JP7698199B2 - Welded H-beam - Google Patents

Description

The present invention relates to a welded H-section steel .

Traditionally, minor beams in steel-framed buildings are not required to be earthquake-resistant. For this reason, rolled H-shaped steel, which has a larger width-thickness ratio of the flanges and webs compared to the major beams, is used for minor beams. This is because it is relatively easy to realize H-shaped steel that is lightweight, highly rigid, and has good cross-sectional efficiency by setting a large width-thickness ratio for the webs.
In recent years, with the increase in the span (length) of the sub-beam, H-shaped steel with a web width-thickness ratio of about 70, which is the manufacturing limit of rolled H-shaped steel, is being used for the sub-beam. This H-shaped steel has a high mass-to-weight ratio and good cross-sectional efficiency.
Furthermore, as a method for increasing the cross-sectional efficiency of H-shaped steel, a method can be considered in which a welded H-shaped steel, which has fewer manufacturing constraints regarding dimensions, is used to increase the width-thickness ratio of the web.

On the other hand, in a welded H-shaped steel with a large width-thickness ratio of the web, when the flange and the web are welded at the intersection, the web may be deformed in the thickness direction after the H-shaped steel is cooled. The cause of this deformation of the web can be explained as the following mechanism.
First, the entire H-shaped steel is heated by the heat input from welding, and the entire H-shaped steel stretches in the length direction (material axis direction) of the member. Next, the central part of the web in the width direction, which is far from the heat input part, starts to cool before other parts. Then, the flanges and the parts of the web near the flanges, which are close to the heat input part, start to cool. When the parts of the web near the flanges, which are cooled later, start to shrink in the length direction of the member, the central part of the web in the width direction that was cooled earlier has already finished shrinking, so the force of the parts of the web near the flanges, which are cooled later, shrinking in the length direction of the member acts as a compressive force on the central part of the web in the width direction that was cooled earlier. This compressive force, which is originally prone to buckling due to the large width-thickness ratio, results in a buckling waveform that bends the web as a residual deformation.

These residual deformations reduce the structural integrity of H-beams, the manufacturability when processing them in factories, and the workability when joining them to other components at construction sites. For this reason, it is necessary to avoid the occurrence of these residual deformations or to limit their occurrence to a certain level or less.
Furthermore, as a prior art document regarding fillet welding of a flange and a web, for example, Non-Patent Document 1 describes that "the size of the fillet weld should be equal to or smaller than the thickness of the thinner base material," or in the case of a plate thickness of 6 mm or less where the width-thickness ratio tends to be large, "the size of the fillet weld should be 1.5 times the plate thickness of the thinner material, and equal to or smaller than 6 mm."

Architectural Institute of Japan, “Steel Structure Allowable Stress Design Criteria”, 1st edition, Maruzen Publishing Co., Ltd., October 15, 2019, p.33-35

However, these values disclosed in Non-Patent Document 1 are set from the viewpoint of reducing the thermal effects on the material of the steel plate and from the viewpoint of suppressing residual deformation of H-shaped steel, but are not values set with sufficient consideration given to suppressing residual deformation of H-shaped steel with a large width-to-thickness ratio of the web.
Furthermore, if the size of the fillet weld portion formed by the fillet welding is too small, the shear force acting on the web cannot be transmitted to the flange.

The present invention has been made in consideration of the above problems, and has an object to provide a welded and assembled H-shaped steel beam in which a fillet weld formed by fillet welding reliably transmits the shear force acting on the web and suppresses the residual deformation of the web to within an allowable value.

In order to solve the above problems, the present invention proposes the following means.
The welded and assembled H-shaped steel of the present invention is a welded and assembled H-shaped steel comprising a pair of flanges and a web joined to each of the pair of flanges by a fillet weld, characterized in that a size s (mm) of the fillet weld is less than a thickness of the web, and the size s satisfies formulas (1) and (2).
where τ _y,depo is the shear yield strength (N/mm ² ) of the fillet weld, I is the second moment of area about the strong axis of the welded assembled H-shaped steel (mm ⁴ ), H is the depth of the welded assembled H-shaped steel (mm), t _f is the thickness of the flange (mm), W is the width (mm) of the welded assembled H-shaped steel, τ _cr is the elastic shear buckling strength (N/mm ² ) of the welded assembled H-shaped steel, and A _w is the cross-sectional area (mm ² ) of the web perpendicular to the material axis direction of the welded assembled H-shaped steel.

In this invention, the size s of the fillet weld is a relatively small value that is less than the thickness of the web, so that the amount of heat input when forming the fillet weld by welding is suppressed and the residual deformation of the web is kept within a predetermined range below an allowable value.
In addition, the elastic shear buckling strength τ _cr is a value that precisely determines the strength when a shear force acts on a welded assembled H-shaped steel and buckles, taking into account the coupled deformation of the web and a pair of flanges in the welded assembled H-shaped steel. Therefore, by satisfying formulas (1) and (2), for example, when the welded assembled H-shaped steel is used as a beam, the size s of the fillet weld is precisely determined so that the shear force acting on the web can be reliably transmitted within a range in which the web does not elastically buckle.
As described above, the fillet welds can reliably transmit the shear force acting on the web, and the residual deformation of the web of the welded H-section steel can be suppressed to within the allowable value.

In the welded H-section steel, the width-to-thickness ratio of the web may be 109 or more.
In the present invention, a welded assembled H-section steel having a width-thickness ratio of the web of 109 or more and a relatively high cross-sectional efficiency can be obtained.

In the welded H-section steel, the fillet weld may be formed on only one side of the web in a thickness direction for each of the pair of flanges.
In the present invention, fillet welding for forming a fillet welded portion can be easily performed to manufacture a welded H-section steel.

In the welded H-section steel of the present invention, the fillet welds formed by fillet welding reliably transmit the shear force acting on the web and can suppress the residual deformation of the web to an allowable value or less.

1 is a perspective view of a building in which a welded H-beam according to one embodiment of the present invention is used. FIG. 4 is a cross-sectional view of the welded H-shaped steel. 13 is a photograph of a cross section around a fillet weld in the welded H-section steel. FIG. 4 is a diagram illustrating a size s of the fillet weld portion. FIG. 13 is a perspective view showing a schematic state in which the welded H-shaped steel is buckled due to the action of a shear force. FIG. 13 is a diagram illustrating a deformation e1 of the web. This is a photograph of the welded H-section steel of Case No. 1. This is a photograph of the welded H-section steel of Case No. 4. FIG. 13 is a diagram showing the relationship between the heat input and the ratio (e1/Δe1) of the deformation amount of the web during welding to the limit tolerance of the web for Cases No. 1 to 4.

Below, a building in which one embodiment of the welded H-beam according to the present invention is used will be described with reference to Figures 1 to 9.

[1. Structure of buildings using welded H-shaped steel beams]
As shown in FIG. 1 , a building 1 includes a plurality of columns 10 , a plurality of girders 15 , welded H-shaped steel beams 25 and the like which serve as minor beams, and a floor slab 35 .
1, the floor slab 35 is indicated by a two-dot chain line. The welded and assembled H-shaped steel 25 may be a rolled H-shaped steel.

The pillars 10 extend in the up-down direction. The pillars 10 are arranged at intervals from one another. The pillars 10 are made of steel, reinforced concrete (RC), steel reinforced concrete (SRC), concrete filled steel tubes (CFT), or the like.
For example, the girder 15 is made of H-shaped steel. The girder 15 includes a first flange 16, a second flange 17, and a web 18 that connects the flanges 16, 17. The second flange 17 is disposed above the first flange 16. A gusset plate (not shown) is joined to the web 18 of the girder 15 by welding or the like.
The girder 15 is disposed between the adjacent columns 10 and extends in a direction along the horizontal plane. Both ends of the girder 15 are joined to the columns 10 by welding or the like.
The girder 15 may be made of reinforced concrete or steel reinforced concrete.

1 and 2 , when the sub-beam is a welded H-shaped steel 25, it has a pair of flanges 26, 27 and a web 28 joined to each of the pair of flanges 26, 27 by fillet welds 29, 30. Hereinafter, one of the pair of flanges 26, 27 may be referred to as a first flange 26, and the other of the pair of flanges 26, 27 may be referred to as a second flange 27.
The second flange 27 is disposed above the first flange 26 .
2, the fillet weld 29 is a weld formed by joining the first flange 26 and the web 28 by fillet welding. Similarly, the fillet weld 30 is a weld formed by joining the second flange 27 and the web 28 by fillet welding.

The fillet welds 29, 30 are formed on only one side of the thickness direction of the web 28 for each of the flanges 26, 27. That is, the fillet weld 29 is formed by fillet welding the first flange 26 and the web 28 on a first side in the thickness direction of the web 28. The fillet weld 30 is formed by fillet welding the second flange 27 and the web 28 on the first side in the thickness direction of the web 28. Note that the fillet weld 30 may be formed by fillet welding the second flange 27 and the web 28 on a second side opposite to the first side in the thickness direction of the web 28.
The width-to-thickness ratio of the web 28 is preferably 109 or greater.

1, the welded H-shaped steel 25 is placed between the opposing girders 15 and extends in a direction along the horizontal plane. Both ends of the welded H-shaped steel 25 in the material axial direction are connected to the gusset plates of the girders 15 by high-strength bolts (not shown) or the like.
Although not shown, the floor slab 35 includes, for example, a deck plate, concrete, reinforcing bars, and shear connectors.
The deck plate is formed by bending a steel plate, etc. The deck plate is disposed on the second flange 27 of the welded H-shaped steel 25. The deck plate and the second flange 27 are joined to each other by a joint made by burn-out plug welding, etc.
The concrete is formed into a flat plate shape with its thickness direction aligned in the vertical direction. The concrete is placed on a deck plate.

The floor slab 35 includes a plurality of reinforcing bars. A first reinforcing bar, which is a part of the plurality of reinforcing bars, extends in the material axis direction of the welded H-shaped steel 25. A second reinforcing bar, which is the remaining part of the plurality of reinforcing bars, extends along the horizontal plane and in a direction perpendicular to the first reinforcing bar. The first reinforcing bar and the second reinforcing bar are embedded in the concrete.
The shear connectors are, for example, headed studs. The floor slab 35 includes a plurality of shear connectors. The lower ends of the plurality of shear connectors are fixed to the upper surface of the second flange 27 of the welded H-shaped steel 25 at intervals in the material axis direction. The shear connectors are embedded in concrete.

FIG. 3 shows a photograph of a cross section of the fillet weld 29 and its surroundings in the welded H-beam 25 .
The size s (mm) of the fillet weld 29 is specified in the 11th edition of "Standard Specifications for Construction Works JASS6 Steel Construction" compiled by the Architectural Institute of Japan, General Incorporated Association, revised in 2018 (hereinafter abbreviated as JASS6).
4, a right-angled isosceles triangle 29a is defined which is in contact with the surface of the first flange 26, the surface of the web 28, and the surface of the fillet weld 29. In this case, the size s is the length of a side of the right-angled isosceles triangle 29a that sandwiches the right angle.
The same applies to welds such as the fillet weld 30.
In addition, in FIG. 4, the throat thickness c and leg length b of the fillet weld portion 29 are shown.

In the following, a study was conducted on how to reliably transmit the shear force acting on the web at the fillet weld in a welded H-shaped steel and suppress the residual deformation of the web to an allowable value or less in a welded H-shaped steel. In the study, the present embodiment uses the elastic shear buckling strength (buckling stress) τ cr (N/mm ² ) of the H-shaped steel when a shear force acts on the H-shaped steel and the H-shaped steel buckles, as disclosed in _JP 2021-6787 A (hereinafter referred to as the related prior application).
Below, an overview of the elastic shear buckling strength τ _cr will be given.

[2. Elastic shear buckling strength of H-shaped steel]
As shown in Fig. 5, the x-axis is defined along the material axis direction of the welded H-beam 25. The web 28 extends along the x-axis and the y-axis, which is the plate width direction of the web 28. That is, the flanges 26, 27 are disposed so as to sandwich the web 28 in the y-axis direction. The axis extending in the plate thickness direction of the web 28 is defined as the z-axis.
The position of the center of the web 28 in the direction along the y axis is defined as the origin of the y axis. The direction from the first flange 26 toward the second flange 27 is defined as the positive direction of the y axis.

Here, as shown in FIG. 2, the dimensions of the welded H-beam 25 are specified.
The thickness of each of the first flange 26 and the second flange 27 is _tf (mm). The width of the welded assembled H-shaped steel is W (mm). Half the width of each of the first flange 26 and the second flange 27 is _bf (mm). In this case, the width W is equal to _2bf .
The thickness of the web 28 is t _w (mm). The width of the welded H-shaped steel 25 is H (mm). The distance between the center of the first flange 26 and the center of the second flange 27 in the direction along the y-axis is b _w (mm). The cross-sectional area of the web 28 perpendicular to the material axis direction of the welded H-shaped steel 25 is A _w (mm ² ).

The Young's modulus of the welded assembled H-shaped steel 25 is E (N/mm ² ). The Poisson's ratio of the welded assembled H-shaped steel 25 is ν (-). The shear yield strength of the fillet welds 29, 30 is τ _y,depo (N/mm ² ). The second moment of area about the strong axis (z-axis) of the welded assembled H-shaped steel 25 is I (mm ⁴ ). The shear yield strength of the welded assembled H-shaped steel is τ _y (N/mm ² ). The shear yield strength τ _y is equal to a value of (F/√3), for example, when F is the design reference strength of the base material of each of a pair of flanges and webs described later.
As shown in FIG. 5, it is assumed that a shear force F1 acts in the y-axis direction on each of end faces 25a of a welded H-shaped steel 25 in the x-axis direction, causing the welded H-shaped steel 25 to buckle.
The half wavelength in the direction along the x-axis of the web 28, which is displaced in a wave-like manner alternately in the positive direction of the z-axis and the negative direction of the z-axis toward the first end of the web 28 in the direction along the x-axis, is a (mm).

In this case, the elastic shear buckling strength τ _cr is obtained using equations (6) to (11) based on a _n , b _n , λ, and half wavelength a, which are real numbers that give the elastic shear buckling strength τ _cr given by equation (12) a minimum positive value.

Here, N is a natural number equal to or greater than 2, and a ₀ , a _n , b _n , and λ are undetermined coefficients.
In the right-hand side of equation (11), the denominator in [ ] in the right-hand side of equation (53) of the related prior application is changed to correspond to the infinitesimal elements dx and dz.
The elastic shear buckling strength τ _cr is a value that is precisely determined as the strength when a shear force acts on the welded H-shaped steel 25 and the welded H-shaped steel 25 buckles, taking into account the coupled deformation of the web 28 and the pair of flanges 26, 27 in the welded H-shaped steel 25.

[3. Consideration of the size of the fillet weld that can reliably transmit the shear force acting on the web]
As a result of careful study, the inventors have found that when the size s of the fillet welds 29, 30 satisfies each of the formulas (15) to (17), the fillet welds 29, 30 can reliably transmit the shear force acting on the web 28.

Here, in formula (17), A _we is the effective cross-sectional area (mm ² ) perpendicular to the material axis direction of the web 28. In formula (16), Q _Max is the shear force (N) acting on the welded assembled H-shaped steel 25 when it buckles in shear. The value on the right side of formula (15) is the size s _req (mm) of the web 28 required to reliably transmit the shear force acting on the web 28 (to ensure the shear strength of the web 28).
In equation (16), by using the effective cross-sectional area _Awe of the web 28, obtained by multiplying the cross-sectional area _Aw by (τ _cr /τ _y ), instead of the cross-sectional area _Aw of the web 28, the range of sizes s of the fillet welds 29, 30 that can reliably transmit the shear force acting on the web 28 can be accurately calculated using equation (15).

Equations (16) and (17) can be summarized as equation (18).

The shear stress intensity τ _w (N/mm ² ) generated at the intersection line between the flanges 26, 27 and the web 28 is given by equation (20).

4. Experimental Results
An experiment was conducted to manufacture welded H-section steel by joining a web to each of a pair of flanges by fillet welding.
The welding was performed by submerged arc welding.
The welding conditions were based on the provisions of quality class S501-H of JIS Z 3183:2012, quality class of submerged arc weld metal for carbon steel and low alloy steel.

Welded assembled H-section steel was manufactured under the conditions of Case No. 1 to 4 shown in Table 1.

In Cases No. 1 to 4, the design standard strength F of the base metal of each of the pair of flanges and the web is 295 N/mm ^2. The design standard strength of the fillet weld is 295 N/mm ² .
For example, in Case No. 1, the cross-sectional shape of the welded H-shaped steel is 700×175×4.5×9.0. That is, the thickness _tw of the web of the welded H-shaped steel in Case No. 1 is 4.5 mm.
The width-thickness ratio of the web is 151.6. The length L of the welded H-beam is 7,000 mm. The heat input during fillet welding is 4.4 kJ/cm.
When the heat input was 4.4 kJ/cm, the current was 330 A, the voltage was 29 V, and the welding speed was 130 cm/min. When the heat input was 2.7 kJ/cm, the current was 280 A, the voltage was 24 V, and the welding speed was 150 cm/min.

Here, a method for measuring the deformation e1 of the web by averaging the deformation over three cross sections will be described.
As shown in FIG. 6, in a certain cross section of the welded H-beam 25, a deformation e1, which is a deflection in the thickness direction of the web 28, is measured.
The cross section of the welded H-section steel for measuring the deformation e1 is as follows: The welded H-section steel is divided into four equal parts in the axial direction, dividing it into a first part, a second part, a third part, and a fourth part. The deformation e1 is measured at each of three cross sections: the cross section at the boundary between the first part and the second part, the cross section at the boundary between the second part and the third part, and the cross section at the boundary between the third part and the fourth part. The three measured deformations e1 are averaged to obtain the average of the three cross sections.

A photograph of the welded H-shaped steel of Case No. 1 is shown in Figure 7. It can be seen that the web of the welded H-shaped steel is deformed in such a way that it is bent in the thickness direction of the web.
A photograph of the welded H-shaped steel of Case No. 4 is shown in Figure 8. It can be seen that the deformation of the web is suppressed in the welded H-shaped steel.

Some of the experimental results are shown in Table 1.
In the welded H-section steel of Case No. 1, the average deformation e1 of the three cross sections was 6.7 mm.
JASS6 specifies that the limit tolerance Δe1 of web deformation is the smaller of the value obtained by dividing the depth H of the welded assembled H-section steel by 100 or 6 mm. Therefore, the limit tolerance Δe1 in Case No. 1 is 6.0 mm. The ratio (e1/Δe1) is 1.11 from the formula (6.7/6.0).
In the welded H-section steels of Cases 1, 2, and 4, weld beads were formed to form fillet welds, and the webs were joined to the pair of flanges by the fillet welds.
On the other hand, in the welded H-section steel of Case No. 3, a weld bead was not formed, and the web was not joined to each of the pair of flanges.

The remainder of the experimental results are shown in Table 2.

In the welded H-beam of Case No. 1, the size s was 4.6 mm in each fillet weld. The throat thickness c was 3.3 mm. The size s _req was 1.9 mm.
In case No. 3, the value of size s could not be obtained and the relationship s ≧ s _req was not satisfied, but it was found that the relationship s ≧ s _req was satisfied in cases No. 1, 2, and 4. When the relationship s ≧ s _req is satisfied, that is, when formula (15) is satisfied, the fillet weld can reliably transmit the shear force acting on the web.

In addition, in the case of Case No. 4 where the size s of the fillet weld is less than the thickness _t of the web ( _t > s), it was found that the amount of heat input when forming the fillet weld by welding is suppressed, and the residual deformation of the web can be suppressed to an allowable value or less, for example, the limit tolerance of JASS6.

The objective of this embodiment is to provide a welded and assembled H-shaped steel beam in which a fillet weld portion formed by fillet welding reliably transmits the shear force acting on the web and suppresses the residual deformation of the web to within an allowable value.
It was found that case No. 4, in which the size s satisfies the formula (t _w >s ≧s _req ), is an embodiment, and case Nos. 1 to 3, in which the size s does not satisfy the formula (t _w >s ≧s _req ), are comparative examples.

Here, for the results of Case Nos. 1 to 4 shown in Tables 1 and 2, the relationship between the heat input and the ratio (e1/Δe1) of the deformation amount of the web during welding to the limit tolerance of the web is shown in Fig. 9. In Fig. 9, the horizontal axis (x-axis) represents the heat input (kJ/cm), and the vertical axis (y-axis) represents the ratio (e1/Δe1) (-).
Case No. 1 and Case No. 4, whose cross-sectional shape is 700×175×4.5×9.0, are indicated by solid circle marks. Case No. 2, whose cross-sectional shape is 500×150×4.5×4.5, is indicated by solid square marks.
For Case Nos. 1 and 4 (heat inputs of 2.7 and 4.4 kJ/cm), approximation was performed using a power function passing through the origin. As a result of the approximation, equation (20) shown by curve L1 was obtained.
y=0.012x ^3.0545 ...(20)

For case No. 2, approximation was performed using a power function that has the same exponent as that of equation (20) and passes through the origin. As a result of the approximation, equation (21) shown by curve L2 was obtained.
y=0.0274x ^3.0545 ...(21)
In formula (20), when the value of y becomes 1.0 (when the deformation e1 of the web becomes equal to the limit tolerance Δe1), the value of x (heat input) is 4.3 kJ/cm.
In formula (21), the value of x when the value of y was 1.0 was 3.2 kJ/cm.

That is, in the case of the two types of cross-sectional shapes described above, if the heat input is 3.2 kJ/cm or less, the deformation e1 of the web is equal to or less than the limit tolerance Δe1.
Here, a manufacturing method of the welded H-beam of this embodiment will be described.
In the manufacturing method of welded H-shaped steel, the web 28 is joined by fillet welding to each of the pair of flanges 26, 27 to manufacture the welded H-shaped steel 25. In the manufacturing method of welded H-shaped steel, the heat input in each fillet weld is preferably 2.3 kJ/cm or more and 3.2 kJ/cm or less.
In the manufacturing method of welded assembled H-shaped steel, for example, when fillet welds 29 are formed on both sides in the thickness direction of the web 28 of the first flange 26, both fillet welds 29 may be formed simultaneously. In this case, it is preferable that the heat input to the entire both fillet welds 29 is 2.3 kJ/cm or more and 3.2 kJ/cm or less.
The same applies to the fillet weld 30 .

As described above, in the welded-assembled H-shaped steel 25 of this embodiment, the size s of the fillet welds 29, 30 is a relatively small value that is less than the thickness t _w of the web 28, so that the amount of heat input when forming the fillet welds 29, 30 by welding is suppressed and the residual deformation of the web 28 is kept within a predetermined range below the allowable value.
Moreover, the elastic shear buckling strength τ _cr is a precisely determined value of the strength when a shear force acts on the welded H-shaped steel 25 and the welded H-shaped steel 25 buckles, taking into consideration the coupled deformation of the web 28 and the pair of flanges 26, 27 in the welded H-shaped steel 25. Therefore, by satisfying formulas (15) to (17), the precisely determined size s of the fillet welds 29, 30 is obtained, which can reliably transmit the shear force acting as the compressive force to the central portion of the web 28 in the width direction when the welded H-shaped steel 25 is used as a sub-beam.
As described above, the fillet welds 29, 30 reliably transmit the shear force acting on the web 28, and the residual deformation of the web 28 of the welded H-section steel 25 can be suppressed to within the allowable value.

When the width-thickness ratio of the web 28 is 109 or more, the welded assembled H-section steel 25 having a width-thickness ratio of the web 28 of 109 or more and a relatively high cross-sectional efficiency can be obtained.
The fillet welds 29, 30 are formed on only one side in the thickness direction of the web 28 for each of the flanges 26, 27. Therefore, fillet welding for forming the fillet welds 29, 30 can be easily performed to manufacture the welded and assembled H-shaped steel 25.

Furthermore, in the manufacturing method of the welded H-beam of this embodiment, the inventors have found, as a result of intensive study, that when the heat input in each fillet weld is 2.3 kJ/cm or more, beads of the fillet welds 29, 30 are reliably formed by the fillet welds, and the fillet welds 29, 30 reliably transmit the shear force acting on the web 28. Furthermore, they have found that when the heat input in each fillet weld is 3.2 kJ/cm or less, the heat input during fillet welding is suppressed, and the residual deformation of the web 28 is suppressed to a predetermined range that is equal to or less than the allowable value that is the limit tolerance of JASS6, for example.
Therefore, the fillet welds 29, 30 formed by fillet welding reliably transmit the shear force acting on the web 28, and the residual deformation of the web 28 can be suppressed to an allowable value or less.
When joining the web 28 to each of the pair of flanges 26, 27 by fillet welding, the size s and the amount of heat input of the fillet welds 29, 30 can be appropriately adjusted.

[5. Size of fillet weld required to reliably transmit shear force acting on the web]
The size of the fillet weld required to reliably transmit the shear force acting on the web was calculated. The results of the calculations are shown in Tables 3 and 4.

For example, a case where the cross-sectional shape is 500 x 150 x 4.5 x 4.5 will be described. In this case, the moment of inertia I of the welded H-shaped steel 25 is 1.27E+08 (1.27 x ¹⁰⁸ ) ^mm4 . The cross-sectional area _Aw of the web 28 is 2,210 ^mm2 . The shear yield strength _τy of the welded H-shaped steel 25 is 170 N/ ^mm2 . From equations (6) to (12), the elastic shear buckling strength _τcr of the welded H-shaped steel 25 is 94 N/ ^mm2 .
According to equation (17), the effective cross-sectional area A _we of the web 28 is 1,219 mm ² .
The design standard strength F of the base metal of each of the pair of flanges and the web is 295 N/mm ^2. The design standard strength F of the fillet weld is 295 N/mm ^2. The shear yield strength τ _y,depo of the fillet welds 29, 30 is 170 N/mm ² .

According to formula (16), the shear force Q _Max of the welded H-shaped steel 25 is 376.3 kN. According to formula (20), the (maximum) shear stress intensity τ _w of the fillet weld 29 is 110 N/mm ^2. The shear stress intensity (τ _w /Q _Max ) per unit shear force Q _Max of the fillet weld 29 is 2.92E-04 (1/mm ² ).
In the fillet weld 29, the shear force Q _w,req acting per unit length in the material axis direction of the welded assembled H-shaped steel (H-shaped steel member) 25 is 495 N/mm ^2. The shear force Q _w,req is calculated by multiplying the (maximum) shear stress intensity τ _w by the thickness t _w of the web 28.

For this welded H-section steel with a cross-sectional shape of 500 x 150 x 4.5 x 4.5, trial calculations were performed by changing the size s of the fillet weld to 2.2 mm, 2.3 mm, and 2.4 mm.
For example, when the size s is 2.2 mm, the throat thickness c is 1.5 mm. In the fillet weld 29, the shear strength _Qw per unit length in the material axis direction of the welded H-shaped steel 25 is 262.3 N/mm. The shear strength _Qw is calculated by multiplying the shear yield strength τy _,depo of the fillet weld 29 by the throat thickness c of the fillet weld 29.
If the value of (Qw _,req / _Qw ) is 1 or less (shear force Qw _,req is equal to or less than shear strength _Qw ), the shear force acting on the web can be reliably transmitted. Therefore, the ability to reliably transmit the shear force acting on the web can be determined by the test value (Qw _,req / _Qw ) being 1 or less. In this case, the test value (Qw _,req / _Qw ) was 1.041, which showed that the shear force acting on the web could not be reliably transmitted.

For welded H-shaped steel with a cross-sectional shape of 500 x 150 x 4.5 x 4.5, the minimum size s at which the test value is less than 1 was found to be 2.3 mm. On the other hand, for welded H-shaped steel with a cross-sectional shape of 700 x 175 x 4.5 x 9.0, the minimum size s at which the test value is less than 1 was found to be 1.9 mm.

[6. Ratio of fillet weld size requirements to web thickness]
The above ratio will be considered using the ratio of the size s of the fillet welds 29, 30 to the thickness t _w of the web 28 (s/t _w , hereinafter referred to as the size-thickness ratio).
The upper limit of the size s of the fillet welds 29, 30 necessary to suppress the residual deformation of the web 28 to a tolerance or less (deformation suppression) can be determined in terms of the size-thickness ratio as shown in Equation (24) since the size s of the fillet welds 29, 30 is less than the web thickness _tw as described above.
・s/t _w =4.5/4.5=1.0 (24)

The lower limit of the size s (size-thickness ratio) of the fillet welds 29, 30 required for the fillet welds 29, 30 to reliably transmit the shear force acting on the web 28 (ensuring the shear force of the web) can be obtained based on the results of [5. ] and on the cross-sectional shape of the welded H-shaped steel 25, as shown in Equation (25) and Equation (26).
・If the cross-sectional shape is 700 x 175 x 4.5 x 9.0,
s/t _w =1.9/4.5=0.42...(25)
・If the cross-sectional shape is 500 x 150 x 4.5 x 4.5,
s/t _w =2.3/4.5=0.51...(26)

In other words, it was found that if the size-thickness ratio for the multiple cross-sectional shapes is greater than or equal to 0.51 and less than 1.0, the desired requirements for the residual deformation and shear force are met.

As a result of intensive studies, the inventors of the present embodiment have found that when the size-thickness ratio is 0.51 or more, beads of the fillet welds 29, 30 are reliably formed, and the fillet welds 29, 30 reliably transmit the shear force acting on the web 28. In addition, they have found that when the size-thickness ratio is less than 1.0, the amount of heat input when forming the fillet welds 29, 30 by welding is suppressed within a predetermined range in which the residual deformation of the web 28 is equal to or less than an allowable value.
Therefore, in a welded and assembled H-shaped steel beam, by setting the size-thickness ratio to be 0.51 or more and less than 1.0, the fillet welds 29, 30 can reliably transmit the shear force acting on the web 28, and the residual deformation of the web 28 of the welded and assembled H-shaped steel beam can be kept below the allowable value.

Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and changes, combinations, deletions, etc. of the configuration are also included within the scope that does not deviate from the gist of the present invention.
For example, in the above embodiment, the fillet welds 29 may be formed on both sides of the first flange 26 in the thickness direction of the web 28. Also, the fillet welds 30 may be formed on both sides of the second flange 27 in the thickness direction of the web 28.
In the welded assembled H-section steel 25, the width-to-thickness ratio of the web 28 may be less than 109.
Welded H-sections may be used as girders.

25 Welded H-beam 26 Flange (first flange)
27 Flange (second flange)
28 Web 29, 30 Fillet weld

Claims (3)

A pair of flanges;
a web joined to each of the pair of flanges by a fillet weld;
A welded assembled H-shaped steel comprising:
The size s (mm) of the fillet weld is less than the thickness of the web,
A welded assembled H-shaped steel beam, the size s of which satisfies the formulas (1) and (2).
where τ _y,depo is the shear yield strength (N/mm ² ) of the fillet weld, I is the second moment of area about the strong axis of the welded assembled H-shaped steel (mm ⁴ ), H is the depth of the welded assembled H-shaped steel (mm), t _f is the thickness of the flange (mm), W is the width (mm) of the welded assembled H-shaped steel, τ _cr is the elastic shear buckling strength (N/mm ² ) of the welded assembled H-shaped steel, and A _w is the cross-sectional area (mm ² ) of the web perpendicular to the material axis direction of the welded assembled H-shaped steel.

The welded assembled H-section steel according to claim 1 , wherein the width-to-thickness ratio of the web is 109 or more. The welded and assembled H-section steel according to claim 1 or 2 , wherein the fillet welds are formed on only one side of the web in a thickness direction for each of the pair of flanges.

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