the through hole and redesign the reinforcement of the through hole.

A method for reinforcing an opening in a beam that solves the above problem includes providing a through hole in the web of an H-shaped cross-section beam, providing a reinforcing material in the flange of the H-shaped cross-section beam, and reinforcing the opening of the through-hole in the beam opening. In the reinforcing method, when the size of the through hole is determined, the length of the reinforcing material in the axial direction of the H-shaped cross-section beam and the length orthogonal to the axial direction are determined according to the size of the through hole. The cross-sectional area of the reinforcing material in the plane to be set is set.
A beam structure that solves the above problem is a beam structure in which a through hole is provided in the web of an H-shaped cross-section beam, and a slab is placed above the H-shaped cross-section beam, and above the through-hole, A reinforcing bar embedded in the slab is provided as an upper reinforcing member, a reinforcing plate fixed to the lower surface of the H-shaped cross-section beam below the through hole is provided as a lower reinforcing member, and a reinforcing plate is provided as a lower reinforcing member below the through hole. The reinforcing member and the lower reinforcing member reinforce the yield strength, which is reduced depending on the size of the through hole.

According to the present invention, through holes can be efficiently reinforced.

FIG. 3 is a front view of the beam structure in the embodiment. FIG. 4 is an explanatory diagram illustrating model conditions for analyzing the structure of a beam in the embodiment. FIG. 1 is a perspective view illustrating the entire FEM analysis model in the embodiment. FIG. 3 is a perspective view illustrating the main parts of the FEM analysis model in the embodiment. FIG. 3 is an explanatory diagram illustrating an example of the distribution of axial stress according to the FEM analysis results in the embodiment, in which (a) is a case without a through hole, (b) is a case without reinforcement, and (c) is a case where the reinforcing material length is (d) when the reinforcing material length is the same as the through-hole diameter; (e) when the reinforcing material length is twice the through-hole diameter. FIG. 4 is an explanatory diagram illustrating an example of Mises stress distribution according to FEM analysis results in the embodiment, in which (a) is a case without a through hole, (b) is a case without reinforcement, and (c) is a case where the length of the reinforcing material is penetrating. (d) when the length of the reinforcing material is the same as the diameter of the through hole; (e) when the length of the reinforcing material is twice the diameter of the through hole. Graphs showing changes in load with respect to displacement according to FEM analysis results in the embodiment, where (a) is a case where the through hole is 1/3 times the size of the beam, and (b) is when the main part of (a) is enlarged. , (c) shows the case where the through hole is 4/5 times the size of the beam, and (d) shows the case where the main part of (c) is enlarged. 5 is a graph showing the relationship between standardized reinforcing material length and proof stress ratio in the embodiment. 7 is a graph showing the relationship between the required reinforcing material length and the standardized through-hole diameter in the embodiment.

Hereinafter, embodiments embodying a beam opening reinforcing method and a beam structure will be described using FIGS. 1 to 9.
As shown in FIG. 1, the beam structure 10 of this embodiment includes a beam 20 and a slab 30 provided on the beam 20. The beam 20 is made of a steel beam, such as an H-beam, and has an upper flange 21, a lower flange 22, and a web 23 connecting these at the center. A through hole 25 having a through hole diameter (diameter of the through hole) φ is formed in the web 23 of the beam 20 . This through hole 25 opens in a horizontal direction perpendicular to the axis C1 direction of the beam 20.

Further, a reinforcing plate 41 is attached to the lower surface of the lower flange 22 of the beam 20 as a lower reinforcing member. This reinforcing plate 41 can be used as a sacrificial plate for finishing material provided on the beam 20. In this embodiment, a lightweight steel partition wall or the like is used as the finishing material.

The reinforcing plate 41 reinforces a part of the yield strength reduced by providing the through holes 25 in the web 23. In this embodiment, the length of the reinforcing plate 41 is 1.5 times the height H1 of the web 23. Further, the reinforcing plates 41 are equally divided and arranged along the vertical axis V1 of the through hole 25. Further, the width of the reinforcing plate 41 (the length in the direction perpendicular to the plane of the drawing) is about 10 mm shorter from both ends of the lower flange 22. Then, the periphery of the reinforcing plate 41 is welded to the lower surface of the lower flange 22 to be integrated.

A slab 30 is provided on the upper surface of the upper flange 21 of the beam 20. This slab 30 is constructed by embedding a plurality of stud bolts 31 and a plurality of slab reinforcements 32 in concrete 35. The plurality of stud bolts 31 are arranged upright so as to be lined up on the upper surface of the upper flange 21. The plurality of slab lines 32 are arranged in a grid pattern.

Furthermore, a plurality of reinforcing bars 42 are embedded within this slab 30 as upper reinforcing members. The reinforcing bars 42 work together with the reinforcing plate 41 to reinforce the yield strength reduced by providing the through holes 25 in the web 23. The plurality of reinforcing bars 42 are used with the cross-sectional area and number of the reinforcing bars determined so that the total cross-sectional area is balanced with the proof stress reinforced by the reinforcing plate 41. This reinforcing bar 42 is arranged at a position corresponding to the reinforcing plate 41. The reinforcing bars 42 have a length that is the length of the reinforcing bar 41 plus the fixing length of the reinforcing bars 42 in both directions.
As described above, the stiffness and strength reduced by the through holes 25 can be reinforced by the reinforcing plates 41 and reinforcing bars 42 provided above and below the beam 20.

(Effect of reinforcing member)
Next, it will be explained that the reinforcing plate 41 and the reinforcing bars 42 described above have the same bending strength as a beam without through holes (a beam without through holes).
Here, this length was calculated by analysis using the finite element method (FEM) using a reinforcing material in which the reinforcing plate 41 and the reinforcing bar 42 were modeled.

As shown in FIG. 2, a mechanically modeled beam 50 in which only a bending moment acts around the through hole 55 was used. It is assumed that reinforcing members 61 and 62 are provided on the upper and lower surfaces of the beam 50 at positions below and above the through hole 55. It is assumed that the reinforcing members 61 and 62 are made of the same material and have the same size (length, width, and thickness).

The beam 50 has a beam length D of 600 mm and a width of 200 mm. The web thickness tw of this beam 50 is 12 mm, and the flange thickness tf is 22 mm. Furthermore, it is assumed that the distance between the supporting points of the beam 50 is 4800 mm, the through hole 55 is located in the center, and half the load (P/2) is applied to a position 1200 mm from each supporting point. Further, it is assumed that the diameter of the through hole is "φ", the length of the reinforcing members 61 and 62 is "Lr", and the thickness is "tr".

FIG. 3 shows how the dynamic model is divided into finite elements. Note that FIG. 4 is an enlarged view of the main part of FIG. 3. As this mechanical model, a 1/2 model in which the web of the beam 50 is divided at the center of the plate thickness is used. In this mechanical model, a condition is added in which the beam 50 is not locally bent by the load. For this purpose, stiffeners are provided at locations where loads are applied. Note that although the mechanical model includes a lower reinforcing member 61, it is omitted in FIGS. 3 and 4.

Using such a mechanical model, a parametric study was conducted in which the through-hole diameter φ and the reinforcing material length Lr were varied.
In this case, the through-hole diameter (beam ratio) φ of the through-hole 55 is "0", "200 (=D/3)", "300 (=D/2)", "315 (=0.525D)" , "330 (=0.55D),""360(=0.6D),""400(=2D/3)," and "500 (=4D/5)" are used. Further, the reinforcing material length Lr is "0 (no reinforcement)", "0.5φ", "0.75φ", "1.0φ", "1.25φ", "1.50φ", "2. 00φ” and “3.00φ” are used.

As shown in FIG. 2, the cross-sections of the reinforcing members 61 and 62 are calculated using a combination of cross-sectional area Br×tr that compensates for the reduction in strength _Mφ due to the through-hole 55. In this case, the following two equations are used.
Amount of proof stress reduction due to through hole M _φ = 1/4×tw×φ ² ×σyw…(1)
Yield strength increase Mr=Br×tr×(D+tr)×σyr due to reinforcing material…(2)
Then, a combination of Br×tr such that M _φ =Mr is calculated.
Here, tw is the web thickness, φ is the through hole diameter, Br is the width of the reinforcing material, tr is the plate thickness of the reinforcing material, D is the beam thickness, σyw is the yield stress of the web, and σyr is the yield stress of the reinforcing material.

It is assumed that the reinforcing members 61 and 62 are arranged in the same size and at corresponding positions, and are joined to the flange of the beam 50 by welding. In this case, as shown in FIG. 4, the outer periphery of the reinforcing member 62 (61) and the flange of the beam 50 share the FEM contact point.
Furthermore, in this embodiment, the yield stress of all materials is 325 N/mm ² . The stress-strain relationship of the material is bilinear, and the stiffness after yielding is 1/200 of the initial stiffness.

(Explanation of analysis results)
5 and 6 respectively show an example of the distribution of axial stress and an example of the distribution of Mises stress when analyzed assuming that the through hole diameter φ is 400 mm. Figures 5(a) and 6(a) have no through holes, Figures 5(b) and 6(b) have no reinforcement, and Figures 5(c) and 6(c) have reinforcing material length equal to the through hole diameter. 5 (d) and 6 (d), the length of the reinforcing material is the same as the diameter of the through hole, and FIG. This shows the case of twice as much. In the example of the distribution of axial stress in FIG. 5, the color becomes darker as the absolute value becomes higher. In the Mises stress distribution example shown in FIG. 6, the color becomes lighter as the stress becomes higher.

As shown in FIGS. 5 and 6, it can be seen that the longer the reinforcing material length Lr is, the more the axial stress can be transmitted to the vicinity of the center of the web of the beam 50, and the higher the yield strength can be exhibited. However, the analysis results also revealed that there is an upper limit to the effective reinforcing material length Lr of the reinforcing materials 61 and 62.

Further, FIG. 7 shows the relationship between load and displacement. In this case, the yield strength Py is defined as the time when the tangential stiffness decreases to 1/3 of the initial stiffness.
7(a) and 7(b) show the case where the through hole diameter φ of the through hole 55 is 200 (=D/3), and FIG. 7(b) shows the case where the load P in FIG. 7(a) is 1000 to 2000 ( This is a graph showing the main part of the graph (kN). Furthermore, FIGS. 7(c) and 7(d) show the case where the through-hole diameter φ of the through-hole 55 is 500 (=4D/5), and FIG. 7(c) shows the case where the load P in FIG. 7(d) is 1000~ This is an enlarged graph of the main part of the 2000 (kN) part.

As shown in FIGS. 7(a) and 7(b), when the through-hole 55 is small, there is no large difference in the yield strength between the case where there is no through-hole and the case where there is no reinforcing material. Furthermore, as shown in FIGS. 7(c) and 7(d), when the through hole 55 is large, the difference in proof strength between the case where there is no through hole and the case where there is no reinforcing material increases. Moreover, overall, as the reinforcing material length Lr of the reinforcing materials 61 and 62 increases, the yield strength tends to increase.

FIG. 8 shows the relationship between the proof stress ratio (P _φy /Py) and the standardized reinforcement length (Lr/φ). Here, the yield strength ratio is the _ratio of the yield strength Py of the beam 50 with the through holes 55 to the yield strength Py of the beam without through holes. Further, the standardized reinforcing material length (Lr/φ) is the reinforcing material length Lr with respect to the through hole diameter φ.

As shown in FIG. 8, there is a tendency for the yield strength to increase as the reinforcing material length Lr increases. Here, it is assumed that a case having a proof stress of 99% or more of the proof stress of a non-penetrating beam is considered to be equivalent to a non-penetrating beam. In this case, if the standardized reinforcing material length (Lr/φ) is 1.5 or more, the strength will be equivalent to that of a non-penetrating beam.

Furthermore, the solid line in Fig. 9 shows the relationship between the length of the reinforcement material (Lr/φ) required to exhibit the same strength as a beam without through holes and the diameter of the through hole (φ/D) standardized by the beam. analysis value). There is a tendency that the larger the through hole 55 becomes, the larger the required reinforcing material length (Lr/φ) becomes.
Moreover, the dotted line in FIG. 9 shows a design formula for the required reinforcement material length approximated based on the analytical values. Here, the length is calculated using different approximate curves in the range of 0.5≦φ<0.55 and the range of 0.55≦φ<0.8. In the range of 0.5≦φ<0.55, the required reinforcing material length (Lr/φ) is calculated as “9×φ/D−4”, and in the range of 0.55≦φ<0.8, , the required reinforcing material length (Lr/φ) is calculated as “1.8×φ/D−0.04”.

If the through hole diameter is divided into three types of threshold values (D/2, 2D/3, 4D/5), by ensuring the following reinforcing material length Lr for the through hole diameter, the beam can be equivalent to a beam without through holes. Can exhibit bending strength.
・If 2D/3<φ≦4D/5, the reinforcing material length Lr is 1.4φ or more. ・If D/2<φ≦2D/3, the reinforcing material length Lr is 1.2φ or more. ・0<φ In the case of ≦D/2, the reinforcement length Lr is 0.5φ or more. Also, from FIG. For example, it can exhibit the same bending strength as a beam without through holes.

(effect)
A reinforcing plate 41 welded to the lower flange 22 below the through hole 25 of the beam 20 and a reinforcing bar 42 buried in the slab 30 above the through hole 25 ensure that the area around the through hole is can transmit stress. In addition, the same proof strength can be maintained when there is no through hole 25.

According to this embodiment, the following effects can be obtained.
(1) In this embodiment, the stiffness and proof strength of the beam 20, which have been reduced due to the through hole 25, are reinforced by the reinforcing plate 41 and the reinforcing bars 42. This makes it possible to eliminate the need for a ring material for reinforcing the inside of the through hole 25 and a plate material for reinforcing the periphery of the through hole 25.

(2) In this embodiment, the reinforcing plate 41 has a length 1.5 times the height H1 of the web 23 of the beam 20. As a result, even if the through-hole diameter φ of the through-hole 25 formed in the beam 20 is changed to the maximum diameter that can be formed in the beam 20, the bending strength of the beam 20 is ensured by the reinforcing plate 41 and the reinforcing bar 42. can. Therefore, even if the through-hole diameter φ of the through-hole 25 is changed, there is no need to change the shape of the reinforcing material accordingly, and there is no need to redesign the reinforcement.

(3) In this embodiment, since the reinforcing plate 41 is smaller in width than the lower flange 22 of the beam 20, the end of the reinforcing plate 41 can be efficiently welded to the lower surface of the lower flange 22.
(4) In this embodiment, since the reinforcing plate 41 can be used as a finishing material waste plate, the number of locations where finishing material waste plates are provided separately from the reinforcing plate 41 can be reduced.

(5) In this embodiment, reinforcing bars 42 corresponding to the reinforcing plates 41 are embedded in the slab 30 above the through holes 25. Thereby, since reinforcing plates are not provided above and below the slab 30, the slab 30 can be formed without unevenness.

(6) In this embodiment, the reinforcing bars 42 are arranged in the number and number of reinforcing bars with a cross-sectional area that has a total cross-sectional area that has the same proof stress as that reinforced by the reinforcing plate 41, and cover the positions corresponding to the reinforcing plates 41. , and further has a length equal to or longer than the required length of the reinforcing material plus the fixing length. Thereby, it is possible to balance with the reinforcing plate 41 and to reinforce the rigidity and proof strength reduced by the through hole 25.

This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- In the above embodiment, the length of the reinforcing plate 41 is 1.5 times the height H1 of the web 23 of the beam 20. The reinforcing material length Lr is not limited to 1.5 times. For example, if the maximum diameter of the through hole is D/2 or less, the reinforcing material length Lr may be 0.5φ or more, and if the maximum diameter of the through hole is 2D/3. For this purpose, the reinforcing material length Lr may be set to 1.2φ or more. Thereby, it is possible to use a reinforcing material with an appropriate length depending on the range of the designed through hole.

- In the above embodiment, reinforcing bars 42 corresponding to the reinforcing plates 41 are provided in the slab 30 above the through holes 25 in the beams 20. The reinforcing member provided above the beam 20 is not limited to reinforcing bars. For example, instead of the reinforcing bars 42, a reinforcing plate 41 may be provided on the upper surface of the upper flange 21 of the beam 20.

- In the above embodiment, the beam 20 provided with the through hole 25 is made of a steel frame with an H-shaped cross section. The beam is not limited to H-shaped steel, and may be a closed box-section beam, for example. Further, the beam 20 is not limited to a steel frame structure, and may be made of any material that can be considered isotropic, such as a steel frame part of a steel reinforced concrete structure, a stainless steel structure, an aluminum alloy structure, etc.

Next, technical ideas that can be understood from the above embodiment and other examples will be additionally described below.
(a) The reinforcing bars have a length that is the sum of the length of the reinforcing material corresponding to the reinforcing plate and the anchoring length at both ends, and are arranged in such a number that the total cross-sectional area is greater than or equal to the cross-sectional area of the reinforcing plate. The beam structure according to claim 2, characterized in that:
(b) The beam structure according to claim 2 or (a), wherein the lower reinforcing member is used as a sacrificial plate for attaching finishing material.

φ... Through hole diameter, C1... Axis, Lr... Reinforcement material length, 10... Beam structure, 20, 50... Beam, 21... Upper flange, 22... Lower flange, 23... Web, 25, 55... Through hole, 30... Slab, 31... Stud bolt, 32... Slab reinforcement, 35... Concrete, 41... Reinforcement plate, 42... Reinforcement bar, 61, 62... Reinforcement material.

Claims (2)

A method for reinforcing an opening in a beam, in which a through hole is provided in a web of an H-shaped cross-sectional beam, and a reinforcing material is provided in a flange of the H-shaped cross-sectional beam to reinforce the opening of the through hole,
When the size of the through hole is determined, the length of the reinforcing material in the axial direction of the H-shaped cross-section beam and the reinforcing material in a plane perpendicular to the axial direction are determined according to the size of the through hole. A beam opening reinforcement method characterized by setting a cross-sectional area of . A beam structure in which a through hole is provided in the web of an H-shaped cross-section beam, and a slab is arranged above the H-shaped cross-section beam,
A reinforcing bar embedded in the slab is provided above the through hole as an upper reinforcing member,
Below the through hole, a reinforcing plate fixed to the lower surface of the H-shaped cross-section beam below the through hole is provided as a lower reinforcing member;
The beam structure is characterized in that the upper reinforcing member and the lower reinforcing member reinforce a proof stress that is reduced depending on the size of the through hole.