JP2013083088A - String beam - Google Patents

Abstract

The present invention provides a stringed beam that facilitates the design of a joint portion between an upper chord member and a lower chord member and can suppress breakage of the joint portion.
An upper chord material 10 made of H steel and having an upper flange 12 and a lower flange 13 disposed above and below a vertically extending web 11, and made of flat steel and joined portions 30 at both ends of the upper chord material 10. In the stringed beam 1 having the lower chord member 22 to be joined together and the bundle member 25 that connects the upper chord member 10 and the lower chord member 22 at an intermediate position in the axial direction, The lower chord member 22 is formed in a straight line from the beam end side 30a to the first bundle member 25 and the lower surface of the upper chord member 10 at the joint 30 is viewed from the side perpendicular to the axis. The inclined surface 17 extends along the material axis direction of the (shaft end portion 24).
[Selection] Figure 3

Description

  The present invention relates to a tension string beam having an upper chord material and a lower chord material suitable for a beam having a composite beam floor structure.

  Many buildings that require large-span columnless spaces such as sports facilities and halls use stringed beams for the roof structure. The tension string beam is a beam having a mixed structure in which a beam having bending rigidity and compression rigidity is used as an upper chord material, a tension material is used as a lower chord material, and an upper chord material and a lower chord material are coupled via a bundle material.

  On the other hand, in a composite beam structure in which a steel beam and a concrete floor slab are integrated, a composite beam structure using a stringed beam instead of a conventional H-shaped steel beam is known (see Patent Document 1). The stringed beam of Patent Document 1 is configured as shown in FIG. That is, in this string 101, the upper chord member 110 is made of H-shaped steel having a small cross section, the lower chord member 122 is made of flat steel, and the end portion of the upper chord member 110 is obliquely cut along the angle of the lower chord member 122, so that the upper chord member The amount of steel used is greatly reduced by welding them so that the web 111 of 110 and the lower chord material 122 are in an inverted T shape, and the same simplicity as the conventional structure using H-shaped steel for the beam Is realized.

JP 2006-328631 A

  By the way, in the tension string beam structure which constitutes a long span composite beam structure such as logistics / commercial / production facilities, a very large force acts on the end portion where the upper chord material and the lower chord material are joined. For this reason, it is necessary to increase the rigidity of the joint and the joint strength between the members. Moreover, the required welding length when welding two members is determined according to the magnitude of the stress generated in the welded portion and the strength of the lower strength base material of the members to be welded.

  In the invention of Patent Document 1, as shown in FIG. 11, in addition to welding the web 111 of the upper chord member 110 and the lower chord member 122, the end of the chord beam 101 is slanted (the bridge of the chord beam 101 is bridged). The upper chord member 110 and the lower chord member 122 can be used together with a plate steel plate for stiffening (hereinafter referred to as an oblique stiffener 127) disposed in a direction (hereinafter referred to as an axial direction). The rigidity of the joint portion and the joint strength of both members are ensured, and the diagonal stiffener 127 bears a part of the tensile force of the lower chord material 122, thereby shortening the welding length along the lower chord material 122. I am trying to let you. Then, the gusset plate 126 provided at the end of the beam to be used for support and the stiffener 103 provided on the large beam 102 orthogonal to the stringed beam 101 (small beam) are connected by the joint plate 104, The stringed beam 101 is supported by the large beam 102. Note that the gusset plate 126 supports only the vertical load received by the stringed beam 101, and a welded portion (not shown) between the gusset plate 126 and the lower chord material 122 does not contribute to the load of the tensile force from the lower chord material.

  However, in the invention of Patent Document 1, the angle α of the oblique stiffener 127 with respect to the pulling direction (material axis direction) of the lower chord material 122 indicated by the white arrow is smaller than 90 degrees. Has a compressive resistance. Therefore, it is necessary to consider buckling in the cross-sectional design of the oblique stiffener 127. As a result, even if the plate thickness of the oblique stiffener 127 has a sufficient allowable compressive stress, if the member length becomes long in order to secure the weld length, the plate thickness must be increased to withstand buckling. In such a case, the cost increases.

  On the other hand, as shown in FIG. 12, a flat steel forming the lower chord material 222 that is bent into a letter-shape when viewed from the side perpendicular to the axis is joined to the lower flange 213 of the H-shaped steel forming the upper chord material 210 by a bolt 233. The configuration is known (see JP 2001-342710 A). According to this configuration, the joining strength can be easily ensured by increasing the region of the joint portion 230 between the upper chord member 210 and the lower chord member 222 and the number of bolts 233. However, in this configuration, the tensile force of the lower chord material 222 is concentrated on the fold-shaped bent portion 222a (the end portion on the beam center side of the joint portion 30). In particular, the floor slab is used as a traveling path of the transportation truck. In such a case, there is a possibility that the joint 230 may undergo fatigue failure sequentially from the bent portion 222a on the beam center side due to vibration.

  The present invention has been made in view of such a background, and it is a main object of the present invention to provide a stringed beam that facilitates the design of the joint portion between the upper chord member and the lower chord member and can suppress breakage of the joint portion. And

  In order to solve the above problems, the present invention includes an upper chord material (10) in which an upper flange (12) and a lower flange (13) are arranged above and below a vertically extending web (11), and a flat upper surface ( 22u), and a lower chord member (22) joined to both ends of the upper chord member with joints (30), and at least one connecting the upper chord member and the lower chord member at an intermediate position in the axial direction. A stringed beam (1) having a bundle member (25), wherein the lower chord member has a straight line shape from an end (30a) on the beam end side of the joint portion to the first bundle member. The lower surface of the upper chord member at the joint is an inclined surface (17) along the material axis direction of the lower chord member in a side view from the direction perpendicular to the axis.

  By adopting such a configuration, a tensile force acts in parallel with the joint portion of the lower chord material with the upper chord material, so that the tensile force transmitted from the lower chord material to the upper chord material is evenly distributed. Therefore, it is possible to suppress the occurrence of breakage in the joint due to the concentration of the tensile force.

  Further, according to one aspect of the present invention, the lower chord member can be configured to be joined to the upper chord member and the bundle member by bolts (33, 28).

  By setting it as such a structure, a lower chord material can be easily isolate | separated from an upper chord material by cancel | releasing the fastening of a volt | bolt. Therefore, the lower chord material can be replaced with a new one before fatigue failure occurs, or the lower chord material can be replaced with a higher-strength material according to changes in the design load of the stringed beam, ensuring that the joint is not damaged. Can be prevented.

  Further, according to one aspect of the present invention, the lower end is formed horizontally on the beam end side of the joint portion in the upper chord member, and the horizontal end portion (16) placed on the cradle (3) is provided. It can be set as the formed structure.

  With such a configuration, the stringed beam can be supported by the pedestal with the horizontal end placed on the cradle, and the support structure of the stringed beam is supported by a pin that supports the vertical load or It can be close to the pin-roller support, and it is possible to prevent unnecessary stress from being generated in the stringed beam.

  Further, according to one aspect of the present invention, the upper chord member is joined to an upper chord member (18) made of H-shaped steel and a lower surface of both end portions of the upper chord member, and has an inclined surface and is tapered. It can be set as the structure which has a pair of lower chord joining member (19) which makes a shape.

  By adopting such a configuration, it is not necessary to perform a process of providing an inclined surface on the upper chord member, and it is only necessary to process the inclined surface on the lower chord joint member, which is a small member, so that processing and handling of each member are easy. .

  As described above, according to the present invention, it is possible to provide a stringed beam that facilitates the design of the joint portion between the upper chord member and the lower chord member and can suppress breakage of the joint portion.

Side view of a stringed beam according to the first embodiment II sectional view in FIG. Fig. 1 is an enlarged side view of the main part of the string string beam shown in Fig. 1. Bottom view of the main part of the string beam shown in FIG. Explanatory drawing of the effect of the string beam shown in FIG. Bottom view of the main part of a stringed beam according to a modification Side view of a stringed beam according to the second embodiment Fig. 7 is an enlarged side view of the main part of the string string beam shown in Fig. 7. Exploded side view of the string beam shown in FIG. Side view of the main part of a stringed beam according to the third embodiment Side view of the main parts of a conventional stringed beam Side view of the main parts of a conventional stringed beam

  Hereinafter, some embodiments of the stringed beam 1 according to the present invention will be described in detail with reference to the drawings. In the second and subsequent embodiments, the same members as those in the first embodiment are denoted by the same reference numerals, and the description overlapping with the first embodiment is omitted.

<< First Embodiment >>
First, with reference to FIGS. 1-6, 1st Embodiment of this invention and its modification are demonstrated. As shown in FIGS. 1 and 2, the string string 1 is placed on a cradle 3 provided on the large beams 2 and 2 and is bridged between the pair of large beams 2 and 2 by a simple support method. The bolts and nuts 5 for prevention are fixed to the cradle 3 with a small axial force. The cradle 3 has a horizontal surface whose top surface is substantially horizontal, and a bolt insertion hole (not shown) is formed on the horizontal surface. Two or more string strings 1 are bridged between the large beams 2 and 2 and support the floor slab 6 arranged thereon to constitute a large span composite beam floor structure. In addition, when the floor slab 6 is already installed, it is also possible to provide the stringed beam 1 below the floor slab 6 and use the stringed beam 1 for reinforcing the floor slab 6.

  The stringed beam 1 is formed by processing an H-shaped steel, and is composed of an upper chord material 10 having an I-shaped cross section in which an upper flange 12 and a lower flange 13 are arranged above and below a vertically extending web 11, and a flat steel. 22u and the lower surface 22l form a horizontal flat surface in a cross-sectional view, and the lower chord member 22 whose ends are joined to both ends of the upper chord member 10 by the joint portions 30, and the upper chord member 10 are divided into three equal parts in the axial direction. It has two bundle members 25 made of H-shaped steel that connect the upper chord member 10 and the lower chord member 22 in the vertical direction at the position.

  In a side view from the direction perpendicular to the axis (FIG. 1), the straight upper chord material 10 is horizontally arranged so that the upper surface forms a horizontal plane. On the other hand, the lower chord member 22 is formed to be bent at the beam end side at the position where the two bundle members 25 are joined and protrude downward, and is disposed horizontally between the two bundle members 25. A straight central portion 23 and a pair of linear axial end portions 24 that are disposed on both sides in the axial direction of the central portion 23 and incline upward toward the beam end.

  The H-shaped steel used for the upper chord member 10 and the bundle member 25 is made of JIS-standard hot rolled steel for general structure (G3101, SS400). The yield strength (yield point or yield strength) of SS400 is 245 N / mm 2 (when the thickness of the steel material is 16 mm or less). On the other hand, the flat steel used for the lower chord material 22 is made of JIS standard rolled steel for welded structure (G3106, SM490), which has higher yield strength and is suitable for welding. The yield strength of SM490 is 325 N / mm 2 (when the thickness of the steel material is 16 mm or less).

  As shown in FIG. 3, the upper chord member 10 includes a tapered portion 15 configured such that the lower flange 13 is inclined upward toward the shaft end so that the height of the web 11 is reduced at the end portion, and the tapered portion 15. Continuing from the portion 15, the lower flange 13 has a horizontal end portion 16 configured to be parallel (horizontal) to the upper flange 12 again while the height of the web 11 is small. A long hole (not shown) for inserting a bolt is formed in the lower flange 13 at the horizontal end 16 of the upper chord member 10 where the lower flange 13 is horizontal.

  On the other hand, the lower surface of the tapered portion 15 in which the lower flange 13 is inclined is an inclined surface 17 having an inclination angle along the material axis direction of the shaft end portion 24 of the lower chord material 22 in a side view from the direction perpendicular to the axis (FIG. 1). ing. The lower chord material 22 is joined to the upper chord material 10 in a state of surface contact with the inclined surface 17 at the joint portion 30. That is, in the lower chord material 22, a portion (a shaft end portion 24) between the end 30 a on the beam end side of the joint portion 30 and the first bundle member 25 is linear.

  As shown in FIG. 4, the lower chord member 22 is narrower than the lower flange 13 of the upper chord member 10, and the joint portion 30 is configured by fillet welding by continuous welding along both side edges and end edges thereof. It is joined to the upper chord material 10 by continuous linear beads 32 formed in three directions. On the other hand, the bundle member 25 is also welded to the upper chord member 10 and the lower chord member 22.

  As shown in FIGS. 1 and 3, a stiffener 14 that connects the upper flange 12 and the lower flange 13 is vertically connected to two joint portions of the upper chord member 10 in the axial direction of the tapered portion 15 and the bundle member 25. It is welded also to the web 11 in the state arrange | positioned in (3).

  Since the stringed beam 1 has such a configuration, the weld length of the joint portion 30 (full length of the bead 32) is ensured sufficiently long, and the tensile force of the lower chord member 22 is applied in parallel with the joint surface of the joint portion 30. Then, it is transmitted to the upper chord member 10 while being dispersed throughout the joint 30. Therefore, it is possible to prevent the joint 30 from being damaged due to the concentration of the tensile force.

  Further, the stringed beam 1 has a simple support type support structure that is supported by the cradle 3 via the horizontal end portion 16 of the upper chord member 10, and therefore has the following operational effects. That is, referring to FIG. 5, first, as shown in FIG. 5C, a gusset plate 126 formed at the lower end of the stringed beam 101 is supported by the stiffener 103 of the large beam 102 via the joint plate 104 (patent). In the stringed beam 101 of Document 1), since the tensile force of the lower chord material 122 indicated by the white arrow acts at a position away from the center of the joint plate 104, a moment as indicated by the black arrow is generated on the joint plate 104. Therefore, not only the joint plate 104 but also the strength of the gusset plate 126 and the stiffener 103 is required. Furthermore, since a moment is generated in the gusset plate 126, the stress condition at the end of the stringed beam 101 becomes complicated. In addition, level adjustment with the large beam 102 is necessary, and it takes time to construct the stringed beam 101.

  On the other hand, in the stringed beam 1 according to the embodiment, as shown in FIG. 5 (A), the upper chord member 10 has a compressive resistance as indicated by the black arrow by the tensile force of the lower chord member 22 indicated by the white arrow. As a result, a compression resistance force in the vertical direction is generated in the cradle 3. That is, the stringed beam 1 has a pin support structure as shown on the left side of (B). Further, a long hole is formed in the horizontal end portion 16 of the upper chord member 10, and it is fixed to the cradle 3 with a small axial force by the bolt and nut 5, so that the support close to the roller type as shown on the right side of FIG. It becomes a structure. Therefore, the tensile force generated in the lower chord member 22 is balanced with the compressive force of the upper chord member 10, and the tensioned string beam 1 is in a completely self-closed stress state, so that the support portion bears only a normal vertical load. Therefore, there is no moment or horizontal force acting on the stringed beam 1, and a simple and rational design is possible.

  Further, when installing the stringed beam 1, leveling and positioning can be performed simply by placing the horizontal end 16 on the cradle 3 and installing the bolts and nuts 5. Reduced. Furthermore, since the support type of the stringed beam 1 is a cradle type, in addition to saving labor when the stringed beam 1 is installed, the vertical rigidity of the support portion is increased compared to the conventional bolted connection method using the joint plate 104. Improvement in usability against vibration can be expected. Further, since the space is generated in this portion by omitting the gusset plate 126 for supporting the stringed beam 1, it is also effective for application to a building that requires piping or the like along the large beam 2.

  Further, a shearing force in the axial direction due to the tensile force of the lower chord material 22 acts on the joint portion 30 between the upper chord material 10 and the lower chord material 22 and is transmitted to the upper chord material 10 as a compressive force. For this reason, there is a concern that shear force acts intensively on the web 11 immediately above the joint 30 and the shear strength of this portion is insufficient, but as described above, the axial direction of the tapered portion 15 in the upper chord material 10 Since the stiffeners 14 for shear reinforcement are provided at both ends, the stiffener 14 forms a rectangular frame together with the upper flange 12 and the lower flange 13, and a panel zone 11a that is strong against the shearing force is formed on the web 11. 11 increases the shear rigidity.

<Modification>
In this modification, as shown in FIG. 6, the width of the lower chord material 22 is made larger than the width of the upper chord material 10 (lower flange 13). Therefore, if the width of the lower flange 13 is the same as that of the above embodiment, the allowable tensile stress degree of the lower chord material 22 is larger than that of the above embodiment, and the load resistance of the floor slab can be further increased. In this case, the lower chord member 22 and the upper chord member 10 are joined together by forming a bead 32a along the end edge of the lower chord member 22 and a bead 32b along the side edge of the upper chord member 10 on the upper surface 22u of the lower chord member 22. Performed by fillet welding. By welding the lower chord material 22 and the upper chord material 10 in this way, even if the width of the lower chord material 22 is larger than the width of the upper chord material 10, the weld length of the joint portion 30 of both members is increased. Sufficient bonding strength can be ensured.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 7, the stringed beam 1 of the present embodiment is formed by processing H-shaped steel as in the first embodiment, and an upper flange 12 and a lower flange 13 are arranged above and below a vertically extending web 11. The upper chord material 10 having an I-shaped cross section, a lower chord material 22 made of flat steel and having its end portions joined to both ends of the upper chord material 10 with joint portions 30, and the upper chord material 10 are divided into three equal parts in the axial direction. And two bundle members 25 made of H-shaped steel for connecting the upper chord member 10 and the lower chord member 22 in the vertical direction at the position. Further, as shown in FIG. 8, the upper chord member 10 includes a tapered portion 15 configured such that the lower flange 13 is inclined upward toward the shaft end, and the lower flange 13 is continuous with the tapered portion 15. The lower chord material 22 is joined to the upper chord material 10 in surface contact with the inclined surface 17 of the taper portion 15.

  On the other hand, the lower chord member 22 is fastened to the lower flange 13 of the upper chord member 10 by bolts and nuts 33. From the viewpoint of increasing fatigue strength, it is preferable to use high strength bolts for the bolts and nuts 33. Further, as shown in FIG. 7, the bundle member 25 is joined to the upper chord member 10 by welding, but the lower chord member 22 is attached to the bundle member 25 via a gusset plate 27 welded to the upper surface 22u thereof. Fastened with bolts and nuts 28.

  By adopting such a configuration, in the stringed beam 1, the lower chord material 22 can be easily separated from the upper chord material 10 by releasing the fastening of the bolts and nuts 33 and 28. When the lower chord member 22 and the upper chord member 10 are joined by welding, particularly when the stringed beam 1 is applied to a composite beam structure such as a logistics / commercial / production facility, the strength of the joint 30 is increased due to fatigue during repeated stress action. There is concern about the decline. Therefore, by making the lower chord member 22 separable from the upper chord member 10 as described above, the lower chord member 22 can be replaced with a new one before fatigue failure occurs, or the lower chord member 1 can be changed according to the change in the load on the stringed beam 1. The material 22 can be replaced with one having higher strength, and the breakage of the joint 30 can be reliably prevented. Moreover, cost saving and stable quality supply can be realized by saving labor during processing of the stringed beam 1 and simplifying quality control of the joint 30.

«Third embodiment»
Next, a third embodiment of the present invention will be described with reference to FIG. As shown in the drawing, the stringed beam 1 of this embodiment includes an upper chord member 18 made of H-shaped steel, an upper chord member 22 made of flat steel, and two bundle members 25 made of H-shaped steel. A pair of lower chord joint members 19 for forming a part of the upper chord member 10 and joining the end portions of the lower chord member 22 to both end portions of the upper chord member 10 with the joint portions 30 are provided. Although the upper chord member 18 has a stiffener 14 provided at an appropriate position, unlike the upper chord member 10 of the above embodiment, the upper chord member 18 has a constant cross section made of H-shaped steel. In addition, the lower chord member 22 has a linear central portion 23 (see FIG. 7) arranged horizontally and a pair of linear shaft end portions 24 inclined upward toward the beam end, as in the above embodiment. It consists of.

  On the other hand, the lower chord joining member 19 has a tapered shape in which the upper surface forms a horizontal plane along the lower flange 13 of the upper chord member 18 and the lower surface forms an inclined surface 17 along the lower chord member 22. The lower chord joint member 19 is fastened to the lower flange 13 of the upper chord member 18 by bolts and nuts 29, and the lower chord member 22 is fastened to the lower surface (inclined surface 17) of the lower chord joint member 19 by bolts and nuts 33.

  With such a configuration, the stringed beam 1 does not need to be processed to provide the inclined surface 17 on the upper chord member 18, and the inclined surface 17 may be processed on the lower chord joint member 19 which is a small member. The processing effort is small, and handling of each member is easy.

  This is the end of the description of specific embodiments, but the present invention is not limited to these embodiments. For example, in the above embodiment, H-shaped steel is used for the upper chord material 10, but I-shaped steel may be used. Moreover, in the said embodiment, although flat steel is used for the lower chord material 22, you may use die steel of the other cross-sectional shape which has a flat upper surface. Moreover, in the said embodiment, although the bundle material 25 is arrange | positioned in two places, you may arrange | position in one place or three places or more. In addition, the specific shape, arrangement, quantity, and the like of each member can be changed as appropriate without departing from the spirit of the present invention. In addition, all the constituent elements of the stringed beam 1 according to the present invention shown in the above embodiment are not necessarily essential, and can be appropriately selected as long as they do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Stretched string 3 Base 10 Upper chord material 11 Web 12 Upper flange 13 Lower flange 15 Tapered part 16 Horizontal end part 17 Inclined surface 18 Upper chord member 19 Lower chord joint member 22 Lower chord material 22u Upper surface 23 Center part 24 Shaft end part 25 Bundle material 28 Bolt・ Nut 30 Joint 30a End 33 Bolt / Nut

Claims (4)

An upper chord material in which an upper flange and a lower flange are arranged above and below a vertically extending web, a lower chord material having a flat upper surface and joined to both ends of the upper chord material with joints, and an intermediate in the axial direction A stringed beam having at least one bundle material connecting the upper chord material and the lower chord material at a position,
The lower chord material has a linear shape from the end of the joint to the first bundle material,
The stringed beam characterized in that the lower surface of the upper chord member in the joint portion has an inclination angle along the material axis direction of the lower chord member in a side view from the direction perpendicular to the axis.   2. The stringed beam according to claim 1, wherein the lower chord member is joined to the upper chord member and the bundle member by a bolt.   The lower end is formed horizontally on the beam end side of the joint portion in the upper chord material, and a horizontal end portion to be placed on the cradle is formed. Zhang string beam as described.   The upper chord member has an upper chord member having a constant cross section made of H-shaped steel, and a pair of lower chord joint members which are joined to the lower surfaces of both end portions of the upper chord member and have a tapered shape with the inclined surfaces. The stringed beam according to any one of claims 1 to 3.

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