Joint structure and joint structure design method

Abstract

To effectively prevent local buckling of a web in pin joints using assembled H-beams.SOLUTION: There is provided a joint structure for joining an axial end of an assembled H-beam, of which the upper and lower flanges are welded to the web, to a member to be joined, in which the web is friction-bonded to the member to be joined with high-strength bolts, and distance d from the top surface of the upper flange to the center of the nearest bolt in the high-strength bolt friction-bonding, distance w from the axial end of the assembled H-beam to the furthest bolt center in the high-strength bolt friction-bonding, and distance H from the top surface of the top flange to the bottom surface of the bottom flange satisfy a relationship d / H-0.19w / H≤0.20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a joining structure and a design method thereof, and more particularly to a joining structure in which an axial end portion of a fabricated H-beam is pin-joined to a member to be joined, and a design method thereof. [Background technology]

[0002] A known structure is a so-called pin joint, in which the web of an H-shaped steel beam constituting a sub-girder is bolted to a joint member such as a shear plate attached to a main girder or a column, without the flange being joined. For example, Patent Document 1 describes a beam joint structure in which the weld where the shear plate is welded to the flange and web of the main girder is separated into an upper weld and a lower weld. Patent Document 2 describes a technology in which each plate portion of a gusset metal fitting, which has plate portions that fit along the web of the main girder and the web of the sub-girder, is bolted to the web of the main girder and the web of the sub-girder, and further a support plate portion is provided on the gusset metal fitting that fits along the underside of the bottom flange of the sub-girder, and the support plate portion is bolted to the bottom flange of the sub-girder and a horizontal floor brace.

[0003] In the above-described joint structure, rolled H-beams formed as a single unit by rolling are generally used as the H-beams that form the sub-beams, but assembled H-beams in which the steel plates that form the flanges and webs are welded together are also known. Patent Document 3 describes a technique in which tack welding or fillet welding in assembled H-beams is performed to a position slightly away from the axial end of the material, and the tip of the groove formed in the flange is processed so that it is approximately the length of the fillet weld in the web, and when joining this assembled H-beam to the members to be joined, the grooved flanges on both sides of the web of the assembled H-beam are welded to the members to be joined, and then the members to be joined and the web are fillet welded to form a so-called rigid joint. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-104960 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-200273 [Patent Document 3] Japanese Patent Application Publication No. 06-126444 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of ordinary H-sections, i.e., rolled H-sections, the flange and web thickness cannot always be optimized for conditions such as stress due to the constraint of being rolled as a single unit. On the other hand, in assembled H-sections, the flange and web are formed separately and then welded together, making it easier to optimize the plate thickness. Therefore, in assembled H-sections, the flange and web plate thickness is often thinner than in rolled H-sections. While reducing the plate thickness is a major advantage as it reduces steel weight, it also makes local buckling more likely to occur, so care must be taken when designing joints, for example.

[0006] As described in Patent Documents 1 and 2, the configuration of a pin joint using a general H-section steel, i.e., a rolled H-section steel, is known. Furthermore, as described in Patent Document 3, the configuration of a rigid joint using a fabricated H-section steel is also known. However, little is known about the configuration and design method of a pin joint using a fabricated H-section steel. For example, considering the thin web thickness of fabricated H-section steel as described above, the configuration of a joint that takes into account the prevention of local buckling is also unknown.

[0007] Therefore, an object of the present invention is to provide a joint structure and a design method thereof that can effectively prevent local buckling of the web in pin joints using assembled H-shaped steel beams. [Means for solving the problem]

[0008] [1] A joining structure in which the axial end of an assembled H-shaped steel beam, in which the upper flange and the lower flange are welded to the web, are joined to a joined member, wherein the web is friction-joined to the joined member with high-strength bolts, and the distance d from the upper surface of the upper flange to the bolt center of the closest high-strength bolt friction joint, the distance w from the axial end of the assembled H-shaped steel beam to the bolt center of the farthest high-strength bolt friction joint, and the distance H from the upper surface of the upper flange to the underside of the lower flange satisfy the relationship d / H-0.19w / H≦0.20. [2] A joining structure in which the axial end of an assembled H-shaped steel beam, in which the upper flange and the lower flange are welded to the web, is joined to a joined member, and the web is joined by a high-strength bolt friction joint. The distance d from the upper surface of the upper flange to the center of the nearest bolt of the high-strength bolt friction joint, the distance H from the upper surface of the upper flange to the lower surface of the lower flange, and the cross-sectional area Aw (mm) of the web are d / H≦-2.35×10 -5 The joint structure according to claim 1, wherein the relationship of Aw+0.29 or d / H≦0.13 is satisfied. [3] A design method for a joining structure in which the axial end of an assembled H-shaped steel beam, in which the upper flange and the lower flange are welded to the web, are joined to a member to be joined, wherein the web is friction-joined to the member to be joined with high-strength bolts, and the distance d from the upper surface of the upper flange to the bolt center of the closest high-strength bolt friction joint, the distance w from the axial end of the assembled H-shaped steel beam to the bolt center of the farthest high-strength bolt friction joint, and the distance H from the upper surface of the upper flange to the underside of the lower flange are expressed by the conditional equation d / H+αw / H≦β, and at least one of the distances d and w is optimized by setting the values ​​of the coefficient α and the constant β. [4] The method for designing a joint structure according to [3], wherein α=-0.19. [Effects of the Invention]

[0009] According to the above configuration, in a pin joint using a prefabricated H-shaped steel beam, the distance d between the upper flange and the bolt closest to the prefabricated H-shaped steel beam constituting the sub-beam is set to a predetermined range or less relative to the beam depth H, and further, by taking into consideration the distance from the axial end of the prefabricated H-shaped steel beam to the farthest bolt, local buckling of the web can be effectively prevented. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams illustrating an example of a joining structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view showing dimensions of the joint structure shown in FIG. [Figure 3] FIG. 10 is a diagram for explaining the conditions of an experiment and analysis for verifying local buckling of a web at a pin joint using assembled H-shaped steel. [Figure 4] 4 is a photograph showing the results of a four-point bending test carried out under the conditions shown in FIG. 3. [Figure 5] 10 is a graph showing the relationship between the maximum strength and the index d / H in the analysis results. [Figure 6] 10 is a graph showing the relationship between the maximum strength and the index d / H in the analysis results. [Figure 7] 10 is a graph showing the relationship between the maximum strength and the index d / H in the analysis results. [Figure 8] 10 is a graph showing the relationship between the maximum strength and the index d / H in the analysis results. [Figure 9] 10 is a graph showing the relationship between the maximum strength and the index w / H in the analysis results. [Figure 10] 10 is a graph showing the change in the correlation coefficient between the index d / H+αw / H and the maximum strength in the analysis results depending on the value of the coefficient α. [Figure 11] 10 is a graph showing the relationship between the maximum strength and the index d / H+αw / H in the analysis results. [Figure 12] 1 is a graph showing the value of the index d / H for each web cross-sectional area in the design standards for beam-joint structures using conventional rolled H-section steel. DETAILED DESCRIPTION OF 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 drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0012] FIG. 1 is a diagram showing an example of a joint structure according to one embodiment of the present invention. In the example of the joint structure shown in the figure, the axial end of a sub-beam 1, which is a prefabricated H-shaped steel beam, is joined to a main girder 2 via a shear plate 31. The sub-beam 1 includes an upper flange 11, a lower flange 12, and a web 13, and the upper flange 11 and the web 13, and the lower flange 12 and the web 13, are welded by fillet welds, respectively. The shear plate 31 is welded to the upper flange 21, the lower flange 22, and the web 23 of the main girder 2, respectively. In this embodiment, the main girder 2 and the shear plate 31 constitute joined members. The web 13 of the sub-beam 1 is friction-joined to the shear plate 31 using bolts 32 with high-strength bolts. This forms a pin joint between the sub-beam 1 and the main girder 2.

[0013] Figure 2 is an enlarged view showing the dimensions of the joint structure shown in Figure 1. Figure 2 shows the sub-joint 1 and shear plate 31, which are components of the joint structure shown in Figure 1. Below, we will consider the conditions for effectively preventing local buckling of the web 13 of the sub-joint 1 at the pin joint, using the distance d from the top surface of the upper flange 11 of the sub-joint 1 to the nearest bolt 32, the distance w from the axial end of the sub-joint 1 to the farthest bolt 32, and the beam depth of the sub-joint 1, i.e., the distance H from the top surface of the upper flange 11 to the bottom surface of the lower flange 12. Figure 2 also shows the spacing pn between bolts 32 in vertically arranged bolt rows, and the spacing pm between bolt rows in the axial direction of the sub-joint 1 when there are two or more bolt rows.

[0014] Figure 3 illustrates the experimental and analytical conditions for verifying local buckling of the web at pin joints using prefabricated H-section steel beams. In the experiment, a prefabricated H-section steel beam with a length of 7000 mm, beam depth H = 700 mm, flange width of 175 mm, web thickness of 4.5 mm, and flange thickness of 9 mm was used. A four-point bending test was conducted using pin joints at both ends of the beam in the axial direction, as shown in Figure 2. Figure 3 shows the beam from one end of the beam in the axial direction to its center. The area from the center to the opposite end of the beam in the axial direction is symmetrical to the illustrated area. Since loading point P is located at 1 / 4 of the beam length, for a beam length of 7000 mm, the shear span L is 1750 mm. At loading point P, the out-of-plane displacement of the web was restrained, and the pin joint was fixed in all directions and rotation on the shear plate side. The shear plate thickness was 9 mm.

[0015] Figure 4 is a photograph showing the results of a four-point bending test conducted under the conditions shown in Figure 3. In the experiment, a row of F10T-M20 high-strength bolts was placed with d = 110 mm, w = 40 mm, and pn = 120 mm as shown in Figure 2, and a standard bolt tension (182 kN) was applied. As a result, local buckling (shear buckling) occurred in the web near the pin joint at the end of the beam in the axial direction. As shown in the photograph, shear buckling of the web occurred in a diagonal direction, starting from the point between the top end of the shear plate and the top flange.

[0016] Table 1 shows the parameters and results of the analysis conducted under the conditions shown in Figure 3. In the analysis, the maximum strength of the pinned joint was calculated using the bolt arrangement in the pinned joint and the shape of the shear plate determined by the bolt arrangement as parameters. The friction coefficient for high-strength bolt friction joints was set to 0.45. In addition to the dimensions shown in Figures 2 and 3 above, in Table 1, the number of bolts, n, is the number of bolts arranged in the vertical direction, and m is the number of bolt rows arranged in the axial direction. When m=1, the bolt row spacing, pm, is set to 0. In the analysis results, max is the maximum load, and max / Pcr is the maximum load, max, normalized by the elastic buckling load, Pcr, of the web plate element. The indices d / H, w / H, and d / H+αw / H will be discussed later.

[0017] [Table 1]

[0018] Figures 5 to 8 are graphs showing the relationship between max / Pcr (the maximum load normalized by the elastic buckling load of the web plate element; hereafter also referred to as maximum strength) and the index d / H in the analysis results. As mentioned above, distance d is the distance from the top surface of the upper flange of the sub-beam to the nearest bolt, and beam depth H is the distance from the top surface of the upper flange to the bottom surface of the lower flange.

[0019] Figure 5 shows the case where the beam depth H is 700 mm, the flange width is 175 mm, the web thickness is 4.5 mm, the flange thickness is 9 mm, and the shear span L is 1750 mm (same conditions as the experiment). Case 1 (6 bolts x 1 row, No. 1-1 to 1-6), Case 2 (3 bolts x 2 rows, pm = 60 mm, No. 2-1 to 2-6), Case 3 (3 bolts x 2 rows, pm = 120 mm, No. 3-1 to 3-6), and Case 4 (3 bolts x 2 rows, pm = 240 mm, No. 4-1 to 4-6) In all cases, the bolt spacing pn in the vertically arranged bolt rows differs for No. x-1 to x-6 (or No. x-1 to x-4), and the distance d also differs accordingly. The bolts in each row are also arranged symmetrically in the vertical direction around the neutral axis of the sub-beam.

[0020] Figure 6 shows Case 5 (6 bolts x 1 row, No. 5-1 to 5-4), which has the same cross section of the sub-beam as Cases 1 to 4 and a shear span L = 875 mm.

[0021] Figure 7 shows the case with a beam depth of 500 mm, a flange width of 125 mm, a web thickness of 4.5 mm, a flange thickness of 6 mm, and four bolts in one row. Case 6 (shear span L = 1750 mm, No. 6-1 to 6-4), and Case 7 (shear span L = 875 mm, No. 7-1 to 7-4) is shown.

[0022] Figure 8 shows Case 8 (No. 8-1 to 8-4) with a beam depth H = 350 mm, flange width 100 mm, web plate thickness 3.2 mm, flange plate thickness 6 mm, shear span L = 1750 mm, and 3 bolts x 1 row.

[0023] In each case shown in Figures 5 to 8, the smaller the value of the index d / H, the greater the maximum strength. In other words, a negative correlation is observed between the index d / H and the maximum strength. This is thought to be due to the large contribution of local buckling of the web between the bolt closest to the top flange and the top flange as a determining factor of the maximum strength. Note that the maximum strength max / Pcr in each case is a value normalized by the elastic buckling load Pcr of the web plate element, and Pcr changes depending on the beam depth H and shear span L, so the slope of the approximate line in the graph does not necessarily indicate the strength of the effect of the index d / H on the maximum strength.

[0024] Figure 9 is a graph showing the relationship between max / Pcr (maximum strength) and the index w / H in the analysis results. As mentioned above, distance w is the distance from the axial end of the sub-beam to the farthest bolt, and beam depth H is the distance from the top surface of the upper flange to the bottom surface of the lower flange. Specifically, Figure 9 shows the relationship between maximum strength and index w / H for the above Cases 1 to 4 (beam depth H = 700 mm, flange width 175 mm, web thickness 4.5 mm, flange thickness 9 mm, shear span L = 1750 mm, number of bolt rows m or bolt row spacing pm is different) and the case where d = 100 mm (Nos. 1-5, 2-5, 3-5, and 4-5; since beam depth H is the same, index d / H is also the same value).

[0025] In each case shown in Figure 9, the larger the value of the index w / H, the greater the ultimate strength. In other words, a positive correlation is observed between the index w / H and the ultimate strength. Here, in each case shown in the graphs of Figures 5 and 9, the elastic buckling load Pcr of the web plate element is the same for each example, and the ultimate strength is normalized using the same standard. Therefore, the slope of the approximation line in the graphs of Figures 5 and 9 indicates that the influence of the index w / H on the ultimate strength is smaller than that of the index d / H.

[0026] From the above results, the inventors came up with the idea of ​​expressing the conditions for effectively preventing local buckling of the web in pin joints using assembled H-shaped steel beams as an index d / H+αw / H, which combines the above indexes d / H and w / H. Here, the coefficient α is the ratio of the effect of the index w / H on the ultimate strength when the effect of the index d / H is set to 1. As shown in the graphs of Figures 5 to 9, there is a negative correlation between the index d / H and the ultimate strength, and a positive correlation between the index w / H and the ultimate strength, so -1<α<0.

[0027] Figure 10 shows the correlation coefficient between the index d / H + αw / H and the maximum strength max / Pcr in the analysis results, as a function of the coefficient α. For Cases 1 to 4, in which the maximum strength max / Pcr was normalized using the same standard, the correlation coefficient between the index d / H + αw / H and the maximum strength max / Pcr in the analysis results was calculated while varying the coefficient α. As mentioned above, the more influential index d / H has a negative correlation with the maximum strength, so the correlation coefficient for the index d / H + αw / H combined with the index w / H is also negative. The calculation results showed that the correlation coefficient was minimized when the coefficient α was -0.19. Therefore, within the scope of the above analysis, the index d / H - 0.19w / H is considered to be the index that best represents the negative correlation between the pin joint dimensions and the maximum strength.

[0028] Figure 11 is a graph showing the relationship between max / Pcr (maximum strength) and the index d / H + αw / H in the analysis results. Based on the results of the study in Figure 10, α was set to -0.19. As shown in Figures 6 to 9, a correlation between the index d / H + αw / H and maximum strength is evident not only in Cases 1 to 4, which were used to calculate the coefficient α, but also in Cases 5 to 8. Therefore, the index d / H + αw / H is considered applicable as a condition for effectively preventing local buckling of the web at pin joints, regardless of the specific beam depth H or shear span L.

[0029] In the above example, the value of coefficient α was calculated using the results of Cases 1 to 4, but the value of coefficient α may also be calculated for cases with beam depth H and shear span L different from these cases. In this case, the value of coefficient α may be different from the above example. By calculating the value of coefficient α for a specific beam depth H and shear span L, it is possible to identify with greater accuracy the conditions for effectively preventing local buckling of the web for the same beam depth H and shear span L.

[0030] Figure 12 is a graph showing the value of the index d / H for each web cross-sectional area in the design standards for beam-joint structures using conventional rolled H-section steel. "SCSS-H97 Standard Steel Structure Joints - H-Section Steel Edition" specifies the number of bolts (number of bolts n in the above explanation) and bolt spacing (bolt spacing pn in the above explanation) in beam-joint structures for each cross section of the rolled H-section steel that makes up the sub-beam. The index d / H in the above explanation can be calculated based on these values. Specifically, the distance d is calculated by subtracting 1 / 2 of the bolt spacing x (number of bolts - 1) from 1 / 2 of the beam depth, and the index d / H is calculated by dividing this by the beam depth H.

[0031] Referring to the graph in FIG. 12, in a beam connection structure using conventional rolled H-section steel, the index d / H and the web cross-sectional area Aw are within the ranges expressed by the following two equations. d / H>-2.35×10 -5 Aw+0.29, and d / H>0.13

[0032] As already mentioned, for beam connection structures using prefabricated H-section steel, there is no known design method for the number of bolts and bolt spacing in beam connection structures, so the number of bolts and bolt spacing are generally set in accordance with the design standards for beam connection structures using rolled H-section steel as described above. However, these design standards do not take into account local buckling of the web, which is likely to occur in prefabricated H-section steel. Therefore, when the conditions for effectively preventing local buckling of the web are taken into consideration as described above, if the index d / H is outside the range shown in Figure 12, i.e. d / H≦-2.35×10 -5 Aw+0.29, or d / H≦0.13 In some cases, bolt spacing may be set so that

[0033] As a result of the study described above with reference to Figure 12, the range of the index d / H + αw / H that is not set in the design standards for beam-to-beam joint structures using rolled H-section steel is shown by the dashed line and arrow in Figure 11. Specifically, this range is expressed by the following formula. d / H-0.19w / H≦0.20 Similarly, the ranges of the indicators d / H and w / H, which are not set in the design standards for beam-joint structures using rolled H-section steel, are shown by dashed lines and arrows in Figures 5 to 9.

[0034] As mentioned above, in the example shown in Figure 11, the coefficient α is calculated using the results of Cases 1 to 4. While this coefficient α can be applied to cases where the beam depth H and shear span L are different from those of Cases 1 to 4, calculating the coefficient α using the results of cases where the beam depth H and shear span L of the sub-beams are actually used, for example, allows for more accurate identification of the conditions for effectively preventing local buckling of the web. Furthermore, the value (0.20) on the right side of the above conditional equation does not necessarily need to be determined based on the design criteria for beam-to-beam connections using rolled H-section steel. It can be appropriately set within the range that achieves the maximum strength required for the design. Therefore, the design method for a connection structure according to an embodiment of the present invention can be generalized as a method of optimizing at least one of the distances d and w by appropriately setting the coefficient α (-1 < α < 0) and the constant β in the following conditional equation, and then setting the bolt spacing and bolt row spacing to achieve those distances. d / H+αw / H≦β

[0035] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0036] 1...minor beam, 11...upper flange, 12...lower flange, 13...web, 2...main beam, 21...upper flange, 22...lower flange, 23...web, 31...shear plate, 32...bolt.

Claims

1. A joining structure for joining an axial end portion of an assembled H-shaped steel in which an upper flange and a lower flange are welded to a web, to a joined member, the web is friction-joined to the workpieces by high-strength bolts, A joining structure in which a distance d (d≧70 mm) from the upper surface of the upper flange to the bolt center of the nearest high-strength bolt friction joint, a distance w (w≧40 mm) from the end of the assembled H-shaped steel in the material axis direction to the bolt center of the farthest high-strength bolt friction joint, a distance H from the upper surface of the upper flange to the lower surface of the lower flange, and a cross-sectional area Aw (mm) of the web satisfy the relationship of formula (i) and also satisfy the relationship of formula (ii) or formula (iii). d / H-0.19w / H≦0.20...(i) d / H≦-2.35×10-5 Aw+0.29...(ii) d / H≦0.13...(iii)

2. A method for designing a joining structure for joining an axial end portion of an assembled H-shaped steel beam, in which the upper flange and the lower flange are welded to the web, to a joined member, comprising: the web is friction-joined to the workpieces by high-strength bolts, The distance d (d≧70 mm) from the upper surface of the upper flange to the bolt center of the closest high-strength bolt friction joint, the distance w (w≧40 mm) from the end of the assembled H-shaped steel in the material axis direction to the bolt center of the farthest high-strength bolt friction joint, and the distance H from the upper surface of the upper flange to the lower surface of the lower flange, d / H+αw / H≦β and optimizing at least one of the distance d and the distance w by setting the values ​​of the coefficient α (−1<α<0) and the constant β. The coefficient α is set to -0.19, or the coefficient α that minimizes the correlation coefficient between the index d / H and the maximum strength at a specified beam depth and a specified shear span is used. A design method for a joint structure in which the constant β is set to 0.20 or within a range in which the maximum strength required for the design is exerted.

3. The method for designing a joint structure according to claim 2, wherein α=−0.19 and β=0.20.

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