JP6779703B2 - Fixed structure at the base of wooden columns - Google Patents

Description

The present invention relates to a column base fixing structure of a wooden column in which the lower end of the wooden column is placed directly or indirectly on a concrete foundation. Specifically, the strength of the joint is relative to the strength of a member such as a column. It relates to a column base fixing structure that has a wooden structure with higher joining efficiency, has extremely high resistance in the horizontal direction when subjected to an earthquake or wind load, and can withstand a large bending moment.

For example, as shown in FIG. 7, the column base of the wooden column 25 passes through the hole-down hardware 24 to the concrete foundation 21, that is, the wooden base 23 fixed by the anchor bolts 22 extending upward from the underground beam. It is fixed by such as. The hole-down hardware acts to prevent the pillars from coming off, but it cannot prevent the pillars from rotating. That is, the resistance in the horizontal direction is extremely weak. Therefore, a brace specification in which a wooden brace 26 is inserted in a frame composed of a column 25 and a base 23, or a bearing wall specification in which a structural plywood 27 is applied to an intersection of a column and a base as shown in FIG. As a result, rotation is suppressed and surface rigidity is increased.

Even if such measures are taken, the unity between the column and the base is still low, and it is hard to say that it will be able to resist earthquakes and wind loads and counter large bending moments. In recent years, in seismic design of wooden houses, there is an increasing demand for structures with a higher degree of planning freedom than construction methods that use bearing walls as seismic elements. It is a wooden rigid frame structure with moment resistance at the joint, and many studies of this kind have been conducted. Typical examples include pull bolt joints, steel plate insertion drift pin joints, and combined beam joints. Although it is an example of each, in order, the joining forms disclosed in Patent Documents 1 to 3 and the like can be mentioned.

Japanese Unexamined Patent Publication No. 10-96262 JP 2016-113805 JP 2013-79542

The reason why the wooden construction with bearing wall specifications and bracing specifications mentioned above must be used is simply because the column bases cannot be fixed. Further, even in the joint form exemplified above, the strength of the joint portion cannot exceed the strength of the member (column or its framework) at all. Therefore, it is said that the design of wooden structures is determined by the joints. Therefore, it is strongly desired to create a column base structure of a wooden structure having high joining strength, that is, joining efficiency.

The present invention has been made in view of the above problems, and the steel pipe and the wooden column are firmly integrated to form a structure in which the joint between the base plate and the anchor bolt is equivalent to or equivalent to the column base of the steel frame. It is an object of the present invention to provide a column base fixing structure for wooden columns, which can remarkably improve difficult points such as workability and insufficient fixation of wooden columns.

The present invention is applied to a column base fixing structure of a wooden column in which the lower end of the wooden column is placed on a concrete foundation such as an underground beam. The feature is that, referring to FIG. 1, a steel pipe 2 accommodating the lower end portion of the wooden pillar 1 is welded to the upper surface of the steel base plate 3 fixed by the anchor bolts 8 struck on the foundation 10. A lug screw 4 that penetrates the steel base plate 3 from the lower surface is screwed and tightened to the column base portion housed in the steel pipe. The gap filling resin 7 is injected into the gap 5 left between the column base and the steel pipe 2 to form a resin layer. The anchor bolt 8 is an unbonded PC steel rod arranged symmetrically or asymmetrically with respect to the axis and the center of gravity of the column base.

Anchor bolts made of ordinary steel (not shown) may be used instead of the unbonded PC steel rods.

As shown in FIGS. 5A and 5B, a reinforcing steel plate 17 that is not exposed may be embedded in the layer of the resin 7. When the steel plate is applied to a wooden prism, it may be a flat steel plate, and when the steel plate is a striped steel plate, it is preferable to arrange the convex surface with protrusions toward the bark of the pillar.

As shown in FIG. 1, a resin nut 12 for raising and leveling the steel base plate 3 is screwed to the lower surface side of the steel base plate, and the anchor is projected onto the steel base plate 3. By tightening the anchor nut 20 of the bolt 8, the screw of the resin nut 12 can be broken.

A gap filling resin injection port 16 (see FIG. 5A) is provided at the hem of the steel pipe 2 so that the gap filling resin is injected, pushed up, and filled.

According to the present invention, since the steel pipe accommodating the lower end of the wooden column is welded to the upper surface of the steel base plate fixed by the anchor bolts struck on the foundation, the column base is firmly fixed. Therefore, the horizontal resistance of the wooden building can be increased. That is, in extreme cases, it is possible to exert high seismic resistance without bearing walls or braces. In addition, the center of gravity of the anchor bolt is designed to match the center of gravity of the column, but in the crimped part where the axial force is introduced into the PC steel rod, the lower surface of the base plate does not separate from the backfill mortar or concrete foundation, so these centers of gravity There is no need to match.

Further, since the lug screw installed to prevent pulling out has a strong tightening force, the relative position between the wooden pillar and the steel pipe can be maintained even when the resin is not cured. This means that the pillars can be handled immediately after injection, resulting in extremely high productivity.

By unbonding the anchor bolts by a coating treatment that cuts off the adhesion with concrete, the extension margin of the bolts when the nuts are tightened is large, and sufficient tightening force can be maintained for a long period of time. The lug screw at the bottom of the wooden column not only facilitates assembly, but also contributes to resist the pull-out stress of the column even when the adhesive force between the filled resin and the inner surface of the polygonal steel pipe decreases due to aging.

Filling with this resin fills the clearance between the steel pipe and the wood, and the play can be suppressed by injecting the resin, and the rigidity can be stably obtained from a small deformation point. Since the initial axial force is introduced into the anchor bolt using an unbonded PC steel rod, this introduced axial force may cause the lower surface of the base plate to separate from the backfill mortar against any horizontal force acting on the column. Can be kept absent. As long as there is no separation, the column and the lower mortar and the concrete foundation are maintained together, and the column base is fixed by crimp joint.

Anchor bolts made of ordinary steel instead of PC steel rods cannot be expected to have the same performance as PC steel rods, but if applied when the integrity of columns with lower mortar and concrete foundation is not required so high, It is convenient because the construction cost can be reduced.

If the steel plate is placed or inserted in the gap between the steel pipe and then the resin is injected to integrate the wooden pillar and the steel plate, it is effective in significantly reinforcing the shearing of this portion.
When applying the steel plate to a wooden prism, it is sufficient to use it as a flat steel plate, but when using the steel plate as a striped steel plate, if the convex surface with protrusions is arranged toward the bark of the pillar, the protrusions will be pillars. Since a substantially uniform resin filling void is left between the two, there is an advantage that almost uniform adhesion is achieved.

If a resin nut is screwed to the anchor bolt on the lower surface side of the base plate, the height and leveling of the base plate can be easily raised. In addition, by tightening the anchor nut on the base plate, the screw of the resin nut can be broken, and smooth tension introduction becomes possible.

If a gap filling resin injection port is provided at the hem of the steel pipe, the resin can be reliably injected, pushed up, and filled, and air entrapment can be suppressed.

(A) is a front view of a column base fixed structure of a wooden column according to the present invention, and (b) is a view taken along the line I-I. (A) is a front view of a column base fixing structure in which four anchor bolts are used in the crimping portion, and the center of gravity and the axis of each member do not match because the lower surface of the base plate, the backfill mortar, and the concrete foundation do not separate from each other. , (B) is the II-II line arrow view. (A) is a front view of a column base fixing structure in which two anchor bolts are used in the crimping portion, and the center of gravity and the axis of each member do not match because the lower surface of the base plate, the backfill mortar, and the concrete do not separate from each other. (B) is a view of the III-III line arrow. (A) is the simplest example of the column base, that is, the front view of the column base fixed structure showing the outline in which the wooden column is made of a uniform cross-sectional material, and (b) is the IV-IV line arrow view. (A) is a front view of an example of a column base fixing structure in which a reinforcing steel plate is inserted in a gap for resin injection, and (b) is a view taken along the line VV. An example of a composition that balances the arrangement of anchor bolts with the anchor frame in the underground beam at the column base where the reinforcing steel plate is introduced. A perspective view of a brace-type column base structure. A perspective view of a column base structure with bearing wall specifications.

Hereinafter, the column base fixing structure of the wooden column according to the present invention will be described in detail with reference to the drawings. 1 (a) and 1 (b) show the column base form. The lower end 1a of the wooden prism 1 is made slightly smaller than one side of the square steel pipe 2 of the column base, and is inserted into the steel pipe 2 at a depth of about twice the column side Lo. Then, it is fixed by the lug screw 4 from the lower surface of the base plate 3. The square steel pipe 2 is welded to the base plate 3. In the gap 5 between the steel pipe 2 and the lower end 1a of the wooden pillar, a pipe 6 (see FIG. 4B) is connected to a resin filling injection port (see reference numeral 16 in FIG. 5 to be described later) at the lowermost side surface (steel pipe hem). ) Is inserted, and the resin 7 is filled from the injection port so as to be pushed up from the lower end. The generation of air pools is surely suppressed.

For the anchor bolt 8, an unbonded PC steel rod (see JIS G3109, Japanese Patent Publication No. 41-13363 and Japanese Patent No. 25563888) was used to determine the initial axial force. Introduce. The introduction axial force is set so that the lower surface of the base plate 3 does not separate from the backfill mortar 9 against any horizontal force acting on the column. Since the column, the lower mortar, and the concrete foundation are integrated as long as they do not separate from each other, the column base can be fixed by crimping. Reference numeral 10 is a concrete foundation such as an underground beam.

The template 11 is a template for accurately positioning the PC steel rod which is the anchor bolt 8, and the polyethylene nut 12 under the template sets the height and level of the base plate 3 before hitting the backfill mortar 9. It is for. When the nut of the PC steel rod 8 is fully tightened, the screw thread is pulled out (much weaker than the screw thread of the PC steel rod), and the initial tension is easily introduced into the PC steel rod by the anchor nut 20. In addition, the material strength of PC steel rods is about 3 to 4 times higher than that of ordinary steel used for ordinary anchor bolts, so the cross section of PC steel rods should be significantly smaller than that of ordinary steel anchor bolts for the same yield strength. Can be done. This means that the elongation of the PC steel rod 8 is 3 to 4 times larger because the same tension is introduced. In addition, since the screw of the PC steel rod is a fine screw, it is easy to control the introduction tension and the tension loss due to the drying shrinkage of concrete is extremely small.

Normally, the center of gravity of the anchor bolt and the center of gravity of the column are arranged so as to coincide with each other. However, in the crimping portion where the axial force is introduced into the PC steel rod 8, the lower surface of the base plate 3, the backfill mortar 9, and the concrete foundation 10 do not separate from each other. , It is not necessary to match these centers of gravity and shaft centers (see FIGS. 2 (a) and 2 (b) and FIGS. 3 (a) and 3 (b)). Further, the number of PC steel rods 8 may be two as shown in FIGS. 3 (a) and 3 (b) (the number of anchor bolts is typically four as shown in FIG. 1 (b)). It is not always necessary to match the centers of gravity of the PC steel rod 8 and the base plate 3, but it is better to match them in terms of simplicity of design and placement work and structural performance. As shown in FIG. 2B, a hakama foundation 13 having a wide foundation is provided to arrange the base plate 3, and as shown in FIG. 3B, a hakama foundation 14 for stabilizing the mounting of the base plate is provided. It may be provided. However, it goes without saying that care must be taken not to move the center of gravity too far.

The lug screw 4 at the bottom of the wooden column 1 is used to facilitate assembly (integration of the column and the base plate), and even if the adhesive strength between the filled resin 7 and the inner surface of the square steel pipe 2 is reduced due to aging. It is introduced to resist the pull-out stress of the column 1.

By the way, the outline of the simplest example of the column base is shown in FIGS. 4 (a) and 4 (b). The filling status of the resin 7 at this time is omitted. A hole 15 of a wooden dowel used for construction adjustment (see (b) in FIG. 5) is provided in advance in the wooden pillar 1, and the wooden pillar 1 is passed through a steel pipe 2 welded to the base plate 3. At that time, a process of aligning the surfaces of the steel pipe 2 and the wooden pillar 1 is performed so that the attachment of the exterior material is not inconvenient. After that, after inserting and positioning the wood dowel, the resin is press-fitted from the injection port 16 by a pump in order to pass the lag screw 4 and fill the clearance 5 between the steel pipe 2 and the wood. As a result, backlash can be suppressed, and it becomes possible to stably obtain rigidity even when the deformation is small.

To give a specific example, the cross section of the wooden pillar 1 has a range of about 5 mm inside the steel pipe 2 and directly above the steel pipe □ -110 × 110 (meaning the pillar cross section is 110 mm long and 110 mm wide), and the others are □- The size is 125 × 125, and the square steel pipe 2 is SHS 125 × 125 × 3.2 ^t (or 4.5 ^t ) specified by JIS. The filling resin may be a room temperature curable epoxy resin. However, as can be seen from FIG. 4, it is preferable to keep the external dimensions of the pillar material constant. If there is no step, the processing step can be omitted, and the existence of a fragile portion that is easily damaged due to stress concentration or the like can be eliminated.

By the way, the wooden column 1 is inserted into a short square steel pipe 2 (pre-welded to the base plate 3 like a steel frame column) having a side length slightly larger than one side of the cross section of the wooden column 1, and the resin 7 is injected into the gap 5. If necessary, flat reinforcing steel plates 17 (including, for example, striped steel plates) as shown in FIGS. 5A and 5B are inserted into this portion on each of the four surfaces. The lug screw 4 is driven from the lower surface of the base plate 3. It has already been mentioned that the wooden pillar 1 is prevented from coming off when a tensile force acts on the pillar 1.

The point of action of the horizontal force that the horizontal force acts on the column due to an earthquake or the like is called the inflection point of the column, and the bending moment of the column becomes zero. When this horizontal force acts, the bending moment acting on the wooden column 1 becomes maximum at the top of the steel pipe and becomes 0 at the bottom. In the steel pipe 2, the moment gradient (change) is significantly larger than that in the column above the steel pipe. This gradient is defined as the shearing force in mechanics, and is the force that crosses the cross section. In the case of wood, the shear strength and shear rigidity are significantly smaller than the compression, tensile and bending strengths, so effective reinforcement of this portion is desirable. In particular, this tendency becomes remarkable when it is desired to lower the steel pipe portion in order to fit the building. Without reinforcement, designing a column base with sufficient fixation can be difficult. Therefore, a flat steel plate, for example, a striped steel plate having a thickness of 1.2 mm or more was inserted into the gap 5 with the steel pipe 2, or fixed to the wooden pillar in advance with nails 19 or wood screws (see FIG. 5A). After that, the resin 7 is injected to integrate the wooden pillar 1, the above-mentioned reinforcing steel plate 17, and the steel pipe 2. By the way, when using a striped steel plate, arrange the convex surface with protrusions toward the bark of the pillar and screw it. The protrusions leave substantially even resin-filled voids between the protrusions and the pillars, and the resin adhesive effect is promoted.

FIG. 6 shows how the anchor bolts 8 are arranged between the anchor frames 18 in the foundation. As can be seen from the above description, if the steel pipe 2 and the wooden column 1 are firmly integrated, the joint between the base plate 3 and the anchor bolt 8 becomes equivalent to that of the steel column base. Problems such as workability and insufficient fixation with conventional wooden pillars are significantly improved. Further, since the lug screw 4 installed to prevent pulling out has a strong tightening force, the relative position between the wooden pillar 1 and the steel pipe 2 can be maintained even when the resin 7 does not harden. This means that the pillar 1 can be handled (processed / operated in the next step) immediately after the injection, so that the productivity becomes extremely high. Normally, when a resin is used, it takes about 24 hours for it to cure and develop strength, so it was necessary to fix it with a jig or the like during that time, but that is no longer necessary.

Furthermore, the anchor bolt 8 is unbonded (coated with a special asphalt polymer and then coated with polypropylene or polyethylene sheath) by a coating treatment that prevents adhesion to the concrete foundation 10, thereby anchor nut 20 (FIG. 1). When the bolt (see (a)) is tightened, the elongation allowance of the bolt becomes a desired amount, and a sufficient tightening force can be maintained for a long period of time. A specific guideline for the tightening force is such that the base plate 3 at the position of the tension side anchor bolt 8 does not separate from the lower mortar when a horizontal force is applied due to an earthquake or a storm. By doing so, the wooden column base and the foundation concrete can be completely integrated together with the reinforcement of the steel pipe portion.

As the anchor bolt 8, a high-strength PC steel rod is practically optimal. Since the strength is high, the rod diameter can be reduced, and as a result, the elongation allowance can be increased. Prevents long-term tension loss and significantly improves the accuracy and workability of tension introduction. The purpose of the resin nut 12 under the base plate 3 is to adjust the level at the time of construction. As mentioned earlier, when the anchor nut 20 is fully tightened after the backfill mortar 9 is cured, the screw of the resin nut 12 is broken, and smooth tension introduction becomes possible. By the way, if it is possible to use ordinary steel anchor bolts instead of PC steel rods, it is not limited to PC steel rods.

The procedure for assembling the column base when the above reinforcing steel plate 17 is used is as follows. First, four reinforcing steel plates are fixed to the lower part of the wooden column 1 with nails or wood screws. However, leave a gap between the surface of the wooden column and the reinforcing steel plate to the extent that resin can be filled. Next, the wooden pillar 1 is inserted into the steel pipe 2, and a wooden dowel for positioning is driven. After that, the lag screw 4 is driven, the wooden pillar 1 is erected, and the resin 7 is injected.

As can be seen from the above details, the present invention is applied to a column base fixing structure of a wooden column in which the lower end of the wooden column is directly or indirectly placed on a concrete foundation (underground beam). It is understood that The configuration is as follows. A square steel pipe 2 accommodating the lower end 1a of the wooden prism 1 is welded to the upper surface of the steel base plate 3 fixed by the anchor bolts 8 struck on the foundation 10. A lug screw 4 that penetrates the base plate 3 from the lower surface is screwed and tightened to the column base portion housed in the square steel pipe 2. The gap filling resin 7 is injected into the gap 5 left between the column base and the square steel pipe 2 to form a resin layer. The anchor bolt 8 is an unbonded PC steel rod that is arranged symmetrically or asymmetrically with respect to the axis and the center of gravity of the column base. In addition, a reinforcing steel plate 17 that is not exposed may be embedded in the layer of the resin 7.

Although the wooden pillars have been described above for wooden prisms, they may be wooden round pillars or pillars having other geometric cross sections. In that case, a short round steel pipe having a diameter slightly larger than the diameter of the wooden pillar is used. Further, the steel plate arranged in the resin layer may be a folded plate or a bent plate having a semicircular arc shape or a shape that fits the cross-sectional shape of other columns. In any case, since the base plate is placed directly or indirectly on the upper surface of the underground beam, the wooden base on the underground beam that has been used in wooden construction is not required in most cases. As shown in FIG. 4, it goes without saying that it is possible for the cross sections of the columns to have the same shape and the same dimensions in FIGS. 1, 2, 3, 3, 5, and 6.

1 ... Wooden prism, 1a ... Lower end of prism, 2 ... Square steel pipe, 3 ... Base plate, 4 ... Lag screw, 5 ... Gap (clearance), 7 ... Filling resin (resin), 8 ... Anchor bolt (PC steel rod) 10, 10 ... Concrete foundation (underground beam), 12 ... Polyethylene nut (resin nut), 16 ... Injection port, 17 ... Reinforcing steel plate, 20 ... Anchor nut.

Claims (9)

In the column base fixing structure of a wooden column in which the lower end of the wooden column is placed on a concrete foundation, the lower end of the wooden column is placed on the upper surface of the steel base plate fixed by the anchor bolts struck on the foundation. The steel pipe to be housed is welded
A lug screw that penetrates the steel base plate from the lower surface is screwed and tightened to the column base portion housed in the steel pipe.
A resin for filling the gap is injected into the gap left between the column base and the steel pipe to form a resin layer.
The anchor bolt is an unbonded PC steel rod arranged symmetrically or asymmetrically with respect to the axis of the column base, and is a column base fixing structure of a wooden column. The column base fixing structure of a wooden column according to claim 1, wherein an anchor bolt made of ordinary steel is used instead of the unbonded PC steel rod. The column base fixed structure of the wooden column according to claim 1 or 2, wherein the wooden column is a wooden prism, and the steel pipe is a square steel pipe. The column base fixed structure of the wooden column according to claim 1 or 2, wherein the wooden column is a wooden round column, and the steel pipe is a round steel pipe. The column base fixing structure of a wooden column according to any one of claims 1 to 4, wherein a steel plate that is not exposed is embedded in the resin layer. The column base fixed structure of a wooden column according to claim 5, wherein the steel plate is a flat steel plate. The column base fixing structure of a wooden column according to claim 6, wherein the flat steel plate is a striped steel plate, and a convex surface having protrusions is arranged toward the wood surface of the column. A resin nut for raising and leveling the steel base plate is screwed onto the lower surface of the steel base plate, and when the anchor nut on the steel base plate of the anchor bolt is tightened, the anchor bolt becomes a resin nut. The column base fixed structure of a wooden pillar according to any one of claims 1 to 7, wherein the screw is broken. Any of claims 1 to 8, wherein an injection port for a gap filling resin is provided at the hem of the steel pipe so that the gap filling resin can be injected, pushed up, and filled. The column base fixed structure of the wooden column described in item 1.