JP2019127800A - Truss beam - Google Patents

Abstract

To provide a truss beam having a high plastic deformation capability in earthquake.SOLUTION: A truss beam (11) has an upper chord material (12), a lower chord material (13) and a plurality of diagonal members (14). The first diagonal material (14a) positioned on the most end side extends obliquely and downwardly toward the center side. The second oblique material (14b) whose the lower end side is joined to the lower end side of the first oblique material extends obliquely and upwardly toward the center side. The lower ends of the first and second oblique materials are joined to the lower chord material through an insulating joint material (15) slidable in the extension direction of the lower chord material.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a truss beam with improved earthquake resistance, in particular deformation capacity during earthquakes.

  A truss beam is a member composed of individual pieces of a chord and a diagonal, which resists the axial force generated in the individual members in the elastic range, and in general, the chord is straight or curved, and the diagonal is a straight line There are many. FIG. 10 (A) shows an example of a truss beam according to the prior art. The truss beam 1 has an upper chord member 2, a lower chord member 3, and a plurality of diagonal members 4, and is supported by a structural member such as a pair of columns 5 or the like. Various structures for improving the earthquake resistance of such truss beams have been proposed.

  For example, Patent Document 1 describes a structure in which a damper is interposed between the lower chord member and the column to dissipate the displacement during the earthquake as energy. Patent Document 2 describes a structure in which a section having high rigidity and a section having low rigidity are provided in the extending direction of the truss beam, and the boundary serves as a hinge in the event of an earthquake and precedes bending yielding. Further, Patent Document 3 describes a structure for preventing lateral buckling by joining a lateral buckling stiffener, which extends in an oblique direction with respect to a structural surface of a truss beam, to a lower chord material.

  By the way, the deformation capacity of the steel frame member is determined mainly by the width-to-thickness ratio of the individual members and the structural characteristic coefficient (hereinafter referred to as "Ds value") is determined and applied to a single-member charging member such as H-shaped steel Yes. The larger the deformation performance, the smaller the Ds value, and the smaller the design seismic force. However, it cannot be applied to the width-thickness ratio of the individual members of the truss beam, and there is no member type of the truss beam itself. Therefore, unless special consideration is made at this time, a large Ds value may be set for the design of the truss beam. It is customary. Therefore, when a truss beam is provided, it is necessary to design it as a “building” with poor deformation performance with a large seismic force (large Ds value), including not only the truss beam but also other columns and beams. It was an uneconomical design.

  In the truss beam 1 as shown in FIG. 10 (A), the chord material at the end of the truss beam is bent and buckled at the end, but the deformation capacity can be deformed in the axial direction without reducing the yield strength. It is supposed to depend on. In particular, a decrease in yield strength after bending buckling of the lower chord material 3 at the end of the truss beam where the axial force is maximum affects the deformation capacity. Here, if the lower chord material 3 that is bent and buckled retains a stable yield strength after buckling and can be deformed in the axial direction without causing a further decline in yield strength, a deformability comparable to that of a satiety material can be obtained. However, it has been confirmed in previous studies. According to these studies, in order to obtain sufficient plastic deformation ability as the truss beam 1, the ratio between the section length l of the lower chord member 3 and the total length L of the beam is 1/8 or more (l / L ≧ 1 / 8) is recommended (non-patent documents 1 and 2).

JP 2006-183324 A JP 2009-185469 A JP 2017-198028 A

The Architectural Institute of Japan “Owned Strength and Deformation Performance in Building Seismic Design (1990)” Architectural Institute of Japan, October 1990 Architectural Institute of Japan "Structural Buckling Design Guideline" Architectural Institute of Japan, November 2009

  FIG. 10 (B) shows an example of a large span truss beam 1. In the truss beam 1 shown in FIG. 10 (B), the ratio of the section length l of the lower chord at the end to the total beam length L is l / L = 1/20. FIG. 10 (C) shows an example of a truss beam with l / L = 1/8 without changing the beam height h in the truss beam 1 having the same span as FIG. 10 (B). In the truss beam 1 shown in FIG. 10 (C), at the same time when the length of the diagonal member 4 becomes longer, the angle θ between the diagonal member 4 and the lower chord member 3 also becomes smaller. The design was uneconomical.

  As described above, the condition of 1 / L ≧ 1/8 is suitable for the truss beam 1 having a relatively small span as shown in FIG. 10A, but is not suitable for the truss beam 1 having a large span.

  In view of such a problem, an object of the present invention is to provide a truss beam having a high plastic deformation capability during an earthquake.

  A truss beam according to at least some embodiments of the present invention comprises an upper chord (12), a lower chord (13) and a plurality of diagonals (14) supported by a pair of structural members (16) The truss beam (11), wherein the plurality of diagonal members are located on the most end side in the extension direction of the lower chord material, and are directed from the end side of the upper chord material toward the central side in the extension direction The first diagonal member (14a) extending obliquely downward, and the second diagonal member (14b) extending obliquely upward toward the center from the vicinity of the lower end of the first diagonal member, The lower end of the first diagonal member and the lower end of the second diagonal member are joined to each other, and through the insulating bonding material (15) slidable in the extending direction when at least a predetermined load is applied. It is joined to the lower chord material.

  According to this configuration, since the insulating bonding material slides along the lower chord material at least during an earthquake of a predetermined scale or larger, the plastic deformation ability of the end portion of the lower chord material is high while maintaining the bending buckling reduction effect. Become.

  In the truss beam according to at least some embodiments of the present invention, the insulating joint material includes a cylindrical member partially covering the lower chord material.

  According to this configuration, the insulating bonding material which slides in the extending direction of the lower chord material and whose movement in the direction orthogonal to the extending direction is restricted can be made with a simple configuration. Further, since the insulating bonding material stiffens the lower chord material, the cross section of the lower chord material at that portion can be further reduced. Since this makes it easy to control the strength of the lower chord material of the portion covered with the insulation joint material, it is possible to concentrate the damage during the earthquake on the portion of the lower chord material covered with the insulation joint material. Therefore, after the earthquake, it is necessary to replace only the portion covered with the insulating joint material in the damaged lower chord material, and the early restoration of the building after the earthquake becomes possible.

  In the truss beam according to at least some embodiments of the present invention, in any of the above-described configurations, the insulating bonding material is broken by a fixture (21) that releases the fixation when the predetermined load is applied. It is fixed to the lower chord material.

  According to this configuration, by using the fixture, the insulating bonding material is normally prevented from sliding against the lower chord material, so that it is possible to prevent an increase in deflection with respect to a long-term load, and when the earthquake occurs, the fixture Since the insulating bonding material is slidable in the extending direction with respect to the lower chord material by breaking, the plastic deformation ability of the end portion of the lower chord material is increased.

  The truss beam according to at least some embodiments of the present invention is characterized in that, in any of the above configurations, the insulating bonding material is separated from the structural member, or the insulating bonding material corresponds. The structure member is in contact with or joined to the structural member.

  According to the former configuration, compared to the latter configuration, the area exposed from the insulating bonding material at the lower chord material end becomes larger, and the lower chord material end is less susceptible to axial deformation restraint. According to the latter configuration, since the insulating bonding material becomes longer than the former configuration, bending buckling of the end portion of the lower chord material can be reduced.

  The truss beam according to at least some embodiments of the present invention further includes a wand (22) whose upper end side is bonded to the insulating bonding material and whose lower end side is bonded to the corresponding structural member in any of the above configurations. It is characterized by that.

  According to this configuration, the rotational rigidity of the end portion of the truss beam 11 is enhanced by having the cane.

  In the truss beam according to at least some embodiments of the present invention, in any of the above-described configurations, the lower chord material is made of H-shaped steel arranged such that a pair of flanges (17) horizontally face each other It is characterized by becoming.

  According to this configuration, since the lower chord material is disposed in a manner more resistant to bending in the horizontal direction than in the vertical direction, bending buckling outside the surface of the lower chord material is reduced.

  In the truss beam according to at least some embodiments of the present invention, in any one of the above configurations, the plurality of diagonal members is an intermediate portion diagonally located on the central side in the extending direction with respect to the second diagonal member. A lower end of at least a portion of the middle portion diagonal member, which has a member (14c), via an intermediate portion insulating bonding member (23) slidable in the extending direction when at least a predetermined load is applied It is joined to the lower chord material.

  According to this structure, the plastic deformation capability of the corresponding part of the lower chord material is enhanced by the intermediate insulating bonding material.

  ADVANTAGE OF THE INVENTION According to this invention, the truss beam with high plastic deformation capability at the time of an earthquake can be provided.

Front view of truss beam according to the embodiment Enlarged front view of the end of the truss beam according to the embodiment III-III sectional view in FIG. Sectional drawing in the same cross section as FIG. 3 of the truss beam which concerns on a 1st modification Enlarged front view of the end of the truss beam according to the second modification Enlarged front view of the end of the truss beam according to the third modification Sectional drawing in the same cross section as FIG. 3 of the truss beam which concerns on a 4th modification Front view of truss beam according to fifth modification Front view of truss beam according to sixth modification Front view of a conventional truss beam

  Hereinafter, a truss beam 11 according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1 and FIG. 2, the truss beam 11 is an insulation interposed between the upper chord 12, the lower chord 13, the plurality of diagonals 14, the lower chord 13 and the diagonals 14 disposed at the end. A bonding material 15 is provided, and both ends thereof are supported by a pair of columns 16, 16.

  The upper chord material 12 and the lower chord material 13 are arranged in parallel to each other substantially along the horizontal direction. The upper chord member 12 and the lower chord member 13 of the present embodiment are linear members, but may be curved members. Although H-shaped steel is used for the upper chord material 12 and the lower chord material 13, long steel materials such as other shaped steels and steel pipes may be used. As shown in FIG. 3, in the lower chord material 13 made of H-shaped steel, the pair of flanges 17, 17 face each other in the vertical direction, and the web 18 is disposed along the vertical plane. The upper chord 12 is also made of H-shaped steel and arranged in the same direction as the lower chord. Both end portions of the upper chord member 12 and the lower chord member 13 are rigidly or pin-joined to the corresponding pillars 16 respectively.

  As shown in FIG. 1 and FIG. 2, the diagonal members 14 are straight steel members, and the plurality of diagonal members 14 are disposed at the most end side in the extending direction of the upper chord 12 and the lower chord 13. The first oblique member 14a, the second oblique member 14b disposed adjacent to the first oblique member 14a, and the middle oblique member 14c disposed on the central side in the extending direction of the second oblique member 14b are included. . A plurality of diagonal members 14 are disposed alternately in a diagonally downward direction and in a diagonally upward direction as going from one end side to the other end side in the extension direction of the truss beam 11. The angle θ with respect to the upper chord 12 and the lower chord 13 of each diagonal 14 is substantially equal, and the section length l of the lower chord 13 (the length between the joining positions of the diagonal 14 in the direction along the lower chord 13) is The lengths of the second diagonal members 14b and the middle diagonal members 14c are substantially equal to each other, and the lengths of the first diagonal members 14a are substantially equal to each other. It is shorter than the oblique member 14c.

  The upper end of the first diagonal member 14 a is rigidly connected or pin-connected to the upper chord member 12 and the column 16. The upper ends of the two diagonal members 14, 14 adjacent to each other are rigidly joined or pin joined to each other and rigidly joined or pin joined to the upper chord member 12. Further, the lower ends of the two middle portion diagonal members 14c and 14c adjacent to each other are rigidly bonded or pin-bonded to each other and rigidly bonded or pin-bonded to the lower chord member 13.

  As shown in FIGS. 1 to 3, the lower end of the first diagonal member 14 a and the lower end of the second diagonal member 14 b are rigidly bonded or pin-bonded to each other, and can be slidable in the extending direction of the lower chord 13. It is joined to the lower chord material 13 via the joining material 15. The insulating bonding material 15 is made of a tubular member such as a square steel pipe coaxial with the lower chord material 13, covers a part of the lower chord material 13 in the extending direction, and is slidably supported by the lower chord material 13. ing. The lower end of the first diagonal member 14 a and the lower end of the second diagonal member 14 b are rigidly bonded or pin-bonded to the insulating bonding material 15.

  In the present embodiment, the upper end of the diagonal member 14 and the upper chord member 12 or the upper chord member 12 and the column 16 are joined, the lower end of the intermediate diagonal member 14c and the lower chord member 13 are joined, and the lower end of the first oblique member 14a. And the lower end of the second diagonal member 14b and the insulating joint material 15 are joined to the upper chord member 12, the upper chord member 12 and the column 16, the lower chord member 13, or the gusset plate 19 welded to the insulating joint member 15 and the diagonal member 14. This is done by fixing the ends of the bolts with bolts (not shown) or the like. Each of the diagonal members 14 is a pair of grooved steels 20, 20 arranged parallel to each other, with the webs 20b facing each other with the openings 20a facing each other, and at their ends, The webs 20b, 20b of the pair of channel steels 20, 20 sandwich the gusset plate 19 (see FIG. 3), which are fixed by bolts (not shown) or the like. In addition, you may use another shape steel and a steel pipe as the diagonal member 14. FIG.

  Since the insulating bonding material 15 slides in the extending direction with respect to the lower chord material 13 at the time of an earthquake, the portion covered with the insulating bonding material 15 is less likely to be subject to axial deformation restraint and is adjacent to the second diagonal material 14b The section (apparent section length l ') from the joint to the lower chord 13 of the middle diagonal 14c to the column 16 can be regarded as an axially deformable section. Therefore, in Non-Patent Documents 1 and 2, it is recommended that the ratio l / L of the section length l of the lower chord 13 to the total beam length L be 1/8 (0.125) or more. In the form, l ′ can be used instead of l. In the truss beam 11 in which 20 diagonal members 14 exist, 1 / L is 1/20 (0.05), but l '/ L is 3/20 (0.15). Therefore, the above-mentioned encouraging value in Non-Patent Documents 1 and 2 can be substantially satisfied. As described above, by using the insulating bonding material 15, the lower chord at the time of an earthquake without changing the shape or member configuration of the truss beam 11 such as the angle θ of the oblique member 14 with respect to the upper chord 12 and the lower chord 13 and the beam h. The plastic deformation ability of the end portion of the material 13 can be increased. Further, since the insulating bonding material 15 covers the lower chord material 13, the movement of the lower chord material 13 in directions other than the extending direction is substantially restricted. Therefore, the bending buckling reduction effect at the end of the lower chord 13 equivalent to the case where the first diagonal 14a and the second diagonal 14b are rigidly joined or pin-joined to the lower chord 13 without using the insulating joint 15 is Have. Thus, since the deformation capacity of the truss beam 11 is improved, it is possible to reduce the Ds value at the time of calculation of the possessed horizontal resistance, and to reduce the amount of steel material.

  Further, since the lower joint material 13 is stiffened so as to restrain the buckling of the portion of the lower chord material 13 covered by the insulation joint material 15, the cross section of the lower chord material 13 in that part is made smaller. can do. This makes it easy to control the strength of the lower chord 13 of the portion covered by the insulating joint 15, so that the damage caused by the earthquake is concentrated on the portion of the lower chord 13 covered by the insulating joint 15. Can do. Therefore, it is only necessary to replace the portion covered with the insulating bonding material 15 in the damaged lower chord 13 after the earthquake, and early restoration of the building after the earthquake becomes possible.

  4-9 shows the 1st-6th modification of the said embodiment. The description of the same configuration as in the above embodiment is omitted.

  In the first modified example shown in FIG. 4, the insulating bonding material 15 is fixed to the lower chord 13 by the fixing tool 21 such as a bolt or a pin, and the fixing tool 21 breaks and releases the fixing when a predetermined load is applied. This is different from the above embodiment. In the above-described embodiment, the rigidity of the truss beam 11 is reduced by using the insulating bonding material 15, and there is a possibility that the deflection with respect to a long-term load such as its own weight may be increased. 15 can be prevented from sliding relative to the lower chord 13 and an increase in deflection can be prevented. In addition, when an earthquake force equal to or greater than a predetermined value acts in the extending direction of the lower chord 13 between the insulating joint 15 and the lower chord 13 at the time of an earthquake, the fixture 21 breaks and the insulating joint 15 becomes the lower chord 13. Slidable in the extending direction. Therefore, during an earthquake, bending buckling is reduced and plastic deformation capability is increased.

  The truss beam 11 according to the second modification shown in FIG. 5 is different from the above-described embodiment in that it has a cane 22 joined to the insulating joining material 15. The crossbar 22 is rigidly bonded or pin-joined to the insulating bonding material 15 at the upper end side, and a structural member of the pillar 16 to which the insulating bonding material 15 is adjacent among the pair of columns 16 and 16 at the lower end side Are rigidly connected or pin-connected. In the illustrated example, the upper end and the lower end of the cane 22 are respectively fixed by bolts (not shown) to the gusset plate 19 welded to the insulating bonding material 15 or the column 16. The cane 22 is, like the diagonal member 14, a straight steel material, and more specifically, is formed of a stack of a pair of grooved steels, another shaped steel, a steel pipe or the like. By using the cane 22, the rotational rigidity of the end of the truss beam 11 is enhanced. The cane 22 may be disposed along the composition surface of the truss beam 11 main body or may be disposed so as to be inclined with respect to the composition surface.

  The truss beam 11 according to the third modification shown in FIG. 6 is different from the above embodiment in the length (ls) and the arrangement of the insulating bonding material 15. In the truss beam 11 shown in FIG. 6 (A), the insulating bonding material 15 is long, and by contacting or joining to the column 16, the effect of reducing the bending and buckling of the end of the lower chord 13 is enhanced. FIG. 6B shows an example in which the insulating bonding material 15 is elongated not only on the column 16 side but also on the opposite side. 6C further shows that the length of the insulating bonding material 15 on the opposite side of the column 16 is increased, and two middle diagonal members 14c, which are the third and fourth diagonal members 14 from the end. , 14c show examples in which rigid bonding or pin bonding is performed on the insulating bonding material 15. FIG. 6D shows the lower ends of the first diagonal member 14a and the second diagonal member 14b, and the lower ends of two middle diagonal members 14c and 14c which are the third and fourth diagonal members 14 from the end. However, rigid joint or pin joint is carried out to the common insulation joint material 15, and the example by which the end by the side of pillar 16 of the insulation joint material 15 estranges from pillar 16 is shown. In the example shown in FIGS. 6C and 6D, the lower end of the first diagonal member 14a and the second diagonal member 14b, and two middle portions that are the third and fourth diagonal members 14 from the end. Since the lower ends of the diagonal members 14c and 14c are rigidly or pin-joined to the insulating joining material 15 slidable with respect to the lower chord material 13, the apparent section length l ′, which is an axially deformable section, is set to the column 16. It can be regarded as a section length from the end to the lower ends of the two middle diagonal members 14c, which are the fifth and sixth diagonal members 14.

  In the 4th modification shown in FIG. 7, the direction of the lower chord material 13 which consists of H-section steel differs from the said embodiment. The lower chord 13 is rotated 90 ° about its extension direction (weak axis) with respect to the aspect shown in FIG. 3, that is, the pair of flanges 17 and 17 face each other in the horizontal direction, and the web 18 is arranged along the horizontal plane. By arranging the lower chord material 13 made of H-shaped steel in such a direction, bending buckling outside the construction surface of the lower chord material 13 is reduced.

  The fifth modified example shown in FIG. 8 is different from the above-described embodiment in that all of the intermediate portion oblique member 14 c is joined to the lower chord member 13 via the intermediate portion insulating bonding member 23. The intermediate portion insulating bonding material 23 has the same structure as the insulating bonding material 15 of the above embodiment. That is, the middle insulating joint material 23 is formed of a tubular member such as a square steel pipe coaxial with the lower chord material 13, covers the periphery for a part in the extension direction of the lower chord material 13, and can slide on the lower chord material 13 It is supported by. The lower ends of the intermediate diagonal members 14c adjacent to each other are bonded to each other and rigidly bonded or pin-bonded to the intermediate insulating bonding material 23. In the illustrated example, the lower ends of the webs 20b and 20b of the pair of channel steels 20 and 20 constituting the intermediate diagonal member 14c sandwich the gusset plate 19 (see FIG. 3), and these are bolts (not shown). ) Etc. By joining the middle diagonal 14c to the lower chord 13 via the middle insulation joint 23, the plastic deformation capability of the corresponding portion of the lower chord 13 is enhanced. The apparent section length l ′, which is an axially deformable section, can be regarded as the beam total length L. The middle insulating joint material 23 may be fixed to the lower chord material 13 by a fixing tool 21 (see FIG. 4) that breaks and releases the fixation when a predetermined load similar to that of the first modification is applied.

  The sixth modification example shown in FIG. 9 is different from the fifth modification example in that a part of the middle portion oblique member 14 c is joined to the lower chord member 13 via the middle portion insulating bonding material 23. Although FIG. 9 shows an example in which the insulating bonding material 15 is in contact with or bonded to the column 16 as in the sixth modification, the insulating bonding material 15 may be separated from the column 16. When a portion of the middle diagonal 14c is joined to the lower chord 13 via the middle insulation joint 23, the plastic deformation capability of the corresponding portion of the lower chord 13 is enhanced.

  Although the description of the specific embodiment is finished above, the present invention can be widely modified and implemented without being limited to the above embodiment. The insulating bonding material may have a shape other than a tubular shape as long as it can slide in the extending direction of the lower chord material and movement in the direction orthogonal to the extending direction is substantially restricted. For example, the upper flange of the lower chord made of H-shaped steel may be covered. The first to fourth modifications may be combined with each other. The fifth modification and the sixth modification may be combined with the first to fourth modifications or a combination thereof. The truss beam may include a vertical member. The truss beam may be supported by another structural member such as a beam instead of the column.

11: Truss beam 12: Upper chord 13: lower chord 14: diagonal 14a: first diagonal 14b: second diagonal 14c: middle diagonal 15: insulation joint 16: pillar 17: flange 21: fixture 22 : Brace 23: Intermediate part insulating bonding material θ: Angle of diagonal material with respect to lower chord material l: Section length of lower chord material L: Total length of beam h: Sei

Claims (8)

A truss beam having an upper chord, a lower chord and a plurality of diagonal members supported by a pair of structural members,
The plurality of diagonal members are located on the most end side in the extending direction of the lower chord and extend obliquely downward from the end side of the upper chord toward the central side in the extending direction. A diagonal member, and a second diagonal member extending obliquely upward from the vicinity of the lower end of the first diagonal member toward the center side,
The lower end of the first diagonal member and the lower end of the second diagonal member are joined to each other, and the lower chord is interposed through an insulating joint member that is slidable in the extending direction when at least a predetermined load is applied. Truss beam characterized by being joined to wood.   The truss beam according to claim 1, wherein the insulating bonding material includes a cylindrical member that partially covers the lower chord material.   The truss beam according to claim 1 or 2, wherein the insulating bonding material is fixed to the lower chord material by a fixing tool that breaks and releases fixation when the predetermined load is applied.   The truss beam according to any one of claims 1 to 3, wherein the insulating bonding material is separated from the structural member.   The truss beam according to any one of claims 1 to 3, wherein the insulating bonding material abuts or is joined to the corresponding structural member.   The truss beam according to any one of claims 1 to 5, further comprising: a crossbar whose upper end is joined to the insulating bonding material and whose lower end is joined to the corresponding structural member.   The truss beam according to any one of claims 1 to 6, wherein the lower chord is made of an H-shaped steel arranged such that a pair of flanges face each other in the horizontal direction. The plurality of diagonal members have a middle diagonal member positioned closer to the center in the extending direction than the second diagonal member,
The lower end of at least a part of the intermediate portion diagonal member is joined to the lower chord member via an intermediate portion insulating bonding member slidable in the extending direction when at least a predetermined load is applied. The truss beam according to any one of claims 1 to 7.

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