JP7116400B2 - truss girder - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to truss beams with high deformability during earthquakes.

A truss girder consists of individual members of chord members and diagonal members, and is a member that resists the axial force generated in each member in the elastic region. Generally, the chord members are straight or curved, and the diagonal members are straight. There are many.

The deformability of steel members is determined mainly by the width-to-thickness ratio of individual members, and is applied to single material filling members such as H-shaped steel. The higher the deformation performance, the smaller the Ds value, and the smaller the seismic force for design. However, it cannot be applied to the width-thickness ratio of individual members of the truss beam, and since there is no member type for the truss beam itself, it is not possible to set a large Ds value in the design of the truss beam unless special consideration is given at this time. It is customary. Therefore, when a truss beam is installed, it is necessary to design it as a "building" with poor deformation performance with a large seismic force (large Ds value). It was an uneconomical design.

In Non-Patent Document 1, in a plane truss member incorporated in a Rahmen frame, by replacing the plasticizing member with a buckling restraint member or a member having stable hysteresis characteristics, the hysteresis is stabilized throughout the truss frame. It is written that it is possible to design to give characteristics, and it is possible to treat the frame in the same way as filling materials (H-shaped steel, etc.) without considering the effects of individual buckling.

For example, Patent Literature 1 describes a buckling restraint member. This buckling restraint member is used as a vibration damping brace that is placed obliquely in the frame structure of the columns and beams of a building. and a filling material filled in the steel pipe so as not to adhere to the core material. The buckling of the plasticized core material is restrained by the steel pipe and the filler material.

JP 2005-146773 A

Architectural Institute of Japan, "Steel Structure Buckling Design Guidelines", Architectural Institute of Japan, November 2009

FIG. 9(A) shows the joint between the top chord and two diagonal members above the buckling restraint when the buckling restraint is applied to a section of the bottom chord of the truss girder. According to FEM analysis, when the buckling restraint member is elongated, the upper flange of the upper chord member made of H-shaped steel and the region near the bolt that fastens the diagonal member to the gusset plate yield at the joint. The other part was the elastic region. In this way, the stress was concentrated on the upper flange of the upper chord member and part of the diagonal members.

In view of such problems, it is an object of the present invention to provide a truss beam that has a high deformability during an earthquake and that suppresses concentration of stress on chord members and diagonal members during an earthquake. do.

At least some embodiments of the present invention are truss beams (1, 31) having a top chord (2), a bottom chord (3) and a plurality of diagonals (4), said bottom chord being elongated a body portion (6) having a lower chord member, and a main body portion (6) arranged to replace the main body portion in a part of the section in the extending direction of the lower chord member, and at least in the event of an earthquake of a predetermined scale or more, the body portion (6) in the extending direction of the lower chord member and a deformation-permitting member (7) whose deformation per unit length is larger than that of the main body portion. ) and a second diagonal member (18), wherein at least a portion of the deformation-allowing member extends below the first diagonal member and/or the second diagonal member, and the upper chord member includes the first diagonal member It has a first upper chord member (15) to which the upper end side of the diagonal member is joined, and a second upper chord member (16) to which the upper end side of the second diagonal member is joined, wherein the first upper chord member and the second upper chord member are are connected to each other by a first pin joint structure (19, 32) that can be regarded as a pin joint at least in the event of an earthquake of a predetermined magnitude or more. The deformation-permitting member is preferably a buckling restraint member (7) including a member (10) that is plasticized before the main body and whose buckling is restrained when a predetermined load is applied.

According to this configuration, even if the deformation-permitting member (buckling restraint member) expands and contracts during an earthquake, the first pin joint structure causes the first upper chord member and the second upper chord member to rotate relative to each other. Concentration of stress on a portion of the material located above the deformation permitting member (buckling restraint member) is suppressed.

In the truss beam (1) according to at least some embodiments of the present invention, in the above configuration, the first upper chord member and the second upper chord member each include H-shaped steel, and the first pin joint structure ( 19) includes a splice plate (14) and a fastener (20) for fastening the splice plate to the web (9) of the first top chord and the second top chord; through-holes (24) are configured such that the shanks of the fasteners are inserted with play and the flanges (8) of the first upper chord and the second upper chord are substantially not joined together; Characterized by

According to this configuration, the first pin joint structure can be produced with a relatively inexpensive configuration.

In the truss beam (1) according to at least some embodiments of the present invention, in the above configuration, the first pin joint structure is welded to the webs of the first top chord member and the second top chord member, and the splice It is characterized by having a reinforcing plate (23) against which the plate abuts.

Since the flanges of the first upper chord member and the second upper chord member are not joined together, the axial force is concentrated on the web. can withstand force.

According to at least some embodiments of the truss beam (1, 31) of the present invention, in any one of the above configurations, both ends of the deformation-allowing member are respectively connected to the first diagonal member and the main body. and the joints between the second diagonal members and the main body, and the joints between both ends of the deformation-allowing member and the main body can be regarded as pin joints at least in the event of an earthquake of a predetermined scale or more. It is characterized by including a pin junction structure (25).

According to this configuration, even if the deformation-allowing member expands and contracts during an earthquake, the main body and the first diagonal member and the second diagonal member rotate relative to each other due to the second pin joint structure. Concentration of stress is suppressed.

At least some embodiments of the truss beam (1, 31) according to any of the above configurations, wherein the first pin joint structure (19, 32) and the deformation-allowing member are The first diagonal member and the second diagonal member are the second and third diagonal members from the end of the truss beam, respectively.

According to this configuration, since the deformation-allowing member is arranged in the vicinity of the end where stress tends to be relatively high, it is possible to efficiently absorb the energy during an earthquake.

Advantageous Effects of Invention According to the present invention, it is possible to provide a truss beam that has a high deformability during an earthquake and that suppresses concentration of stress on chord members and diagonal members during an earthquake.

The front view which shows the truss beam which concerns on embodiment The front view which shows the 1st pin joint part in the truss girder which concerns on embodiment The top view which shows the 1st pin joint part in the truss beam which concerns on embodiment The front view which shows the 1st pin joint part in the truss girder which concerns on embodiment (illustration of a splice plate and a fastener is abbreviate|omitted) A top view showing the 1st pin joint part in the truss girder concerning an embodiment (illustration of a splice plate and a fastener is omitted) The front view which shows the 2nd pin joint part in the truss beam which concerns on embodiment The front view which shows the truss beam which concerns on a modification The front view which shows typically the truss beam which concerns on an Example Front views showing FEM analysis results of joints in truss beams according to comparative examples and examples (A: comparative example, B: example)

A truss beam 1 according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, the extending direction of the truss beam 1 is defined as the horizontal direction.

FIG. 1 shows a truss beam 1 according to an embodiment. The truss beam 1 has an upper chord member 2, a lower chord member 3 arranged below the upper chord member 2, and a plurality of diagonal members 4 having both ends joined to the upper chord member 2 and the lower chord member 3, respectively. is supported by the pillar 5. Since the truss beam 1 is generally bilaterally symmetrical, one of both ends will be described as an example, but the other end has the same configuration.

The upper chord members 2 and the lower chord members 3 are arranged parallel to each other along the generally horizontal direction. Although the upper chord member 2 and the lower chord member 3 of the present embodiment are straight members, they may be curved members. The upper chord member 2 is formed by connecting a plurality of elongated members such as H-shaped steel. The lower chord member 3 is arranged so as to replace the main body portion 6 formed by connecting a plurality of long members such as H-shaped steel, and the vicinity of both end portions in the extending direction of the lower chord member 3. and a deformation permitting member such as a buckling restraint member 7 having both ends connected to the body portion 6 . That is, the body portion 6 is separated near the left and right ends of the lower chord member 3, and the three divided body portions 6 are connected by two buckling restraint members 7 extending in the left-right direction. . The H-section steel used for the entire upper chord member 2 and the main body portion 6 of the lower chord member 3 is arranged such that a pair of flanges 8 face each other vertically and a web 9 extends along a vertical plane.

The plurality of diagonal members 4 are alternately arranged diagonally downward and diagonally upward from one end side to the other end side in the extending direction of the truss beam 1 . Each diagonal member 4 consists of a pair of steel strips, such as channel steels, arranged parallel to each other. The angles of each diagonal member 4 with respect to the upper chord member 2 and the lower chord member 3 are approximately equal to each other.

The buckling restraint member 7 includes a core material 10 having both ends joined to the body part 6, a cylindrical body 11 through which the core material 10 is inserted so that the ends of the core material 10 protrude from the both ends, A filling material (not shown) such as grout is filled in the cylindrical body 11 so as not to adhere to the core material 10 . The core material 10 is a member that plasticizes before the body part 6 when a predetermined load is applied. It consists of a steel material welded with a steel plate. The cylindrical body 11 is made of a rectangular or circular steel pipe and restrains the buckling of the core material 10 in cooperation with the filler. When the core member 10 expands and contracts without buckling during an earthquake, energy is absorbed by the core member 10 and the load on other members of the truss beam 1 is reduced. The deformation-allowing member is a member that deforms more per unit length in the extending direction of the lower chord member 3 than the main body portion 6 at least during an earthquake of a predetermined scale or more. An example of a deformation-allowing member other than the buckling restraint member 7 is a vibration damper.

The joints between the H-section steels forming the upper chord member 2 and the joints between the H-section steels forming the body portion 6 of the lower chord member 3 are rigid joint structures 13 except for the joint above the buckling restraint member 7. . The rigid joint structure 13 applies a splice plate 14 to the respective surfaces of the web 9 and the flange 8 of the end of the H-beam to be joined together, and the web 9 and the flange 8 respectively and the splice plate 14 attached thereto. are fastened with fasteners (not shown) such as bolts and nuts.

The top chord 2 has a first top chord 15 and a second top chord 16 joined together above the buckling restraint member 7 . The first upper chord member 15 is the H-section steel arranged at the end, and the second upper chord member 16 is the H-section steel arranged second from the end. The diagonal member 4 has a first diagonal member 17 and a second diagonal member 18 which are adjacent to each other on the upper end side and have the buckling restraint member 7 arranged between their lower ends. The first diagonal member 17 is the second diagonal member 4 from the end of the truss beam 1 , and the second diagonal member is the third diagonal member 4 from the end of the truss beam 1 . The first upper chord member 15 and the second upper chord member 16 are joined to each other at the joining portions of the upper ends of the first diagonal member 17 and the second diagonal member 18 to the upper chord member 2 . The joint between the first top chord member 15 and the second top chord member 16 is a first pin joint structure 19 that can be regarded as a rigid joint in normal times, but can be regarded as a pin joint in the event of an earthquake of a predetermined scale or larger.

As shown in FIGS. 2 and 3 , the ends of the first top chord member 15 and the second top chord member 16 joined by the first pin joining structure 19 are splice plates 14 attached to both surfaces of the web 9 . are fastened by fasteners 20 such as bolts and nuts, but the flanges 8 are not joined together. The gusset plate 21 to which the upper end portion of the first diagonal member 17 is fastened and the gusset plate 21 to which the upper end portion of the second diagonal member 18 is fastened are separate members, and are the first upper chord member 15 and the second upper chord member 15, respectively. It is welded to the top chord material 16 . The joining of the upper ends of the first diagonal member 17 and the second diagonal member 18 to the first upper chord member 15 and the second upper chord member 16 via the gusset plate 21 can be regarded as a rigid joint. As shown in FIG. 1, joining two diagonal members 4 adjacent to each other on the upper end side other than the upper ends of the first diagonal member 17 and the second diagonal member 18 to the upper chord member 2 is Through the gusset plate 22, which is integral. Similarly, two diagonal members 4 adjacent to each other on the lower end side are joined to the lower chord member 3 via an integral gusset plate 22 .

As shown in FIGS. 2 and 3, the gusset plate 21 is arranged and attached to the first steel plate 21a arranged parallel to the horizontal direction and the vertical direction of the truss beam 1 so as to be perpendicular to the horizontal direction. and a second steel plate 21b welded to the end portion of the first steel plate 21a on the laterally outer side of the first diagonal member 17 or the second diagonal member 18, and welded to the first upper chord member 15 or the second upper chord member 16 at the upper end. It is Similarly, as shown in FIG. 1, the gusset plate 22 is arranged so as to be perpendicular to the first steel plate 22a arranged in the left-right direction and the up-down direction in parallel with the surface of the first steel plate 22a. It has a second steel plate 22b welded to the center of the left and right, and is welded to the upper chord member 2 at its upper end or welded to the lower chord member 3 at its lower end. A pair of channel steels forming each diagonal member 4 are arranged so as to sandwich the first steel plates 21a, 22a.

As shown in FIGS. 2 and 3, in the first pin joint structure 19, the flanges 8 of the first upper chord member 15 and the second upper chord member 16 are not joined together, but are joined only by the webs 9. , the axial forces transmitted between the first top chord 15 and the second top chord 16 are concentrated in the web. Therefore, as shown in FIGS. 4 and 5, reinforcing plates 23 are welded to both surfaces of the web 9 at the ends of the first upper chord member 15 and the second upper chord member 16 on the first pin joint structure 19 side. . The reinforcing plate 23 is equivalent to the upper and lower flanges 8. For example, if the reinforcing plate 23 and the flange 8 are made of the same material, the total cross-sectional area of the two reinforcing plates 23 in a cross section perpendicular to the left-right direction is Approximately equal to the total cross-sectional area of the upper and lower flanges 8 . Therefore, in the first upper chord member 15 and the second upper chord member 16, the axial force transmitted by the flange 8 in the intermediate portion is directed to the web 9 by the first pin joint structure 19, and the axial force is concentrated on the web 9. However, the web 9 reinforced by the reinforcing plate 23 can withstand the force.

The web 9 of the first upper chord member 15 and the second upper chord member 16 and the reinforcing plate 23 are provided with through holes 24 through which the shaft portions of the bolts constituting the fasteners 20 are inserted. Since the diameter of the through hole 24 is larger than the diameter of the shank, there is play between the through hole 24 and the shank. Normally, the rigid joint state is maintained by the frictional force between the fastener 20, the splice plate 14 and the reinforcing plate 23. FIG. During an earthquake of a predetermined magnitude or greater, slippage occurs between the bolt heads and nuts constituting the fastener 20 and the splice plate 14 or between the splice plate 14 and the reinforcing plate 23 . At this time, since there is play between the through-hole 24 and the shaft portion of the bolt, the first upper chord member 15 and the second upper chord member 16 move relative to each other with respect to the direction orthogonal to the left-right direction and the up-down direction. Can rotate within range. The amount of play is determined according to the desired range of rotation. The through hole 24 may be an elongated hole.

As shown in FIG. 6, the joint between the main body 6 and the buckling restraint member 7 is a second pin joint structure 25 which can be regarded as a rigid joint in normal times, but can be regarded as a pin joint in the event of an earthquake of a predetermined magnitude or larger. At the end of the main body 6 made of H-shaped steel on the side joined to the buckling restraint member 7, a web 9 is formed so as to correspond to the cross-shaped cross-sectional shape of the core material 10 of the buckling restraint member 7. A third steel plate 26 is welded to both surfaces. A splice plate 14 is attached to the surface of the core material 10 having a cross-shaped cross section and the surfaces of the web 9 and the third steel plate 26 of the main body 6 and fastened with fasteners 20 . A filler plate (not shown) is used when the web 9 of the main body 6 and the steel material of the core material 10 connected thereto have different thicknesses. The core member 10 , the main body 6 , and the through holes (not shown) of the splice plate 14 have diameters larger than the diameter of the shaft of the bolt that constitutes the fastener 20 . Therefore, for the same reason as the first pin-joint structure 19, the second pin-joint structure 25 can be regarded as a rigid joint in normal times, and can be regarded as a pin-joint in the event of an earthquake of a predetermined magnitude or greater.

A fourth steel plate 27 is welded to the end of the third steel plate 26 opposite to the core material 10 so as to receive the axial force transmitted from the core material 10 to the third steel plate 26 . The fourth steel plate 27 is arranged so as to be orthogonal to the left-right direction, and its edge is welded to the flange 8 and the web 9 of the body portion 6 . The fourth steel plate 27 makes it easier for the axial force transmitted from the core material 10 to the main body 6 to be transmitted not only to the web 9 of the main body 6 but also to the flange 8, and the axial force that was transmitted by the flange 8 of the main body 6 is easily transmitted to the core material 10. In addition, the fourth steel plate 27 may be changed into a V shape in a front view so as to approach the upper and lower flanges 8 as it is separated from the core member 10 in the left-right direction.

The effects of the truss beam 1 will be described. In the case where the joint portion between the first upper chord member 15 and the second upper chord member 16 is a rigid joint, or the intermediate portion of one elongated member that constitutes a part of the upper chord member 2, the first diagonal member 17 and the second diagonal member 17 are connected to each other. When the upper ends of the two diagonal members 18 are joined, large bending stress is generated at this portion of the upper chord member 2 and the upper ends of the first upper chord member 15 and the second upper chord member 16 due to expansion and contraction of the core member 10 during an earthquake. On the other hand, by forming the first pin joint structure 19 at the joint between the first upper chord member 15 and the second upper chord member 16, even if the core member 10 expands and contracts during an earthquake, this joint rotates. Concentration of bending stress on the upper chord member 2 , the first upper chord member 15 and the second upper chord member 16 can be suppressed. Similarly, by forming the joint portion between the main body portion 6 of the lower chord member 3 and the buckling restraint member 7 as the second pin joint structure 25, the main body portion 6, the core member 10, and the diagonal members in the vicinity of this joint portion are formed. Concentration of bending stress on 4 can be suppressed.

FIG. 7 shows a truss beam 31 according to a modification. In the explanation, the same reference numerals are given to the configurations common to the above-described embodiment, and the explanation thereof is omitted. In this truss beam 31, the first upper chord member 15 and the second upper chord member 16 are joined to each other by a first pin joint structure 32 formed by a clevis. That is, the joining of the first upper chord member 15 and the second upper chord member 16 can be regarded as pin joining not only during an earthquake but also during normal times.

The FEM analysis result of the model shown in FIG. 8 is shown in FIG. 9(B). FIG. 9A shows, as a comparative example, a case where the upper ends of the first diagonal member 17 and the second diagonal member 18 are joined to the intermediate portion of one elongated member forming part of the upper chord member 2. An FEM analysis result is shown. FIG. 9 shows a state in which the core material 10 (see FIG. 1) of the buckling restraint member 7 arranged below is stretched, and the portion indicated by the dot pattern reaches the yield zone due to concentrated stress. This is the part where

In the comparative example shown in FIG. 9A, the upper flange 8 of the upper chord member 2 and the vicinity of the upper ends of the first diagonal member 17 and the second diagonal member 18 reach the yield region. On the other hand, in the embodiment shown in FIG. 9B, the yield zone is reached near the splice plate 14 and the web 9 of the first top chord 15 and the second top chord 16 . It is believed that the splice plate 14 reached the yield zone because the bolt slipped against the edge of the through hole 24 (see FIG. 4) and a portion of the web 9 reached the yield zone at this splice. It is believed that stress was transmitted from the plate 14 . Therefore, by strengthening the splice plate 14, the earthquake resistance of the truss beam 1 can be improved.

Although the specific embodiments have been described above, the present invention is not limited to the above embodiments and can be widely modified. A truss beam may be supported by structural members of a building other than columns, such as beams.

1, 31: truss beam 2: upper chord member 3: lower chord member 4: diagonal member 6: body portion 7: buckling restraint member (deformation permitting member)
8: Flange 9: Web 10: Core 14: Splice plate 15: First upper chord member 16: Second upper chord member 17: First diagonal member 18: Second diagonal member 19, 32: First pin joint structure 20: Fastening Tool 23: Reinforcing plate 24: Through hole 25: Second pin joint structure

Claims (6)

A truss girder having a top chord, a bottom chord and a plurality of diagonal members,
The lower chord member has a main body portion having a long member, and is arranged to replace the main body portion in a part of the section in the extending direction of the lower chord member. a deformation-allowing member having a deformation per unit length in a direction greater than that of the main body,
The diagonal member includes a first diagonal member and a second diagonal member that are adjacent to each other such that the upper end side is closer than the lower end side,
At least part of the deformation-allowing member extends below the first diagonal member and/or the second diagonal member,
The upper chord member has a first upper chord member to which the upper end side of the first diagonal member is joined, and a second upper chord member to which the upper end side of the second diagonal member is joined,
A truss girder, wherein the first upper chord member and the second upper chord member are joined to each other by a first pin joint structure that can be regarded as a pin joint in the event of an earthquake of at least a predetermined scale or more. 2. The deformation-permitting member according to claim 1, wherein the deformation-permitting member is a buckling restraint member including a member that is plasticized before the main body and whose buckling is restrained when a predetermined load is applied. truss girder. The first upper chord member and the second upper chord member each include an H-section steel,
The first pin connection structure includes a splice plate and a fastener for fastening the splice plate to the webs of the first upper chord member and the second upper chord member, and the splice plate and the web have through holes. 3. The fastener according to claim 1, wherein the shaft portion of the fastener is inserted with play so that the flanges of the first upper chord member and the second upper chord member are substantially not joined to each other. truss beam. 4. The truss girder according to claim 3, wherein said first pin joint structure includes a reinforcing plate welded to said web of said first top chord member and said second top chord member and against which said splice plate abuts. both ends of the deformation-allowing member are respectively joined to a joint portion between the first diagonal member and the main body portion and to a joint portion between the second diagonal member and the main body portion;
5. The connection between both ends of the deformation-allowing member and the main body includes a second pin connection structure that can be regarded as a pin connection at least in the event of an earthquake of a predetermined magnitude or more. truss girder described in . The first pin joint structure and the deformation-allowing member are provided at both ends of the truss girder, and the first diagonal member and the second diagonal member are respectively second and third from the end of the truss girder. The truss girder according to any one of claims 1 to 5, characterized in that it is the second diagonal member.

Images