Joint structure

Abstract

Provided is a joining structure for connecting a large beam having an H-shaped cross section, and an end section in the material axis direction of a small beam having an H-shaped cross section and extending in a direction which intersects the large beam, said joining structure being: provided with at least a gusset plate joined to the upper flange and the web of the large beam, and a bolt row which is arranged in the small beam depth direction and joins the gusset plate to the web of the small beam; and configured in a manner such that the distance from the axial center of the bolt positioned at the bottom end of the bolt row to the lower surface of the lower flange of the small beam is less than 1 / 5 of the beam depth of the small beam.

Description

Technical Field

[0001] The present invention relates to a joining structure.

Background Art

[0002] The joists that support the floors of steel frame structures or composite structures are treated as non-seismic members. Generally, the joist end joints bolt the joist web to a gusset plate (also called a fin plate) provided on the girder, and the upper and lower flanges of the joist are pin joints that are not joined to the girder. When a vertical load acts on the joist supported by such a pin joint, the acting center of the force mainly acting on the joist (the plate thickness center of the joist web) and the acting center of the reaction force from the gusset plate (the plate thickness center of the gusset plate) are eccentric. Therefore, additional bending acts on the joist web and the gusset plate. Generally, since the out-of-plane bending rigidity of the joist web and the gusset plate is small, out-of-plane deformation occurs in the joist web due to the above-mentioned additional bending, and accordingly, the lower flange of the joist is displaced, resulting in a decrease in the transmission efficiency of the compressive force acting on the joist end. Then, sufficient rotational rigidity and load-bearing capacity of the joint cannot be obtained to reduce the deflection of the joist.

[0003] On the other hand, rigid joints that join the upper and lower flanges to the girder by bolting or welding in addition to the joist web, and semi-rigid joints that join only the lower flange as described in Patent Document 1, Patent Document 2, and Patent Document 3 are also known. In these joints, the deflection and moment applied to the central part of the joist are suppressed compared to pin joints. Therefore, it is possible to reduce the cross-sectional area and weight of the joist, and it is being utilized in large-span structures and the like.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] However, in the case of rigid connections as described above, the secondary beam flange is joined on-site to the main beam or a bracket attached to the main beam. This requires processes such as beveling and on-site welding at the flange end in the case of welding, and drilling holes at the flange end, friction surface treatment, and installation of splice plates in the case of bolt connections. Semi-rigid connections also require processes such as welding and installation of contact members. In other words, pin connections are advantageous in terms of reducing the amount of work involved.

[0006] Therefore, the present invention aims to provide a joint structure that ensures rotational rigidity and load-bearing capacity of the joint by suppressing out-of-plane deformation of the beam web without impairing the constructability of the pin joint, and enables miniaturization and weight reduction of the beam cross-section by suppressing deflection and moment acting on the central part of the beam. [Means for solving the problem]

[0007] [1] A joint structure for connecting a main beam having an H-shaped cross-section and the end of a secondary beam having an H-shaped cross-section and extending in a direction intersecting the main beam, comprising a gusset plate joined to at least the web and upper flange of the main beam, and a row of bolts arranged in the beam depth direction of the secondary beam and joining the gusset plate to the web of the secondary beam, wherein the distance from the axis of a bolt located at the lower end of the row of bolts to the lower surface of the lower flange of the secondary beam is less than 1 / 5 of the beam depth of the secondary beam. [2] The joining structure according to [1], further comprising reinforcing ribs that intersect the plate-shaped main body of the gusset plate and also intersect the web of the main beam, and are joined to at least the gusset plate. [3] The joint structure according to [1] or [2], further comprising at least one reinforcing plate positioned below the height centerline of the web of the beam and in contact with the side end face of the gusset plate, wherein the reinforcing plate is bolted to the web of the beam. [4] The reinforcing plate is friction-bonded to the web of the beam with high-strength bolts, as described in [3]. [5] The gusset plate is friction-bonded to the web of the beam with high-strength bolts, according to any one of items [1] to [4]. [6] The joint structure according to any one of [1] to [5], further comprising a concrete floor slab constructed above the main beam and the secondary beam, wherein the upper flange of the secondary beam is joined to the concrete floor slab.

[0008] With the above configuration, the bolts at the lower end of the bolt row connecting the gusset plate and the beam web are positioned close to the lower flange of the beam. This enhances the effect of the gusset plate in restraining out-of-plane deformation of the beam web, suppressing displacement of the lower flange of the beam and ensuring rotational rigidity and load-bearing capacity of the joint. As a result, deflection and moment acting on the central part of the beam are suppressed, making it possible to reduce the size and weight of the beam's cross-section. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing a joint structure according to the first embodiment of the present invention. [Figure 2] This figure shows a first example of the embodiment, corresponding to the view along lines AA and BB in Figure 1. [Figure 3] This figure shows a second example of an embodiment in which reinforcing ribs and reinforcing plates have been added, corresponding to the view along lines AA and BB in Figure 1. [Figure 4] This figure shows a third example of an embodiment in which a reinforcing plate with a different shape from that in Figure 3 has been added, corresponding to the view along lines AA and BB in Figure 1. [Figure 5]Figures 2 to 4 are diagrams illustrating how the distance 'ev' is determined. [Figure 6] Figures 2 to 4 are diagrams illustrating how the distance 'ev' is determined. [Figure 7] This figure shows the method for calculating the rotation angle of the joint in the analysis of the embodiment. [Figure 8] This figure shows the method for calculating the displacement of the lower flange of the beam in the analysis of the embodiment. [Figure 9] This graph shows the relationship between the joint moment and rotation angle of beam section No. 1 in the examples and comparative examples. [Figure 10] This graph shows the relationship between the joint moment and rotation angle of beam section No. 2 in the examples and comparative examples. [Figure 11] This graph shows the relationship between the joint moment and rotation angle of beam section No. 3 in the examples and comparative examples. [Figure 12] This graph shows the initial stiffness and maximum joint moment of beam section No. 1 in the examples and comparative examples, as a ratio with the reference case set to 1. [Figure 13] This graph shows the initial stiffness and maximum joint moment of beam section No. 2 in the examples and comparative examples, as a ratio with the reference case set to 1. [Figure 14] This graph shows the initial stiffness and maximum joint moment of beam section No. 3 in the examples and comparative examples, as a ratio with the reference case set to 1. [Figure 15] This graph shows the relationship between the displacement and rotation angle of the lower flange of beam section No. 1 in the examples and comparative examples. [Figure 16] This graph shows the relationship between the displacement and rotation angle of the lower flange of beam section No. 2 in the examples and comparative examples. [Figure 17] This graph shows the relationship between the displacement and rotation angle of the lower flange of beam section No. 3 in the examples and comparative examples. [Figure 18A] This figure shows the deformation state and equivalent plastic strain contour at maximum load capacity in the example. [Figure 18B] This figure shows the deformation state and equivalent plastic strain contour at maximum load capacity in the example. [Figure 18C] This figure shows the deformation state and equivalent plastic strain contour at maximum load capacity in the example. [Figure 19A] This figure shows the deformation state and equivalent plastic strain contour at maximum load in the comparative example. [Figure 19B] This figure shows the deformation state and equivalent plastic strain contour at maximum load in the comparative example. [Figure 19C] This figure shows the deformation state and equivalent plastic strain contour at maximum load in the comparative example. [Figure 20] This graph shows the relationship between the ratio of the rotational stiffness of the joint to the reference case and ev / H in the examples and comparative examples. [Figure 21] This graph shows the relationship between the ratio of the maximum load-bearing capacity of the joints in the examples and comparative examples to the standard case and ev / H. [Figure 22] This graph shows the relationship between the upper limit of the live load supported by the concrete floor slab when the joint of beam cross section No. 1 in the examples and comparative examples is at its maximum moment, and the deflection reduction rate for a beam supported at both ends by pin connections. [Figure 23] This graph shows the relationship between the upper limit of the live load supported by the concrete floor slab when the joint of beam section No. 2 in the examples and comparative examples is at its maximum moment, and the deflection reduction rate for a beam supported at both ends by pin connections. [Figure 24] This graph shows the relationship between the upper limit of the live load supported by the concrete floor slab when the joint of beam section No. 3 in the examples and comparative examples is at its maximum moment, and the deflection reduction rate for a beam supported at both ends by pin joints. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0011] Figure 1 is a perspective view showing a joint structure according to an embodiment of the present invention, and Figures 2 to 4 (A) and (B) correspond to views along lines AA and BB in Figure 1, respectively. As shown in the figures, the joint structure according to this embodiment is formed between a gusset plate 2 joined to a main beam 1 and a secondary beam 3 extending in a direction intersecting the main beam 1. In the following figures, the longitudinal direction of the secondary beam is shown as the X direction, the beam depth direction of the secondary beam is shown as the Y direction, and the longitudinal direction of the main beam is shown as the Z direction. The main beam 1 and secondary beam 3 are each made of H-shaped steel, with the main beam 1 having a web 11, an upper flange 12 and a lower flange 13, and the secondary beam 3 having a web 31, an upper flange 32 and a lower flange 33. The gusset plate 2 is welded to the web 11, upper flange 12 and lower flange 13 of the main beam 1, and the gusset plate 2 and the web 31 of the secondary beam 3 are bolted together using bolts 41. Furthermore, the main beam 1 and secondary beam 3 are not limited to H-shaped steel, as long as they have an H-shaped cross-section; for example, they may be composed of welded members having an H-shaped cross-section.

[0012] Furthermore, as shown in Figures 2 to 4, a concrete floor slab 5 is constructed above the main beam 1 and the secondary beam 3. In the illustrated example, the concrete floor slab 5 is a deck composite slab and includes concrete 51, reinforcing bars 52, and a deck plate 53. Studs 6 are erected on the upper flanges 12 and 32 of the main beam 1 and the secondary beam 3, penetrating the deck plate 53, and the studs 6 are anchored to the concrete 51. In other words, in the illustrated example, the secondary beam 3 is joined to the concrete floor slab 5, thereby transmitting the tensile force acting on the upper flange of the secondary beam 3 to the concrete floor slab 5. On the other hand, the lower flange 33 of the secondary beam 3 is not directly joined to the main beam 1 and the gusset plate 2.

[0013] Of Figures 2 to 4, Figure 2 shows the simplest example in which the above-described components are arranged. Figures 3 and 4 show examples in which additional components not shown in Figure 1 are arranged in the joint structure, as will be explained below. Figures 2 to 4 also show dimensions that will be referenced in the embodiments described later. In the examples in each figure, the bolts 41 that join the gusset plate 2 to the web 31 of the beam 3 constitute a row of bolts arranged in the beam depth direction of the beam 3, and the distance e from the axis of the bolt 41 located at the lower end of this row of bolts to the lower surface of the lower flange 33 of the beam 3 v This is less than 1 / 5 of the beam depth H of the secondary beam 3. This enhances the effect of the gusset plate 2 in restraining the out-of-plane deformation of the web 31 of the secondary beam 3, thereby suppressing the displacement of the lower flange 33 and maintaining the efficiency of transmitting compressive force acting on the end of the secondary beam. Distance e v The ratio of e to the beam depth H v / H is preferably less than 0.18, and more preferably 0.16 or less. For simplicity, distance e v Other dimensions are shown only in Figure 3, but the same applies to the examples in Figures 2 and 4.

[0014] In the examples shown in Figures 3 and 4, reinforcing ribs 21 and reinforcing plates 7 are arranged in addition to the components described in Figure 1. The reinforcing ribs 21 are plate-shaped portions that intersect the plate-shaped main body of the gusset plate 2, which is arranged along the web 31 of the secondary beam 3, and also intersect the web 11 of the main beam 1. Such reinforcing ribs 21 may be formed, for example, by fillet welding a separate plate-shaped member to the gusset plate 2, or the gusset plate 2 may be pre-formed into an L-shaped cross-section. The reinforcing ribs 21 may also be joined to the web 11 of the main beam 1 by fillet welding or the like. In the examples shown in Figures 3 and 4, there is no portion of the gusset plate 2 below the reinforcing ribs 21, and the gusset plate 2 is not welded to the lower flange 13 of the main beam 1, unlike in the example in Figure 1. However, in other examples, the gusset plate 2 may have a portion below the reinforcing ribs 21 and be welded to the lower flange 13. In this case, the reinforcing rib 21 is attached to the middle part of the gusset plate 2, and a notch may be formed in the portion of the reinforcing rib 21 that is in contact with the web 11 of the main beam 1 to avoid interference with the weld between the gusset plate 2 and the web 11.

[0015] The placement of the reinforcing ribs 21 suppresses out-of-plane deformation of the gusset plate 2 due to additional bending caused by, for example, eccentricity of the plate thickness center between the web 31 of the beam 3 and the gusset plate 2. Since the gusset plate 2 is joined to only one side of the web 31 of the beam 3 (single-sided friction), the reinforcing ribs 21 are also formed on only one side of the web 31. This ensures that the compressive force generated by the bending of the beam 3 is reliably transmitted from the web 31 to the main beam 1 via the gusset plate 2. For the transmission of compressive force, the gusset plate 2 is positioned below the height centerline C of the web 31 of the beam 3, and the reinforcing ribs 21 are positioned in the region below the height center of the web 31. Note that the reinforcing ribs 21 are different from ribs that are positioned to abut end faces with, for example, the lower flange 33 of the beam 3, and are located at a different height from the lower flange 33 of the beam 3, more specifically, above the lower flange 33 of the beam 3. By forming the reinforcing ribs 21 along almost the entire length of the gusset plate 2 when viewed in the direction of the axial axis of the beam 3, and overlapping them with the lower flange 33 of the beam 3, the effect of the reinforcing ribs 21 in suppressing out-of-plane deformation of the gusset plate 2 can be further enhanced.

[0016] The reinforcing plate 7 is positioned below the height centerline C of the web 31, in contact with the side end face of the gusset plate 2, and is bolted to the web 31 of the beam 3 with additional bolts 71. A reinforcing plate 7 the size of two rows of additional bolts may be positioned as shown in the example in Figure 3, or a reinforcing plate 7A the size of one row of additional bolts may be positioned as shown in the example in Figure 4. In addition, for example, another reinforcing plate may be positioned adjacent to the reinforcing plate 7A. Here, the side end faces of the gusset plate 2 and the reinforcing plates 7 and 7A are the end faces facing the axial direction of the beam 3. Unlike the gusset plate 2, the reinforcing plates 7 and 7A do not have reinforcing ribs formed on them.

[0017] By placing the reinforcing plates 7 and 7A, the number of bolts placed below the height centerline C of the web 31, when combined with the bolts 41 and the additional bolts 71, becomes greater than the number of bolts placed above the height centerline C. This allows the lower side of the joint to bear a greater compressive force that acts as a couple with the tensile force borne by the reinforcing bars 52 of the concrete floor slab 5. The additional bolts 71 may also be high-strength bolts, similar to the bolts 41, in which case the behavior of the joint structure can be further stabilized by high-strength bolt friction jointing. Note that reinforcing plates 7 and 7A may be placed in addition to the reinforcing ribs 21, as in the examples in Figures 3 and 4, or reinforcing plates 7 and 7A may be placed in contact with the side end faces of the gusset plate 2 even if no reinforcing ribs are placed, as in the example in Figure 2.

[0018] Furthermore, when the reinforcing plates 7,7A are frictionally bolted to the web 31 with additional bolts 71, by attaching the reinforcing plates 7,7A after the construction of the concrete floor slab 5, the reinforcing plates 7,7A are not involved in the bending moment generated by the weight of the concrete floor slab 5, and the number of additional bolts 71 required to maintain the frictional connection between the reinforcing plates 7,7A and the web 31 can be reduced.

[0019] The embodiments of the present invention described above can be said to be methods for semi-rigidizing pin joints at the ends of beams without adding any steps (example in Figure 2) or with only simple reinforcement (examples in Figures 3 and 4). In pin joints, if large out-of-plane deformation of the gusset plate occurs due to additional bending caused by eccentricity of the gusset plate and beam web, the rigidity and load-bearing capacity decrease rapidly, making it impossible to consider the degree of fixation of the joint in the design. In contrast, in this embodiment, by bringing the lower end position of the gusset plate closer to the lower end of the beam web, the gusset plate is used not only as a shear force transmission member but also as a reinforcing material for the out-of-plane rigidity of the beam web, thereby suppressing out-of-plane deformation of the web. As described above, the distance e from the axis of the lower end bolt to the lower surface of the lower flange of the beam vBy setting the gusset plate to less than 1 / 5 of the beam depth H of the secondary beam, the lower end of the gusset plate will be near the lower end of the secondary beam web (near the fillet of rolled H-shaped steel or the upper end of the welded fillet of welded assembled H-shaped steel), and the effect of suppressing out-of-plane deformation of the secondary beam web can be sufficiently obtained as described above. Furthermore, by placing the horizontal ribs that suppress out-of-plane bending of the gusset plate closer to the lower flange of the secondary beam, the effect of suppressing horizontal displacement of the lower flange of the secondary beam and rotational deformation (torsion) around the material axis of the secondary beam may be enhanced. Alternatively, by placing a reinforcing plate, more bolts can be placed on the lower flange side of the secondary beam web, and the stability of the joint can be increased by placing more compressive force on the lower part of the secondary beam end joint, which acts as a couple with the tensile force borne by the reinforcement in the floor slab after the concrete floor slab is poured. The rotational deformation (torsion) of the secondary beam around the material axis is also suppressed by the concrete floor slab restraining the horizontal movement of the upper flange of the secondary beam, and the compressive force from the lower flange of the secondary beam can be stably transmitted to the main beam. In this embodiment, the above configuration significantly improves the yield strength of the joint, which exhibits nonlinear behavior compared to a general pin joint, while also achieving higher rotational rigidity of the joint. This allows for a reduction in deflection that takes into account the degree of fixation of the joint in the design.

[0020] Figures 5 and 6 are shown in Figure 3 and The distance e shown in Figure 4 v This diagram illustrates how to specify the distance e v This is the distance from the axis of bolt 41 at the lower end of the bolt row to the lower surface of the lower flange of the beam. Additional bolt 71 is shown in Figure 3 andIt may be positioned at the same height as the bolt 41 at the lower end of the bolt row as in the example of FIG. 4, may be positioned above the bolt 41 at the lower end as in the example of FIG. 5, or may be positioned below the bolt 41 at the lower end as in the example of FIG. 6, but the distance e v is not affected by the position of the additional bolt 71.

Embodiment

[0021] Hereinafter, the results of FEM analysis for verifying the effects of the embodiments of the present invention as described above will be described. For the joint between the main beam and the secondary beam, the initial stiffness and ultimate strength of the joints of the prior art and the embodiments of the present invention were calculated. The joint shapes of each example are shown in FIGS. 2 to 4, and the dimensional parameters are mainly shown in FIG. 3 (the same applies to FIGS. 2 and 4). The main parameters are the beam height H of the secondary beam, the flange width B f , the web plate thickness t w and the flange plate thickness t f The following three types of cross-sections No. 1 to No. 3 defined by, the number n b in the beam direction of the bolts joining the secondary beam web and the gusset plate, the interval p v and the height h fin of the gusset plate, and the distance e v (e v was changed within the range of 0.125 to 0.

[0022] <Secondary beam cross-section> No. 1: H = 700 mm, B f = 200 mm, t w = 9 mm, t f = 16 mm No. 2: H = 450 mm, B<00000​​​​​​​​​​​​​​​ Table 1 shows the conditions for each example. For the analysis model name, the first number "1" to "3" indicates which of the above No. 1 to No. 3 the beam cross-section is. "R" indicates that a concrete floor slab has been constructed and the movement of the upper flange in the horizontal plane is constrained by the anchoring of studs erected on the upper flange of the beam to the concrete (this applies to all examples). "MG", "TG", and "HG" indicate the height h of the gusset plate. fin This indicates that the height is higher than usual, and therefore the lower end of the gusset plate is closer to the lower end of the beam web (height h fin (The order of "MG", "TG", and "HG" is from highest to lowest). "EXC2" and "EXC" show cases where reinforcing plates and additional bolts are arranged as in the examples in Figures 3 and 4. Note that in "EXC2", two rows of additional bolts are arranged as in the example in Figure 3, and in "EXC", one row of additional bolts is arranged as in the example in Figure 4. (t6) and (t9) indicate that the thickness of the gusset plate is 6 mm and 9 mm, respectively. In the embodiment, the distance e from the lower surface of the lower flange of the joist to the axis of the lower end bolt is as shown in the examples in Figures 2 to 4 above. v Since is less than 1 / 5 of the beam depth H, and therefore e v / H < 0.2. The comparative example is e v This includes examples where / H≧0.2, and examples of rigid connections where the upper and lower flanges of the secondary beam are welded to the main beam.

[0024] [Table 1]

[0025] In the analysis, a predetermined initial tension is first applied to the bolts connecting the beam web and the gusset plate. More specifically, in the examples of beam sections No. 1 and No. 3, an initial tension of 180kN is applied to the F10T-M20 bolt, and in the example of beam section No. 2, an initial tension of 110kN is applied to the F10T-M16 bolt. Next, in a cantilever beam configuration, a forced displacement of up to 20mm is applied to the beam end opposite the joint, and the joint moment M is calculated. j [kNm] and rotation angle φ jThe displacement in rad and the displacement of the lower flange of the beam in the direction perpendicular to the beam (Z direction) [mm] were calculated.

[0026] Figure 7 shows the rotation angle φ of the joint in the analysis. j The method for calculating the rotation angle φ is shown. j This is the longitudinal displacement δ of the beam at each of the two points where the line of intersection between the vertical center of the bolts joining the beam web and the gusset plate and the thickness center of the beam web intersects with the thickness centers of the upper and lower flanges of the beam. ft ,δ fb The difference between these two points is the vertical distance Ht f (t f This is the value obtained by dividing by the flange plate thickness. Figure 8 shows the method for calculating the displacement of the lower flange of the beam in the analysis. Displacement z of the lower flange of the beam in the horizontal plane in the direction perpendicular to the beam (-Z direction) fb This is the Z-direction displacement of the lower flange side of the two points mentioned above.

[0027] The main beam was designed with a depth of 800 mm, a flange width of 300 mm, a web plate thickness of 12 mm, and a flange plate thickness of 25 mm. The coefficient of friction between the bolted gusset plate and the secondary beam web, and between the reinforcing plate joined by additional bolts and the secondary beam web, were set to 0.6 based on experimentally obtained slip coefficients. The coefficients of friction for all other contact surfaces were set to 0.2, corresponding to the coefficient of friction between mill-scale surfaces. In all models, the length from the center of the main beam's web plate thickness to the forced displacement point of the secondary beam was set to 1.5 m (nominal length of the secondary beam). Joint moment M j This was defined as the product of the reaction force at the forced displacement point and the arm length of 1.3m (the value obtained by subtracting the distance of 0.2m from the nominal length of the secondary beam, which is 1.5m, from the center of the vertical row of bolts connecting the secondary beam web and the gusset plate to the center of the web plate thickness of the main beam).

[0028] Table 2 shows the analysis results of the examples and comparative examples, and the joint moment M. j and rotation angle φ j The relationship is shown in Figures 9 to 11. In Table 2, the initial stiffness S j,ini [kNm / rad] is the secant stiffness at 1 / 3 of the maximum yield strength, Mj,max [kNm] is the maximum value of the joint moment. Figures 12 to 14 show the S of the examples and comparative examples for beam sections No. 1, No. 2, and No. 3, respectively. j,ini and M j,max This graph shows the ratios of analysis models 1-R(t9), 2-R(t6), and 3-R(t6), with the reference case set to 1. Comparing the example with the comparative example, by increasing the height of the gusset plate (TG,MG), e v In the example where / H < 0.2, e v Compared to the comparative example where / H≧0.2, the same M j,max For the value of S j,ini It can be seen that the performance has improved. Furthermore, in the examples with reinforcing ribs and reinforcing plates (1EXC2-TG-R, 2EXC2-TG-R, 3EXC2-TG-R and 3EXC2-MG-R), the examples without reinforcing ribs and reinforcing plates and the examples with reinforcing ribs and reinforcing plates are shown to be improved. v S can be linearly predicted from the results of the comparative example where / H≧0.2 j,ini and M j,max S exceeding j,ini and M j,max This result yields e v It can be seen that a synergistic effect can be obtained by setting / H < 0.2, in addition to adding reinforcing ribs and reinforcing plates.

[0029] [Table 2]

[0030] Figures 15-17 show the Z-direction displacement (z) and rotation angle φ of the lower flange of the examples and comparative examples for beam cross-sections No. 1, No. 2, and No. 3, respectively. jThis graph shows the relationship. As already mentioned, when the Z-direction displacement (z) of the lower flange increases, the eccentricity distance in the plate thickness direction increases between the compressive force transmitted from the lower flange of the beam to the gusset plate via the web and the reaction force on the gusset plate side, which promotes out-of-plane deformation of the beam web and gusset plate and reduces the efficiency of transmission of compressive force from the lower flange. As shown in Figures 15 to 17, e v In the example where / H < 0.2, the same configuration was used for e v Compared to the example where / H≧0.2, it can be seen that the Z-direction displacement of the lower flange before the maximum load-bearing capacity is suppressed. By arranging reinforcing ribs and reinforcing plates, the Z-direction displacement of the lower flange can be further suppressed.

[0031] Figures 18A to 18C show the deformation state and equivalent plastic strain contour at maximum load capacity for Example (3-TG-R(t6)). Figures 19A to 19C similarly show the deformation state and equivalent plastic strain contour at maximum load capacity for Comparative Example (3-R(t6)). Compared to the Comparative Example, the region of large equivalent plastic strain in the web in Example is narrower and tends to shift towards the lower flange side. In other words, it can be seen that out-of-plane bending deformation is suppressed over a wide area of ​​the web in Example.

[0032] Figure 20 shows the rotational stiffness R_S of the joint in the examples and comparative examples. j,ini The ratio of the baseline case and e v This graph shows the relationship with / H. Figure 21 similarly shows the maximum load-bearing capacity R_M of the joint. j,max The ratio of the baseline case and e v This is a graph showing the relationship with / H. From Figures 20 and 21, e v By setting / H<0.2, S j,ini M j,max It can be seen that both show a significant increase compared to the baseline case. Furthermore, e v By setting / H to less than 0.18, and more preferably 0.16 or less, S j,ini M j,max It can be seen that both cases show a more significant increase compared to the baseline case.

[0033] Table 3 and Figures 22-24 show that the joint is M in the examples and comparative examples. j,max The upper limit of the live load supported by the concrete floor slab (Design load capacity) and the deflection reduction rate (δ) for the beams supported at both ends by pin connections. pin -δ) / δ pin by S j.ini The relationship with ) is shown. The preconditions for the analysis are as follows.

[0034] • Initial stiffness S obtained from analysis j,ini The study will focus on the third span of a five-span continuous beam, where intermediate supports are provided at a joint with a certain feature (roughly corresponding to any span in an infinitely continuous beam). The span L of the secondary beam shall be 15m for section No. 1, and 7.5m for sections No. 2 and No. 3. The dominant width B of the joists (the distance between joists in the direction perpendicular to the longitudinal direction of the joists) shall be 3m. The concrete floor slab will be 180 mm thick and will be joined to the upper flange of the joist with headed studs with a diameter of 19 mm and a pitch of 200 mm. The concrete floor slab will be reinforced with D10@200 bars throughout, and D10@100 bars will be placed in the negative bending areas. The bending stiffness of the secondary beams is calculated as the stiffness of a fully composite beam. Negative bending stiffness considers the stiffness of the reinforcement in the floor slab, ignoring the concrete in the floor slab. Positive bending stiffness uses the Young's modulus of the concrete in the floor slab as well as the Young's modulus of the steel frame, which is 210,000 N / mm². 2 It is calculated as 1 / 15 of that. For the comparative rigid joints (1Rigid, 2Rigid, 3Rigid), FEM analysis was not performed. The joint was found to have a rotational stiffness 100 times the value obtained by dividing the positive bending stiffness of the secondary beam by the span length (composite beam bending stiffness per unit length), and a yield stress of 325 N / mm². 2 The fully plastic bending strength of the two-flange model is calculated assuming it is the maximum strength.

[0035] [Table 3]

[0036] As shown in Table 3 and Figures 22-24, e v In the example where / H < 0.2, the same configuration was used for e v Compared to the example where / H≧0.2, the deflection reduction effect is greater, and the upper limit of the load capacity is also higher. By arranging reinforcing ribs and reinforcing plates, the deflection reduction effect and the upper limit of the load capacity can be further improved.

[0037] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention pertains that various modifications or variations can be conceived within the scope of the technical idea described in the claims, and these are also understood to naturally fall within the technical scope of the present invention. [Explanation of Symbols]

[0038] 1...Main beam, 11...Web, 12...Upper flange, 13...Lower flange, 2...Gusset plate, 21...Reinforcement rib, 3...Secondary beam, 31...Web, 32...Upper flange, 33...Lower flange, 41...Bolt, 5...Concrete floor slab, 51...Concrete, 52...Reinforcement, 53...Deck plate, 6...Stud, 7,7A...Reinforcement plate, 71...Additional bolt.

Claims

1. A joint structure for connecting a main beam having an H-shaped cross-section and the end of a secondary beam having an H-shaped cross-section and extending in a direction intersecting the main beam, in the direction of the material axis, A gusset plate joined to at least the web and upper flange of the main beam, Arranged in the beam direction of the beam, the bolt rows connect the gusset plate to the web of the beam. Equipped with, The distance from the axis of the bolt located at the lower end of the bolt row to the lower surface of the lower flange of the secondary beam is less than 1 / 5 of the beam depth of the secondary beam. The lower flange of the secondary beam is not joined to the main beam. A joining structure further comprising reinforcing ribs that intersect the plate-shaped main body of the gusset plate and also intersect the web of the main beam, and are joined to at least the gusset plate and located above the lower flange of the secondary beam.

2. The system further comprises at least one reinforcing plate positioned below the height centerline of the web of the beam and in contact with the side end face of the gusset plate, The reinforcing plate is bolted to the web of the beam, the joining structure according to claim 1.

3. The joint structure according to claim 2, wherein the reinforcing plate is friction-joined to the web of the beam with high-strength bolts.

4. The joint structure according to claim 1, wherein the gusset plate is friction-joined to the web of the beam with high-strength bolts.

5. The concrete floor slab is further constructed above the main beam and the secondary beam, The joining structure according to claim 1, wherein the upper flange of the secondary beam is joined to the concrete floor slab.

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