JP3574948B2 - Truss point structure - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a point structure of a truss used in fields such as civil engineering and construction.
[0002]
[Prior art]
BACKGROUND ART A structure obtained by combining units in which pipe members are joined in a triangular shape is widely used as a pipe truss in fields such as bridges and other civil engineering and construction.
In such a pipe truss, a plurality of diagonal members are joined in a triangular shape between an upper chord member and a lower chord member, and the upper chord member and the diagonal member and the lower chord member and the diagonal member are generally joined by welding. This joint is called the point.
[0003]
Conventionally, in a truss structure made of a steel pipe member having a circular cross section, when constructing a point portion, as shown in FIG. 8, a structure in which a plurality of diagonal members 23a and 23b and a chord member 21 are directly joined by welding. This structure is used in point sections such as the Lurie Bridge in Switzerland.
[0004]
In the point portion having such a structure, the end of one diagonal member (for example, 23a) on which a compressive force acts is brought into close contact with the surface of the chord member 21, and the end of the other diagonal member 23b is formed. The three-dimensional processing is performed so as to cover the diagonal member 23a, overlap with each other, and sufficiently adhere to the chord member 21.
Further, in order to improve the penetration of the welding, it is necessary to provide a groove at the end of the diagonal members 23a and 23b, and these points are joined by butt welding or the like to form a graded portion.
[0005]
When the compressive or tensile axial force acts on the diagonal members 23a and 23b, the string member 21 locally deforms at the graded portion configured as described above, and the stress accompanying the local deformation occurs to generate fatigue strength. Decreases.
In order to prevent such a problem, as shown in FIG. 9, a cover plate 24 is joined to the chord material 21 by welding to locally increase the thickness of the chord material 21, and the cover plate 24 In general, diagonal members 23a and 23b are joined in the manner described above to prevent local deformation of the chord material 21.
[0006]
[Problems to be solved by the invention]
FIG. 10 is a schematic diagram of a truss bridge. Such a structure at the truss bridge 20, the live load P ₁ of an automobile or the like is loading, diagonal members 23a, 23b are compression force and tensile force symmetrically to the center as a boundary acts alternately, lower chord A tension force acts on the material 21 and a compression force acts on the upper chord material 22. As shown in FIG. 11, a compressive force acts on the diagonal member 23a and a tensile force acts on the other diagonal member 23b, and the diagonal point on the lower chord member 21 side is exerted on the diagonal point part. Tensile force acts on the point on the upper chord material 22 side, and compressive force acts on it. Therefore, under such conditions, the following problem occurs.
[0007]
FIG. 12 shows the flow of the diagonal member axial force acting to push and pull between the diagonal members 23a and 23b by an arrow A. Due to this axial force, stress concentration 31 occurs due to local shearing force at the joint between the diagonal members 23a and 23b, and thus the fatigue strength at the critical point decreases. In addition, the axial force from the diagonal member 23a flows into the welded portion of the cover plate 24 to generate a stress concentration 32, which causes the fatigue strength of the chord member 21 to decrease.
[0008]
FIG. 13 shows the flow of the stress due to the tensile axial force of the chord by arrow B. Since the stress has a property of being attracted to a portion having high rigidity, the stress generated by the tensile force flows toward the cover plate 24 having relatively high rigidity and rapidly flows from the welded portions at both ends of the cover plate 24. As a result, stress concentration 33 occurs in the welded portion, and the fatigue strength of the chord material 21 may be reduced. This shows the same property when the chord axial force is a compressive force.
[0009]
In addition, as shown in FIGS. 8 and 9, in the conventional point structure, in order to form the point part, welding must be applied to a structurally important part where stress in the point part acts in a complicated manner. In addition, residual heat and deformation are likely to occur due to rapid heating and rapid cooling due to this welding, and strength reliability is significantly reduced.
Further, complicated three-dimensional processing is required at both ends of the diagonal material, and it is necessary to provide a groove on the diagonal material and to perform welding, so that it is inevitable that the cost is increased in terms of construction.
[0010]
The present invention has been made to solve the above-described problems, and by reducing stress concentration with a simple structure, while preventing fatigue destruction of the string material, processing and joining are easy and highly reliable, In addition, the purpose is to obtain a truss point structure composed of metal fittings that can reduce the total construction cost.
[0011]
[Means for Solving the Problems]
The point structure of the truss according to the present invention includes a bottom having a shape corresponding to a part of the outer shape of the chord, and a plurality of hollow branches which are erected at a predetermined angle from the bottom and to which the diagonal is joined at the tip. A pipe having an opening communicating with the hollow portion of the branch pipe at the bottom, and a partition connected to the peripheral wall of the branch pipe at an intersection of the branch pipe and integrally forming these. It is composed of metal fittings.
[0012]
The above-mentioned joint fitting was integrally formed by casting.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a front view of an embodiment of a truss point structure of a truss according to the present invention, a part of which is shown in cross section, FIG. 2 is a sectional view taken along line II of FIG. 1, and FIG. 3 is a side view of FIG. . In the drawing, reference numeral 1 denotes a joining metal part forming a point portion, 11 denotes a chord material made of a steel pipe and joined to the joining metal part 1, and 13 denotes a diagonal member made of a steel pipe and joined to the joining metal part 1.
[0014]
The joint fitting 1 has an arcuate shape corresponding to a part of the outer shape of a lower chord material 11 (or an upper chord material 12, which will be hereinafter simply referred to as a chord material 11 in some cases), and an oval bottom portion having a planar shape. 2 and a plurality of hollow branch pipes 3a (two are shown in the figure) having an outer diameter substantially equal to the outer diameter of the diagonal member 13 protruding upward at a predetermined angle from the bottom 2. 3b and the hollow portions of the branch pipes 3a and 3b communicate with the opening 4 provided in the bottom portion 2, respectively.
[0015]
A partition wall 5 having a predetermined thickness is formed at the intersection of the branch pipes 3a and 3b (the center of the joint 1), and the inner walls of the branch pipes 3a and 3b are formed so that the partition wall 5 has a predetermined thickness. The branch pipes 3a and 3b are formed so as to be eccentric with respect to the axial center thereof, so that the inner (center side) plate thickness is larger than the outer plate thickness. Here, it is desirable that the plate thickness of the partition wall 5 is, for example, about twice the plate thickness inside the branch pipes 3a and 3b.
The joining fitting 1 is integrally formed by casting, forging, or the like using a material having excellent weldability, but it is preferable that the joining fitting 1 be manufactured by casting that can easily cope with changes in the inner walls of the partition walls 5 and the branch pipes 3a and 3b.
[0016]
In order to manufacture a pipe truss using the above-described joint fitting 1, as shown in FIG. 4, in a factory or the like, a lower chord material 11 cut into a length that can be loaded on a transport vehicle is provided in a longitudinal direction thereof. Positioning for attaching the joint fittings 1 is performed at predetermined intervals, the joint fittings 1 are arranged at each position, and the bottom 2 is joined to the lower chord material 11 by fillet welding.
Similarly, the upper chord material 12 is positioned at the same pitch (however, usually positioned at the middle of the joint fitting 1 joined to the lower chord material 11), and the bottom 2 of the joining fitting 1 is filled with the upper chord by fillet welding. It is joined to the material 12.
[0017]
The lower chord 11, the upper chord 12, and the oblique material 13 cut to a predetermined length to which the joint 1 has been joined are transported to a site by a carrier, and for example, the joint 1 joined to the lower chord 11. One end of the diagonal member 13 is brought into contact with the branch pipes 3a and 3b, and is joined by full-circumferential welding or the like. Further, if the other ends of the diagonal members 13 are respectively joined to the branch pipes 3a and 3b of the joint fitting 1 joined to the upper chord member 12 by welding all around, a pipe truss as shown in FIG. 5 is completed. In joining the diagonal members 13 to the branch pipes 3a and 3b, an appropriate means may be used, such as inserting a backing metal between the two, or welding the entire circumference by spigot-linking the two. The steps up to the joining of the diagonal members 13 may be performed in a factory or the like.
[0018]
According to the present invention configured as described above, the structure of the joint fitting 1 is simple, the attachment to the lower chord material 11 is easy, and it is not necessary to apply three-dimensional processing to the end of the diagonal member 13. It is possible to obtain a highly reliable point structure, shorten the construction period, and reduce the total construction cost.
[0019]
Further, the partition wall 5 is provided at the intersection of the branch pipes 3a and 3b of the joint fitting 1, and the inner wall of the branch pipes 3a and 3b is eccentric with respect to the axis of the branch pipes 3a and 3b, so that stress concentration occurs. Since the thickness of the partition wall 5 at the central portion (intersection), which is likely to be large, is increased, the stress due to the shearing force is reduced, and the concentration of stress can be suppressed.
[0020]
Further, by providing the partition wall 5 at the center of the joint 1, a compressive force acts on one branch pipe (for example, 3 a) and a tensile force acts on the other branch pipe 3 b , as shown in FIG. 6, for example. In this case, as indicated by the arrow A, most of the flow of stress is exchanged between the branch pipes 3a and 3b via the partition wall 5, so that the direction of the stress flowing into the welded portion with the chord material 11 must be changed. This can reduce the concentration of stress on the weld.
[0021]
Further, as shown in FIG. 2, an opening 4 communicating with the branch pipes 3a and 3b is provided at the bottom 2 of the joint 1 so that the portion other than the peripheral wall and the partition 5 is hollow, and The rigidity in the direction is extremely small. For this reason, the acting stress due to the axial force of the chord material 11 flows as shown by an arrow B in FIG. 7, and stress concentration hardly occurs in the welded portion of the bottom 2.
[0022]
Furthermore, since the joining fitting 1 is integrally manufactured by casting, it is not necessary to perform welding in the corners, so that there is no residual stress or deformation due to welding, and therefore, the strength reliability is improved.
In addition, by manufacturing the metal joint 1 by casting, the shape, thickness, etc. of each part can be easily changed according to the applied stress. By adding, the change in cross section can be reduced. Furthermore, since the amount of material used is small, it is possible to obtain the joint 1 with reduced stress concentration without increasing the material cost.
[0023]
Furthermore, not only is it unnecessary to machine a groove for joining the joint 1 that is a cast product to the chord material 11, but since the bottom 2 is oval, complicated welding is not required. Further, the end of the diagonal member 13 only needs to be cut at a right angle to the axial direction, and the joining with the branch pipes 3a and 3b is easy. In addition, the cost can be reduced because mass production is possible, so that the total construction cost can be reduced.
[0024]
【The invention's effect】
The point structure of the truss according to the present invention includes a bottom having a shape corresponding to a part of the outer shape of the chord, and a plurality of hollow branches which are erected at a predetermined angle from the bottom and to which the diagonal member is joined at the tip. A pipe, and an opening communicating with the hollow portion of the branch pipe is provided at the bottom, and a partition wall connected to the peripheral wall of the branch pipe is provided at the intersection of the branch pipe at the intersection of the branch pipe, and these are provided. Since it is constituted by integrally formed joints, it is not necessary to perform a simple and complicated welding, and therefore, the construction period can be shortened and the total construction cost can be reduced. In addition, since local stress concentration such as stress concentration due to a chord axial force generated near the bottom can be reduced , a highly reliable point structure can be obtained.
[0027]
Since the above-mentioned joining metal fitting is formed by casting, it is not necessary to perform welding in the point part, so that residual stress or deformation due to welding does not occur, so that a point structure with high strength reliability can be obtained.
In addition, by making the metal fittings by casting, the shape and thickness of each part can be easily changed according to the applied stress, and since the amount of material used is small, stress concentration can be achieved without increasing material costs. Can be reduced. In addition, since mass production is possible, an inexpensive metal fitting can be obtained.
[Brief description of the drawings]
FIG. 1 is a front view showing a part of an embodiment of the present invention in cross section.
FIG. 2 is a sectional view taken along line II of FIG.
FIG. 3 is a side view of FIG. 1;
FIG. 4 is an explanatory view showing a procedure for manufacturing a pipe truss using the joint fitting according to the present invention.
FIG. 5 is a completed view of FIG. 4;
FIG. 6 is an operation explanatory view of the joining fitting according to the present invention.
FIG. 7 is an operation explanatory view of a chord material joined with the joint fitting according to the present invention.
FIG. 8 is an explanatory diagram of an example of a conventional point structure.
FIG. 9 is an explanatory diagram of another example of the conventional point structure.
FIG. 10 is an explanatory diagram of a compressive force and a tensile force acting on a pipe truss.
FIG. 11 is an explanatory diagram of a point portion in FIG. 10;
FIG. 12 is an operation explanatory view of the point structure of FIG. 9;
FIG. 13 is an explanatory diagram of the operation of the chord material having the point structure of FIG. 9;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Joining metal fitting 2 Bottom part 3a, 3b Branch pipe 4 Opening part 5 Partition wall 11 Lower chord material 12 Upper chord material 13 Diagonal material

Claims (2)

A bottom portion having a shape corresponding to a part of the outer shape of the chord material, and a plurality of hollow branch pipes to which a diagonal member is joined to a tip portion erected at a predetermined angle from the bottom portion; The truss is characterized by being provided with an opening communicating with the hollow portion of the branch pipe, and at the intersection of the branch pipes, provided with a partition wall connected to the peripheral wall of the branch pipe and integrally forming these with a joint fitting. Case structure. 2. A truss point structure according to claim 1, wherein said joint is integrally formed by casting.

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