JP7207982B2 - Steel beams and how to design steel beams - Google Patents

Description

The present invention relates to steel beams and methods for designing steel beams.

Conventionally, various steel frame beam end web reinforcement methods have been proposed for the purpose of reducing the amount of steel used in steel framed buildings. In the steel frame beam end web reinforcement method, the beam cross-sectional size is set according to the center of the span where the design stress generated in the steel frame beam is low, and a stiffening material such as a stiffener is welded to the web near the hinge formation position of the beam end. and reinforced.
In this way, by reinforcing only the necessary parts of the steel beams, it is possible to reduce the amount of steel materials for the entire frame while ensuring the necessary plastic deformation capacity of the entire steel beams (see, for example, Patent Documents 1 and 2).

On the other hand, webs of steel beams are often provided with through-holes for inserting equipment pipes and the like. In such a case, there is a method of reinforcing the area around the through-hole (beam through-hole reinforcement method) in order to prevent the reduction of the yield strength of the steel frame beam due to the provision of the through-hole. In the beam through-hole reinforcement method, for example, a through-hole reinforcing member such as a reinforcing plate or a sleeve pipe is provided around the through-hole of the web of the steel frame beam to reinforce the through-hole (see, for example, Patent Document 3).

Japanese Patent No. 6105878 JP 2014-43751 A JP-A-9-32197

The above beam end web reinforcement method and beam through hole reinforcement method are designed independently. However, if the location where the stiffener is installed by the beam end web reinforcement method interferes with the location where the through hole and through hole reinforcing member are installed by the beam through hole reinforcement method, the stiffener by the beam end web reinforcement method and the beam It may be necessary to install one of the through-hole reinforcing members by the through-hole reinforcing method so as to straddle the other, and there is a problem that processing of the steel beam such as welding becomes difficult. In addition, if the stiffening member by the beam end web reinforcement method and the through-hole reinforcing member by the beam through-hole reinforcement method are designed so as not to interfere with each other, the size of the through-hole is limited, and the degree of design freedom is reduced. There is a problem.

The present invention has been made in view of the problems described above. A steel frame beam that can be provided without interfering with a through hole reinforcing member by a beam through hole reinforcement method), can prevent buckling of the web, and can prevent a decrease in the yield strength of the web due to the through hole. The purpose is to provide a design method for

In order to achieve the above object, a steel beam according to the present invention is a steel beam in which a through-hole is formed in the vicinity of an end in the length direction of the web and penetrates the web in the thickness direction. A first reinforcing member that is joined to the web in the vicinity of a direction end to prevent the web from buckling; 2 reinforcing members, wherein the first reinforcing member is not provided in a second reinforcing member installation range where at least the second reinforcing member is provided in the length direction of the web, and The buckling resistance of the first reinforcing member-omitted range in which the first reinforcing member is not provided in the vicinity of the ends in the length direction of the web is determined by the through-hole not formed in the first reinforcing member-omitted range, It is characterized in that the buckling strength is set to be greater than the buckling strength that would be obtained if the first reinforcing member were provided.

In addition, a steel beam design method according to the present invention includes through holes provided near ends in the length direction of a web and passing through the web in the thickness direction, and near ends in the length direction of the web. a first reinforcing member that is joined to the web to prevent the web from buckling; and a second reinforcing member that is provided around the through hole and prevents a decrease in yield strength of the web due to the through hole. In the method for designing a steel frame beam having The buckling strength of the first reinforcing member-omitted range in which the first reinforcing member is not provided in the vicinity of the end of the direction is determined by the first reinforcing member-omitted range where the through hole is not formed and the first reinforcing member It is characterized in that it is designed to be larger than the buckling strength when it is assumed that the member is provided.

In the present invention, the buckling resistance of the first reinforcing member-omitted range in which the first reinforcing member is not provided in the vicinity of the ends in the length direction of the web is calculated as follows: , is set to be larger than the buckling resistance strength when it is assumed that the first reinforcing member is provided. As a result, buckling is prevented in the region of the web where the first reinforcing member is omitted even if the first reinforcing member is omitted.
The second reinforcing member installation range in which the through hole and the second reinforcing member are installed is included in the first reinforcing member omission range, and the first reinforcing member is not provided. Therefore, even if a through-hole of a desired size is provided in the web, the first reinforcing member and the second reinforcing member can be provided so as not to interfere with each other. A decrease in yield strength can be prevented.

According to the present invention, even if a through-hole of a desired size is provided in the web, the first reinforcing member and the second reinforcing member can be provided so as not to interfere with each other. It is possible to prevent the yield strength of the web from decreasing due to holes.

It is a perspective view showing an example of a steel frame beam by an embodiment of the present invention. (a) is a diagram showing the range where stiffeners are installed on steel beams (stiffener stiffening range), (b) is a moment diagram of the web during a design level 2 earthquake, (c) is a through hole and a through hole reinforcing member It is a figure which shows the range (through-hole installation possible range) which can provide. 1 is a diagram showing a steel frame beam (No. 1) in which no through-holes are formed and only stiffeners are provided; FIG. FIG. 10 is a diagram showing a steel frame beam (No. 2) in which a through hole is formed and a through hole reinforcing member is provided, and a stiffener is provided so as to cover the installation range of the through hole reinforcing member; 4 is a table showing a list of FEM analysis results; (a) is a graph showing the load deformation relationship of No. 1 steel beam, (b) is a graph showing the load deformation relationship of No. 2 steel beam, (c) is a graph showing the load deformation relationship of No. 3 steel beam It is a graph which shows load-deformation relationship. (a) is a diagram showing the ultimate state deformation and stress contours of No. 1 steel beam, (b) is a diagram showing the ultimate state deformation and stress contours of No. 2 steel beam, (c) Fig. 3 is a diagram showing deformation and stress contours of the No. 3 steel beam in the ultimate state; This is the design flow of steel beams. It is a figure explaining the buckling test in the design flow of a steel frame beam. (a) is a side view illustrating another configuration of a stiffener stiffening range and a range in which the stiffener is omitted, and (b) is a cross-sectional view taken along the line AA of (a).

A steel frame beam and a steel frame beam design method according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 9. FIG.
As shown in FIG. 1 , the steel beam 1 according to this embodiment is H-section steel and has an upper flange 2 , a lower flange 3 and a web 4 . FIG. 1 shows a vicinity 11 of one end in the length direction of the steel beam 1 (a predetermined range from one end 1a in the length direction of the steel beam 1 toward the center).

A vicinity 41 of the lengthwise end of the web 4 (a portion of the web 4 corresponding to the vicinity of the lengthwise end 11 of the steel beam 1, a predetermined range from one end 4a in the lengthwise direction toward the center) is provided with a stiffener 5 (first reinforcing member) for preventing the web 4 from buckling. In this embodiment, two stiffeners 5 are provided on each side of the web 4 with a space therebetween in the vertical direction. The upper stiffener 5 is spaced below the upper flange 2 and the lower stiffener 5 is spaced above the lower flange 3 . A stiffener 5 is provided parallel to the upper flange 2 and the lower flange 3 .
A range in which the stiffener 5 is not provided in the vicinity 41 of the longitudinal end portion of the web 4 is defined as a stiffener-omitted range 42 (a first reinforcing member-omitted range).

A through-hole 43 is formed in the vicinity of an end portion 41 of the web 4 in the longitudinal direction, for example, for passing an equipment pipe. The through-hole 43 penetrates the web 4 in the thickness direction and is provided on the other side of the stiffener 5 in the length direction at a position toward the center of the web 4 from the end 4 a in the length direction. The through hole 43 is provided in the stiffener-omitted range 42 .
The through hole 43 is formed in a circular shape.
The web 4 is provided with a through-hole reinforcing member 6 (second reinforcing member) around the through-hole 43 . The through-hole reinforcing member 6 is provided to prevent a reduction in yield strength of the steel frame beam 1 due to the provision of the through-hole 43 .

The through-hole reinforcing member 6 has a flat plate portion 61 formed in a flat plate shape and joined to the web 4 , and a cylindrical portion 62 projecting from the flat plate portion 61 .
The flat plate portion 61 is a steel plate having a plate surface larger than the through hole 43 , and a circular hole portion 63 having the same diameter as the through hole 43 is formed in the center.
The cylindrical portion 62 is a cylindrical steel pipe having the same diameter as the hole portion 63 , one end portion 62 a is connected to the edge portion 63 a of the hole portion 63 of the flat plate portion 61 , and the other end portion 62 b is connected to the flat plate portion 61 . placed in a protruding position.

The through-hole reinforcing member 6 is joined to the web 4 so that the surface on the side where the tubular portion 62 does not protrude is in surface contact with the web 4 , and the hole portion 63 and the tubular portion 62 overlap the through-hole 43 . Through-hole reinforcing members 6 are provided on both sides of the web 4 respectively.
The through hole reinforcing member 6 is provided in the stiffener omission range 42 and does not interfere with the stiffener 5 .
A range in which the through-hole reinforcing member 6 is provided in the length direction of the web 4 is defined as a through-hole reinforcing member installation range 44 (second reinforcing member installation range). The through-hole reinforcing member installation range 44 is smaller than the stiffener-omitted range 42 and is provided inside the stiffener-omitted range 42 .

In the steel beam 1 according to the present embodiment, the buckling resistance of the stiffener-omitted range 42 in the vicinity of the end portion 41 in the length direction of the web 4 is as follows. It is set larger than the buckling strength when it is assumed that In the design method of the steel beam according to the present embodiment, the buckling resistance of the stiffener-omitted range 42 in the vicinity of the end portion 41 in the length direction of the web 4 is calculated as follows. Set the buckling strength to be larger than the one assumed to be provided.

As shown in FIGS. 2(a) and 2(b), in the present embodiment, the range in which the stiffeners 5 are installed on the steel frame beam 1 (stiffener stiffening range 45) is limited to the designed level 2 earthquake (vertical motion). In the stress state of (addition of stress due to FIG. 2(b) is a design moment diagram for a Level 2 earthquake.
In FIG. 2A, the stiffeners 5 are provided over the entire stiffener stiffening range 45, but the stiffener stiffening range 45 includes the stiffener-omitted range 42 (see FIG. 1).

As shown in FIG. 2(c), in the present embodiment, the range where the through-hole 43 and the through-hole reinforcing member 6 can be provided (through-hole installable range 46) is the plasticization of the end 1a of the steel beam 1. A range other than the area 48 (0.5 times the beam length) is set. Therefore, a range 47 where the stiffener 5 can be omitted by providing the through hole 43 and the through hole reinforcing member 6 is a range where the stiffener stiffening range 45 and the through hole installable range 46 overlap.
If the form of the through-hole reinforcing member 6 is other than the above, the through-hole installable range 46 is set according to each guideline.

An FEM analysis of the steel beam 1 according to this embodiment was performed.
Analysis cases are the following No. 1-No. 3 of 3 cases.
No. 1: Steel frame beam 1A provided with only stiffeners 5 without through-holes (see Fig. 3)
No. 2: A steel frame beam 1B in which a through-hole 43 is formed and a through-hole reinforcing member 6 is provided, and a stiffener 5 is provided so as to extend over a through-hole reinforcing member installation range 44 (see FIG. 4)
No. 3: Steel beam 1C of this embodiment (see FIG. 1)

FEM analysis was performed by MD. A nonlinear static incremental analysis was performed using Nastran (SOL106), taking into account material nonlinearity and geometric nonlinearity. As boundary conditions, the ends 1a (left side in the figure) of the steel beams 1A to 1C were completely fixed, and the other ends were forcedly deformed to form a cantilever beam.

A list of FEM analysis results is shown in the table of FIG. 5, and the obtained load-deformation relationship is shown in the graphs of FIGS. 6(a)-(c). Fig. 6(a) shows the load deformation relationship of No. 1 steel beam 1A, Fig. 6(b) shows the load deformation relation of No. 2 steel beam 1B, and Fig. 6(c) shows the No. .3 shows the load deformation relationship of the steel beam 1C.
Here, the load and deformation in the figure are non-dimensionalized with the calculated value of the total plastic strength of the beam cross section and the deformation at that time. Ultimate state deformation and stress contours (von MisesStress) are also shown in FIG. Fig. 7(a) shows the ultimate state deformation and stress contour of No. 1 steel beam 1A, Fig. 7(b) shows the ultimate state deformation and stress contour of No. 2 steel beam 1B, FIG. 7(c) shows the deformation and stress contours of No. 3 steel beam 1C in the ultimate state.
As shown in FIG. 6, the load deformation relationship indicates that the No. 1 steel frame beam and the No. 2 steel frame beam have the same yield strength and plastic deformation ability. Also, as can be seen from FIG. 3, it can be seen that the through-hole reinforcing member 6 sufficiently restrains the buckling of the web 4 even in the range 42 where the stiffener is omitted.
From the above, the effectiveness of the steel frame beam 1 (No. 3) according to this embodiment has been confirmed.

Next, the design flow of the steel frame beam according to this embodiment will be described.
In the design flow of the steel beam according to the present embodiment, in addition to confirmation by FEM analysis (buckling eigenvalue analysis) of the steel beam 1, it is confirmed that the following conditions are satisfied. FIG. 8 shows the design flow of the steel beam 1 .

First, the design moment (M) and shear force (Q) of the steel beam 1 are calculated (step 1 (S-1)).
The cross section of the steel frame beam 1 is set from the design moment (M) and shear force (Q) calculated in step 1 (S-1) (step 2 (S-2)).
Subsequently, stiffener stiffening design (setting of the stiffening section in which the stiffeners 5 are installed, the spacing of the stiffeners 5, and the dimensions of the stiffeners 5) is performed (step 3 (S-3)). If a problem arises in the design of the stiffener stiffening, return to step 2 (S-2) and set the cross section of the steel frame beam 1 again.

Before, after, or at the same time as the stiffener stiffening design in step 3 (S-3), the design of the through-hole 43 (setting of hole diameter and position) is carried out according to the plan for piping (step 4 (S-4)). (Step 5 (S-5)).
Based on the shape of the through-hole 43 designed in step 5 (S-5), the through-hole reinforcing member 6 is designed (step 6 (S-6)).

It is determined whether or not the stiffener 5 designed in step 3 (S-3) interferes with the through-hole reinforcing member 6 designed in step 6 (S-6) (step 7 (S-7)).
If it is determined in step 7 (S-7) that the stiffener 5 and the through-hole reinforcing member 6 do not interfere with each other, a steel beam having a stiffener and a through-hole reinforcing member based on the conventional construction method (this embodiment not apply steel beams by
If it is determined in step 7 (S-7) that the stiffener 5 interferes with the through-hole reinforcing member 6, a range in which the stiffener 5 can be omitted (stiffener omission range 42) is set (step 8 (S-8)). ).

In the stiffener omission range 42 set in step 8 (S-8), a buckling test as a beam web plate is performed on the upper region A and the lower region A' of the through-hole reinforcing member 6 shown in FIG. (step 9 (S-9)). In addition, in the steel beam 1 of FIG. 9 , the through hole 43 and the through hole reinforcing member 6 are positioned above the center in the web height direction, and the stiffeners 5 are provided on both sides of the through hole reinforcing member 6 .
The buckling test is based on the test method shown in Architectural Institute of Japan: Steel Structure Design Standards. Note that the portion dr provided with the through-hole reinforcing member 6 does not require a buckling test as a beam web plate if the conventional design for through-hole reinforcement of a steel frame beam is satisfied.

If the buckling test in step 9 (S-9) satisfies the criteria, the above FEM analysis (buckling eigenvalue analysis) is performed for confirmation (step 10 (S-10)).
If the effectiveness of the steel beam can be confirmed in step 10 (S-10), the stiffener 5 can be omitted (step 11 (S-11)), and the design of the stiffener 5 and through-hole reinforcing member 6 is completed.

In step 9 (S-9), if the buckling test criteria are not satisfied, the process returns to step 8 (S-8). Also, in step 10 (S-10), if the validity of the steel frame beam cannot be confirmed, the process returns to step 8 (S-8).
In step 8 (S-8), the stiffener omission range 42 is set again, in step 9 (S-9), the buckling test criteria are satisfied, and in step 10 (S-10), the effectiveness of the steel beam is confirmed. If possible, the stiffener 5 can be omitted (step 11 (S-11)), and the design of the stiffener 5 and the through-hole reinforcing member 6 is completed.
If the buckling test criteria cannot be satisfied in step 9 (S-9), or if the effectiveness of the steel beam cannot be confirmed in step 10 (S-10), the stiffener 5 cannot be omitted.

Next, the operation and effects of the steel frame beam 1 and the steel frame beam design method according to the present embodiment described above will be described with reference to the drawings.
In the steel frame beam 1 and the design method of the steel frame beam according to the present embodiment described above, the buckling capacity of the stiffener-omitted range 42 of the web 4 is as follows: It is set larger than the buckling strength when it is assumed that As a result, buckling of the stiffener-omitted area 42 of the web 4 is prevented even if the stiffener 5 is omitted.
A through-hole reinforcing member installation range 44 in which the through-hole 43 and the through-hole reinforcing member 6 are installed is included in the stiffener-omitted range 42, and the stiffener 5 is not provided. Therefore, even if the through holes 43 of a desired size are provided in the web 4, the stiffeners 5 and the through hole reinforcing members 6 can be provided so as not to interfere with each other. It is possible to prevent the reduction in yield strength of the web 4 due to

Although the embodiments of the steel beam 1 and the method of designing the steel beam according to the present invention have been described above, the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the invention.
For example, in the above-described embodiment, the stiffener 5 is provided only on one side in the length direction of the through-hole reinforcing member 6, but the stiffener 5 may be provided on both sides in the length direction. The stiffener omission range 42 may be the same range as the through-hole reinforcing member installation range 44 or may be a range larger than the through-hole reinforcing member installation range 44 .

Further, in the above-described embodiment, the stiffener 5 is provided as a first reinforcing member for preventing buckling of the web 4 in the vicinity 41 of the lengthwise end portion of the web 4 . As a member other than the stiffener 5 may be provided. Further, the position and orientation of the stiffeners 5 and the number of stiffeners 5 may be appropriately set.

In the above embodiment, the range in which the stiffeners 5 are installed in the steel frame beam 1 (the stiffener stiffening range 45) is the stress state of the design level 2 earthquake (stress due to vertical movement is also added). The range exceeds the local buckling critical strength MD of the web 4 of the beam 1 .
On the other hand, as shown in FIG. 10, the stiffener stiffening range 45 extends from the plastic hinge forming position of the steel beam 1 (the end 1b of the widened haunch) to the center of the steel beam 1 in the length direction. It is good also as a range to the headed position for the dimension of 1.0 times. For example, when the beam height is 1200 mm, the stiffener stiffening range 45 is a range from the end 1b of the widened haunch to a position 1200 mm toward the center of the steel frame beam 1 in the longitudinal direction.

When the through hole 43 is formed in the stiffener stiffening range 45 and the through hole reinforcing member 6 is provided, the stiffener omitted range 42 is the range in which the through hole reinforcing member 6 is provided (through hole reinforcing member installation range). 44). For example, when forming a through hole 43 of 400 mm in the stiffener stiffening range 45 and providing a through hole reinforcing member 6 having a flat plate portion 61 of 600 mm square and a cylindrical portion 62 of 400 mm, the stiffener omission range 42 is a range of 600 mm where the through-hole reinforcing member 6 is provided (through-hole reinforcing member installation range 44).

Further, in the above-described embodiment, the through-hole reinforcing member 6 having the flat plate portion 61 and the cylindrical portion 62 is provided as the second reinforcing member for preventing the decrease in yield strength of the steel frame beam 1 due to the provision of the through-hole 43. However, a ring-shaped member or the like may be provided as the second reinforcing member.

1 steel beam 4 web 5 stiffener (first reinforcing member)
6 through-hole reinforcing member (second reinforcing member)
41 Near end 42 Stiffener omission range (first reinforcing member omission range)
43 through hole 44 through hole reinforcing member installation range (second reinforcing member installation range)

Claims (2)

In a steel beam in which a through hole is formed through the web in the thickness direction near the end in the length direction of the web,
a first reinforcing member joined to the web near the lengthwise end of the web to prevent buckling of the web;
a second reinforcing member that is provided around the through hole and prevents a decrease in yield strength of the web due to the through hole;
The first reinforcing member is not provided in a second reinforcing member installation range where at least the second reinforcing member is provided in the length direction of the web,
The buckling resistance of the first reinforcing member-omitted range in which the first reinforcing member is not provided in the vicinity of the ends in the length direction of the web is , a steel frame beam characterized by being set to be larger than the buckling strength when it is assumed that the first reinforcing member is provided. a through hole provided in the vicinity of the end in the length direction of the web and penetrating the web in the thickness direction;
a first reinforcing member joined to the web near the longitudinal end of the web to prevent buckling of the web;
and a second reinforcing member provided around the through-hole and preventing a decrease in yield strength of the web due to the through-hole,
The first reinforcing member is not provided in a second reinforcing member installation range where at least the second reinforcing member is provided in the length direction of the web,
The buckling resistance of the first reinforcing member-omitted range in which the first reinforcing member is not provided in the vicinity of the ends in the length direction of the web is calculated as follows: 1. A method for designing a steel frame beam, characterized in that the design is made so as to be larger than the buckling resistance force when it is assumed that the first reinforcing member is provided.

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