H-shaped steel

Abstract

To provide a H-beam capable of easily preventing stress concentration with which scallop is arranged without making processing and welding work difficult, and increasing welding work.SOLUTION: A H-beam 1 in accordance with the present invention is configured with two edges of flanges 3 and one edge of a web 5, yield point or a specification value of yield strength of steel material forming the web 5 is equal to yield point or a specification value of yield strength of steel material forming the flange 3. When a yield ratio of the steel material of the web 5 is YRw, and a yield ratio of the steel material of the flange 3 is YRf, those are YRw>YRf.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to H-beams used in the construction field. [Background technology]

[0002] H-shaped steel beams, consisting of flanges on two sides and a web on one side, are used as columns and beams in buildings. When H-shaped steel is used as a pillar or beam component, the component may bend and deform during a major earthquake, causing plastic deformation. When this happens, the component undergoes plastic deformation and absorbs the earthquake energy, thereby reducing the shaking of the building and preventing it from collapsing.

[0003] However, there is a risk that components will break before absorbing enough earthquake energy due to the use of materials with poor toughness, the presence of welding defects, the presence of stress concentration areas due to geometric discontinuity, etc. For this reason, in the field of architecture, there are strict regulations regarding material standards, welding conditions to prevent the occurrence of welding defects, and processing methods for components to prevent geometric discontinuity.

[0004] FIG. 9 shows a part of a frame in which a beam 11 made of an H-shaped steel 13 having a web 5 and a flange 3 is joined to a square steel pipe column 7 via a diaphragm 9, and a scallop 13, which is a notch for inserting a backing metal 17, is provided at the joint between the beam end and the steel pipe column. It is known from past earthquake damage that in a structure such as that shown in Fig. 9, cracks will develop starting from the scallop bottom 13a (the contact point between the scallop 13 and the flange 3). For this reason, in order to prevent stress concentration at the scallop bottom 13a, it has been proposed to devise a shape for the scallop 13.

[0005] For example, Patent Document 1 discloses a scallop shape in which the curved surface of the scallop bottom is in contact with the flange. Moreover, Patent Document 2 proposes a method of preventing stress concentration by filling the scallops with a weld metal. Furthermore, Patent Document 3 proposes a method of reducing the stress generated at the bottom of the scallop by fixing a reinforcing steel plate to the side surface of the scallop. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-23785 A [Patent Document 2] JP 2015-224427 A [Patent Document 3] JP 2015-67995 A Summary of the Invention [Problem to be solved by the invention]

[0007] The method of Patent Document 1 has a problem in that the shape of the scallops is complicated, making cutting of the members difficult. Furthermore, the method of Patent Document 2 has the problem that the welding work increases and the welding work is performed horizontally, which makes the welding difficult. Furthermore, the method of Patent Document 3 also has a problem in that the welding work increases, similar to Patent Document 2.

[0008] The present invention has been made to solve such problems, and aims to provide an H-shaped steel beam that can prevent stress concentration even when scallops are provided, without making processing or welding work difficult or increasing the amount of welding work. [Means for solving the problem]

[0009] (1) The H-shaped steel of the present invention is composed of flanges on two sides and a web on one side, and is characterized in that the standard value of the yield point or yield strength of the steel material constituting the web is equal to the standard value of the yield point or yield strength of the steel material constituting the flanges, and when the yield ratio of the steel material constituting the web is YRw and the yield ratio of the steel material constituting the flanges is YRf, YRw>YRf.

[0010] (2) Further, in the one described in the above (1), it is characterized in that YRf ≦ 80 and 80 < YRw ≦ 90.

Advantages of the Invention

[0011] In the H-shaped steel according to the present invention, the specified value of the yield point or yield strength of the steel material constituting the web is equal to the specified value of the yield point or yield strength of the steel material constituting the flange. When the yield ratio of the steel material constituting the web is YRw and the yield ratio of the steel material constituting the flange is YRf, since YRw > YRf, stress concentration can be prevented even when a scallop is provided without making processing or welding work difficult or increasing welding work.

Brief Description of the Drawings

[0012] [Figure 1] It is an external view of the H-shaped steel according to an embodiment of the present invention. [Diagram 2] It is an explanatory view of the FEM analysis model used for confirming the effects of the invention. [Diagram 3] It is an explanatory view of Analysis Condition 1. [Figure 4] It is an explanatory view of Analysis Condition 2. [Diagram 5] It is a graph showing the analysis results (Part 1). [Figure 6] It is a graph showing the analysis results (Part 2). [Figure 7] It is a contour diagram of the analysis results (Part 1). [Figure 8] It is a contour diagram of the analysis results (Part 2). [Figure 9] It is an explanatory view explaining the problem to be solved by the invention.

Embodiments for Carrying Out the Invention

[0013] First, the background leading to the present invention will be described. When H-shaped steel is used as a column or beam, the member undergoes bending deformation and plasticity during an earthquake. In such cases, members with a small yield ratio (yield strength / tensile strength x 100 (%)) will experience a small increase in strength after plasticity and the area in which the member becomes plastic will also be small, meaning that there is a risk of destruction from a small earthquake energy. For this reason, an upper limit on the yield ratio is set for steel materials used in the construction industry. Specifically, it is set at 490 N / mm 2 SN490 and 590N / mm 2 In the case of SA440 grade steel, the yield ratio is limited to 80% or less.

[0014] Considering the deformation performance of the beam as a component, as shown in Figure 9, scallops 13 are provided at the ends of the beam to attach welding backing metal 17. When scallops 13 are provided, stress concentration occurs at the scallop bottom 13a, where the cross section is discontinuous, and this can become the starting point of brittle fracture.

[0015] In recent years, as structures have become larger, thicker steel plates are used for the webs and flanges of beams. However, the thicker the plate, the more likely it is that brittle fracture will occur due to the size effect. On the other hand, since the scallop bottom, which is the starting point of destruction during an earthquake, is located on the web, it is thought that destruction from the scallop bottom can be prevented by reducing the stress flowing through the web.

[0016] In other words, it is believed that the stress generated at the scallop bottom can be reduced by making the yield ratio of the steel material constituting the web greater than the yield ratio of the steel material constituting the flange and reducing the increase in stress after plasticization. The present invention is based on these findings, and specific embodiments are described below.

[0017] The H-shaped steel 1 of this embodiment, as shown in Figure 1, is composed of flanges 3 on two sides and a web 5 on one side, and is characterized in that the standard value of the yield point or yield strength of the steel material constituting the web 5 is equal to the standard value of the yield point or yield strength of the steel material constituting the flanges 3, and when the yield ratio of the steel material constituting the web 5 is YRw and the yield ratio of the steel material constituting the flanges 3 is YRf, YRw>YRf. The H-shaped steel 1 may be a rolled steel (see FIG. 1(a)) or a welded and assembled steel (see FIG. 1(b)).

[0018] The reason why the standard value of the yield point or yield strength of the steel material constituting the web 5 is set to be equal to the standard value of the yield point or yield strength of the steel material constituting the flange 3 is as follows. When the difference in strength between the web 5 and the flange 3 becomes large, stress concentration occurs on one side, so this is to eliminate the difference in strength and prevent stress concentration.

[0019] The standard value of the yield strength or strength of the H-shaped steel 1 of the present invention is 235 to 440 N / mm 2 However, in the case of large-scale buildings, beams 11 with high strength and large plate thickness are used, so that destruction from the scallop bottom 13a is likely to occur. Therefore, the standard value of the yield strength or strength of the H-shaped steel 1 is set to 355 N / mm 2 It is believed that applying the present invention to the beams 11 described above will produce greater effects.

[0020] With the H-shaped steel 1 of this embodiment, even when it is used in a beam 11 constituting a structure to form a scallop, the stress increase after plasticization of the web 5 can be reduced, and the stress generated at the scallop bottom 13a can be reduced.

[0021] It is preferable that the yield ratio YRf of the steel material of the flanges 3 constituting the H-shaped steel 1 and the yield ratio YRw of the steel material of the web 5 are set as follows. YRf≦80% and 80% <YRw≦90% Setting YRf ≤ 80% is to ensure the soundness of the structure. Also, setting 80% < YRw is because although the yield point and tensile strength may be temperature-controlled during the manufacturing process, allowing values exceeding 80% can relax the manufacturing conditions. Furthermore, setting YRw ≤ 90% is because YRw = 90% has been proven in the analysis of the following examples, so YRw = 90% is set as the upper limit value to ensure soundness.

Example

[0022] Since FEM analysis was carried out to confirm the effects of the present invention, it will be described below. As shown in Fig. 2, the analysis model is a T-shaped structure in which a beam 11 made of an H-shaped steel 1 is joined to a square steel pipe column 7 via a diaphragm 9, and a scallop 13 is provided at the joint of the beam end with the square steel pipe column 7. The square steel pipe column 7 is □800×40 (BCP325), the beam 11 is H-1000×400×19×40 (the standard value of yield strength or proof strength is 355 N / mm 2 of steel material), the through diaphragm 9 is 50 mm thick (the standard value of yield strength or proof strength is 355 N / mm 2 of steel material), and the length of the beam 11 is 5,600 mm (the beam 11 with a span of 12,000 mm is halved due to symmetry). The width-thickness ratio ranks of the flange 3 and the web 5 of the beam 11 are both FA.

[0023] Regarding the yield ratio, which is a material property of the beam 11, the analysis parameters were as follows: when the yield ratio (YRf) of the flange 3 was set to 70% and the yield ratio (YRw) of the web 5 was varied in the range of 70 - 80% (Analysis condition 1: see Fig. 3), and when the yield ratio (YRf) of the flange 3 was set to 80% and the yield ratio (YRw) of the web 5 was varied in the range of 80 - 90% (Analysis condition 2: see Fig. 4). The analysis is to confirm the plastic strain generated at the scallop bottom 13a during large deformation with an inter-story drift angle R = 1 / 20 rad. for Analysis conditions 1 and 2.

[0024] The results of Analysis 1 are shown in Fig. 5, and the results of Analysis 2 are shown in Fig. 6 respectively. 5 and 6, the vertical axis indicates the reduction rate of the equivalent plastic strain of the scallop bottom 13a, and the horizontal axis indicates the YRw (%) of the web 5. As shown in FIG. 7 and 8 show contour diagrams showing the magnitude of equivalent plastic strain when YRw (%) of the web 5 under analysis condition 2 is set to 80% and 90%.

[0025] As shown in Figs. 7 and 8, regardless of the YRw of the web 5, it is understood that the maximum equivalent plastic strain occurs at the scallop bottom 13a. In addition, as shown in Figs. 5 and 6, regardless of the YRf of the flange 3, the larger the YRw of the web 5, the smaller the plastic strain of the scallop bottom 13a. From the above, it has been demonstrated that when the yield ratio of the steel material constituting the web 5 of the H-shaped steel 1 is YRw and the yield ratio of the steel material constituting the flange 3 is YRf, by making YRw > YRf, stress concentration can be prevented even when scallops 13 are provided. [Explanation of symbols]

[0026] 1 H-beam 3 Flange 5. Web 7 Square steel pipe column 9 Diaphragm 11 Beam 13 Scallop 13a Scalloped bottom 15 H-beam (conventional example) 17 Backing plate

Claims

[Claim 1] An H-shaped steel consisting of flanges on two sides and a web on one side, a standard value of the yield point or yield strength of the steel material constituting the web is equal to a standard value of the yield point or yield strength of the steel material constituting the flange, and when a yield ratio of the steel material constituting the web is YRw and a yield ratio of the steel material constituting the flange is YRf, YRw>YRf; An H-shaped steel characterized in that YRf≦80 and 80<YRw≦90.

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