JP2021183782A - Design method of steel beam - Google Patents

Abstract

To provide a design method of a steel beam in which a through hole does not interfere with a steel beam end reinforcement member (a first reinforcement member) and in which a through hole size is not restricted.SOLUTION: An upper side equivalent width-thickness ratio of stiffeners 51, 52 (first reinforcement members) and a lower side equivalent width-thickness ratio of the stiffeners 51, 52 in a web 4 respectively satisfy a required width-thickness ratio condition of the web 4. A length dimension of the stiffeners 51, 52 and a range where the stiffeners 51, 52 are installed are set so that a setting moment of a part where the stiffeners 51, 52 are provided in a steel beam 1 is larger than a local buckling limit strength of a part where the stiffeners 51, 52 are not provided in the steel beam 1. A shear margin of a part where the stiffeners 51, 52 are not provided in the web 4 is set to be equal to or larger than 1.29.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for designing a steel beam.

Various methods for reinforcing steel beam end webs have been proposed for the purpose of reducing the amount of steel material in steel beams in steel-framed buildings (see, for example, Patent Documents 1 and 2). In this method, the beam cross-sectional size is determined according to the central part of the span where the stress generated in the design is low, and a reinforcing member such as a stiffener is welded to the web near the hinge formation position at the end of the steel frame beam to reinforce it. In this way, by reinforcing only the necessary parts, it is possible to reduce the amount of steel material in the entire frame while ensuring the required plastic deformation capacity of the entire steel frame beam. Basically, it is common to install a reinforcing member such as a stiffener to reinforce the buckling of the web of the steel beam, and the design method is also shown in the appendix of the Steel Structure Design Standard (AIJ). ..

On the other hand, through holes are often provided in the steel beam for the arrangement of equipment piping and the like. In this case, in order to prevent the strength of the steel beam from being lowered due to the installation of the through hole, there is a method of reinforcing the steel beam by providing a reinforcing member around the through hole (steel beam through hole reinforcement method). This is also a general construction method, and in the conventional construction method, for example, a reinforcing plate and a reinforcing member by a sleeve pipe are provided. In addition, various ring-shaped reinforcing members that reinforce the circumference of the through hole are also sold.
A steel beam end web reinforcement method that provides a reinforcing member (referred to as a steel beam end reinforcing member) that reinforces the web at the steel beam end, and a steel frame that provides a reinforcing member (referred to as a through hole reinforcing member) that reinforces the circumference of the through hole. It is designed independently of the beam through hole reinforcement method.

Japanese Patent No. 6105878 Japanese Unexamined Patent Publication No. 2014-43751

However, when a through hole penetrating the web is provided in the area where the steel beam end reinforcing member is installed, the through hole reinforcing member interferes with the steel beam end reinforcing member, and the through hole reinforcing member and the steel beam end reinforcing member are processed. Welding can be difficult. Further, in order to prevent the through hole reinforcing member from interfering with the steel beam end reinforcing member, the size of the through hole is limited, and the degree of freedom in design is reduced.

Therefore, an object of the present invention is to provide a method for designing a steel frame beam in which the through hole does not interfere with the steel beam end reinforcing member (first reinforcing member) and the size of the through hole is not limited.

In order to achieve the above object, in the method for designing a steel beam according to the present invention, a through hole penetrating the web in the thickness direction is formed in the vicinity of the end portion in the length direction of the web to buckle the web. A first reinforcing member for preventing and a second reinforcing member for preventing a decrease in the strength of the web due to the through hole are provided, and the first reinforcing member extends in the length direction of the web and has the length of the web. The second reinforcing member is formed in a ring shape and is joined to an intermediate portion in the height direction of the web in the vicinity of the end in the buckling direction and on the end side in the length direction of the web from the through hole. In the method of designing a steel beam joined along the edge of the through hole, the equivalent width-thickness ratio on the upper side of the first reinforcing member and the equivalent width-thickness ratio on the lower side of the first reinforcing member in the web are respectively. The design moment of the portion of the steel beam where the first reinforcing member is provided satisfies the requirement of the required width-thickness ratio of the web, and the local seat of the portion of the steel beam where the first reinforcing member is not provided. The length dimension of the first reinforcing member and the range in which the first reinforcing member is installed are set so as to be larger than the buckling limit strength, and the shear margin of the portion of the web where the first reinforcing member is not provided is set. The first reinforcing member is designed to have a length of 1.29 or more, and is 1.5 times the inner diameter of the second reinforcing member from the core of the through hole toward the end side in the length direction of the web. (1) It is characterized in that the installation of the reinforcing member can be partially omitted.

In the present invention, the installation of the first reinforcing member can be partially omitted in the length range of 1.5 times the inner diameter of the second reinforcing member from the core of the through hole toward the end side in the length direction of the web. It is configured in. As a result, when the through hole interferes with the installed position of the designed first reinforcing member, the through hole is installed so as not to interfere with the first reinforcing member by partially omitting the first reinforcing member. be able to. In addition, the size of the through hole is not limited, and the degree of freedom in design can be increased.

According to the present invention, the through hole does not interfere with the first reinforcing member, the size of the through hole is not limited, and the degree of freedom in design can be increased.

It is a horizontal sectional view (A-A line sectional view of FIG. 2) which shows an example of the steel frame beam by embodiment of this invention. It is a side view of a steel beam. (A) is a diagram showing the compressive stress distribution coefficient shown in the steel structure design standard, and (b) is a diagram showing the compressive stress distribution coefficient of the present embodiment. It is a figure which shows the moment distribution for design. It is a graph which shows the relationship between the shear margin, the plastic deformation magnification, and the stiffening length. It is a figure which shows the omission range of a stiffener. It is a figure which shows the steel beam in the final state. It is a graph which shows the load deformation relation which became dimensionless. It is a table which shows the plastic deformation ratio and the cumulative plastic deformation ratio at 90% of the maximum proof stress and at the maximum proof stress, respectively. It is a table which shows the list of the test piece. (A) is the test piece No. A side view of C-1, (b) is a plan view, and (c) is a cross-sectional view of a stiffener installation portion. (A) is the test piece No. A side view of C-3, (b) is a plan view, and (c) is a cross-sectional view of a stiffener installation portion. (A) is the test piece No. A side view of D-1, (b) is a plan view, and (c) is a cross-sectional view of a stiffener installation portion. (A) is the test piece No. A side view of D-2, (b) is a plan view, and (c) is a cross-sectional view of a stiffener installation portion. It is a graph which shows the loading amplitude. Specimen No. It is a figure which shows the force device of C-1 and C-3. Specimen No. It is a figure which shows the momentary apparatus of D-1 and D-2. It is a figure which shows the displacement measurement position. It is a graph which shows the evaluation method of a plastic deformation ability. (A) is the experimental result of the plastic deformation magnification at the maximum yield strength of each test piece, (b) is the experimental result of the plastic deformation magnification at 90% of the maximum yield strength of each test piece, and (c) is the cumulative result of each test piece. It is an experimental result of the plastic deformation magnification. It is a list of experimental results. Specimen No. It is a photograph which shows the deformation property of each cycle of C-1. Specimen No. It is a graph which shows the relationship between the dimensionless load of C-1 and a member angle. Specimen No. It is a figure which shows the skeleton curve of C-1. Specimen No. It is a table which shows the experimental result of C-1. Specimen No. It is a photograph which shows the deformation property of each cycle of C-3. Specimen No. It is a graph which shows the relationship between the dimensionless load of C-3 and a member angle. Specimen No. It is a figure which shows the skeleton curve of C-3. Specimen No. It is a table which shows the experimental result of C-3. Specimen No. It is a photograph which shows the deformation property of each cycle of D-1. Specimen No. It is a graph which shows the relationship between the dimensionless load of D-1 and a member angle. Specimen No. It is a figure which shows the skeleton curve of D-1. Specimen No. It is a table which shows the experimental result of D-1. Specimen No. It is a photograph which shows the deformation property of each cycle of D-2. Specimen No. It is a graph which shows the relationship between the dimensionless load of D-2 and a member angle. Specimen No. It is a figure which shows the skeleton curve of D-2. Specimen No. It is a table which shows the experimental result of D-2.

Hereinafter, a method for designing a steel beam according to an embodiment of the present invention will be described with reference to FIGS. 1 to 9.
As shown in FIGS. 1 and 2, the steel beam 1 according to the present embodiment is an H-shaped steel and has an upper flange 2, a lower flange 3, and a web 4. FIG. 1 shows the vicinity of one end of the steel beam 1 in the length direction (a predetermined range from one end 1a of the steel beam 1 in the length direction toward the center). The end portion 1a of the steel frame beam 1 is joined to the column 12. A haunch 13 is formed in the vicinity of the end portion 1a of the steel frame beam 1.

41 near the end of the web 4 in the length direction (a portion of the web 4 corresponding to the vicinity of the end 11 of the steel beam 1 in the length direction, a predetermined range from one end 4a in the length direction toward the center) Is provided with stiffeners 51 and 52 (first reinforcing member) for preventing buckling of the web 4. In the present embodiment, two stiffeners 51 and 52 are provided on one side (one side in the thickness direction) of the web 4 at intervals in the vertical direction. The upper stiffener 51 (hereinafter referred to as the upper stiffener 51) is provided on the lower side of the upper flange 2 at intervals, and the lower stiffener 52 (hereinafter referred to as the lower stiffener 52) is provided on the upper side of the lower flange 3. It is provided at intervals. The stiffeners 51 and 52 are provided in parallel with the upper flange 2 and the lower flange 3. The upper stiffener 51 and the lower stiffener 52 are formed in substantially the same shape.
The upper stiffener 51 and the lower stiffener 52 are provided near the ends 41 on both sides of the web 4 in the length direction, respectively.

For example, a through hole 43 for passing equipment piping is formed in the vicinity of the end portion 41 in the length direction of the web 4. The through hole 43 penetrates the web 4 in the thickness direction and is provided on the other side of the stiffeners 51 and 52 in the length direction at a position toward the center of the end portion 4a in the length direction of the web 4. .. The through hole 43 is provided in a section in the vicinity of the end portion 41 in the length direction of the web 4 where the stiffeners 51 and 52 are not provided. On one side (one side in the thickness direction) of the web 4, a ring-shaped through hole reinforcing member 6 (second reinforcing member) is provided along the edge of the through hole 43.

In the method for designing a steel beam according to the present embodiment, the equivalent width-thickness ratio of the web, the length dimension of the stiffener (stiffening length le, see FIGS. 1 and 2) and the installation position, the required rigidity of the stiffener, and the shear margin of the web. Consider the position of the through hole.

(Examination of equivalent width-thickness ratio of the web)
In the examination of the equivalent width-thickness ratio of the web, the upper region 45 (referred to as the outer subpanel 45) of the upper stiffener 51 in the web 4 and the lower region 46 (outer subpanel 46) of the lower stiffener 52 in the web 4 shown in FIG. The equivalent width / thickness ratio of each of the region 47 (referred to as the inner subpanel 47) between the upper stiffener 51 and the lower stiffener 52 in the web 4 is examined. In the present embodiment, the ratio of the cause d of the outer subpanel 45, the cause d of the outer subpanel 46, and the cause d of the inner subpanel 47 is 1: 2: 1.
Equivalent width-thickness ratio is the calculation method of equivalent width-thickness ratio (Tsutomu Hoshikawa, Yukihiro Harada: Plastic deformation ability of H-shaped steel beam with web reinforced with axial stiffener, Steel Structure Papers, Vol. 20, No. 80, P.19-32, 2013.12) shall be applied mutatis mutandis, and the calculation shall be made using the following equations (1)-(4). Design so that the calculated equivalent width-thickness ratio satisfies the width-thickness ratio limit required for steel beams. FIG. 3A shows the compressive stress distribution coefficient shown in the steel structure design standard, and FIG. 3B shows the compressive stress distribution coefficient of the present embodiment.

The equivalent width / thickness ratio of the web 4 is adopted by adopting the calculated equivalent width / thickness ratio of the outer subpanel 45, the equivalent width / thickness ratio of the outer subpanel 46, and the equivalent width / thickness ratio of the inner subpanel 47. Examine the ratio.
If only one stiffener is provided on one side of the web, the equivalent width-thickness ratios of the upper region of the stiffener on the web and the lower region of the stiffener on the web are examined, and a large equivalent width is obtained. The width-thickness ratio is adopted to check the width-thickness ratio limit. Also, if three or more stiffeners are provided on one side of the web, the area above the top stiffener on the web and the area below the bottom stiffener on the web, above and below the web. The equivalent width-thickness ratio of each area between the lined stiffeners is examined, and a large equivalent width-thickness ratio is adopted to check the width-thickness ratio limitation.

(Examination of the length dimension and installation position of the stiffener)
The length dimension (stiffening length le, see FIG. 1) and the installation position where the stiffeners 51 and 52 are provided are set according to the design moment distribution of the steel beam. As shown in FIG. 4, the stiffener for the design for the moment _M'D end 71 of the portion stiffener 51 and 52 steel beam 1 is provided (HoTsuyoshitan unit), the steel beam 1 51 to verify that the local buckling limit strength M _c of the beam cross section of the portion not provided above. Here, the local buckling limit yield strength is calculated based on "Architectural Institute of Japan: Steel Structure Limit State Design Guideline". Focusing on the thinned web 4, the local buckling limit proof stress is calculated using the following equations (5)-(7).

(Examination of required rigidity of stiffener)
The required rigidity of the stiffener will be examined based on "Architectural Institute of Japan: Steel Structure Design Standards". Confirm that the geometrical moment of inertia i (calculated with the web surface as the main axis) of the stiffener is equal to or greater than the value calculated using the following equations (8)-(12).

(Examination of web shear margin)
We will examine the collapse due to shear buckling in the section where the stiffener is not provided on the web (hereinafter referred to as the non-stiffening section), focusing on the shear margin. Here, the shear margin can be expressed as _{Q w} / Q _{p , which is the ratio of the shear strength Q w of the} web to the shear force Q p acting on the steel beam when the end of the steel beam reaches the total plastic moment. Considering the effect of increased yield strength of steel beams, design so that a shear margin of 1.29 or more can be secured in the unstiffened section of the web. The shear strength Q _{w of the} web is calculated using the following equation (13). FIG. 5 shows a graph showing the relationship between the shear margin, the plastic deformation magnification, and the stiffening length.

(Examination of the position of the stiffener and the through hole)
The stiffener designed as described above adopts the stiffening length and installation position of the stiffener as described above when it does not interfere with the through hole (through hole reinforcing member). If the stiffener interferes with the through hole, use the stiffener within a length range of 1.5 times (1.5φ) the inner diameter φ of the through hole reinforcing member that goes from the core of the through hole to one side in the length direction of the web. It can be omitted. FIG. 6 shows the optional range 53 of the stiffeners 51 and 52 and the omitted portions 511, 521 of the stiffeners 51 and 52.

From the figure showing the steel beam in the final state of FIG. 7, the graph showing the dimensionless load deformation relationship of FIG. 8, and the FEM analysis result of FIG. 9, the plastic deformation magnification μ _90% at 90% of the maximum yield strength is 4 or more ( It is considered that it has a sufficient plastic deformation ability (equivalent to FA rank). η indicates the cumulative plastic deformation magnification.

Next, the operation and effect of the steel beam design method according to the above embodiment will be described.
In the method for designing a steel beam according to the present embodiment, when the stiffeners 51 and 52 and the through hole 43 interfere with each other, the through hole reinforcing member 6 is directed from the core of the through hole 43 to one side in the length direction of the web 4. It is possible to omit the stiffeners 51 and 52 within a length range of 1.5 times the inner diameter φ of (1.5φ). As a result, the through hole 43 can be provided so as not to interfere with the stiffeners 51 and 52, and the size of the through hole 43 is not limited, and the degree of freedom in design can be increased.

An experiment was conducted to confirm the effect of the steel beam design method according to this embodiment.
In the experiment, the test piece No. shown in FIG. C-1, Specimen No. C-3, test piece No. D-1, Specimen No. A total of 4 test pieces of D-2 were used. As shown in FIGS. 11-14, the four test pieces each use the same H-shaped steel, and two upper and lower stiffeners 51 and 52 are joined to one side of the web 4, and a through hole 43 is formed in each. There is. Specimen No. C-1 and test piece No. Three through holes 43 are formed in C-3 at intervals in the length direction of the steel beam. Specimen No. D-1 and test piece No. Two through holes 43 are formed in D-2 at intervals in the length direction of the steel frame beam. Each of the four test pieces is provided with a through hole reinforcing member 6 at the edge of the through hole 43.

Specimen No. shown in FIG. C-1 and the test piece No. shown in FIG. The beam length and the installation position of the through hole 43 are the same as those of the C-3, and the through hole reinforcing member 6 is different. Specimen No. In C-1, the EG ring (registered trademark) of Nippon Fabtech Co., Ltd. is adopted as the through hole reinforcing member 6, and the test piece No. In C-2, Hiring (registered trademark) of Senxia Co., Ltd. is adopted as the through hole reinforcing member 6.
Specimen No. C-1 and test piece No. Each of C-3 has a beam length of 2112 mm and an inner diameter of the through hole reinforcing member 6 of 192 mm.

Specimen No. shown in FIG. D-1 and the test piece No. shown in FIG. The beam length and the through hole reinforcing member 6 are the same as those of D-2, and the installation intervals of the two through holes 43 are different. Specimen No. D-1 and test piece No. Both D-2 use the EG ring (registered trademark) of Nippon Fabtech Co., Ltd. as the through hole reinforcing member 6. Specimen No. Test piece No. than D-1. In D-2, the installation interval of the through holes of the two through holes 43 is set wider. The installation intervals of the through holes of the through holes 43 are set to the test piece No. In D1, 720 mm, test piece No. In D-2, it is 864 mm.
Specimen No. D-1 and test piece No. Each of D-2 has a beam length of 3312 mm and an inner diameter of the through hole reinforcing member 6 of 288 mm.

The loading on the test piece shall be a gradual increase displacement amplitude repeated loading as shown in FIG. For repeated loading of gradual displacement amplitude, the loading history shown in the previous literature (Building Research Institute, Japan Iron and Steel Federation: Research Committee Report on Structural Performance Evaluation Test Method for Steel Structure Buildings, 2002.04) is used, and θp is used as a reference. The incremental displacement was set to 2θp, and each amplitude was repeated twice. In the control of the experiment, the value of θp was calculated for each test piece parameter and used in the experiment.
FIG. 16 shows the test piece No. C-1 and test piece No. The force device of C-3 is shown in FIG. 81, and FIG. 17 shows the test piece No. D-1 and test piece No. The force device FIG. 82 of D-2 is shown. The force is statically loaded using a 2000 kN skewer jack. A load cell attached to a jack is used to measure the load. For the deformation of each of the four test pieces, the displacement of the position in the test piece shown in FIG. 18 is measured by a displacement meter. Horizontal displacement (d1, d2), horizontal displacement (d3 to d6) and vertical displacement (d7 to d10) of the end plate at the force point of the test piece axis are measured.
FIG. 19 shows an evaluation method of plastic deformation ability.

20 and 21 show the maximum proof stress, the plastic deformation ratio at the maximum proof stress, the plastic deformation ratio at 90% of the maximum proof stress, and the cumulative plastic deformation ratio in the experimental results. _{It can be confirmed that μ 90%} of all the test specimens subjected to the experiment secures the plastic deformation magnification of 4 or more required for the steel beam corresponding to FA rank. From the results of this experiment, it was possible to show the effectiveness of using the steel beam construction method according to this embodiment for improving the plastic deformation ability.

The experimental results for each test piece will be described.
(Test No. C-1)
As shown in FIGS. 22 to 25, the test piece No. C-1 shows stable history properties up to _{4θ p.} + 6θ _p flanges and steel beam end in the first cycle, section stiffener in the web is provided (hereinafter, stiffener stiffening section) local buckling of confirmed significantly, yield strength decreased. As for the deformation properties at the end, local buckling of the flange at the start of haunch widening and shear type local buckling of the stiffener stiffening section of the web were confirmed.

(Test No. C-3)
As shown in FIGS. 26-29, the test piece No. In C-3, local buckling of the web occurred between the stiffeners in the first cycle of _{-4θ p.} + 4θ strength decreases under the influence of the web of local buckling between the stiffener to the second cycle of _p has been confirmed. + 6θ progress is local buckling in the middle loading of the first cycle of _p, strength increase has finished loading in the middle of the first cycle of the order that can not be expected + 6θ _p.

(Test No. D-1)
As shown in FIGS. 30-33, the test piece No. _{In the second cycle of +4 θ p} , the yield strength of D-1 decreased due to the local buckling of the flange at the end of the steel frame beam. At this time, the twist of the steel beam due to the influence of the overall buckling mode was also confirmed. + 6θ _p overall buckling mode beyond the first cycle of 2 [Theta] _p of remarkably appears, the deformation of the flange near the through-hole reinforcement has finished loading in the middle of the first cycle of rapidly because of the progress + 6θ _p.

(Test No. D-2)
As shown in FIGS. 34-37, the test piece No. In D-2, local buckling occurred in the flange near the through hole reinforcing member on the end side of the steel frame beam in the first cycle of _{4θ p.} 4θ strength reduction due to local buckling of the flange around the through-hole reinforcing members steel beam end in the second cycle of _p occurs. During the first cycle of + 6θ _p , the local buckling of the flange near the through hole reinforcement member on the steel beam end side and the web of the stiffener stiffening section rapidly progresses, and the bearing capacity cannot be expected to increase. Therefore, one cycle of _{+ 6θ p.} I finished loading in the middle of my eyes.

Although the embodiment of the steel beam design method according to the present invention has been described above, the present invention is not limited to the above embodiment and can be appropriately modified without departing from the spirit of the present invention.
For example, in the above embodiment, the stiffeners 51 and 52 are provided on only one side of the web 4, but the stiffeners 51 and 52 may be provided on both sides of the web 4. Further, the position and orientation in which the stiffeners 51 and 52 are provided and the number of stiffeners 51 and 52 may be appropriately set.
In the above embodiment, the through hole reinforcing member 6 is provided only on one side of the web 4, but the through hole reinforcing member 6 may be provided on both sides of the web 4.

In the above embodiment, the stiffeners 51 and 52 are provided as the first reinforcing member for preventing the web 4 from buckling, but members other than the stiffeners 51 and 52 may be provided.

1 Steel beam 1a End 4 Web 5 Through hole reinforcement member (second reinforcement member)
4a End 41 Near the end 43 Through holes 51, 52 Stiffener (first reinforcing member)

Claims (1)

A through hole that penetrates the web in the thickness direction is formed near the end in the length direction of the web.
The first reinforcing member for preventing buckling of the web and
A second reinforcing member is provided to prevent the web from reducing its proof stress due to the through hole.
The first reinforcing member extends in the length direction of the web, and is in the height direction of the web in the vicinity of the end portion in the length direction of the web and on the end side in the length direction of the web with respect to the through hole. Joined in the middle,
In the method for designing a steel beam, the second reinforcing member is formed in a ring shape and joined along the edge of the through hole.
Each of the equivalent width-thickness ratio on the upper side of the first reinforcing member and the equivalent width-thickness ratio on the lower side of the first reinforcing member in the web satisfies the required width-thickness ratio of the web.
The first reinforcing member so that the design moment of the portion of the steel beam where the first reinforcing member is provided is larger than the local buckling limit strength of the portion of the steel beam where the first reinforcing member is not provided. And set the range to install the first reinforcing member.
Designed so that the shear margin of the portion of the web where the first reinforcing member is not provided is 1.29 or more.
Installation of the first reinforcing member can be partially omitted in a length range of 1.5 times the inner diameter of the second reinforcing member from the core of the through hole toward the end side in the length direction of the web. A method of designing a steel beam, which is characterized by being configured in.

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