Beam end joint construction

Abstract

The more rational structure, which also takes construction into consideration, stably transmits bending moments between the beam web and the structure. [Solution] A beam end joint structure is provided, comprising a support member, an H-shaped beam including a pair of flanges and a web, the pair of flanges being welded to the support member, and a shear plate protruding from the side of the support member intersecting the H-shaped beam in the direction of the material axis and superimposed on the web, wherein the shear strength per row of the joint between the web and the upper and lower regions of the shear plate divided into three equal parts vertically is three times or more the shear strength per row of the joint between the central region and the web.

Description

[Technical Field]

[0001] This invention relates to a beam end joint structure. [Background technology]

[0002] As a beam end joint structure for joining an H-section beam to a support member such as a steel column, the bracket type and the field-mixed type, as described as prior art in Patent Document 1, are commonly used. In the bracket type, a bracket having the same cross-sectional shape as the beam is welded to the steel column at the factory, and the bracket and beam are friction-jointed with high-strength bolts at site. In the field-mixed type, a shear plate (also called a gusset plate) is welded to the side of the steel column at the factory, the beam flange is welded to the steel column at site, and the beam web is friction-jointed with high-strength bolts to the shear plate. Comparing the bracket type and the field-mixed type, the field-mixed type is easier to handle because there is no bracket that protrudes significantly from the steel column, but it is more prone to premature fracture of the beam flange due to repeated bending deformation compared to the bracket type. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-20329 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Figure 12 shows an example of a conventional mixed-type beam end joint structure. For example, as shown in the “Design Guidelines for Steel Structure Joints, Revised 4th Edition” (Architectural Institute of Japan, February 2021), when a hollow cross-section steel column undergoes out-of-plane deformation, the bending moment is not transmitted near the neutral axis C of the beam joined to the steel column. Therefore, the bolts close to the neutral axis C bear the helical force S, while the bolts near the upper and lower edges of the beam bear the bending stresses B1 and B2. Here, the bending moment M of the entire beam is equal to the bending moment M borne by the flange. fand the bending moment M borne by the web w Because it is a combination of these, if the bolts near the upper and lower edges of the beam cannot bear sufficient bending stresses B1 and B2, the bending moment M will be borne by the flange. f If this becomes excessive, it could lead to fracture.

[0005] On the other hand, Figure 13 shows the bending moment M borne by the beam web relative to the deformation amount in a mixed-type beam end joint structure and a beam end joint structure in which both the beam flange and beam web are welded to the steel column, as in the bracket type described above. w This is a schematic graph comparing the two. In the case of beam web welding, the bending moment M1 increases monotonically with respect to the deformation δ and reaches its maximum value. On the other hand, in the case of the field mixed type, the bending moment M2 increases initially, stagnates in the range α of the deformation δ, then increases again and reaches its maximum value in the range β of the deformation δ. Range α is the range in which slippage occurs in the high-strength bolt friction joint and sufficient frictional force is no longer acting, and range β is the range in which the bending moment is transmitted solely by the bearing pressure of the bolts rather than frictional force.

[0006] From the facts shown in Figures 12 and 13 above, for example, if repeated bending deformation occurs within the range α of the deformation amount δ, the bending moment M borne by the beam web in the field mixed type is w Because it is small, the bending moment M borne by the beam flange f It can be seen that the relative size increases, which may lead to premature fracture of the beam flange. In the above-mentioned Patent Document 1, in a field mixed type, both the upper and lower edges of the shear plate are field-welded to the beam web, and the bending moment M in the range α shown in Figure 13 w This problem is solved by preventing stagnation. However, welding work, especially at the lower edge of the shear plate, is difficult because it is performed in an upward position. Also, in order to reduce the amount of welding work, it is sometimes desirable to minimize welding other than on the beam flange.

[0007] Therefore, the present invention aims to provide a beam end joint structure that can stably transmit bending moments between the beam web and the beam end in a more rational structure that also takes construction into consideration. [Means for solving the problem]

[0008] [1] A beam end joint structure comprising a support member, an H-shaped beam including a pair of flanges and a web, the pair of flanges being welded to the support member, and a shear plate protruding from the side of the support member intersecting the H-shaped beam in the direction of the material axis and superimposed on the web, wherein the shear strength per row of the joint between the upper region and the lower region of the region obtained by dividing the shear plate into three equal parts vertically is three times or more the shear strength per row of the joint between the central region and the web. [2] The beam end joint structure according to [1], wherein the shear plate is joined to the web with high-strength bolts, and at least one of the number of rows of high-strength bolts arranged in the upper region and the number of rows of high-strength bolts arranged in the lower region is three times or more the number of rows of high-strength bolts arranged in the central region. [3] The beam end joint structure according to [2], wherein the shear plate has a notch at the end opposite to the support member such that the central region is concave compared to the upper region and the lower region. [4] The beam end joint structure according to [1], wherein the shear plate is welded to the web in at least one of the upper or lower regions and bolted to the web in the central region. [5] The beam end joint structure according to [4], wherein the shear plate has a notch in at least one of the upper region or the lower region such that the end opposite to the support member is concave, and at least one of the upper region or the lower region is welded to the web at the lower edge of the notch. [6] The beam end joint structure according to any one of [1] to [5], wherein the support member includes a steel column and a diaphragm interposed in the middle of the steel column, the pair of flanges are each welded to the diaphragm, and the shear plate protrudes from the side of the steel column. [Effects of the Invention]

[0009] According to the above configuration, the shear strength of the joints between the upper and lower regions of the shear plate and the beam web is designed to be at least three times the shear strength of the joint between the central region and the beam web. As a result, the joints near both the upper and lower edges of the shear plate, which mainly bear bending stress, have sufficient shear strength, and even if the amount of deformation increases, slippage does not occur between the shear plate and the beam web, allowing for stable transmission of bending moments. The method of joining the shear plate and the beam web is not limited; for example, it may be a high-strength bolt joint, or it may be a welded joint that can be worked on in a downward position, which is relatively easy to construct. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a beam end joint structure according to the first embodiment of the present invention. [Figure 2] This figure shows a beam end joint structure according to a second embodiment of the present invention. [Figure 3] This figure shows a beam end joint structure according to a third embodiment of the present invention. [Figure 4] Figures 2 and 3 show examples of how to cut the shear plate from a steel sheet. [Figure 5] This figure shows a beam end joint structure according to a fourth embodiment of the present invention. [Figure 6] This figure shows a beam end joint structure according to a fifth embodiment of the present invention. [Figure 7] This figure shows a beam end joint structure according to the sixth embodiment of the present invention. [Figure 8] This figure shows a design example for verifying the effects of the embodiments of the present invention. [Figure 9]This is a diagram showing a design example for verifying the effects of the embodiments of the present invention. [Figure 10] This is a diagram showing a design example for verifying the effects of the embodiments of the present invention. [Figure 11] This is a diagram showing a design example for verifying the effects of the embodiments of the present invention. [Figure 12] This is a diagram showing an example of a conventional beam-end joint structure in the field mixing type. [Figure 13] This is a schematic graph comparing the bending moment borne by the beam web with respect to the deformation amount in the beam-end joint structure.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0012] FIG. 1 is a diagram showing a beam-end joint structure according to the first embodiment of the present invention. The beam-end joint structure 1 includes an H-shaped cross-section beam 2, steel columns 3 and diaphragms 31, 32 constituting the support members, and a shear plate 34. The diaphragms 31, 32 are inserted into the middle part of the steel column 3 and welded to the steel column 3. The H-shaped cross-section beam 2 includes a pair of flanges, namely an upper flange 21 and a lower flange 22 and a web 23. The upper flange 21 and the lower flange 22 are field-welded to the diaphragms 31, 32 by welding parts 41, 42, respectively. The shear plate 34 projects from the side surface of the steel column 3 and is overlapped with the web 23 of the H-shaped cross-section beam 2. The shear plate 34 is pre-joined to the steel column 3 by welding or the like, and a high-strength bolt friction joint is formed between the shear plate 34 and the web 23 using high-strength bolts 51, 52, 53.

[0013] In the beam end joint structure 1 described above, the number of rows of high-strength bolts 51 (3 rows) in the upper region R1 and the number of rows of high-strength bolts 53 (3 rows) in the lower region R3 are three times the number of rows of high-strength bolts 52 (1 row) in the central region R2. The number of high-strength bolts 51 and 53 in the upper and lower regions R1 and R3 may be greater. As a result, in this embodiment, the shear strength per row n2 × qbu of the joint between each of the upper and lower regions R1 and R3 and the web 23 of the H-shaped beam 2 is three times or more the shear strength per row of the joint between the central region R2 and the web 23. Here, the shear strength per row refers to the shear strength in the region of one row, where the high-strength bolts arranged in the direction of the material axis of the H-shaped beam 2 are considered as one row. As a result, the bolted joints near the upper and lower edges of the shear plate 34, which primarily bear the bending stress, have sufficient shear strength, and even if the amount of deformation increases, slippage does not occur between the shear plate 34 and the web 23, allowing for stable transmission of the bending moment. Here, qbu represents the maximum shear strength per bolt calculated according to the steel structure joint design guidelines, and n2 represents the number of bolt rows in the central region R2.

[0014] As a non-limiting example, in this embodiment, it is desirable that the maximum bending strength Σwqs × y, due to the maximum shear strength Σwqs at the joints in the upper and lower regions of the shear plate, exceeds the maximum bending strength jMwu / 2 of the beam web joint multiplied by the safety factor βn. Here, y is the distance between the centroid of the web bolt group, web weld group, or both, in the upper and lower regions of the shear plate and the neutral axis at the beam end.

[0015] Figure 2 shows a beam end joint structure according to a second embodiment of the present invention. The beam end joint structure 1 in the example of Figure 2 has the same configuration as the example of Figure 1, except for the shear plate 34A. The shear plate 34A has a notch at the end opposite to the steel column 3, which is the supporting member, such that the central region R2 is concave compared to the upper region R1 and the lower region R3. As already mentioned, in this embodiment, the number of high-strength bolts 51 and 53 arranged in the upper and lower regions R1 and R3 is three times or more the number of high-strength bolts 52 arranged in the central region R2. Therefore, the space for arranging the high-strength bolts 52 in the central region R2 can be smaller than that in the upper and lower regions R1 and R3, so the weight of the steel can be reduced by forming a concave notch as in the example of Figure 2.

[0016] Figure 3 shows a beam end joint structure according to a third embodiment of the present invention. The beam end joint structure 1 in the example of Figure 3 has welds 61 and 62 added to the example of Figure 2. Both welds 61 and 62 are fillet welds formed between the end face of the shear plate 34A and the face of the web 23. Weld 61 is formed on the upper edge of the shear plate 34A, and weld 62 is formed on the lower edge of the concave notch formed in the shear plate 34A. Since both of these edges are upward-facing edges along the material axis direction of the H-shaped beam 2, welding can be performed in a downward position, and welding is relatively easy. Thus, the shear plate 34 and the web 23 do not necessarily have to be joined only by high-strength bolt friction joints, and welds may be formed in parts that are easy to work with, as in the example of Figure 3.

[0017] Figure 4 shows an example of how to cut out the shear plates from the steel sheet in the examples shown in Figures 2 and 3. In the above examples, the shear plate 34A having a concave notch can be cut out from the steel sheet PL such that the concave portion and the convex portions on both sides are combined, as shown in Figure 4, for example. This improves the yield when cutting out a large number of shear plates 34A from the steel sheet. When using this cutting method, a processing allowance is required between the concave portion and the convex portion, so the concave portion becomes slightly wider and extends into the upper and lower regions R1 and R3. However, as long as the space required for the installation of the high-strength bolts 51 and 53 is secured, there is no problem even if the concave portion extends into the upper and lower regions R1 and R3.

[0018] Figure 5 shows a beam end joint structure according to a fourth embodiment of the present invention. The beam end joint structure 1 in the example of Figure 5 includes an H-shaped beam 2, a steel column 3, and diaphragms 31, 32, and a shear plate 34B, similar to the example in Figure 1. The shear plate 34B is joined to the web 23 of the H-shaped beam 2 by welds 61, 62, 63, 64 and bolts 54. The welds 63, 64 are also fillet welds formed between the end face of the shear plate 34B and the face of the web 23. Of the three equally divided regions R1, R2, and R3, the upper region R1 is joined to the web 23 by welds 61, 63, and the lower region R3 is joined to the web 23 by welds 62, 64. The shear plate 34B has a plurality of notches such that the end opposite to the steel column 3, which is a supporting member, is concave, and the welds 62, 63, 64 are formed on the lower edges of these notches. Together with the weld 61 formed on the upper edge of the shear plate 34B, welds 61, 62, 63, and 64 are all formed on the upward-facing edges along the material axis of the H-shaped beam 2, so welding can be performed in a downward position, making welding relatively easy. On the other hand, no weld is formed in the central region R2, which is joined to the web 23 with bolts 54. The joint with bolts 54 only needs to be able to withstand the shear force, so it does not necessarily have to be a high-strength bolt friction joint. As a result, even in the example in Figure 5, the shear strength of the joints between the upper and lower regions R1 and R3 of the shear plate 34B and the web 23 of the H-shaped beam 2 is more than three times the shear strength of the joint between the central region R2 and the web 23.

[0019] Figure 6 shows a beam end joint structure according to a fifth embodiment of the present invention. In the example of Figure 6, the beam end joint structure 1 is the same as in the example of Figure 5 for the upper region R1 of the three regions R1, R2, and R3 obtained by dividing the shear plate 34C vertically into three equal parts, and the central and lower regions R2 and R3 are the same as in the example of Figure 1. That is, a concave notch is formed in the shear plate 34C in the upper region R1, and a welded portion 63 is formed on the lower edge of this notch. The upper region R1 is joined to the web 23 by welded portions 61 and 63 formed on the upper edge of the shear plate 34C. On the other hand, the central and lower regions R2 and R3 are friction-jointed to the web 23 by high-strength bolts 52 and 53, respectively, and the number of high-strength bolts 53 arranged in the lower region R3 is three times or more the number of high-strength bolts 52 arranged in the central region R2. As a result, even in the example in Figure 6, the shear strength per row of the joint between the upper and lower regions R1 and R3 of the shear plate 34B and the web 23 of the H-shaped beam 2 is more than three times the shear strength per row of the joint between the central region R2 and the web 23. The shear strength wqi per row of the weld 63 is calculated as a × le, which is the value obtained by multiplying the throat thickness a of the fillet weld by the weld length le.

[0020] Figure 7 shows a beam end joint structure according to the sixth embodiment of the present invention. In the example of Figure 7, the beam end joint structure 1 has welds 61, 63, and 64 formed between the shear plate 34E and the web 23, similar to the example of Figure 5, while the lower region R3 is also joined to the web 23 by a weld 66 formed on the lower edge of the shear plate 34E. The weld 66 is also a fillet weld formed between the end face of the shear plate 34E and the face of the web 23. Since the upper region R1 of the shear plate 34E is joined to the web 23 by welds 61 and 63, and the lower region R3 is joined to the web 23 by welds 64 and 66, the shear strength of the joints between the upper and lower regions R1 and R3 and the web 23 of the H-shaped beam 2 is three times or more the shear strength of the joint between the central region R2 and the web 23 by bolts 54. As already mentioned, the welding of the welded joint 66 formed on the lower edge of the shear plate 34E is performed in an upward position, but this is not necessarily excluded as an embodiment of the present invention if it is possible under the construction conditions.

[0021] Figures 8 to 11 show design examples for verifying the effects of embodiments of the present invention. The units of measurement in the drawings are mm. According to Tetsuya Yamada, Dong-Seok Lee, Shoichi Yoshiki, Takanori Ishida, and Norihito Miki, "Small Amplitude Repeated Loading Experiment of Field-Use Mixed-Type Beam End Joints with Bolt Arrangement as a Parameter" (Journal of Structural Engineering, Architectural Institute of Japan, Vol. 81, No. 727, pp. 1541-1551, 2016.9), when the sliding strength jMy1 of a high-strength bolt friction joint in the web is greater than or equal to the yield strength sMy of the entire cross-section of the shear plate, the repeated deformation performance is said to be comparable to that of a welded joint. Therefore, in the design examples, the sliding strength of the high-strength bolt friction joint exceeding the yield strength of the entire cross-section of the shear plate is used as an indicator of bending moment transmission performance. Each design example is designed under the following conditions. Assuming that a moment 1.2 times the full plastic bending moment Mp acts on the beam end joint during an earthquake, the shear force bearing bolts are designed to withstand the shear force at the time of the full plastic bending moment, specifically a shear force of 1.2 Mp / lb, which is the acting moment of 1.2 Mp divided by the shear span length lb. · Assume that the steel column is sufficiently rigid and set the dimensionless flexural strength ratio m of the beam web to 1. · Set the sliding coefficient μ to 0.45. · As the shape of the H-shaped cross-section beam, do not consider the fillet part between the flange and the web. · Assume that there is a cross-sectional defect with a height of 35 mm at both the upper and lower ends of the beam web due to the scallop formed for flange welding. · Calculate the shear strength jMwy1 in accordance with the "Design Guide for Steel Structure Joints, Revised 4th Edition" (Architectural Institute of Japan, February 2021).

[0022] In Design Example 1 shown in Fig. 8 and Design Example 2 shown in Fig. 9, the cross-section of the H-shaped cross-section beam is H-500×200×10×16 (beam height × flange width × web plate thickness × flange plate thickness. The same applies hereinafter), the shear span length lb = 2500 mm, and the steel type is SN490B (yield strength σ y = 325 N / mm 2 ). The shear plate has a thickness of 12 mm and the steel type is SN490B (yield strength σ y = 325 N / mm 2In this case, the total cross-sectional yield strength of the shear plate is 88 kNm. In design example 1 shown in Figure 8, the number of rows of high-strength bolts arranged in the upper region of the shear plate (2 rows) and the number of rows of high-strength bolts arranged in the lower region (2 rows) is less than three times the number of rows of high-strength bolts arranged in the central region (1 row), and therefore does not satisfy the requirements of the embodiment of the present invention described above. In this case, the sliding strength jMy1 of the high-strength bolt friction joint is 55 kNm, which is below the yield strength of the shear plate. In contrast, in design example 2 shown in Figure 9, the number of rows of high-strength bolts arranged in the upper region of the shear plate (3 rows) and the number of rows of high-strength bolts arranged in the lower region (3 rows) is three times the number of rows of high-strength bolts arranged in the central region (1 row), and therefore satisfies the requirements of the embodiment of the present invention described above. In this case, the sliding strength of the high-strength bolt friction joint is 93 kNm, which exceeds the yield strength of the shear plate. These results show that, in design examples 1 and 2, by designing the shear strength of the joints between the upper and lower regions of the shear plate and the beam web to be at least three times the shear strength of the joint between the central region and the beam web, the bending moment can be stably transmitted between the shear plate and the beam web.

[0023] In design example 3 shown in Figure 10 and design example 4 shown in Figure 11, the cross-section of the H-shaped beam is H-700×200×16×32, the shear span length is lb=3500mm, and the steel type is SN490B (yield strength σ y = 325 N / mm 2 The shear plate is 16mm thick and made of SN490B steel (yield strength σ). y = 325 N / mm 2In this case, the total cross-sectional yield strength of the shear plate is 278 kNm. In design example 3 shown in Figure 10, the number of rows of high-strength bolts arranged in the upper region of the shear plate (2 rows) and the number of rows of high-strength bolts arranged in the lower region (2 rows) is less than three times the number of rows of high-strength bolts arranged in the central region (1 row), and therefore does not satisfy the requirements of the embodiment of the present invention described above. In this case, the sliding strength jMy1 of the high-strength bolt friction joint is 144 kNm, which is below the yield strength of the shear plate. In contrast, in design example 2 shown in Figure 11, the number of rows of high-strength bolts arranged in the upper region of the shear plate (4 rows) and the number of rows of high-strength bolts arranged in the lower region (4 rows) is four times the number of rows of high-strength bolts arranged in the central region (1 row), and therefore satisfies the requirements of the embodiment of the present invention described above. In this case, the sliding strength of the high-strength bolt friction joint is 282 kNm, which exceeds the yield strength of the shear plate. These results show that, in design examples 3 and 4, the bending moment can be stably transmitted between the shear plate and the beam web by designing the joints between the upper and lower regions of the shear plate and the beam web so that the shear strength of the joints between the central region and the beam web is at least three times that of the joints between the central region and the beam web. [Explanation of Symbols]

[0024] 1...Beam end joint structure, 2...H-shaped section beam, 3...Steel column, 21...Upper flange, 22...Lower flange, 23...Web, 31,32...Diaphragm, 34,34A,34B,34C,34D,34E...Shear plate, 41,42...Welded joint, 51,52,53...High-strength bolt, 54...Bolt, 61,62,63,64,65,66...Welded joint.

Claims

1. Support member and An H-shaped cross-section beam including a pair of flanges and a web, wherein the pair of flanges are each welded to the support member, A shear plate that protrudes from the side of the support member intersecting the material axis direction of the H-shaped cross-section beam and is superimposed on the web and A beam end joint structure including, A beam end joint structure in which, of the regions obtained by dividing the shear plate vertically into three equal parts, the shear strength per row of the joint between the upper region and the lower region and the web is three times or more the shear strength per row of the joint between the central region and the web.

2. The shear plate is bolted to the web with high-strength bolts. The beam end joint structure according to claim 1, wherein at least one of the number of rows of high-strength bolts arranged in the upper region and the number of rows of high-strength bolts arranged in the lower region is three times or more the number of rows of high-strength bolts arranged in the central region.

3. The beam end joint structure according to claim 2, wherein the shear plate has a notch such that the end opposite to the support member is concave in the central region compared to the upper region and the lower region.

4. The beam end joint structure according to claim 1, wherein the shear plate is welded to the web in at least one of the upper or lower regions and bolted to the web in the central region.

5. The shear plate has a notch in at least one of the upper or lower regions such that the end opposite to the support member is concave. The beam end joint structure according to claim 4, wherein at least one of the upper region or the lower region is welded to the web at the lower edge of the notch.

6. The support member includes a steel column and a diaphragm interposed in the middle of the steel column. The pair of flanges are each welded to the diaphragm. The beam end joint structure according to any one of claims 1 to 5, wherein the shear plate protrudes from the side surface of the steel column.

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