JP7043358B2 - Prestressed wooden beams - Google Patents

Description

The present disclosure relates to prestressed wooden beams arranged to be curved and / or bent so that the tension material is convex downward.

A beam of a general wooden house has a span of about 4 to 6 m or less. When the office or store is made of wood, it is preferable to make the span of the beam larger than this. For example, Patent Documents 1 and 2 show that the span of a beam can be increased by introducing prestress into a wooden beam. In the beam described in Patent Document 1, the laminated lumber is cut and divided into two, a groove is provided on the cut surface, and the divided laminated lumber is adhered, so that the groove provided on the cut surface is a tension material. It becomes a through hole through which. The through hole is curved so as to be convex downward when viewed from the width direction of the beam. Further, in the beam described in Patent Document 2, the intermediate portion of the tension material is supported by a saddle provided so as to bulge downward from the lower surface of the beam, and both ends of the tension material are provided on the lower surface of the beam. By arranging in the hollow hole, the tension material is curved so as to be convex downward when viewed from the width direction of the beam. In this way, it is possible to introduce prestress so as to efficiently cancel the long-term load by arranging the tension material so as to be convex downward instead of linearly.

Japanese Unexamined Patent Publication No. 6-229065 Japanese Unexamined Patent Publication No. 2013-189763

In the structure described in Patent Document 1, it takes time and effort to create a through hole through which the tension material is inserted. In addition, wood-based materials such as laminated wood and laminated wood have the property of orthogonal anisotrophic properties, that is, they are strong against the compressive force in the direction parallel to the fiber but weak against the compressive force in the direction perpendicular to the fiber. Due to the lifting force of the glulam, a force in the direction orthogonal to the fiber is applied to the upper surface of the convexly formed through hole. Therefore, when a large prestress is applied, the upper surface of the through hole is dented, so that a large prestress cannot be applied. In the structure described in Patent Document 2, since the saddle is attached to the lower surface of the wooden beam main body, the beam sill becomes large as a whole beam and the space below the beam becomes narrow.

In view of these problems, the present invention provides a prestressed wooden beam that can be constructed relatively easily and can give a large tension to a tension material arranged in a convex shape without increasing the beam length. The purpose.

The prestressed wooden beam (1,21) according to at least some embodiments of the present invention has a wooden beam body (2) and a tensioning material (3) that prestresses the beam body. A groove (4) for receiving the tension material is provided on the lower surface of the main body along the extending direction of the beam main body, and the bottom surface of the groove is the beam main body at least in an intermediate portion in the extending direction. A reinforcing plate (5) is attached while being curved and / or bent so as to be convex downward when viewed from the width direction of the tension material, and at least an intermediate portion of the tension material is pressed against the lower surface of the reinforcing plate. The groove is characterized in that it has a depth deeper than the intermediate portion of the groove at both ends in the extending direction .

According to this configuration, since the reinforcing plate resists the lifting force of the tension material, it is possible to prevent the bottom surface of the groove from being dented without increasing the beam length. In addition, since a groove can be formed by cutting, construction is relatively easy.

At least some embodiments of the present invention are characterized in that, in the above configuration, the reinforcing plate comprises steel or compression processed wood.

When a steel material is used as the material of the reinforcing plate, the rigidity is high, so that the reinforcing effect is high and the construction is easy. Further, when compression-processed wood is used as the material of the reinforcing plate, an increase in the weight of the beam can be suppressed.

In at least some embodiments of the present invention, in any of the above configurations, the prestressed wooden beam (21) is supported by a column (22) or girder, penetrates the column or girder, and inserts the tension material. The pipe (23) to be made to be attached, the first plate (24) attached to the end of the pipe on the side of the beam body and abutting against the beam body, and the opposite end of the pipe. It further has a second plate (25), and one end side of the tension material is locked to the second plate.

According to this configuration, the tension of the tensioning material is transmitted to the beam body via the second plate, the pipe and the first plate and does not affect the column or girder, so that the strength of the column or girder is not taken into consideration. You can set the amount of stress.

In at least some embodiments of the present invention, in the above configuration, the first plate has a first recess (27) into which the end of the pipe is inserted, and the end of the beam body is the first. It is characterized by having a second recess (28) into which at least a part of the plate is inserted.

According to this configuration, the first recess and the second recess, as well as the end of the pipe penetrating them and the first plate function as shear keys, so that the shear force is transmitted from the beam to the column or the girder.

According to the present invention, it is possible to provide a prestressed wooden beam that can be constructed relatively easily and can give a large tension to a tension material arranged in a convex shape without increasing the beam length.

(A) side view and (B) BB sectional view of the prestressed wooden beam according to the first embodiment. (A) plan view, (B) front view showing an example of a joint portion between a prestressed wooden beam and a pillar according to the first embodiment. (A) Plan view, (B) Front view showing another example of the joint portion between the prestressed wooden beam and the column according to the first embodiment. Front view showing a joint portion of a prestressed wooden beam according to a second embodiment with a column.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a prestressed wooden beam (hereinafter, simply referred to as “beam”) 1 according to the first embodiment. The beam 1 has a wooden beam main body 2 and a tension material 3 that prestresses the beam main body 2.

In the beam body 2, the wood fibers generally extend in the extending direction of the beam body 2. The beam body 2 is made of a wood-based material having the same fiber direction, that is, wood is cut into a ground lumber, a small square lumber or a veneer, and after removing defects, a large number of them are piled up again with the same fiber direction and bonded. -It is preferable that it is a molded laminated lumber or a veneer laminated lumber.

A groove 4 for receiving the tension member 3 is provided on the lower surface of the beam body 2 so as to pass through the center in the width direction along the extending direction of the beam body 2. The depth of the groove 4 is the shallowest in the center and becomes deeper toward the end. That is, the bottom surface (upper surface) of the groove 4 is curved so as to be convex downward when viewed from the front (viewed from the width direction of the beam body 2). The groove 4 is formed by cutting the lower surface of the material of the beam body 2.

A reinforcing plate 5 is attached to the bottom surface of the groove 4. The reinforcing plate 5 is made of steel or compressed wood, and is a flexible flat plate or a curved plate similar to the bottom surface of the groove 4. The reinforcing plate 5 is fixed to the bottom surface of the groove 4 with an adhesive or the like. When a steel material is used as the material of the reinforcing plate 5, the rigidity is high, so that the reinforcing effect is high and the construction is easy. Further, when compression-processed wood is used as the material of the reinforcing plate 5, an increase in the weight of the beam 1 can be suppressed. The depth of the shallowest portion in the groove 4 may be 0, but is equal to or greater than the sum of the thickness of the reinforcing plate 5 and the thickness of the tension material 3 so that the tension material 3 does not protrude from the lower surface of the beam body 2. Is preferable.

The tension material 3 is an unbonded tension material made of a PC steel rod, a PC steel wire, a PC steel stranded wire, or a rod or cable made of fiber reinforced plastic such as aramid fiber, carbon fiber or glass fiber. The tension material 3 is received by the groove 4, and after tensioning, the tension material 3 is pressed against the lower surface of the curved reinforcing plate 5. As shown in FIG. 2, the tension member 3 is fixed to the end of the beam body 2 by the fixing tool 6. The fixing tool 6 is locked to the chamfered upper portion of the end portion of the beam body 2 via the steel plate 7.

The beam 1 of the first embodiment is supported by a wooden girder 8. The girder 8 has wood fibers extending in the extending direction thereof, and is preferably a laminated lumber or a veneer laminated lumber. The girder 8 has a pair of steel connecting plates 9 and 9 protruding toward the beam 1. At the end of the beam body 2, a projecting portion 10 that penetrates between the pair of connecting plates 9 and 9 is provided. The pair of connecting plates 9, 9 and the protrusions 10 are provided with a plurality of first through holes 11, 11 and second through holes 12 that are aligned with each other. It is preferable that a steel tubular member (not shown) for reinforcement is fitted in the second through hole 12. The connecting rod 13 having threaded portions at both ends is inserted into the first through holes 11 and 11 and the second through hole 12, and the nuts 14 are fastened to both ends of the connecting rod 13 to form the beam 1. Pin-coupled to the girder 8. The distance between the outer surfaces of the pair of connecting plates 9 and 9 is substantially equal to the width of the beam body 2.

FIG. 3 shows another example of joining the beam 1 and the girder 8 to each other. As shown in FIG. 3, the end surface of the beam body 2 is inclined so as to face diagonally upward, and the plate 7 is attached. The fixing tool 6 under the tension of the tension material 3 is locked to the plate 7. The beam body 2 has a pair of second connecting plates 15 and 15 made of steel that project from the plate 7 toward the girder 8 instead of the projecting portion 10. The second connecting plate 15 has a second through hole 12 that matches the first through hole 11 of the corresponding connecting plate 9. The beam 1 is pin-bonded to the girder 8 by joining the connecting plate 9 and the second connecting plate 15 corresponding to each other by bolts 16 and nuts 14. Since the pair of the second connecting plates 15 and 15 can be arranged so as to overlap the fixing tool 6 in the front view, they can be joined to the girder 8 not only on the lower side but also on the upper side of the beam 1.

Since the tension material 3 presses against the bottom surface of the groove 4 via the reinforcing plate 5, even if the prestress is increased, the bottom surface of the groove 4 is prevented from being dented by the lifting force. Since the reinforcing plate 5 is attached to the bottom surface of the groove 4, it does not increase the beam length. Further, since the force from the fixing tool 6 to the beam main body 2 is dispersed by the plate 7 having a large contact area with the beam main body 2, even if the prestress is increased, the pressure from the fixing tool 6 to the beam main body 2 causes the force. Damage to the beam body 2 is prevented.

Since the groove 4 is formed by cutting the lower surface of the beam body 2, it can be formed relatively easily.

FIG. 4 shows the beam 21 according to the second embodiment. In the description, the configurations common to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The beam 21 is supported by a wooden pillar 22. The pillar 22 is preferably made of a wood-based material in which wood fibers are generally aligned in the vertical direction.

The beam 21 is made of a steel pipe 23 that penetrates the column 22 along the extending direction of the beam body 2 and allows the tension member 3 to pass through, and a steel pipe 23 attached to the end of the pipe 23 on the beam body 2 side. The first plate 24 and the steel second plate 25 attached to the end on the opposite side thereof and facing or abutting on the pillar 22 are screwed into the screw portion provided at the end of the tension member 3. It has a fixing tool 26 such as a nut in contact with the second plate 25, and the tension material 3 is fixed by these. By fastening the fixing tool 26 to the end portion of the tensioning material 3, the fixing tool 26 is locked to the second plate 25 in a state where the tensioning material 3 is tense. The tension of the tension material 3 is transmitted from the fixing tool 26 to the beam body 2 via the second plate 25, the pipe 23, and the first plate 24 without being applied to the column 22. Wood-based materials with aligned fiber orientation have orthogonal anisotropy and are vulnerable to forces in the direction orthogonal to the fibers. However, since the tension of the tension material 3 acting in the direction orthogonal to the fibers of the column 22 does not directly affect the column 22, the tension of the tension material 3 is increased to give a large prestress to the beam 21. be able to.

The first plate 24 has a first recess 27 into which the end of the pipe 23 is inserted. The end of the beam body 2 has a second recess 28 into which the first plate 24 is partially inserted. Since these function as shear keys, shear force is transmitted from the beam 21 to the column 22. Further, since the second plate 25 has a third recess 29 into which the end portion of the pipe 23 is inserted, movement in the direction orthogonal to the pipe 23 with respect to the pipe 23 is restricted.

Although the description of the specific embodiment is completed above, the present invention can be widely modified without being limited to the above embodiment. The bottom surface of the groove may have a bent shape instead of the curved shape in front view, and may have both a curved portion and a bent portion. Further, the bottom surface of the groove may be curved and / or bent downwardly at least in the middle portion when viewed from the front, and the end portion may be linear or convex upward. In this case, the reinforcing plate may be attached to a portion that is convexly curved and / or bent downward. The girders or columns may be reinforced concrete, steel, or steel reinforced concrete. The beam of the first embodiment may be supported by a column, or the beam of the second embodiment may be supported by a girder.

1,21: Prestressed wooden beam 2: Beam body 3: Tension material 4: Groove 5: Reinforcing plate 8: Girder 22: Column 23: Pipe 24: First plate 25: Second plate 27: First recess 28: Second Recess

Claims (4)

The wooden beam body and
It has a tensioning material that gives prestress to the beam body,
A groove for receiving the tension material is provided on the lower surface of the beam body along the extending direction of the beam body.
The bottom surface of the groove is curved and / or bent so as to be convex downward when viewed from the width direction of the beam body at least in the middle portion in the extending direction, and a reinforcing plate is attached.
At least the middle portion of the tension material is in pressure contact with the lower surface of the reinforcing plate .
The groove is a prestressed wooden beam having a depth deeper than the intermediate portion of the groove at both ends in the extending direction . The prestressed wooden beam according to claim 1, wherein the reinforcing plate includes a steel material or a compressed wood. The prestressed wooden beam is supported by a column or girder and is supported by a pillar or girder.
A pipe that penetrates the pillar or girder and allows the tension material to pass through,
It further comprises a first plate attached to the side end of the beam body in the pipe and abutting the beam body, and a second plate attached to the opposite end of the pipe.
The prestressed wooden beam according to claim 1 or 2, wherein one end side of the tension material is locked to the second plate. The first plate has a first recess into which the end of the pipe is inserted.
The prestressed wooden beam according to claim 3, wherein the end portion of the beam body has a second recess into which at least a part of the first plate is inserted.

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