JP2014109149A - Rolled h-shaped steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolled H-shaped steel, in which the cross-sectional secondary moment in the circumference of a strong shaft and the efficiency to weight of a section modulus are equal to or more than those of a conventional rolled H-shaped steel, and furthermore buckling (lateral buckling) in the lateral direction (direction perpendicular to the plate surface of a web) hardly occurs.SOLUTION: For a rolled H-shaped steel, assuming that a design yield stress of a steel material of the rolled H-shaped steel is F(N/mm), a height dimension of the rolled H-shaped steel is H, and a width dimension of a flange is B: the rolled H-shaped steel satisfies the following expression (1); when a total cross-sectional area is assumed to be A, the width dimension B of the flange satisfies the following expression (2); when the width dimension of the flange is assumed to be tand a width dimension of a web is assumed to be t, the following expressions (3), (4) are satisfied: (B/H)≤0.77 ...(1), B<B≤(β×H+β√(H-(1+β×γ)×(H-γ×A)))/(1+β×γ) ...(2), t≥B/(2×β) ...(3), and t≥(H-2×t)/γ ...(4).

Description

  The present invention relates to a rolled H-section steel having a shape that is difficult to be laterally buckled and has a high cross-sectional performance per unit steel weight.

  Conventionally, various rolled H-section steels such as the following (1) to (3) are known as rolled H-section steels.

(1) After the flange width / thickness ratio is 10 or less and work hardening is started, the work hardening index in the strain range up to 6% is 0.2 or more, and the plastic deformation stress increases in the strain range of 6% or more. Rolled H-section steel excellent in earthquake resistance in which the gradient is larger than the moment gradient in the vicinity of the position where the maximum moment is generated, and the plastic zone generated at the position where the maximum moment is generated is expanded to the periphery thereof (for example, Patent Document 1) reference).

(2) Thin web-rolled H-section steel with a web thickness / flange thickness ratio of 0.5 or less, and irregularities formed on the web at predetermined intervals to prevent web waviness during rolling production. Rolled H-section steel (see, for example, Patent Document 2).

(3) Thin web-rolled H-section steel, the web thickness / flange thickness ratio is 0.5 or less, and in order to prevent the web waviness phenomenon during rolling manufacture, Rolled H-section steel provided with at least one protrusion reinforcing rib (for example, see Patent Document 3).

  In addition, as techniques related to conventional rolled H-section steel, the following techniques (A) to (C) are also known.

(A) In order to realize a thin web rolled H-section steel while preventing web waviness during rolling production, the web thickness / flange thickness ratio is set to a relatively small numerical range (the upper limit of the web thickness / flange thickness ratio is 0). .5) (see, for example, Patent Document 2 and Patent Document 3).

(B) It is a beam used within an elastic design range such as a small beam, and in order to improve the weight efficiency of the cross-sectional performance of the strong shaft and reduce the weight, the width-thickness ratio is compared with the shape steel of Non-Patent Documents 1-6. It is defined in a large numerical range (see Patent Document 4).

(C) In addition to the above, the rolled H-shape standardized in ASTM (American Society for Testing and Materials), BS (British Standards), EN (European Standard, EN) There is steel (see Non-Patent Documents 1 to 7).

Japanese Unexamined Patent Publication No. 2002-88974 Japanese Unexamined Patent Publication No. 59-141658 Japanese Unexamined Patent Publication No. Sho 61-162658 Japanese Patent No. 4677059

JIS (Japanese Industrial Standard) ASTM (American Society for Testing and Materials) BS (British Standards) EN (European Standard, EN) (HYPER BEAM catalog) (SHH catalog (JFE)) BS EN1993-1-1: 2005 Eurocode 3: Design of steel structures pp. 56-61 AISC 341-10 Seismic Provisions for Structural Steel Buildings pp. 9.1-14, 2011.6 Editorial Committee for Structural Technical Standards for Buildings, Supervised by Ministry of Land, Infrastructure, Transport and Tourism Housing Bureau Architectural Guidance Section, etc. 593-596, National Gazette Sales Cooperative, 2007

Meanwhile, rolled H-section steel strong axis of the second moment _{I x,} section modulus _{Z x,} bending moment _{M y} at yield are determined respectively by the following formulas (8) to (10). However, H is the height of the rolled H-shaped steel, B is the width of the flanges of the rolled H-shaped steel, t _f is the thickness of the flange, t _w is the thickness of the web of rolled H-shaped steel, σ _y is the yield stress of the steel material.
^{_{I x = B × H 3 /}} 12- (B-t w) × (H-2t f) 3/12 ··· (8)
Z _x = I _x / (H / 2) (9)
M _y = Z _x × σ _y (10)

Further, the theoretical value M _cr of the side seat bending moment of the both-end simply supported member subjected to bending is obtained by the following equation (11). However, E (205000N / mm ²⁾ is the Young's modulus of the steel, _{I w} warp sectional torsional constant, A is the cross-sectional area of the member, _{l b} is between supporting length member (Lateral屈長of), G is the shear modulus, is J _t is San safe torsional constant.
M _cr = r _y √ (π ⁴ × E ² × I _w × A / l _b ⁴ + π ² × E × G × J _t × A / l _b ² )
(11)
Here, r _y is the secondary axis radius of the weak axis and is defined by the following equation (12).
r _y = √ (I _y / A) (12)
Here, the cross-sectional secondary moment I _y of the weak axis is expressed by the following equation (13).
^{_{I y = B 3 × t f}} / 6 + (H-2t f) × t w 3/12 ··· (13)
Here, the above LATERAL屈長of l _b, for example, girders 2 shown in FIG. 1, as the fulcrum intervals supported by posts 1, joists 3, and Lateral屈補Tsuyoshizai 4, the lateral displacement This represents the distance between the support points (lateral stiffening) by the member that restrains.

From the above formulas (8) to (10), in general, in the rolled H-section steel, the higher the height H, the larger the cross sectional moment I _x and the section modulus Z _x of the strong axis, and the load that can be supported is H It increases with the following function.
On the other hand, from the above equations (12) and (13), the secondary axial moment I _y of the weak axis is a linear function of the height H, so the weak secondary axial radius r _y is relative to the performance of the strong axis. Become smaller.
Relatively Thus, Lateral bending up the theoretical value of the moment M _cr obtained by the above formula (11), as compared to the bending moment M _y at yield when bending in the strong axis direction obtained by the above equation (10) Therefore, the rolled H-section steel has a problem that lateral buckling (buckling in the direction perpendicular to the acting direction of the load) is likely to occur.

Here, the lateral buckling means that when an open cross-section member such as a rolled H-section steel is subjected to a bending load, the compression-side flange and the like are buckled out of the plane on which the bending load acts with a twist. It is a phenomenon. When deformation due to lateral buckling occurs in the rolled H-section steel, even if the width-thickness ratio of the cross section is made sufficiently small, local buckling tends to be induced in that region, and the bending resistance moment of the entire beam deteriorates.
Here, the above-mentioned width thickness ratio, the ratio of one side width of the flange to the thickness dimension t _f of the flange B / 2 (flange width-thickness ratio), and a web of height to thickness dimension t _w of the web ( H-2t _f ) ratio (web width-thickness ratio), and the larger this value, the smaller the plate thickness and the more likely local buckling.

FIG. 2 shows various rolled H-section steels described in Non-Patent Documents 1 to 6 in which the horizontal axis is a strong secondary cross-sectional radius r _x and the vertical axis is a weak secondary cross-sectional radius r _y. Among them, a graph plotting all sizes having a ratio (B / H) of the flange width dimension B to the height H of the rolled H-section steel of 0.77 or less (a circle mark). In addition, x mark plots the rolled H-section steel which concerns on this invention mentioned later.
From this Figure 2, the maximum value of the performance range of the cross-sectional secondary radius r _y of the weak axis is a 1/4 of the maximum value of the performance range of the cross-sectional secondary radius r _x of the strong axis, the strong axis section two It can be seen that it is smaller than the next radius r _x . Further, in the case of non-stiffening, the maximum proof stress is determined by lateral buckling with the secondary axis radius r _y of the weak axis becoming a neck as the secondary axis radius r _x of the strong axis increases. not greater performance range of the secondary radius r _y, can not be sufficiently exhibited strong axis performance.

In order to improve the resistance to such lateral buckling, it is most effective to provide a large number of lateral stiffeners. However, the total weight of the steel structure frame increases due to the increase in the small beams and lateral buckling stiffeners. Therefore, in order to prevent lateral buckling while omitting lateral stiffening, it is effective to increase the cross-sectional performance around the weak axis.
However, the rolled H-section steel as disclosed in Patent Documents 1 to 4 has not been devised to prevent lateral buckling in the rolled H-section steel itself, and is small in order to prevent lateral buckling. Since many beams and transverse stiffening members are required, there is a problem in that the weight of the entire steel structure frame increases and the cost increases.

By the way, FIG. 3 shows the total size of various rolled H-section steels described in Non-Patent Documents 1 to 6 with the horizontal dimension of the height dimension H of the rolled H-section steel and the vertical dimension of the width dimension B of the flange. The rolled H-section steel according to the present invention, which will be described later, is indicated by a circle with a circle-shaped rolled H-section having a flange width dimension B / height H ratio (B / H) of 0.77 or less. Plotted with marks.
Here, the ratio of the width dimension B of the flange to the height H of the rolled H-section steel (B / H) is in the range of 0.77 or less. Series or medium width series rolled H-section steels that are commercially available in Japan are classified as beams.
On the other hand, a ratio of the width dimension B of the flange to the height H of the rolled H-shaped steel (B / H) is in a range exceeding 0.77 (the width of the flange in the rolled H-shaped steel, Those that are commercially available as rolled H-section steel) can be classified into pillars and braces (see Patent Document 4).

At this time, if the ratio of the width B of the flange and the height H of the rolled H-shaped steel (B / H) is limited to 0.77 or less, the main application is a beam. From this, it can be seen that the width B of the flange is in the range of the following formula (14).
B ≦ 0.15H + 295 (provided that H ≦ 1080), B ≦ 457 (provided that H> 1080) (14)

The reason why the width B of the flange is expressed by the above formula (14) is as follows.
(A) The cross-sectional secondary radius of the weak axis can be improved by increasing the width dimension B of the flange from the above equations (12) and (13).
(B) In order to improve the weight efficiency of the cross-sectional performance around the strong axis, the effect of increasing the height H of the rolled H-section steel is greater than increasing the width dimension B of the flange.
(C) The required performance in the design of rolled H-section steel is determined by the cross-sectional performance around the strong axis, and the lack of cross-sectional performance around the weak axis is more than that of the above equation (11). shorter transverse stiffening spacing l _b arranged to, that idea to increase the M _cr is common.

  For the reason of (c), the rolled H-section steel uses a large amount of lateral stiffening with a small beam and a lateral buckling stiffener to prevent lateral buckling, while maintaining the weight efficiency of the cross-sectional performance around the strong axis. If the secondary radius of the cross section around the weak axis can be increased, the cross-sectional performance around the weak axis can be improved, so these lateral stiffening can be omitted or reduced, which can greatly contribute to the cost reduction of the entire structure. . Furthermore, the reduction of the seismic load by reducing the weight of the structure can contribute to the improvement of the seismic performance of the structure.

  In the present invention, the secondary moment of inertia around the strong axis and the weight efficiency with respect to the section modulus are equal to or higher than those of the conventional rolled H-section steel, while further buckling (lateral seating) An object of the present invention is to provide a rolled H-section steel that is less likely to cause bending.

  As a result of diligent research, the inventors have determined the upper and lower limits of the width dimension of the flange of the rolled H-section steel, while ensuring the cross-sectional performance around the strong axis and in the lateral direction (with respect to the plate surface of the web). It was found that buckling in the vertical direction can be prevented.

In addition, as shown in FIG. 4, for example, the rolled H-section steel applied as the beam center connected to the bracket is directly joined to the beam end that reaches the total plastic bending moment. Is effective to prevent lateral buckling until the end of the beam reaches full plasticity. In FIG. 4, M ₁ is the smaller of the beam end bending moments, M ₂ is the maximum bending moment at the center of the beam, M ₃ is the larger bending moment of the beam end, and M _p is the total plastic bending moment of the beam. is there.
Furthermore, since the rolled H-section steel applied as the beam central portion is used within the elastic design range, the flange may be widened to the width-thickness ratio limit to prevent local buckling to the elastic limit. Thus, the performance around the weak axis can be improved without degrading the performance around the strong axis.

The gist of the present invention is as follows.
(A) A rolled H-section steel having a web and a flange, wherein the design yield stress of the rolled H-section steel is F (N / mm ² ), and the height of the rolled H-section is H ( mm), when the width dimension of the flange is B (mm), the following formula (1) is satisfied, and when the total cross-sectional area is A, the width dimension B of the flange satisfies the following formula (2), wherein the thickness of the flange and t _f, the thickness of the web when the t _w, the following formula, respectively (3), (4) and satisfies the rolled H-shaped steel.
(B / H) ≦ 0.77 (1)
B _min <B
≦ (β × H + β√ (H ² − (1 + β × γ) × (H ² −γ × A))) / (1 + β × γ) (2)
t _f ≧ B / (2 × β) (3)
t _w ≧ (H−2 × t _f ) / γ (4)
However, B _min is defined by the following formula (5), β is defined by the following formula (6), and γ is defined by the following formula (7).
B _min = 0.15H + 295 (provided that H ≦ 1080), B _min = 457 (provided that H> 1080) (5)
β = 215 / √ (F) (6)
γ = 1100 / √ (F) (7)

(B) The rolled H-section steel according to (a), which is applied as a beam.

(C) The rolled H-section steel according to (a), wherein both ends are applied as a central portion of a beam connected to a column via a bracket.

According to the rolled H-section steel of the present invention, the cross-sectional shape of a rolled H-section steel having high strong shaft performance and strong lateral buckling can be easily defined even when a material whose design yield stress F changes is used. .
That is, this rolled H-section steel has high shaft performance due to the relationship between the height dimension H and cross-sectional area A of the rolled H-section steel, the design yield stress F of the steel material, and the width dimension B of the flange. Moreover, the dimension of the rolled H-section steel strong against lateral buckling can be set easily.
In particular, the rolled H-section steel of the present invention can greatly improve the cross-sectional performance around the weak axis as compared with the conventional rolled H-section steel defined in major countries in the United States, the United Kingdom, Europe, or Japan. Moreover, the weight efficiency of the cross-sectional performance around the strong axis of the rolled H-section steel can be equal to or higher than that of the corresponding rolled H-section steel in the major countries.
Thereby, high-performance rolled H-section steel can be easily dimensioned and applied in countries around the world including the main countries.

Moreover, since the rolled H-section steel of the present invention has an effect of preventing buckling in the lateral direction (perpendicular to the web plate surface), the unit weight remains constant and the lateral buckling is higher than that of the conventional rolled H-section steel. The moment _Mcr can be greatly improved. Furthermore, since the strength against lateral buckling has increased, the lateral buckling length can be made longer than that of conventional rolled H-section steel, and the small beams and lateral buckling stiffeners for lateral stiffening can be omitted. There is a remarkable effect that a significant cost reduction can be realized. Thereby, the weight reduction of a building, resource saving, and construction labor saving are realizable.

It is a perspective view showing the state where the rolled H section steel of the present invention was applied as a small beam. In the rolled H-section steel according to the present invention, various rolled H-section steels conforming to the standards of ASTM, JIS, EN, and BS, and hyperbeam, the cross-sectional secondary radius r _x of the strong axis and the secondary cross-section of the weak axis is a graph showing the relationship between the radius r _y. The height H of the rolled H-shaped steel and the width dimension B of the flange in the rolled H-shaped steel according to the present invention, various rolled H-shaped steels conforming to the standards of ASTM, JIS, EN, BS, and Hyperbeam. is a graph showing the relationship between the lower limit B _min of the width of the flange B of the present invention embodiment. It is a figure which shows the bending moment distribution example of a bracket and a beam center part at the time of attaching a bracket to the both ends of rolled H-section steel, and applying this rolled H-section steel as a beam center part. FIG. 6 is a curve showing an elongate ratio λ _LT related to lateral buckling and a lateral buckling moment reduction rate χ _LT defined in Non-Patent Document 7 for each Impact Factor, α _LT defined in Non-Patent Document 7. FIG. It is a figure which shows the representative dimension of each part of rolled H-section steel, Comprising: It is sectional drawing cut | disconnected in the part orthogonal to the axial direction. It is a perspective view which shows the state by which the rolled H-section steel of this invention was applied as a center part of the beam which both ends are connected to a column via a bracket.

The reason why the subject of the present invention is a rolled H-section steel is that, as shown in Non-Patent Document 7, a rolled H-section steel can ensure higher dimensional accuracy than a welded assembly H-section steel, and thus has a high resistance to resistance. This is because it is evaluated to have buckling performance. Table 1 shows the impact factor and α _LT defined in Non-Patent Document 7 in comparison with a rolled H-section steel and a welded assembly H-section steel. Further, FIG. 5 is a reduction ratio chi _LT of Lateral bending up moments for each alpha _LT, it showed slenderness ratio lambda _LT relates Buckling Lateral abscissa. Here, χ _LT is calculated by the following equation (15).
χ _LT = 1 / (Φ _LT + √ (Φ _LT ² −λ _LT ² )) (15)
However, λ _LT is defined by equation (16), and Φ _LT is defined by equation (17).
λ _LT = √ (W _y × f _y / M _cr ) (16)
Φ _LT = 0.5 (1 + α _LT (λ _LT −0.2) + λ _LT ² ) (17)
Here, W _y is an elastic section modulus (Z _x ) or a plastic section modulus (Z _px ) determined according to the width-thickness ratio of the member in Non-Patent Document 7.

In the case of the same shape and material from Table 1 and FIG. 5, the rolled H-section steel has a larger χ _LT than the welded assembly H-section steel, and has a greater buckling resistance. The problem to be solved by the present invention is to provide an H-section steel having a high strong shaft performance and a high resistance to lateral buckling. Therefore, in the present invention, the subject is a rolled H having a higher buckling resistance than a welded assembly H-section steel. Limited to shape steel.

[First embodiment]
FIG. 1 shows an embodiment of a rolled H-section steel of the present invention. The rolled H-section steel of this embodiment is applied as a large beam 2 and a small beam 3 that form a part of a steel structural framework. Shows the case.
That is, this steel structure frame is provided with respect to the lateral buckling of the plurality of columns 1, the large beam 2 spanned between these columns 1, and the large beam 2 spanned between a pair of opposed large beams 2, 2. And a lateral buckling stiffener 4 which stiffens against the lateral buckling of the small beam 3 bridged between the middle portion of the small beam 3 and the large beam 2. Yes.
FIG. 6 shows representative dimensions of each part of the rolled H-section steel according to the present invention.
In Figure 6, reference numeral H is the height of the rolled H-section steel (mm), symbol B the width of the flange 6 of the rolled H-section steel (mm), reference numeral t _f is the thickness of the flange 6 (mm ), and reference numeral t _w is the thickness of the web 7 (mm), reference numeral r flange 6 and the radius of curvature of Uchisumi portion of the web 7 (mm), strong axis of the dashed line the cross section indicated by the symbol X The alternate long and short dash lines indicated by the symbol Y indicate the weak axes of the cross section.

In the rolled H-section steel of this embodiment, the relationship between the height dimension H of the rolled H-section steel and the width dimension B of the flange 6 and the range of the width dimension B of the flange 6 are defined.
As already stated, the present inventors have conducted extensive research, and as a result, by defining the upper and lower limits of the width dimension of the flange of the rolled H-section steel, while ensuring the cross-sectional performance around the strong axis (X axis), It was also found that buckling in the lateral direction (perpendicular to the web surface) can be prevented.
Therefore, as described below, the range of the ratio (B / H) between the height dimension H of the rolled H-section steel 1 that can be applied as a beam and the width dimension B of the flange is defined, and the strong axis (X The range of the width dimension B of the flange that can prevent lateral buckling while ensuring the cross-sectional performance around the axis) is defined.

First, in order to use the main application as a beam, in the rolled H-section steel of this embodiment, the relationship between the height dimension H of the rolled H-section steel and the width dimension B of the flange 6 satisfies the following formula (1). (See Patent Document 4).
(B / H) ≦ 0.77 (1)

The reason why the relationship between the height dimension H of the rolled H-section steel and the width dimension B of the flange 6 is defined as in the formula (1) is the same as the reason for the conventional product.
That is, the side (width dimension of the flange 6) / height ratio B / H, which is the ratio of the height dimension H of the rolled H-section steel and the width dimension B of the flange 6, is 0.77 or less or exceeds it. It depends on its use. In other words, when the side / height ratio B / H exceeds a width of 0.77, it is mainly used for a column, and when the side / height ratio B / H is a medium width or a small width of 0.77 or less. Is mainly used for beams, and such a practical index is also adopted in this embodiment.
Therefore, the rolled H-section steel of interest in this embodiment is a rolled H-section steel mainly for beams belonging to a side / height ratio B / H of 0.77 or less.

Further, the following formula (2) defines the upper and lower limits of the width dimension B (mm) of the flange 6.
B _min <B
≦ (β × H + β√ (H ² − (1 + β × γ) × (H ² −γ × A))) / (1 + β × γ) (2)
However, B _min (mm) in the formula (2) is defined by the following formula (5).
B _min = 0.15H + 295 (provided that H ≦ 1080), B _min = 457 (provided that H> 1080) (5)

  The lower limit (left side) of the width dimension B of the flange 6 in the equation (2) is the height of the rolled H-section steel in various rolled H-section steels and hyperbeams that conform to the standards of ASTM, JIS, EN, BS. This is the upper limit of the width B of the flange with respect to the length H, and is represented by a solid line in FIG.

On the other hand, the upper limit value (right side) of the width dimension B of the flange 6 in the formula (2) is uniquely defined as the height dimension H, the cross-sectional area A, the width-thickness ratio β of the flange 6 and the width-thickness ratio γ of the web 7. The dimension of the width dimension B of the flange 6 determined as follows is derived.
In addition, the rolled H-section steel of this embodiment is a rolled H-section steel that does not locally buckle to its elastic limit, and the required plastic deformation capacity of the beam member is a plastic ratio of 1.0 or more. In order to realize this, the upper limit value of the width dimension B of the flange 6 of the rolled H-section steel in this embodiment is the upper limit value of the width-thickness ratio B / (2 × t _f ) of the flange 6 in the formula (2). And the upper limit value of the width-thickness ratio (H−2 × t _f ) / (t _w ) of the web 7.

Further, the following equation (3) defines the lower limit of (4) In the formula, the thickness t _f of the flange _6, and the thickness t _w of the web 7.
t _f ≧ B / (2 × β) (3)
t _w ≧ (H−2 × t _f ) / γ (4)

The (3) thickness lower limit of the dimension t _f of the flange 6 (right side) in the expression, the width of the flanges 6 B, the thickness t _f of the flange 6 uniquely determined as the width-thickness ratio of the flange 6 beta The dimensions are derived.
The (4) thickness lower limit of the dimension t _w of the web 7 (the right side) in the expression, the height H, the dimension of the thickness t _f of the flange 6 uniquely determined as the width-thickness ratio of the web 7 gamma It is what led.

The flange width-thickness ratio β and web width-thickness ratio γ of the rolled H-section steel in this embodiment are defined by the same method as in Patent Document 4.
First, regarding the flange width-thickness ratio B / (2 × t _f ) of the rolled H-section steel, as shown in Table 2, when the design yield stress F of the steel material is 235 (N / mm ² ), the upper limit value. However, it is defined as 16.5 in the AISC design standard and 16.2 in the BS design standard. Further, EN design standards in Europe are defined as 14.0, which is the strictest design standard.
Therefore, in this embodiment, 14.0 is adopted as the upper limit value of the flange width thickness ratio B / (2 × t _f ) of the rolled H-section steel, and (B / 2t _f ) = X / √ (F) The value of X is calculated so that the value of becomes 14.0,
(B / 2t _f ) = 215 / √ (F) = β (6)
Is generalized using the yield stress F for design.

Also, the web width-thickness ratio of the rolled H-beams for _{(H-2 × t f)} / (t w) is a design for yield stress F of the steel material (235N / mm ^2), when designing allowable stress, As shown in Table 2, it is not defined in the AISC design standard and the BS design standard, and is defined as 124.0 in the EN design standard. Further, the AIJ design standard defines the upper limit of the web width / thickness ratio as 71.0, which is the strictest design standard.
Therefore, in this embodiment, 71.0 of the web width thickness ratio (H−2 × t _f ) / (t _w ) defined in the AIJ design standard is adopted as the upper limit value,
The value of Y is calculated so that the value of ((H−2 × t _f ) / t _w ) = Y / √ (F) is 71.0,
((H−2 × t _f ) / t _w ) = 1100 / √ (F) = γ (7)
And the design yield stress F (N / mm ² ).

By the way, considering the flange and the web constituting the rolled H-shaped steel as plate elements, and examining the elastic local buckling strength σ _cr and the prescribed values in each country, the elastic local buckling theoretical value of the plate is expressed by the following equation (18 ).
σ _cr = k × (π ² × E) / (12 × (1−ν ² )) × (t / b) ² (18)
Here, k is a buckling coefficient, E (205000 N / mm ² ) is a Young's modulus, ν (0.3) is a Poisson's ratio, t is a plate thickness, and b is a plate width.

In rolled H-section steel, the flange is a simple plate with 3 sides and a single free rectangular plate (buckling coefficient k = 0.425), and the web is a rectangular plate with simple support around it (buckling coefficient k = 4.00). When idealized, in order not to cause local buckling until these plate elements reach the yield stress, the above equation (18) should be simplified as follows, with the elastic local buckling strength σ _cr = F. Can do.
In the case of three-side simple support and one piece free (in the case of a flange), since the plate thickness t = t _f and the plate width b = B / 2, (B / 2t _f ) = 281 / √ (F) From this, 18.3 described in Table 2 can be obtained as a theoretical value.
In the case of simple peripheral support (in the case of the web), the plate thickness t = t _w and the plate width b = H−2 × t _f , so ((H−2 × t _f ) / t _w ) = 861 / √ (F), and from this, 56.2 described in Table 2 above can be obtained as a theoretical value.

Here, the rolled H-section steel has a cross-sectional shape in which lateral buckling and bending torsional buckling are likely to occur. In particular, the flange is the most important part for securing the strength of the beam.
From this, the flange width-thickness ratio is set slightly stricter than the elastic local buckling limit, and in the case of three-side simple support and one-piece free (in the case of a flange), the allowable stress design is 14.0. The value of X is calculated so that the value of (B / 2t _f ) = X / √ (F) is 14.0,
(B / 2t _f ) = 215 / √ (F) = β (6)
Is generalized using the yield stress F for design.

Moreover, in the beam using rolled H-section steel, as long as the acting shear force does not exceed the total plastic shear strength of the web 7, it has been found that the decrease in the total plastic moment due to the shear force can be ignored. Therefore, the web 7 is set as follows so as to be slightly gentler than the elastic local buckling.
In the case of simple peripheral support (in the case of web), since the allowable stress design is 71.0, the value of ((H−2 × t _f ) / t _w ) = Y / √ (F) is The value of Y is calculated so as to be 71.0,
((H−2 × t _f ) / t _w ) = 1100 / √ (F) = γ (7)
And the design yield stress F (N / mm ² ).

Therefore, the relationship between the length dimension B and the flange thickness t _f of the edges is the width of the flange 6,
B / (2 × t _f ) = 215 / √ (F) = β (6)
In countries where the flange width / thickness ratio B / (2 × t _f ) is prescribed, rolled H-section steel with a new cross-sectional shape can reduce the cross-sectional performance around the strong axis against the steel heavy efficiency. It is possible to provide a rolled H-section steel that can increase the performance around the weak axis while maintaining the dimensions, and can be easily dimensioned.

It rolled H-section steel having the above configuration, even with a material of varying design for yield stress F, the thickness t _w of the height H and the flange thickness t _f and the web of rolled H-shaped steel From the cross-sectional area A, the yield stress F (N / mm ² ) for design of the steel material, and the width dimension B of the flange 6, a rolled H-section steel that can be applied as a beam, has strong axis performance, and is resistant to lateral buckling. Can be set very easily.
In particular, the rolled H-section steel of the present invention can greatly improve the cross-sectional performance around the weak axis as compared with the conventional rolled H-section steel defined in major countries in the United States, the United Kingdom, Europe, or Japan. In addition, the weight efficiency of the cross-sectional performance around the strong axis of the rolled H-section steel can be equal to or higher than that of the corresponding rolled H-section steel in the major countries.
Thereby, high-performance rolled H-section steel can be easily dimensioned and applied in countries around the world including the main countries.

Moreover, even if the height dimension H and the cross-sectional area A are the same as those of the prior art, by reducing the flange width dimension B within the range specified in the present invention, the yield strength is deteriorated due to local buckling to the elastic limit. without keeping the cross-sectional performance around conventional equal or strong axis, increasing the cross-sectional performance around weak axis, it is possible to increase the Lateral屈長of l _b.

[Second Embodiment]
In the above embodiment, the case where the rolled H-section steel of the present invention is applied to the entire length of the large beam and the small beam is described. However, the rolled H-section steel of the present invention has both ends as shown in FIG. It can be applied as the central part 8 of the beam whose side is connected to the column 1 via brackets 7, 7.
Even in this case, the height dimension H of the rolled H-shaped steel, the flange thickness dimension t _f , the web thickness dimension _tw , the cross-sectional area A, the steel design yield stress F, and the flange width dimension B Therefore, the dimension of the rolled H-section steel having high strong shaft performance and strong lateral buckling can be set very easily.

When the rolled H-section steel of the present invention is applied as the beam central portion in this way, it is directly joined to the beam end portion (bracket) reaching the total plastic bending moment (see FIG. 4), so that the cross-sectional performance around the weak axis It is possible to exert an effect of preventing lateral buckling until the end of the beam reaches full plasticity.
Also, when applied as the beam central part, since it is used within the elastic design range, the flange may be widened up to the width-thickness ratio limit so as not to be locally buckled to the elastic limit. It is possible to improve the performance around the weak axis without deteriorating the surrounding performance.
Furthermore, according to the present invention, as shown in FIG. 2, the performance of the weak shaft is the same as that of the conventional example, while the strong shaft performance is the same for all rolled H-section steel cross sections with B / H ≦ 0.77. It can be improved from the example. Thereby, the small beam 3 and the lateral buckling stiffener 4 can be reduced. For example, if the member length of the beam 3 in FIG. 1 is 12 (m), F = 325 (MPa), and the AIJ design is equally stiff, the cross-sectional dimension of the beam 3 is the conventional example A3 in Table 3. The lateral buckling length when there is only one lateral buckling stiffener needs to be not less than the required minimum lateral stiffening interval of 5.43 (m), and the lateral buckling stiffener has a member length of 12 (m). The lateral buckling stiffener 4 is required in two or more places in order to exceed the lateral stiffening interval 6 m when one is provided. However, in the case of the present invention example B3, the minimum lateral stiffening interval is 8.30 (m), and the lateral buckling stiffener 4 may be installed at one place, and the amount of steel material can be reduced.

In order to confirm the effect of the present invention, the rolled H-section steel according to the present invention (hereinafter referred to as “example of the present invention”) and the rolled H-section steel not dependent on the present invention (hereinafter referred to as “comparative example”) are strong. Experiments were conducted to compare axial performance, weak axial performance, and maximum lateral stiffening interval (maximum length that can be passed without lateral stiffeners).
In this comparative experiment, comparative examples A1 to A7 set to various dimensions and invention examples B1 to B7 set to dimensions corresponding to these comparative examples A1 to A7 were used. In AISC, design yield stress was used. Various performances were measured for F = 344.75 (MPa) and AIJ for F = 325 (MPa). And about each measured value, the performance in the same dimension was compared as each ratio of B1 / A1, B2 / A2, B3 / A3, B4 / A4, B5 / A5, B6 / A6, B7 / A7.
The results are shown in Table 3-1 and Table 3-2. Further, Invention Examples B1 to B7 in Table 3-1 and Table 3-2 correspond to plot points of Invention Examples B1 to B7 shown in FIG.

The explanation of * 1 in Table 3-1 and * 2, * 3 in Table 3-2 is as follows.
* 1 F = 6.895 (ksi) = 344.75 (MPa) in AISC, and F = 325 (MPa) in AIJ.
* 2 AISC Unlengthed Length: Maximum lateral stiffening interval L _b of Moderate Ductile Members in Non-Patent Document 8
* 3 AIJ Unlengthed Length: In Non-Patent Document 9, described in Securing Deformation Performance by Transverse Stiffening of Beams (Retained Strength Lateral Stiffening) The maximum lateral stiffening interval is calculated with n = 1.
The maximum lateral stiffening interval is defined based on Non-Patent Document 8 and Non-Patent Document 9.

As shown in Tables 3-1 and 3-2, in the case of the example of the present invention, the unit steel weight is equal to or less than that of the conventional example in any dimension, and the strong shaft cross-sectional performance I _x , Z _x , r _x while maintaining an equivalent or more, the weak axis sectional performance _{I y,} Z y, it has improved the _{r y} 20 to 150%. Thereby, it becomes a cross-sectional shape strong against lateral buckling while maintaining the strength and rigidity of the strong shaft, and as shown in Table 3, the minimum lateral stiffening interval can be increased by 30 to 60%.

  According to the present invention, the rolling H-section steel standardized in the major advanced countries including the United States, the United Kingdom, Europe and Japan, and the conventional rolling H Further, it is possible to provide a rolled H-section steel that is less likely to buckle in the lateral direction (perpendicular to the plate surface of the web) than the conventional rolled H-section steel while maintaining the same or better shape steel.

1 Column 2 Large beam 3 Small beam (rolled H-section steel)
4 Lateral buckling stiffener 5 Flange 6 Web 7 Bracket 8 Beam center (rolled H-section steel)

Claims (3)

A rolled H-section steel having a web and a flange,
The design yield stress of the rolled H-section steel is F (N / mm ² ), the height of the rolled H-section is H (mm), and the width of the flange is B (mm). If the following formula (1) is satisfied,
When the total cross-sectional area is A (mm ² ), the flange width dimension B satisfies the following formula (2), the flange thickness dimension is t _f (mm), and the web thickness dimension is t Rolled H-section steel characterized by satisfying the following formulas (3) and (4) respectively when _w (mm).
(B / H) ≦ 0.77 (1)
B _min <B
≦ (β × H + β√ (H ² − (1 + β × γ) × (H ² −γ × A))) / (1 + β × γ) (2)
t _f ≧ B / (2 × β) (3)
t _w ≧ (H−2 × t _f ) / γ (4)

However, B _min (mm) is defined by the following formula (5), β is defined by the following formula (6), and γ is defined by the following formula (7).
B _min = 0.15H + 295 (provided that H ≦ 1080), B _min = 457 (provided that H> 1080) (5)
β = 215 / √ (F) (6)
γ = 1100 / √ (F) (7)   The rolled H-section steel according to claim 1, which is applied as a beam.   The rolled H-section steel according to claim 1, wherein both ends are applied as a central portion of a beam connected to a column through a bracket.

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