JP5510597B1 - Circular ring reinforcing beam member - Google Patents

Abstract

An object of the present invention is to improve the plastic deformation capacity of a beam having a thin plate structure subjected to shear bending by preventing a decrease in yield strength of a web subjected to in-plane shear and maintaining the bending strength of the beam after flange yielding.
For a beam having flanges at both ends of a web, a circular ring 3 is provided on one side of the web, and vertical stiffeners 4 are provided on the left and right sides. The inner web is used as a tensile stress surface and the surrounding member and a truss-like force balance field are formed. Further, a member 5 having an L-shaped cross section or a rectangular cross section is disposed on the opposite side of the web in parallel with the upper and lower flanges, and one end of the cross section is attached to the web 1 along the circular arc of the circular ring and the other end is flange 2. A rectangular or triangular tubular body is formed at the corner of the cross-section to suppress the local buckling deformation of the cross-section plate element, and the torsional rigidity of the beam member is increased to obtain a beam member having a high plastic deformation capability.
[Selection] Figure 1

Description

  The present invention relates to a beam member having flanges at both ends of a web subjected to shear bending, avoiding a decrease in yield strength due to the shear buckling of the web against the applied shear force, and maintaining the plastic bending moment of the beam even after the flange yields. This is intended to increase the plastic deformation capacity of the beam. In particular, an optimum shape for a beam member made of a thin plate is proposed and a reinforcement structure as simple as possible is provided.

  There have been many proposals for reinforcement methods for shear buckling of webs subjected to in-plane shear and for maintaining flange yield strength near the ends of beam members subjected to antisymmetric bending moments from both ends. However, the web and the flange are often handled from different viewpoints, and the mechanical behavior after the beam yielding has a problem in dealing with it because there are factors that straddle both.

  In general, for beams where yielding progresses from both ends of the member, in order to maintain the proof strength of the web as a result of plasticization, use a steel material with a low yield point to increase the plate thickness, or reinforce the web surface for shear buckling. In order to maintain the yield strength of the flange after yielding, the width-to-thickness ratio is mainly restricted to a small size, and the bending strength after yielding is intended to be maintained, such as by devising the joint part of the beam end. An attempt is made.

Japanese Patent Laid-Open No. 06-017507 Japanese Patent Laid-Open No. 10-220061 Japanese Patent Application Laid-Open No. 2002-173977 Japanese Patent Application Laid-Open No. 2003-064901 JP 2008-133694 A Japanese Patent Application Laid-Open No. 2011-113264 Japanese Patent Application Laid-Open No. 2011-202424

  The problem to be solved is for the beam subjected to shear bending to avoid the decrease in yield strength due to the shear buckling of the web subjected to in-plane shear, and to the plasticization of the flange proceeding from both ends of the beam after yielding. It is to be able to maintain the plastic bending strength of the beam. In particular, it is regarded as a flat plate buckling that is mutually related to the shearing of the web and the bending of the flange, and is made of a thin plate as much as possible and has a high plastic deformation capability.

  Basically, the web surface subjected to in-plane shear is reinforced by attaching a circular ring to the web surface so that the yield strength does not decrease even during the buckling deformation growth. The web surrounded by the circular ring is attached to the metal plate by attaching the circular ring to the region where the principal tensile stress dominates.Furthermore, a vertical stiffener is placed near both sides of the circular ring to surround the periphery with the upper and lower flanges, and the truss-like force balance field. Configure.

  A circular ring and vertical stiffeners on both sides of the web are attached to each side in the longitudinal direction of the beam on one side of the web, and an L-shaped or rectangular cross-section member is arranged on the back side in parallel with the upper and lower flanges. One end of the cross section of the member is brought into contact with the web and the other end of the member at a substantially equal distance from the corner, and the web and the flange are fastened to stabilize the plate elements constituting the cross section of the member.

  The multiple circular rings that are continuous on the web surface against the overall buckling or torsional buckling of the beam due to shear bending are resistant to torsion, and the effect of a rectangular or triangular tubular body formed by reinforcing the corners of the cross section is also added to bend the beam. Increases torsional rigidity and avoids overall buckling. In addition to the rectangular cross section, the flange is intended as a groove-shaped cross section in which a rib is provided at the front end of the flange to make the flange thinner.

FIG. 13A is a schematic diagram showing a balance of in-plane stresses of a circular metal plate surrounded by a circular ring. When a shearing force is applied from the circular ring frame, the circular metal plate along with the circular ring extends in an oblique 45 degree direction. Deforms into an ellipse with a short axis The compressive principal stress -σ of the dotted arrow due to in-plane shear is balanced with the axial force σ _c of the circular ring, and the tension field controlled by the tensile principal stress + σ of the solid arrow from the initial stage of the applied force to the plastic deformation region Become.

  FIG. 13 (b) shows a case where the circular ring receives torsion, and even if the member has a rectangular cross section with low torsional rigidity, it is equivalent to the fact that the torsional rigidity becomes extremely high because rotational deformation is constrained. In addition, it is effective not only for local buckling of the cross-section component plate element but also for bending torsional buckling of the entire member, by arranging a circular ring for every fixed section and connecting the web and flange continuously. It leads to the bending strength maintenance of the beam.

  Although the circular ring provided on the web surface is effective in reducing the web plate thickness, the flange is made thinner by reinforcing the crossing portion of the cross-sectional plate elements using the circular ring. A beam member having a flange with a rib protruding at the tip in addition to a flange with a rectangular cross section is possible, and a stable beam having a high plastic deformation capability even with a groove-shaped cross-section beam in which the flange protrudes in one direction on one side of the web. can do.

It is a typical view of the beam which arrange | positions a circular ring on a web and reinforces the corner | angular part with a flange. It is explanatory drawing of the elastoplastic mechanical behavior of a flange bending yield and a web shear yield. It is explanatory drawing of the elastoplastic mechanical behavior in case a flange bending yield predominates. It is a layout view on a web surface in which circular holes that are concentric circles are provided in a circular ring inner region. It is explanatory drawing of reinforcement of the cross-sectional corner above and below the opening part of a beam both ends part, and a mechanical effect. It is a block diagram of circular reinforcement of a web and local reinforcement in both end plasticization regions. It is explanatory drawing of the maintenance of the plastic bending strength after a flange yield, and the plastic deformation capability of a beam. It is a block diagram which considers the cross-sectional corner symmetrical reinforcement of the beam which provides a rib at the flange front-end | tip part. It is explanatory drawing of the mechanical behavior and plastic deformation capability of the H-shaped cross section beam comprised with a thin plate. It is a block diagram of circular ring reinforcement and cross-sectional corner reinforcement for a groove-shaped cross-section beam member. It is explanatory drawing in the case of carrying out circular ring reinforcement limited to the plasticization area | region of beam both ends vicinity. It is explanatory drawing of the elastoplastic mechanical behavior which provides a circular hole in a web circular ring inner side area | region. It is a schematic diagram of the circular ring which receives the in-plane stress and twist of the flat plate enclosed by the circular ring.

  FIG. 1A shows the web surface of a beam member from the front. A circular ring 3 and vertical stiffeners 4 adjacent to the left and right are provided on one side of the web. Individually reinforce the web. By attaching the circular ring, the web inside the circular ring is used as a tensile stress surface, and the circular ring is surrounded by a flange and a vertical stiffener to form a balance field between the oblique tensile force and the truss force of the web surface.

  FIG. 1 (b) shows the reverse side surface of the reinforcing web, in which a member 5 having an L-shaped cross section or a rectangular cross section is arranged in parallel with the upper and lower flanges, and one end of the member cross section is along the circular arc of the circular ring. In addition, the other end is also attached to the flange, and a rectangular or triangular tubular body is provided at the corner of the cross section, and this is disposed over both ends of the beam or over the entire length to constitute a beam member.

  FIG. 8 shows the case where the flanges 2 at both ends of the beam web are provided with protruding ribs at the tip of the cross section, and the cross section corners are formed in parallel with the flange so that the web surface is symmetrical along the circular arc of the continuous circular ring. The reinforcing member 5 constitutes a V-shaped tubular body. By reinforcing the corners of the cross section, it is possible to reduce the thickness of the plate as well as the flange of the web, so that a thin plate cross-section beam having a high plastic deformation capability with respect to a large-span beam.

  FIG. 10 shows a so-called groove-shaped cross-section beam 7 having a flange on one side of the web surface. A triangular tubular body is formed by a reinforcing member 5 at a corner inside the cross-section, and a circular ring 3 and a vertical stiffener 4 are formed on the web surface. Provide. A tubular body formed at the cross-sectional corner over the entire length of the member works effectively with respect to the groove-shaped cross-section beam that is weak against torsion. In the cold-formed member, the web having the same thickness as the flange is strong, and a circular ring reinforcement is limited to both ends of the beam (a), and a concentric opening hole is provided (b).

  In FIG. 1, the circular ring 3 and the vertical stiffeners 4 on both sides of the web are arranged at five positions at equal intervals in the longitudinal direction of the member on the one side (a) of the web, and parallel to the flange on the upper and lower sides of the reverse side (b). In addition, one end of the L-shaped or rectangular cross-section member 5 is attached to the web and the other end is attached to the flange so as to overlap with the circular arc of the circular ring, and a rectangular or triangular tubular body is provided over the entire length of the member at the corner of the cross section. Configure.

  A circular ring with a diameter of 720 mm and a left and right vertical stiffener with a width of 900 mm are enclosed in a square with respect to 900 mm of the beam, and the outer region width is adjusted according to the beam span. A beam member is configured by attaching a member having an L-shaped cross section of 75 mm x 75 mm x 9 mm to a rectangular cross section of 105 mm x 12 mm having substantially the same cross-sectional area at the cross-sectional corner of the back side surface of the web. The cross section of the circular ring and stiffener is 100 mm x 12 mm.

Figure 2 shows a beam with a length of 7,200mm. The solid line is a flange with a rectangular cross section of 300mmx19mm. When a rectangular tubular body is provided with an L-shaped cross section at the upper and lower corners of the web, the dotted line is a flange with a grooved cross section of 300mmx90mmx10mmx15mm. The results for web plate thicknesses of 6.0 mm, 4.5 mm, and 3.2 mm are obtained when a strip is obliquely attached to the upper and lower corners and a triangular tubular body is provided. The vertical axis indicates the plastic bending moment M _p , and the horizontal axis indicates the end deformation angle, but with a thin plate thickness, the shear yield of the web precedes and the bending strength decreases.

  FIG. 3 shows a beam with a length of 9,000 mm. The area surrounded by the vertical stiffener around the circular ring is 900 mm wide, while the outer area is also the same width, so it is divided into 450 mm width. The width-thickness ratio accompanying the shear buckling of the region including the circular ring is converted to the diameter width of the circular ring of 720 mm, and the interval between the other web regions may be slightly less than the above value. Web sheet thicknesses of 6.0mm and 4.5mm are preceded by flange yielding and 3.2mm by shear yielding, but all exhibit high plastic deformation capacity.

  FIG. 4 shows a beam having the same configuration as that of the first embodiment, but a circular hole 6 having an arbitrary diameter which is a concentric circle is provided in a circular ring inner region. In this example, a circular hole with a diameter of 450 mm, which is 50% of the beam, is used, but in the plasticized region at both ends of the beam, reinforcing members at the corners of the cross section are arranged on both sides of the web above and below the circular ring to reinforce the flange. Since the web surface inside the circular ring is in a tensile stress state, it is not necessary to reinforce around the circular hole in principle.

  Fig. 5 shows the results of web thickness of 6.0mm, 4.5mm, and 3.2mm for a 9,000mm-long beam, solid line is a flange with a rectangular cross section of 300mmx19mm, dotted line is a groove with a grooved cross section of 300mmx90mmx10mmx15mm. The reinforcing material at the corners of the cross section was 105 mm × 6 mm in cross section and was 1/2 the plate thickness as compared with the previous example. Compared with the result of FIG. 3, it can be seen that the present example in which the circular holes are provided in the web is more stable after yielding, and corner reinforcement from both sides of the web surface is more effective.

  When a concentric circular hole is provided in the web inside the circular ring, the shear strength of the member is not determined by the minimum cross section on the center line of the circular hole, and it is necessary to convert it as the ratio of the cross-sectional defect to the web area over the entire length of the member There is. In this case, the reduction rate of the shear strength of the opening having the same width as the beam surrounding the circular hole is totaled and divided by the member length to obtain an approximate value. In this example, it is converted to about 75%.

  FIG. 6 shows a reinforcing structure in which a circular ring and a vertical stiffener are attached from both sides of the web. The circular ring 3 is attached to one side of the web and the vertical stiffener 4 is attached to the opposite side of the web so as to overlap the arc and the neutral axis. In parallel with the upper and lower flanges, the member 5 is arranged in a V shape over the entire length of the beam. Supporting the intermediate portion of the flange projecting in both directions against the plasticization proceeding from both ends of the beam is effective in reducing the thickness.

  Fig. 7 shows the analysis results for a beam with a length of 9,000mm. The H-shaped cross-section beam has a rectangular cross section, and the plate thickness is 16mm, 14mm, 12mm for the width of 300mm, and the web plate thickness is 6.0mm. The solid line shows the result of the continuous arrangement of the circular ring in the longitudinal direction of the member shown in (a), and shows sufficient plastic deformation capability, while the dotted line shows the circular ring only in the plasticized region near both ends of the beam shown in (b). The result is a little inferior to the former.

  When the flange is thin and plasticization proceeds from both ends of the beam, the width-to-thickness ratio is reduced by supporting both intermediate portions of the projecting flange in a V shape, which is effective in securing the plastic deformation capability. In addition, the tubular body at the cross-sectional corners over the entire length of the beam increases the torsional rigidity of the beam, thus delaying the occurrence of overall buckling. It needs to be limited to when bending does not occur.

  In FIG. 8, the flange 2 constituting the beam member is provided with a protruding rib at the tip of the cross section, and the cross section corners are reinforced so as to be V-shaped along the circular arc of the circular ring with the web surface symmetrical. The flange is intended to be thinned in cooperation with the reinforcing material on the web surface. Since the bending rigidity around the beam weak axis is increased by the rib at the tip of the flange cross section, the plastic deformation capacity of the large span beam is improved.

  FIG. 9 shows a result of a beam member having a web thickness of 2.3 mm, a width-to-thickness ratio of 400 and a span of 10,800 mm with respect to 900 mm of the beam, a flange having a groove-shaped cross section of 300 mm × 90 mm, and a plate thickness of 6 mm, 7 mm, and 8 mm. The solid line shows the case where the cross-section corner reinforcement is on both sides of the web surface (b-1), and the dotted line shows the case where the web surface is on one side (b-2). However, the plastic deformation ability is slightly inferior to that of the former.

  Although the web region surrounding the circular ring and the left and right rectangular regions have substantially the same width, a shear yield load is secured by balancing as a tensile stress surface inside the circular ring. In addition, low-order mode shear buckling occurs early in the web, which leads to the fact that the torsional buckling of the member due to high-order mode shear does not occur, and the large-span beam has high plasticity without suppressing lateral deformation. It is thought that it shows deformation ability.

  FIG. 10 shows a so-called groove-shaped beam 7 having a flange protruding in one direction on the upper and lower sides of the web surface. The corner reinforcing member 5 on the inner side of the cross section forms a triangular tubular body. A vertical stiffener 4 is provided. A tubular body provided over the entire length of the groove-shaped cross-sectional beam that is weak against torsion is effective. The cold-formed member has a thick web and is intended to be used for (a) a drawing in which circular ring reinforcement is limited to both ends of the beam and (b) a drawing in which concentric opening holes are provided.

  FIG. 11 shows the analysis results when the material length is 9,000 mm and the cross section is 900 mm × 225 mm × 75 mm and the plate thickness is 6.0 mm, 7.5 mm, 9.0 mm. The solid line shows the case where transverse deformation is restrained at 1,350 mm from both ends of the beam, but the torsional rigidity is increased by the reinforcement in the vicinity of both ends of the beam and the tubular body at the cross-sectional corner over the entire length of the member, and the plastic deformation capacity is high. The dotted line shows the case where there is no lateral deformation constraint, but the torsion of the member occurs with the plasticization of the end portions of both materials, and the yield strength decreases according to the cross-sectional plate thickness difference.

  FIG. 12 shows the result when the material length and the member cross-section are the same as the cold-formed groove-shaped cross section as in the previous example, and five circular rings are evenly arranged in the longitudinal direction of the member and concentric circular holes are provided inside the circular ring. It is. The solid line is the case where the circular hole diameter is 40% of the beam at both ends of the beam and 60% at the middle part, and the dotted line is the case where all the hole diameters are 50%, but the circular shape at the ends of both materials Both have high plastic deformation ability, although the hole slightly affects the bending strength at the start of yielding of the flange.

Metallic material covered in this specification, yield stress of σ _y = 30kN / cm ^2, but utilizing the generally plain steel, which is frequently used as a steel material of Young's modulus E = 20,500kN / cm ^2, the reinforcing structure Then, it is not related to the type and material of the metal, and may be high yield point steel or low yield point steel. In particular, the web surface of the beam member is used as a balance field by tensile stress, which is considered extremely effective for light metal materials having low rigidity.

  As a reinforcement method for the web of the beam, by arranging a plurality of circular rings and longitudinal stiffeners on both sides of the web, the web becomes a tensile stress surface against in-plane shear, and the web plate thickness is much thinner than the current situation. it can. The minimum web thickness required for in-plane shear without being governed by the width-to-thickness ratio associated with conventional shear buckling, so the cross-section of the thin plate without reducing the mechanical performance of the beam member Can be realized.

  As a method of reinforcing the flange of the beam, a member having an L-shaped cross section or a rectangular cross section is arranged in parallel with the upper and lower flanges, and one end of the cross section at a substantially equal distance from the cross section corner is joined to the web and the other end is joined to the flange. Although a tubular body is provided, local buckling deformation of the flange and the web can be suppressed, and the tubular body at the corner of the cross section can increase the bending torsional rigidity of the member and eliminate the lateral buckling restraint in the beam longitudinal direction. Great design advantage.

  In the beam of the present invention, a flange provided with a rib protruding at the end of the cross section is also targeted, but this can not only reduce the plate thickness of the flange, but also greatly increase the bending rigidity around the weak axis of the beam and stabilize the entire member Turn into. Furthermore, the provision of a tubular body at the cross-sectional corner of a beam having a groove-shaped cross section in which the web surface is in an eccentric position greatly improves the weakness against torsion, and may be widely used as an asymmetric cross-section member with high plastic deformation capability. It ’s big.

1. 1. Beam member web 2. Beam member flange 3. Circular ring reinforcing member Vertical stiffener 5. 5. Cross-section corner reinforcing member 6. Circular hole on the web surface Groove-shaped cross-section member

Claims (4)

  For beams having flanges on both ends of the web subjected to shear bending, a plurality of circular rings and vertical stiffeners adjacent to the left and right are attached to one side of the web in the longitudinal direction of the member, and parallel to the upper and lower flanges on the opposite side of the web An L-shaped cross-section member or a rectangular cross-section member is arranged, and one end of the L-shaped cross-section member or the rectangular cross-section member is attached to the web so as to follow the circular arc of the circular ring, and the other end is abutted to the flange. A reinforcing structure that suppresses buckling deformation of the cross-section plate element and increases the torsional rigidity of the member and improves the plastic deformation capacity of the beam by providing a triangular tubular body.   For a beam having flanges at both ends of a web subjected to shear bending, a circular ring on one side of the web and a plurality of vertical stiffeners overlapping the arc and the neutral axis on the opposite side of the web are attached in the longitudinal direction of the member. In parallel with the upper and lower flanges, a rectangular cross-section member is disposed obliquely, and one end of the rectangular cross-section member is attached to the web along the circular arc of the circular ring and the other end is abutted to the flange. A reinforcing structure that suppresses buckling deformation of the cross-section plate element and increases the torsional rigidity of the member by providing a tubular body, thereby improving the plastic deformation capacity of the beam.   For beams with flanges on both ends of the web subjected to shear bending, the flange is a member with protruding ribs on one side or both sides of the two ends of the rectangular cross section, delaying the local buckling of the flange and ensuring the yield load of the beam 3. The beam according to any one of claims 1 and 2, which increases the bending rigidity in the lateral direction of the beam, suppresses lateral buckling deformation, maintains a stable mechanical balance over the entire length of the member, and improves the plastic deformation capacity of the beam. Reinforcing structure described in the section.   For beams that have a flange only in one direction on one side on both ends of the web subjected to shear bending, a plurality of circular rings and vertical stiffeners adjacent to the left and right are attached to the web surface on the flange protruding side in parallel with the upper and lower flanges. The rectangular cross-section member is arranged obliquely, and one end of the rectangular cross-section member is attached to the web and the other end to the flange so as to follow the circular arc of the circular ring, and a triangular tubular body is provided at the cross-sectional corner of the beam. A reinforcing structure that suppresses buckling deformation of cross-section plate elements and increases the torsional rigidity of the members to improve the plastic deformation capacity of the beam.

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