JP2022030382A - Steel beam, column-beam joint structure and structure provided therewith - Google Patents

Abstract

To provide a steel beam, a column-beam joint structure and a structure provided therewith in a simple structure capable of improving plastic deformation capacity at an end part in a material axis direction upon short load action such as earthquake force.SOLUTION: A steel beam 1 has an upper flange 11, a lower flange 12, and a web 13 jointing the upper flange and the lower flange, which is provided with: main stiffeners 14 jointing a space between the upper flange and the lower flange at a predetermined position in its material axial direction; and through hole 13h formed in the web to overlap the main stiffeners in a beam width direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to a steel beam, a column-beam joint structure, and a structure having the same.

In a structure such as a rigid frame structure, for example, a building, the end portion of the beam in the material axial direction, that is, the portion connected to the column, receives a large bending moment when a short-term load is applied during an earthquake. In particular, in the case of steel beams, when a bending moment is applied when a short-term load such as seismic force is applied, local buckling occurs in the web and flange at the end in the material axial direction, and the yield strength and deformation capacity of the steel beam are increased. It may drop sharply.

Specifically, at the end of the steel beam in the material axial direction, the web buckles locally, the flange breaks from the scallop bottom provided on the web due to the need for on-site welding, and the steel beam joins the column. The welded portion to be welded may be broken, and the plastic deformation ability of the steel beam may not be fully exerted, resulting in unexpected damage to the structure.

In the plastic design of steel structures, a plastic hinge that can be greatly plastically deformed without breaking even after the end of the steel beam in the material axial direction receives a bending moment and is plastically deformed when a short-term load such as seismic force is applied. By doing so, it is designed to absorb the energy received by the steel beam. Therefore, it is necessary to surely prevent local buckling and premature fracture of the end portion of the steel beam in the material axial direction so that the steel beam can exhibit sufficient plastic deformation ability.

In addition, in structures such as buildings, in order to effectively utilize the space under the beam to reduce the floor height and reduce the construction cost of the structure, the beam is provided with a through hole for passing equipment piping and wiring. Is often done. When a through hole is provided in a steel beam having a cross section such as H-shaped, I-shaped, or groove-shaped, the through hole is provided in the web and a cross-sectional defect occurs.

The through hole provided in the web of the steel beam reduces the buckling resistance of the web, so that local buckling of the web is likely to occur, which causes a decrease in the plastic deformation ability of the steel beam. From the viewpoint of preventing the occurrence of such local buckling, it is common to form a through hole in the plasticized region at the end of the steel beam in the direction of the material axis, which receives a large bending moment when a short-term load such as seismic force is applied. It is said that it should be avoided.

On the other hand, as disclosed in Non-Patent Document 1, for example, a through hole is formed at an axial end of a steel beam, and a web around the through hole is formed when the axial end receives a bending moment. It is also known that when the steel frame is deformed, the sharp decrease in the yield strength borne by the web is suppressed, and the plastic deformation ability of the steel beam may be improved. At this time, by setting the size of the through hole so that the total plastic yield strength due to the effective cross section of the web at the position of the through hole is equal to or greater than the bending moment acting on the position of the through hole, the cross section of the position of the through hole is formed. It is possible to suppress the rate of decrease in the yield strength of the steel beam due to the defect.

In addition, it is widely practiced to reinforce the circumference of the through hole in order to prevent the strength and deformation capacity of the steel beam from being reduced due to the cross-sectional defect when the through hole is formed in the web of the steel beam. There is. As a method of reinforcing the periphery of the through hole formed in the web of the steel beam, a plate 88 having the through hole 88h is welded to the web 83 around the through hole 83h as in the steel beam 8A shown in FIG. And a method of inserting a ring or a sleeve tube 89 into the inner circumference of the through hole 83h and joining them, as in the steel beam 8B shown in FIG.

Whether or not it is necessary to reinforce the circumference of the through hole can be determined from the magnitude relationship between the bending strength and shearing force of the steel beam at the position of the through hole and the magnitude of the bending moment and the shearing force acting on the position of the through hole. Patent Document 1 discloses a range in the lumber axis direction in which it is not necessary to reinforce even if a through hole is formed in the web of the steel frame beam in order to secure the yield strength of the steel frame beam.

Japanese Patent No. 3238540

Takashi Namba, 1 outsider, "Improvement of Deformation Ability of Beams Joined to Square Steel Pipes by Drilling Beam Webs", Annual Papers on Steel Structures, Japanese Society of Steel Construction, November 2006, Vol. 14, pp. .. 673-680

Here, Patent Document 1 defines a range in which the distance from the tip of the steel frame beam in the timber axial direction satisfies a predetermined condition, and defines this as a range in the timber axial direction in which it is not necessary to reinforce the through hole. In the plasticized region at the end of the steel beam in the material axial direction outside this range, the periphery of the through hole is reinforced by the method shown in FIGS. 16 and 17.

FIG. 1 is a graph schematically showing the relationship between the bending moment M applied to the end portion of the steel frame beam in the material axial direction and the deformation angle θ generated in the steel frame beam. The solid line in FIG. 1 shows a case where a conventional steel beam without a through hole sufficiently exerts its plastic deformation ability without causing local buckling or fracture. In such a case, the proof stress M of the steel beam reaches the total plastic proof stress Mp, then continues to rise on a gentle slope to reach the maximum proof stress, then descends on a gentle slope, and then the total plastic proof stress again. It behaves as if it drops to Mp. In the example shown in FIG. 1, after the proof stress M of the steel frame beam reaches the total plastic proof stress Mp, the upper limit of the deformation angle capable of maintaining the total plastic proof stress Mp or more is θ3. The larger the upper limit of the deformation angle θ that can maintain the total plastic proof stress Mp or more, the higher the plastic deformation capacity of the steel frame beam.

However, after the end of the steel beam in the material axis direction receives a bending moment and the deformation angle θ increases and exceeds the total plastic bearing capacity Mp, the deformation angle θ becomes as shown by a cross in FIG. If the end portion in the material axial direction breaks at θ1, the plastic deformation ability of the steel beam is completely lost at this point. That is, the plastic deformation ability is significantly reduced as compared with the above-mentioned deformation angle θ3 when the steel beam sufficiently exhibits the plastic deformation ability without causing local buckling or fracture.

When a steel beam is repeatedly loaded with a seismic force or the like, strain is concentrated on the tip in the material axis direction, and fracture of the tip in the material axis direction often occurs. In order to prevent this, it is important to alleviate the concentration of strain at the tip of the steel beam in the material axial direction.

Further, even if the tip of the steel beam in the material axial direction does not break, if the wall thickness of the web is small, local buckling occurs at the end of the steel beam in the material axial direction, and FIG. 1 As shown by the broken line inside, the bearing capacity M of the steel beam may drop sharply. In order for the steel beam to absorb the energy input to the steel beam while maintaining sufficient yield strength against repeated loads such as seismic force, it is necessary not only to break the tip of the steel beam in the material axial direction but also in the material axial direction. It is also necessary to suppress the local buckling at the end of the beam.

Here, as disclosed in Non-Patent Document 1, an attempt is made to improve the plastic deformation capacity of the steel beam by providing a through hole at the end in the material axial direction of the steel beam, which is shown by a dotted line in FIG. As such, the maximum strength of the steel beam is reduced due to the cross-sectional defect at the position of the through hole. As described above, it is conceivable to improve the proof stress of the steel frame beam by reinforcing the periphery of the through hole by the method shown in FIGS. 16 and 17 to deal with this decrease in proof stress.

However, in the reinforcement by the ring or sleeve pipe as shown in FIGS. 16 and 17, when the steel beam is subjected to a short-term load such as seismic force and the end portion in the material axial direction receives a bending moment, the end portion in the material axial direction is in this material axial direction. The effect of suppressing local buckling that occurs in the flange at the end cannot be obtained. Further, since the ring and the sleeve tube need to be processed and manufactured according to the diameter and shape of the through hole, those made of cast steel are often used, and there is a problem that the cost of these parts is high.

Further, if the circumference of the through hole is reinforced by the method shown in FIGS. 16 and 17 to restrain the deformation of the through hole, it is possible to secure the same plastic deformation ability as that of the steel beam without the through hole. However, it cannot be expected that the deformation ability will be improved more than that of a steel beam without a through hole. This is because the reinforcing member such as a ring or a sleeve pipe and the web are welded and joined to restrain the web around the through hole and prevent deformation. In addition, since the welding between the ring or sleeve pipe and the web is performed around the through hole provided in the web, which has a small wall thickness and is easily deformed, it is expensive to weld so that the steel beam and the through hole do not undergo welding deformation. There is also a problem that skill is required.

Further, in Non-Patent Document 1, the behavior when the end portion of a steel beam made of H-shaped steel having a size of H-500 × 200 × 10 × 16 in the material axial direction receives a bending moment is calculated by elasto-plastic finite element analysis. However, it is known that buckling is less likely to occur in such a steel beam with a small width-thickness ratio of the web, and that the plastic deformation ability is higher than that of a steel beam with a small web thickness. ing. In recent years, steel frames as in Non-Patent Document 1 have been increasingly adopted in order to reduce the weight of steel materials due to the increase in the height of buildings. Since the plastic deformation capacity of the steel beam is not necessarily improved only by providing a through hole at the end of the beam in the material axial direction, local buckling of the end in the material axial direction is also suppressed in order to obtain sufficient plastic deformation capacity. There is a need.

Further, in Non-Patent Document 1, in the example in which a through hole having a diameter of 360 mm is provided in a steel frame beam having a beam length of 500 mm, the flange in the vicinity of the through hole is locally buckled, and the plastic deformation ability of the steel frame beam is improved. It is shown not to. Therefore, Non-Patent Document 1 proposes a method of providing a large number of small through holes when forming through holes at the end portion of the steel frame beam in the material axial direction. However, such a method has a problem that man-hours increase because a large number of through holes are formed.

The present invention has been made in view of the above circumstances, and is a steel beam capable of improving the plastic deformation ability of the end portion in the material axial direction when a short-term load such as a seismic force is applied by a simple structure. It is an object of the present invention to provide a beam-column joint structure and a structure having the same.

In order to solve the above problems, the present invention has the following features.

[1] A steel beam having an upper flange, a lower flange, and a web connecting the upper flange and the lower flange, and the upper flange and the lower flange at a predetermined position in the material axial direction of the steel beam. A steel beam characterized in that a main stiffener connecting between flanges is provided, and a through hole is formed in the web so as to overlap the main stiffener in the beam width direction.

Here, "the through hole is formed so as to overlap the main stiffener in the beam width direction" means that at least a part of the through hole overlaps with the main stiffener when viewed in the beam width direction.

[2] The steel beam according to [1], wherein the predetermined position is an end portion in the material axial direction.

Here, the "end" in the lumber axial direction means a plasticized region when a short-term load such as a seismic force acts on a structure in which the tip of the steel beam in the lumber axial direction is connected to a column. For example, it refers to a region from the tip of the steel beam in the lumber axis direction to 1.5 times the beam length in the lumber axis direction.

[3] The steel beam according to [1] or [2], wherein the main stiffener is not joined to the web.

[4] The steel frame beam according to any one of [1] to [3], wherein the main stiffener is disposed at the tip portions of the upper flange and the lower flange in the beam width direction.

[5] The steel frame beam according to any one of [1] to [4], wherein the main stiffener has a flat plate shape and is arranged in a direction intersecting the material axial direction.

[6] The upper flange and the lower flange are connected by an auxiliary stiffener at a position where the through hole is not formed in the end portion in the material axial direction [1]. ] To the steel beam according to any one of [5].

[7] The steel beam according to [6], wherein the sub-stiffener is provided between the through hole and the tip in the length direction of the steel beam.

[8] The steel beam according to [67] or [7], wherein the secondary stiffener is not joined to the web.

[9] A beam-column joint structure characterized in that the tip of the steel frame beam according to any one of [1] to [8] in the lumber direction is connected to a column.

[10] A structure characterized by having the beam-column joint structure according to [9].

According to the steel beam, the column-beam joint structure of the present invention, and the structure having the same, the web around the through hole precedes the tip of the steel beam in the material axial direction when a short-term load such as a seismic force is applied. By deforming and yielding, the concentration of strain at the tip of the steel beam in the material axial direction is alleviated, and the plastic deformation capacity of the steel beam is improved.

Further, since the upper flange and the lower flange are connected by a main stiffener arranged so as to overlap at least a part of the through hole in the beam width direction, even if the thickness of the web of the steel beam is small, the thickness of the web is small. Local buckling of the web is suppressed and the plastic deformation capacity of the steel beam is improved.

Further, the upper flange and the lower flange are connected by a main stiffener arranged so as to overlap at least a part of the through hole in the beam width direction, and the upper flange and the lower flange are stiffened, so that a small penetration is made. Even if it is a simple structure in which only one or a small number of relatively large through holes are provided instead of a complicated structure in which many holes are provided, local buckling of the upper and lower flanges in the vicinity of the through holes is suppressed, and the steel beam. The plastic deformation ability of is improved.

Further, the total plastic strength of the steel beam can be easily adjusted by changing the diameter of the through hole provided in the web of the steel beam.

Further, since the main stiffener and the sub stiffener are attached so as to connect between the upper flange and the lower flange, the shapes of the main stiffener and the sub stiffener can be determined without being influenced by the shape of the through hole.

It is a graph which shows typically the load-deformation relationship in the steel frame beam of this invention and the conventional steel frame beam. It is a figure which shows the steel frame beam and column beam joint structure of one Embodiment of this invention, (a) is a side view, (b) is a sectional view. It is a side view schematically showing the deformation state when the bending moment and the shearing force act on the end portion of the steel beam of the present invention in the material axial direction. It is a figure which shows the steel frame beam and column beam joint structure of another embodiment of this invention, (a) is a side view, (b) is a sectional view. It is a figure which shows the steel frame beam and column beam joint structure of still another embodiment of this invention, (a) is a side view, (b) is a sectional view. It is a figure which shows the steel frame beam and column beam joint structure of still another embodiment of this invention, (a) is a side view, (b) is a sectional view. It is a figure which shows the steel frame beam and column beam joint structure of still another embodiment of this invention, (a) is a side view, (b) is a sectional view. It is a figure which shows the steel frame beam and column beam joint structure of still another embodiment of this invention, (a) is a side view, (b) is a sectional view. It is a figure which shows the analysis model for calculating the deformation when the steel frame beam of this invention receives a load by numerical analysis, (a) is a side view, (b) is a sectional view. It is a figure which shows the analysis model for calculating the deformation when a conventional steel beam receives a load by numerical analysis, (a) is a side view, (b) is a sectional view. It is a figure which shows the analysis model for calculating the deformation when a conventional steel beam receives a load by numerical analysis, (a) is a side view, (b) is a sectional view. It is a graph which compares and shows the result of having calculated the load-deformation relationship in the present invention and a conventional steel beam by numerical analysis. It is a contour diagram which shows the numerical analysis result of the strain distribution generated in the steel frame beam of this invention, (a) is a side view, (b) is a top view. It is a contour diagram which shows the numerical analysis result of the strain distribution generated in the conventional steel frame beam, (a) is a side view, (b) is a top view. It is a contour diagram which shows the numerical analysis result of the strain distribution generated in the conventional steel frame beam, (a) is a side view, (b) is a top view. It is a figure which shows an example of the conventional steel frame beam, (a) is a side view, (b) is a sectional view. It is a figure which shows another example of the conventional steel frame beam, (a) is a side view, (b) is a sectional view.

Hereinafter, embodiments of the steel beam, column-beam joint structure, and the structure having the same will be described in detail with reference to the drawings.

The steel beam of the present embodiment is provided in a steel-framed building (structure) (not shown). 2 (a) and 2 (b) are a side view of the steel frame beam 1 of the present embodiment and a cross-sectional view cut along a plane orthogonal to the lumber axis at the position of the through hole 13h described later, respectively. .. In the steel beam 1, the end portion of the H-shaped steel having the upper flange 11, the lower flange 12, and the web 13 connecting the upper flange 11 and the lower flange 12 in the material axial direction, that is, the pillar 2 of the building. A main stiffener 14 for connecting between the upper flange 11 and the lower flange 12 of the H-shaped steel is provided in the vicinity of the portion connected to the H-shaped steel.

Further, the web 13 of the H-shaped steel is formed with a through hole 13h so as to overlap the main stiffener 14 in the beam width direction. That is, the main stiffener 14 connecting between the upper flange 11 and the lower flange 12 is arranged so as to overlap at least a part of the through hole 13h in the beam width direction. As shown in FIG. 2B, the main stiffener 14 has a flat plate-like shape, and the direction intersecting the material axial direction of the steel frame beam 1, that is, with respect to each of the web 13, the upper flange 11, and the lower flange 12. Is arranged vertically.

Further, as shown in FIG. 2, at the position where the through hole 13h is not formed in the end portion of the steel frame beam 1 in the material axial direction, the web of the steel frame beam 1 is between the upper flange 11 and the lower flange 12. It is connected by the auxiliary stiffeners 16 arranged on both sides of the 13. Specifically, the auxiliary stiffener 16 is provided at one position between the tip of the steel frame beam 1 in the lumber direction and the through hole 13h. As shown in FIG. 2A, the sub stiffener 16 and the main stiffener 14 are arranged at equal intervals in the lumber axis direction of the steel frame beam 1. Like the main stiffener 14, the sub stiffener 16 has a flat plate shape and is perpendicular to each of the web 13, the upper flange 11, and the lower flange 12 in a direction intersecting the material axial direction of the steel frame beam 1. It is arranged.

The main stiffener 14 and the sub stiffener 16 are joined to the tips of the upper flange 11 and the lower flange 12 in the beam width direction to restrain the out-of-plane deformation of the upper flange 11 and the lower flange 12. The main stiffener 14 and the sub stiffener 16 are arranged so as to form a gap between the main stiffener 14 and the sub stiffener 16, and are not joined to the web 13.

Then, the tip of the steel frame beam 1 in the lumber direction is connected to the column 2 to form the column-beam joint structure 3.

FIG. 3 schematically shows a deformed state when a bending moment acts on the end portion of the steel frame beam 1 of the present embodiment in the material axial direction.

As described above, since the main stiffener 14 and the sub stiffener 16 are not joined to the web 13, the deformation of the web 13 around the through hole 13h is not restrained. Therefore, as shown in FIG. 3, the web 13 around the through hole 13h is deformed and yields ahead of the tip of the steel beam 1 in the material axis direction, so that the web 13 is deformed and yields at the tip of the steel frame beam 1 in the material axis direction. The concentration of strain is relaxed and the plastic deformation capacity of the steel beam 1 is improved.

Further, the local buckling of the upper flange 11, the lower flange 12 and the web 13 in the vicinity of the through hole 13h due to the cross-sectional defect of the through hole 13h and the small wall thickness of the web 13 causes the main stiffener 14 and the sub stiffener 16. It is suppressed by connecting between the upper flange 11 and the lower flange 12.

As a result, as shown by the alternate long and short dash line in FIG. 1, the steel beam of the present embodiment has a proof stress with a gentler slope than the conventional steel beam having no through hole after reaching the total plastic strength Mp. M will rise and then fall. In the steel beam of the present embodiment, the deformation angle at the limit where the proof stress M can maintain the total plastic proof stress Mp or more is θ5, and a conventional steel beam without a through hole or a main stiffener having a through hole is provided. The plastic deformation ability is improved as compared with the conventional steel beam without the provision of the or secondary stiffener.

4 to 8 show other embodiments of the steel beam and column-beam joint structure of the present invention.

The steel beam 1A and the column-beam joint structure 3A shown in FIGS. 4 (a) and 4 (b) are different from the steel beam 1 and the column-beam joint structure 3 shown in FIGS. 2 (a) and 2 (b). The main stiffener 14A is arranged in a direction parallel to the web 13 of the steel frame beam 1, and the sub stiffener 16 is not disposed. Others are configured in the same manner as the steel frame beam 1 and the column-beam joint structure 3 shown in FIGS. 2 (a) and 2 (b).

By arranging the main stiffener 14A having a flat plate shape in a direction parallel to the web 13 of the steel beam 1, in this way, the beam width direction of the upper flange 11 and the lower flange 12 where out-of-plane deformation is likely to occur. Out-of-plane deformation of the upper flange 11 and the lower flange 12 can be more effectively suppressed at the tip of the upper flange 11, and local buckling of the upper flange 11 and the lower flange 12 can be prevented.

The steel beam 1B and the column-beam joint structure 3B shown in FIGS. 5 (a) and 5 (b) are different from the steel beam 1 and the column-beam joint structure 3 shown in FIGS. 2 (a) and 2 (b). The main stiffener 14B having a flat plate shape is arranged so as to cover the entire through hole 13h so as to be overlapped on both sides of the web 13 around the through hole 13h, and is joined to the upper flange 11 and the lower flange 12. .. The main stiffener 14B is arranged so as to overlap the web 13, but is not joined to the web 13, so that the surface deformation of the web 13 is constrained, but the shear deformation of the web 13 is not constrained.

In this way, by arranging the main stiffener 14B having a flat plate shape on both sides of the web 13 around the through hole 13h so as to cover the entire through hole 13h, the out-of-plane deformation of the web 13 can be caused. It is suppressed and the torsional deformation of the steel frame beam 1 is suppressed.

The steel beam 1C and the column-beam joint structure 3C shown in FIGS. 6 (a) and 6 (b) are flat plates of the steel beam 1B and the column-beam joint structure 3B shown in FIGS. 5 (a) and 5 (b). The main stiffener 14B is replaced with the main stiffener 14C made of a molded product such as a shaped steel. In this way, the shape of the main stiffener may be changed as needed.

7 (a) and 7 (b), and in the steel beam 1D and 1E and the column-beam joint structure 3D and 3E shown in FIGS. 8 (a) and 8 (b), FIGS. 2 (a) and 2 ( Unlike the steel beam 1 and the column-beam joint structure 3 shown in b), the through holes 13hD and 13hE are formed in an elliptical shape or a polygonal shape instead of a circular shape. In this way, the shape of the through hole may be changed as needed.

In the steel beam of the present invention, the size of the through hole is preferably half or less of that of the beam, and the total plastic strength of the steel beam is adjusted by changing the size of the through hole within that range. can do.

A steel beam of the present invention provided with a through hole, a main stiffener and a sub stiffener (example of the present invention), and a conventional steel beam beam provided with no through hole, a main stiffener or a sub stiffener (conventional example 1). , A numerical analysis by the finite element method was performed on a conventional steel beam (conventional example 2) in which a through hole was provided and a main stiffener and a sub stiffener were not provided, and the yield strength and deformation ability were confirmed.

The analysis models in this numerical analysis are shown in FIGS. 9 to 11. As shown in FIG. 9, as an analysis model of the steel beam 1F of the example of the present invention, an H-shaped steel web 13 having an H-1000 (H) × 300 (B) × 12 × 25 and a total length L = 20000 mm has a diameter of 500 mm. Through holes 13h are formed, and the upper flange 11 and the lower flange 12 of the H-shaped steel are connected by a main stiffener 14 and sub stiffeners 16 and 17 arranged in a direction orthogonal to the material axis direction. It was set. The sizes of the main stiffener 14 and the sub stiffeners 16 and 17 were 950 mm in height, 144 mm in width, and 12 mm in thickness.

The center position of the through hole 13h was set to a position 600 mm from the tip of the steel frame beam 1F in the material axial direction. Further, on each of both sides of the web 13 on the steel beam 1F, in order from the tip in the lumber direction, there is one sub-stiffener 16, one main stiffener 14, two sub-stiffeners 17, and even intervals in the lumber direction. It was assumed that the arrangement was L1 = 300 mm. Further, the main stiffener 14 and the sub stiffeners 16 and 17 are joined to the lower surface of the upper flange 11 and the upper surface of the lower flange 12 of the steel frame beam 1F, but are not joined to the web 13. Each weld is a non-scallop type.

Then, assuming that the steel beam 1F of the example of the present invention is subjected to antisymmetric bending, in consideration of symmetry, an analysis model is made up to half L / 2 of the total length L of the steel beam 1F.

As the mechanical properties of H-section steel, stress-strain relationship assuming SN490B equivalent (tensile strength: 557N / mm ² , yield strength: 385N / mm ² , Young coefficient: 205000) of JIS G3136 (rolled steel for building structure) Was used. The mechanical properties of the main stiffener 14 and the sub stiffeners 16 and 17 are equivalent to SS400 of JIS G3101 (rolled steel for general structure) (tensile strength: 425 N / mm ² , yield strength: 295 N / mm ² , Young coefficient: 205000. ) Was used for the stress-strain relationship.

Further, as shown in FIG. 10, as the conventional example 1, none of the through hole 13h, the main stiffener 14, the sub stiffeners 16 and 17 of the present invention example is provided, and the other parts are the same as the present invention example. I set up the model. Further, as shown in FIG. 11, as the conventional example 2, the main stiffener 14 and the sub stiffeners 16 and 17 of the present invention example are not provided, the through hole 13h is formed in the same manner as the present invention example, and the others are also present. An analysis model was set to be the same as that of the invention example.

For these analysis models, the tip of the steel beam 1F in the lumber direction (the tip on the side where the through hole 13h is formed in the examples of the present invention and Comparative Example 2) is completely fixed, and half of the total length L is L / 2. The position of was used as the loading point. As shown in FIGS. 9 to 11, a load P upward in the beam strain direction is applied to this loading point, and this load P is gradually increased. Deformation of each part of the analysis model by elasto-plastic finite element method analysis. The quantity and equivalent plastic strain were calculated.

The relationship between the bending moment M applied to the tip of the steel beam in the lumber axis direction and the deformation angle θ of the steel beam obtained as a result of performing the above numerical analysis for each of the examples of the present invention, the conventional example 1 and the conventional example 2. , FIG. 12. Here, the bending moment M applied to the tip of the steel beam in the material axial direction was calculated by the product of the load P acting on the loading point and the distance L / 2 from the loading point to the fixed end. The deformation angle θ of the steel frame beam was calculated by dividing the vertical displacement δ of the loading point of the steel frame beam by the above distance L / 2. In the graph of FIG. 12, the vertical axis is a value M / Mp obtained by dividing the bending moment M by the total plastic moment Mp of the conventional example 1. Further, the horizontal axis is a dimensionless deformation angle θ / θp obtained by dividing the deformation angle θ by the deformation angle θp at the time of the total plastic moment Mp of the conventional example 1.

As shown in FIG. 12, in the conventional example 2 in which the through hole is provided and the main stiffener and the sub stiffener are not provided, the maximum is compared with the conventional example 1 in which none of the through hole, the main stiffener, and the sub stiffener is provided. It can be seen that the deformation angle θ at the time of exerting the proof stress, that is, when the bending moment M is maximized is large, and the deformation ability of the steel frame beam is improved by providing the through hole. However, it can be seen that the maximum proof stress of the conventional example 2 is lower than the maximum proof stress of the conventional example 1, and the maximum proof stress is lowered due to the influence of the through hole.

On the other hand, in the example of the present invention in which the main stiffener and the sub stiffener are provided in addition to the through hole, the deformation angle θ at the time of demonstrating the maximum proof stress, that is, the deformation performance is significantly higher than that of the conventional example 1 and the conventional example 2. It is improving. Further, the maximum proof stress of the present invention example exceeds the maximum proof stress of the conventional example 1 and the conventional example 2.

13 to 15 show the equivalent plastic strains of each part of the steel beam at the dimensionless deformation angle θ / θp = 5.0, which were obtained as a result of the above numerical analysis, in the examples of the present invention and conventional examples. It is the figure which showed the contour of the shade for each of 1 and 2.

In Conventional Example 1, as shown in FIG. 13, the equivalent plastic strain is intensively generated near the tip in the material axial direction of the steel beam, and the position where the equivalent plastic strain is maximum is the material of the steel beam. The upper flange at the tip in the axial direction.

Further, in the conventional example 2, as shown in FIG. 14, the position where the equivalent plastic strain is maximum is the upper flange near the through hole of the steel frame beam. That is, as in the conventional example 2, the position where the equivalent plastic strain is intensively generated is moved from the tip in the material axial direction of the steel frame beam to the vicinity of the through hole due to the provision of the through hole, and the steel frame beam is formed. It can be seen that the effect of preventing breakage at the welded portion joined to the column can be obtained.

Further, in the example of the present invention, as shown in FIG. 15, the position where the equivalent plastic strain is maximized is the web above the through hole of the steel beam. That is, as in the example of the present invention, the position where the equivalent plastic strain is intensively generated by providing the main stiffener and the sub stiffener in addition to the through hole is located above the through hole from the upper flange near the through hole. It can be seen that the effect of moving to the web and suppressing the local buckling of the flange near the through hole is further obtained. Local buckling of the flange is the main factor that determines the maximum strength of the steel beam, and in the example of the present invention, it was confirmed that the plastic deformation capacity of the steel beam is significantly improved by suppressing the local buckling of the flange. Was done.

1, 1A ~ 1F Steel beam 2 columns 3, 3A ~ 3E Column beam joint structure 11 Upper flange 12 Lower flange 13 Web 13h, 13hD, 13hE Through hole 14, 14A ~ 14C, 14F Main stiffener 16, 17 Sub stiffener

Claims (10)

A steel beam having an upper flange, a lower flange, and a web connecting the upper flange and the lower flange.
A main stiffener connecting the upper flange and the lower flange is provided at a predetermined position in the material axis direction of the steel frame beam, and a through hole is formed in the web so as to overlap the main stiffener in the beam width direction. A steel beam characterized by being. The steel beam according to claim 1, wherein the predetermined position is an end portion in the lumber axial direction. The steel beam according to claim 1 or 2, wherein the main stiffener is not joined to the web. The steel frame beam according to any one of claims 1 to 3, wherein the main stiffener is disposed at the tip portions of the upper flange and the lower flange in the beam width direction. The steel beam according to any one of claims 1 to 4, wherein the main stiffener has a flat plate shape and is arranged in a direction intersecting the material axial direction. Claims 1 to 5 are characterized in that the upper flange and the lower flange are connected by an auxiliary stiffener at a position where the through hole is not formed in the end portion in the material axial direction. Steel beam described in any of. The steel frame beam according to claim 6, wherein the sub-stiffener is provided between the through hole and the tip in the length direction of the steel frame beam. The steel beam according to claim 6 or 7, wherein the sub-stiffener is not joined to the web. A beam-column joint structure characterized in that the tip of the steel frame beam according to any one of claims 1 to 8 in the material axial direction is connected to a column. A structure characterized by having the beam-column joint structure according to claim 9.

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