JP4126514B2 - Kibashi with pre-stressed wood deck - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wooden bridge that employs a laminated wood floor slab in which laminated wood floor slabs are arranged in parallel to constitute a wooden floor, and prestressing force is introduced into the wooden floor body.
[0002]
[Prior art and problems to be solved by the invention]
When constructing a large concrete structure, a method for improving the reliability of the structure by introducing a pre-stress using a PC steel rod to improve the mechanical strength of the structure has been conventionally performed.
On the other hand, among various structural materials, the use of wood has been refrained from adapting to large structures for reasons such as depletion of forest resources, protection of the natural environment, and unstable material characteristics. Especially for large bridges, steel frames and reinforced concrete structures dominate. However, the active post-war afforestation measures will bear fruit, and the use of domestic timber is expected to gradually expand in the future, and effective use of small-diameter trees and thinned wood generated for the proper maintenance of forests. As urgent issues have arisen and new technologies are being developed one after another, there has been an active movement to review wood as a new material.
One of the new technologies is the development of laminated timber. In general, it is extremely difficult to obtain long log-like wood with uniform material and excellent dimensional accuracy, and even if it can be obtained, the quantity is limited and it is difficult to adopt it as a material due to high cost. Many of these problems have been largely solved by the development of laminated timber.
The laminated wood is a log-like wood processed product made by pressure-bonding and laminating lamina (single plate) having a thickness of 4 to 20 mm, a length of about 2 m, and a width of about 200 mm. When lamina is laminated, square members of a necessary length can be easily supplied by shifting the joints in a staggered manner. In addition, it has excellent characteristics such as material uniformity, dimensional accuracy, selection of lamina material according to application, and cost advantage.
[0003]
The background of these technological developments is that the demand for construction of structures using the characteristics of wood is gradually increasing. In society's development period, values that emphasize the function and economics of materials are dominant, but with the maturity of society, the evaluation criteria for materials gradually change, pursuing cultural elements, and mental comfort. A background that emphasizes sex is nurtured, and the background for reviewing timber is growing. As an example, the construction of wooden bridges that match the surrounding landscape has been studied positively during the maintenance, maintenance, and renewal of important cultural properties that require harmony with the natural environment.
Taking advantage of laminated wood, wooden bridges made of laminated wood are also used in and outside the country. When using laminated timber, a prestressed structure with a proven track record in reinforced concrete structures is often applied, and this technology is effective in forming a strong floor slab by arranging multiple floor slabs side by side. Working.
The technical outline of the prestressed structure of laminated timber that has been conventionally used is as follows.
(1) The prestressed wooden slab is made by arranging a large number of laminated timbers with a width of 15-20cm in parallel and inserting a PC steel rod into each of a large number of through-holes drilled in the side surface to introduce tension and integrate them. It is manufactured by converting.
(2) The frictional force generated between the laminated members due to the prestressing force prevents each shift and generates a compressive stress in the floor slab.
(3) When the span length of the wood floor slab increases, the thickness of the laminated material also increases in order to maintain the support strength as a structure. (For example, in the case of a wooden bridge with a span length of 22 m, the thickness of the laminated lumber beam will be close to 1 m)
(4) In order to generate a pre-stress force uniformly in the laminated slab, it is important to provide a large number of through holes into which a large number of PC steel rods are inserted in the central portion of the laminated slab. is there.
[0004]
Next, problems and issues of the current technology are shown below.
(1) In order to generate a prestress force in a large number of laminated wood through the laminated wood floor slab, the compressive force obtained by tensioning the PC steel bar is applied to the laminated wood floor via a metal fixing plate. Transmitted to the end face of the plate. At this time, it is very difficult for the metal fixing plate and the side surfaces of the laminated slab to be in close contact with each other and to transmit uniform stress.
Although the side of the laminated slab has a laminated structure of lamina and is processed with high accuracy, delicate unevenness is inevitable, and between the metal fixing plate that is relatively smooth and difficult to deform, Contact at a point or line occurs, and the transmission of compressive force is unevenly distributed. In other words, the “familiarity” between the laminated slab and the metal fixing plate is bad.
(2) In addition, the area of the fixing plate is smaller than the side surface area of the laminated slab, and the floor slab behind the surface not in contact with the fixing plate is not sufficient in introducing prestressing force. This tendency is more conspicuous in structures that employ large laminated slabs, and is a major issue from the viewpoint of buildings that require a stable structure over a long period of time.
In order to quantitatively prove the above problems, the present inventors have clarified them by three-dimensional FEM analysis. As a result, laminated wood slab body 25kgf / cm ² ~75kgf / cm has changed ² to a uniform prestressing force stress difference occurring in laminated wood bed version by the position in the vicinity of the end portion is generated Turned out not to have.
Further, in the direction perpendicular to the prestressing force direction of the laminated wood near deck end, become undesirable stress distribution for a tensile stress (15 kgf / cm ² or so) is laminated wood deck is composed of laminated has occurred Turned out to be.
[0005]
[Means for solving the problems]
As a result of studies to solve the above problems, the present inventors have found that the non-uniformity of the stress generated at the end of the floor slab in which the laminated slabs are arranged side by side is a PC steel having a tension generating function. It was found that there is a relationship with the stick fixing structure.
In the prior art, a compressive force is generated by tightening a nut inserted into the threaded portion of the end of the PC steel bar, and the compressive force is transmitted in the order of the metal bearing plate and the metal fixing plate. It is necessary to convey the whole thing uniformly.
In particular, in the contact between the metal fixing plate and the laminated slab end portion, if the contact portion is made with a point or a line, the prestress force generated inside the floor slab body varies depending on the part.
That is, since a metal plate was used for this fixing plate, uniform transmission could not be performed due to a low metal deformability and insufficient smoothness of the laminated slab surface.
The inventors of the present application have made various studies by paying attention to the above problems, developed an effective tension transmission method, and have made the present invention having the following configuration. That is, (1) a floor slab formed by a large number of long laminated timbers abutting and closely contacting each other in the front and rear and left and right sides, and a floor slab surface at the center of the thickness of the laminated slab A large number of through-holes drilled perpendicular to the fiber direction of the laminated wood, PC steel bars inserted through the through-holes, and wooden bars disposed at both ends of the inserted PC steel bars A prestressed wooden slab comprising a fixing tool using a fixing plate and having a prestressing force introduced into the PC steel bar and the laminated slab slab through the fixing tool is used for the wooden slab. A wooden bridge that employs a prestressed wood deck that features
: In order to transmit a uniform compressive force to the floor slab in which the laminated slabs are arranged side by side, good adhesion between the fixing plate and the edge of the laminated slab slab is required. Therefore, the material of the fixing plate is changed from a conventional metal plate to a wooden one, and the fixing plate and the floor slab are integrated by solid phase bonding as a result of the “familiar” effect on the contact surface with the laminated slab. (Hereinafter, the wooden fixing plate is simply referred to as a fixing plate). As a result, the compressive force generated by tightening the bolts at the fixing parts at both ends of the laminated slab is transmitted to the fixing plate and the contacting floor slab through the metal support plate, and the floor slab Uniform prestressing force can be introduced.
[0006]
(2) A wooden bridge using the prestressed wooden floor slab described in item 1 above, wherein the fixing plate is made of the same material as the laminated material.
: Adequate and good adhesion due to the “familiarity” effect between the laminated wood slab and the fixing plate, it is clear that the material of both the laminated wood floor slab and the fixing plate is more similar, so fixing The board is made of laminated material.
[0007]
(3) The fixing plate according to any one of (1) and (2), wherein the fixing plate is formed by fitting a ring made of a high-strength material made of metal or plastic around the periphery thereof. A wooden bridge using a prestressed wooden floor.
: When the floor slab becomes large and the prestressing force to be generated in the laminated slab increases, the compressive force applied by the fixing tool naturally increases. In such a case, the force perpendicular to the direction of the prestressing force of the fixing plate also increases, and there is a concern about the deterioration of the fixing plate in the inventions of the preceding items 1 and 2.
Therefore, a ring made of high-strength material such as metal or plastic is fitted around the periphery of the fixing plate in a round shape to prevent deterioration and damage to the fixing plate due to tensile stress acting in a direction perpendicular to the pre-stress force. Structure.
[0008]
(4) The item 1 described above , wherein the fixing plate is attached to the remaining surface excluding the surface in contact with the laminated slab with a cap made of a high-strength material made of metal or plastic. Or the wooden bridge which employ | adopted the pre-stress wooden deck of any one of 2.
When the compression force applied to the fixing plate is further increased, and there is a further concern about the deterioration, damage or insufficient strength of the fixing plate in the inventions of the preceding paragraphs 1 and 2, the surface of the fixing plate that comes into contact with the support plate at the fixing portion is increased. The structure is covered with a cap made of strong material.
That is, a structure in which the fixing plate is mounted with the cap made of a high-strength material attached to the fixing plate according to the inventions of the preceding paragraphs 1 and 2 other than the surface in contact with the wood floor slab, and the inner surface is closely attached. To do.
In this case, an increased thickness of the cap, particularly the thickness of the ceiling plate, is also used as the bearing plate, which is preferable because it is not necessary to separately prepare the bearing plate.
[0009]
(5) A wooden bridge using the prestressed wood slab according to any one of items 1 to 4, wherein the fiber direction of the fixing plate is parallel to the direction in which the prestress force is introduced.
: As a general characteristic of wood, its physical compressive strength is closely related to its fiber direction. That is, the compressive strength in the direction parallel to the fiber direction is overwhelmingly higher than the compressive strength in the direction perpendicular to the fiber direction. Therefore, the durability of the fixing plate is greatly improved by taking into consideration the fiber direction of the wood and the laminated material used for the fixing plate. A structure in which the fiber direction of the fixing plate is parallel to the prestressing force direction is employed.
[0010]
(6) A wooden bridge adopting the prestressed wooden slab described in any one of (1) to (5) above, wherein the fixing plate has a disk shape.
: The square fixing plate widely used in the conventional method, when receiving a large compressive force from the fixing tool, also generates a tensile force in the direction perpendicular to the pressing direction at the same time. Is often damaged. In addition, when installing the fixing tool, it is necessary to install the rectangular fixing plate so that the upper and lower sides of the square fixing plate are parallel to the upper and lower surfaces of the floor slab, which requires complicated work such as temporarily fixing the fixing plate. . In order to solve these problems, a disk-shaped fixing plate is adopted.
[0011]
(7) The prestress wooden floor according to any one of the preceding items 1 to 6, wherein the fixing tool has a configuration in which support pressures of a plurality of fixing plates are gathered together and fixed. Kibashi which adopted version.
: Ideally, the area of the fixing plate should be the same as the end face of the floor slab in order to uniformly transmit the pressure generated by the fixing tool to the end face of the floor slab via the fixing plate. However, as long as the prestressing force introduction method using the PC steel bar is assumed, the area of the fixing plate is reduced with respect to the end face of the floor slab. However, the fixing plate can be dispersed and the compressive force of the central portion of the PC steel bar can be divided equally to achieve uniformity. That is, a plurality of fixing plates are arranged at an equal distance from the central portion of the pressing force.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An example in which the prestress structure according to the present invention is adopted when a wooden floor slab of a wooden bridge is configured by arranging a large number of long laminated slabs will be described with reference to the drawings.
FIG. 9 shows a schematic view of the wooden bridge of the present invention. A prestressed wooden slab 20 according to the present invention is installed on the support bodies 14 and 14 arranged side by side on the left and right abutments 13 and 13. Composed.
FIG. 1 is a partial sectional perspective view of a fixing portion of a wood floor slab according to the present invention, and FIG. 2 is a sectional view thereof.
FIG. 1 shows a structure in which a prestressing force is introduced by a fixing portion 1 to a floor slab in which a large number of laminated members 2 are arranged in parallel and in a staggered manner.
A through-hole 40 is formed in the center of the long laminated material 2 in the thickness direction, and penetrates in the width direction of the floor slab of the wooden bridge. A compression force is generated by attaching the nut 8 to the portion and tightening the nut 8 in the direction of the floor slab.
This compressive force is transmitted to the metal support plate 5 via the washer 9 and then transmitted to the side surface of the wood floor slab via the fixing plate 3. This compressive force becomes prestressing force in the main body of the wood deck, and the whole wood deck 20 is integrated as a building, that is, it becomes the prestress floor slab of the wooden bridge and is the same as the reinforced concrete bridge floor surface. Will play a role.
Here, the contact state between the fixing plate 3 and the end face of the floor slab becomes very important. If the fixing plate is in contact with only a part of the floor slab, the compressive force generated by the fixing tool is transmitted only to the part that is in contact, and the pre-stress force in the floor slab is The value required to construct the structure is not reached, resulting in an incomplete structure.
In the present invention, a wooden fixing plate is adopted as the fixing plate 3 to improve the adhesion to the laminated wood floor slab and to introduce a uniform prestress force into the floor slab.
When the span distance of the wooden deck 20 of the wooden bridge becomes large and it is necessary to increase the prestressing force, a wooden fixing plate having a reinforcing structure is effective.
[0013]
7A and 7B are perspective views of a fixing plate in which a ring 10 made of a high-strength material such as metal or plastic is fitted in a square shape to a square fixing plate and a disk-type fixing plate, respectively. In the center of the fixing plate, a through hole 11 through which a PC steel bar is inserted is provided for introducing a prestressing force. The action of the ring 10 can prevent the fixing plate from being deteriorated or damaged by a tensile stress generated in the fixing plate 3 in a direction perpendicular to the prestressing force direction when the prestressing force is increased.
FIG. 7C shows a wooden fixing plate having another reinforcing structure. In other words, the fixing plate has a reinforcing structure with a cap 100 in which the reinforcing ring 10 and the ceiling plate 100a are integrated. In addition, what comprised the ceiling board 100a of the cap 100 thickly can also serve as a bearing plate. Any of the reinforcing fixing plates can introduce a prestressing force while avoiding deterioration and breakage of the wooden fixing plate due to the compressive force from the fixing tool, while ensuring a close contact structure with the end surface of the laminated wood floor plate. ((D) and (e) in FIG. 8 are the same as (c), but the support pressures of the plurality of fixing plates shown in FIGS. 5 and 6 are gathered together and transmitted to the laminated wood deck. It is used for the system to be used, and has a dowel insertion hole 12 and does not have a through hole 11 for inserting a PC steel rod.)
[0014]
3 and 4 are a partial cross-sectional perspective view and a cross-sectional view showing a state in which a disk-type fixing plate is mounted on the fixing portion. A ring 10 ′ made of high strength material is fitted in the shape of a ring around the periphery of the fixing plate and is in close contact with the fixing plate 3 and the end face of the laminated wood floor slab.
5 and 6 are a partial cross-sectional perspective view and a cross-sectional view of a structure in which a compressive force generated from one PC steel bar is transmitted to the laminated wood floor slab by a plurality of fixing plates.
In the case of a large laminated timber slab, the thickness of the laminated timber slab increases, and the compressive force from the fixing plate in the central part is not easily transmitted to the vertical position of the laminated timber slab. Therefore, a plurality of fixing plates can be used to disperse the compressive force applied to the laminated wood floor slab, so that a uniform pre-stress force can be introduced into the wood floor slab body.
5 and 6 show a state in which two fixing plates are used. The compressive force generated by tightening the bolts 8 is distributed in the thickness direction of the laminated slab by the flange 7 and passes through the sole plate 6, the metal support plate 5 and the fixing plate 3 at the upper and lower pressure positions, respectively. Compress the side of the laminated timber deck 2. At this time, it is important that the distance to the center portion of each fixing plate is equal to the center point of the PC steel bar.
The centering fixing work can be easily performed by providing the dowel insertion hole 12 at the center of the fixing plate in FIG. 8D and fitting with the dowel 11 at the center of the bearing plate 5.
Note that the stress distribution generated in the laminated wood floor slab when the fixing method using a fixing plate made of the same material as the laminated wood is adopted is calculated as a result of three-dimensional FEM analysis. stress difference due to the position of the plate to ^{18kgf / cm 2 ~10kgf / cm 2} , prestress direction of the perpendicular tensile stresses are significantly reduced ^{8kgf / cm 2 ~10kgf / cm 2} .
[0015]
Next, the outline | summary of the Example which employ | adopted this invention for the wooden deck of the actual wooden bridge is introduced.
Wooden floor slab length: 22m
Width: 5m
Glulam: 34 floor plates (width 150mm, 200mm, 2 types, height 1040-1070mm, length 22.8m, material)
PC steel rod: diameter 32v, length 6.130m, 46 fixing plates: length 320mm, width 320mm, thickness 25mm, 92 sheets Asphalt pavement (wood thickness 7. 1cm) is used and used as a general motorway without problems.
[0016]
【The invention's effect】
According to the present invention, when a large laminated slab is applied to a bridge or the like of a building that requires high strength, the necessary prestress can be applied uniformly and accurately, and it is safe and highly reliable. Construction of wooden bridges with laminated slabs became possible.
Further, since no metal material is used for the fixing plate, the weight and cost of the wooden bridge can be reduced.
Therefore, it will not only open up a more effective path for the use of low timber and thinned wood, which have been highly demanded for effective use of conventional resources, but also to meet society's demand for wooden structures from landscape and environmental improvements. I can respond.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional perspective view of a fixing portion of a wooden bridge slab according to the present invention. FIG. 2 is a sectional view of a fixing portion of a wooden bridge slab according to the present invention. FIG. 4 is a partial cross-sectional perspective view of a fixing portion fitted with a fixing plate fitted with a ring of the same. FIG. 4 is a sectional view of a fixing portion fitted with a fixing plate fitted with a ring of high strength material according to the present invention. FIG. 6 is a partial cross-sectional perspective view of a fixing portion that generates prestressing force on a wooden bridge slab by a plurality of fixing plates according to the present invention. FIG. 6 shows prestressing force on a wooden bridge slab by a plurality of fixing plates according to the present invention. FIG. 7 is a partial cross-sectional perspective view and cross-sectional view of a square and disk-shaped wooden fixing plate in which a reinforcing measure is applied in a ring shape and a cap shape with a high-strength material according to the present invention. Square shape with ring-shaped and cap-shaped reinforcement measures made of high-strength material according to the present invention Some of the fine disk-shaped wooden fixing plates sectional perspective view and a cross-sectional view 9 overview diagram of wooden bridge adopts the assembled timber deck EXPLANATION OF REFERENCE NUMERALS
1: fixing part, 2: laminated wood,
3: Fixing plate, 4: PC steel bar,
5: Pressure plate, 6: Sole plate,
7: Flange, 8: Nut,
9: Washer, 10: Ring,
11: Dowel, 12: Dowel insertion hole,
20: Wood floor slab, 40: Through hole,
100: Cap

Claims (6)

A floor slab formed by a large number of long laminated timbers in contact with each other in front and rear and side-by-side and closely arranged in a staggered manner, and the central part of the laminated slab floor slab is assembled parallel to the floor slab surface A large number of through-holes drilled perpendicular to the fiber direction of the material, PC steel bars inserted through the through-holes, and wooden fixing plates provided at both ends of the inserted PC steel bars And a prestressed wooden slab in which a prestressing force is introduced to the PC steel bar and the laminated slab slab through the fixing tool. A wooden bridge that uses prestressed wooden floors. 2. A wooden bridge using a prestressed wood deck according to claim 1, wherein the fixing plate is made of the same material as the laminated wood. 3. The pre-treatment according to claim 1, wherein the fixing plate is formed by fitting a ring made of a high-strength material made of metal or plastic around the periphery thereof. A wooden bridge using a stress wooden floor. 3. The fixing plate is formed by adhering the remaining surface excluding the surface in contact with the laminated slab with a cap body made of a high-strength material made of metal or plastic. The wooden bridge which employ | adopted the pre-stress wooden floor slab of any one of these. 5. The wooden bridge using the prestressed wood slab according to claim 1, wherein the fiber direction of the fixing plate is parallel to the direction in which the prestressing force is introduced. The wooden bridge employing the prestressed wooden slab according to any one of claims 1 to 5, wherein the fixing plate has a disk shape.

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