JP2014148880A - Truss structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a truss structure in which chord materials are combined in favorable balance by optimum lengths and numbers.SOLUTION: A truss structure comprises: a plurality of triangular trusses 1a, 1b-1 to 1c-3 which are aligned so that triangular faces which are obliquely erected are substantially parallel with one another; two upper chord materials 2b, 2c which connect opposite vertexes 5b-1 to 5b-3 of a plurality of the triangular trusses 1b-1 to 1c-3 with an opposite vertex 5a of a bottom side of the largest triangle truss 1a as a starting point; and two pairs of two lower chord materials 2b, 3c, 4b, 4c which connect both ends of bottom sides of a plurality of the triangular trusses 1b-1 to 1c-3 with both ends of the bottom side of the largest triangular truss 1a as starting points, respectively. By considering that the two upper chord materials 2b, 2c, the two pairs of the two lower chord materials 2b, 3c, 4b, 4c, and the largest triangular truss 1a as plane trusses which use one chord material, respectively, the opposite vertexes 5a, 5b-1 to 5b-3 of triangular bottom sides of a plurality of the triangular trusses 1a, 1b-1 to 1c-3 are inclined to the side of a support point A.

Description

  The present invention relates to a truss structure of a cantilever support structure used for a bridge or the like.

  As a load support mechanism of a structure using a truss, there are a bridge (truss bridge) in civil engineering, a dome with a hut and a three-dimensional truss in architecture, and a tower crane in machinery. The truss structure used for the load support mechanism of the cantilevered support structure is generally the same as the truss type crane etc. There is to support in. In the truss type crane, the tensile material portion of the axial force of the member is mainly supported by a wire, and the compression material portion is mainly supported by a truss assembled with a steel frame.

  In the truss used for the load support mechanism of such a cantilever support structure, the most serious problem is buckling of the compressed material. For example, a truss type crane prevents structural buckling (overall buckling) and local buckling (member buckling) by assembling a truss to prevent buckling of a compressed material. In other words, the truss can be configured very easily, and the beam and the ramen support the load by bending and shearing, whereas the truss supports the load by an axial force, so it supports a very large load. be able to. The truss generally includes a flat truss and a solid truss, and is practically used for construction machines such as cranes and bridges.

  Various prior arts have been disclosed for this type of truss structure. For example, Patent Document 1 discloses a truss structure used for various wooden load support mechanisms. However, Patent Document 1 describes only the use of wood, and does not describe the use of other materials. In addition, since the axial force applied to each member is structurally different, there is a member that receives a strong axial force, and measures against damage such as buckling due to this are not considered.

  In addition, Patent Document 2 discloses that its own weight / loading load is applied to eliminate bending moments caused by bending of building materials such as beams and slabs, and to reduce the burden on vertical members such as columns and walls that support the building materials. In the direction opposite to the direction in which the building material bends due to, etc., it is formed in a slightly curved shape, and tension reinforcing material is arranged along the bending direction so as to add tension due to pre-stress inside the building material. Thus, there is disclosed a gravity deflection correction method for building structure building materials, characterized in that the bending moment generated by the bending deformation of the building materials is corrected.

  Patent Document 3 discloses a suspension bridge structure using a cantilever structure and a tension structure. This suspension bridge structure is a bridge structure constructed with superstructures and substructures consisting of piers and abutments, and the superstructure pulls high-tensile steel threaded steel bars that are arranged in parallel as the main girder. A pair of cantilever box girder provided on opposite sides of a tension structure formed in a horizontal direction, a steel cantilever girder extending in the horizontal direction, and a cantilever box girder extending in both ends in the horizontal direction. And a fixing part for fixing the screw-fushi steel bar to the steel-concrete composite abutment, and the substructure consists of a steel-concrete composite abutment and a pier that supports the cantilever box girder.

JP 2002-531731 A JP 2001-214563 A JP 2011-6944 A

  An object of the present invention is to provide a truss structure in which chord members are combined with an optimal length and number in a well-balanced manner.

  The truss structure of the present invention is a triangular truss formed by arranging a chord material on each side of a triangle raised obliquely with the bottom side being substantially horizontal, with the largest triangular truss being approximately centered toward both sides thereof Starting from the triangle trusses with the triangle trusses that are gradually made smaller and arranged so that the planes of the triangles are approximately parallel to each other, and the bases of the triangles of the triangle of the largest triangle truss, Starting from the two upper chords that connect the opposite vertices of the base of each triangle and the ends of the base of the triangle of the largest triangular truss, the ends of the triangles of each of the triangular trusses on both sides are connected Two sets of two lower chords, two upper chords, two sets of two lower chords and the largest triangular truss, one chord As a plane truss, the intersection of one of the upper chord material and the lower chord material is a support point A, the other intersection is a loading point C, and the base of the triangle of the largest triangular truss is the support point B. In this example, the bottom vertex is inclined toward the support point A.

  FIG. 1 is a perspective view schematically showing the truss structure of the present invention, and FIG. 2 is a plan view in which the truss structure of FIG. 1 is regarded as a flat truss. As shown in FIG. 1, the truss structure of the present invention has a plurality of triangular trusses 1a, 1b-1, 1b- formed by arranging a chord material on each side of a triangle raised obliquely with the bottom side being substantially horizontal. 2, 1b-3, ..., 1c-1, 1c-2, 1c-3, .... These triangular trusses 1a, 1b-1, 1b-2, 1b-3,..., 1c-1, 1c-2, 1c-3,. , Truss truss 1b-1, 1b-2, 1b-3,..., 1c-1, 1c-2, 1c-3,... Arranged side by side so that their triangular faces are substantially parallel. It is.

  Further, the truss structure of the present invention has a triangular base truss 1a of the largest triangular truss 1a as a starting point and a plurality of triangular trusses 1b-1, 1b-2, 1b-3,. , 1c-2, 1c-3,..., 5c-1, 5c-2, 5c-3,. The upper chords 2b, 2c and the ends of the base of the triangle of the largest triangular truss 1a are used as starting points, and a plurality of triangular trusses 1b-1, 1b-2, 1b-3,. .., 2c-3,... Have two sets of two lower chord members 3b and 3c and lower chord members 4b and 4c that respectively connect both ends of the bases of the triangles.

  In the truss structure of the present invention, the largest triangular truss 1a, two upper chord members 2b and 2c, and two sets of two lower chord members 3b and 3c and lower chord members 4b and 4c, as shown in FIG. Are regarded as flat trusses having one chord member 11, 12, 13, 14, 15 respectively, and one intersection of the upper chord member 2b, 2c and the lower chord member 3b, 4b, 3c, 4c (upper chord member 2b, 3b, 4b Is the support point A, the other intersection (the intersection of the upper chords 2c, 3c, 4c, ie, the intersection of the chords 13, 15) is the loading point C, and the largest triangular truss 1a. The base BB ′ of the triangle is a support point B. Note that the vertex D in FIG. 2 is the paired vertex 5a of the triangle base of the largest triangular truss 1a, that is, the intersection of the chords 11, 12, and 13.

  Further, as shown in FIG. 2, when the chord material 15 is placed horizontally, the vertex D is shifted to the support point A side from the vertical upper side of the support point B, and the chord material 11 is inclined to the support point A side. doing. Therefore, also in the truss structure shown in FIG. 1, the triangular trusses 1a, 1b-1, 1b-2, 1b-3,..., 1c-1, 1c-2, 1c-3,. 5a, 5b-1, 5b-2, 5b-3,..., 5c-1, 5c-2, 5c-3,.

  With the above structure, when the truss structure of the present invention is regarded as a flat truss, a tensile force acts on the chord members 12, 13 and a compressive force acts on the chord members 11, 14, 15. Then, with respect to the chord members 14 and 15 on which the compressive force acts, the chord member 11 is tilted toward the support point A, thereby balancing the axial force applied to the chord members 14 and 15 and buckling the chord members 14 and 15. Can be prevented.

  That is, in the truss structure of the present invention, the upper chord members 2b and 2c have a tensile force, and the lower chord members 3b, 3c, 4b and 4c and the triangular trusses 1a, 1b-1, 1b-2, 1b-3,. A compressive force acts on 1, 1c-2, 1c-3,. Then, triangular truss 1a, 1b-1, 1b-2, 1b-3, ..., 1c-1, 1c-2, 1c-3, ... are applied to the lower chord members 3b, 3c, 4b, 4c on which the compressive force acts. By inclining toward the support point A, the axial force applied to the lower chord members 3b, 3c, 4b, 4c can be balanced, and buckling of the lower chord members 3b, 3c, 4b, 4c can be prevented.

  Further, in the truss structure of the present invention, the lower chord members 3b, 3c, 4b, 4c on which the compressive force acts are set in two sets, and a plurality of triangular trusses 1a, 1b-1, 1b-2, 1b-3,. 1, 1c-2, 1c-3,... Are arranged in parallel and connected to the upper chord members 2b, 2c to prevent buckling of the lower chord members 3b, 3c, 4b, 4c with the upper chord members 2b, 2c. Can do. Further, in the case where the chord material on the hypotenuse of the triangular truss is a band plate material, the flat truss can be considered as a surface, and buckling of the lower chord materials 3b, 3c, 4b, 4c can be prevented.

  According to the truss structure of the present invention, it is possible to balance the axial force applied to the lower chord material by the lower chord material on which the compressive force acts and the triangular truss, and to prevent buckling of the lower chord material. A truss structure with a well-balanced combination can be obtained. Further, since the upper chord material which is a tensile material can be reduced, the number of joints and members can be reduced, and an economically excellent truss structure can be obtained.

It is the perspective view which modeled the truss structure of this invention. It is the top view which considered the truss structure of FIG. 1 as a plane truss. It is the top view which considered the truss structure in embodiment of this invention as a plane truss. Is an explanatory view showing the condition of calculating the shift distance L _X of the vertex D. It is a model photograph of the bridge using the truss structure in the Example of this invention.

  FIG. 3 is a plan view in which the truss structure in the embodiment of the present invention is regarded as a plane truss. The flat truss shown in FIG. 3 shows an embodiment of the truss structure of the present invention and the flat truss described with reference to FIGS. 1 and 2, and the same reference numerals are given to common components.

When designing the plane truss in the present embodiment, as shown in FIG. 3, the load is applied to the corner of the lower side of the rectangle drawn with the long side of the length L being horizontal and the short side of the length H being vertical. The loading point C to be applied is provided, the supporting point B is located at the position L ₁ from the lower loading point C (the length L ₁ from the loading point C to the supporting point B), and the supporting point A is the height of H _{1 on} the short side. At each position (length H _{1 of the} vertical line extending from the support point A to the straight line connecting the support point B and the loading point C), the vertex D is shifted L _X from the center of the upper side to the right. 11 to 15 are arranged.

  In this plane truss, when a load is applied to the loading point C, the support point A supports the plane truss vertically from the bottom to the top, and the support point B vertically supports from the top to the bottom. Tensile force acts on the chord material 12 between the apexes D and the chord material 13 between the loading point C and the apex D, respectively. Further, a compressive force acts on the chord material 15 between the loading point C and the support point B, the chord material 14 between the support point B and the support point A, and the chord material 11 between the support point B and the apex D.

The vertex D is set by shifting the intersection of the line extending vertically upward from the support point B and the upper side of the rectangle to the right side of the distance L _X , which is a string connecting the loading point C and the support point B. This is to balance the compressive force applied to the chord 14 connecting the material 15 and the support point A to the support point B. That is, by making the central chord material 11 diagonal, the chord material 11 is slightly lengthened, and the chord material 15 between the loading point C and the support point B and the chord material 14 between the support point B and the support point A are shown. This balances the axial force and reduces the risk of buckling.

In the present embodiment, the shift distance L _X of the vertex D is obtained as follows on the condition that the chord members 14 and 15 simultaneously buckle.

When the same member (cross section, material) is used for the chord members 14 and 15 in FIG. 3, the linear buckling loads P _CR1 and P _CR2 of the chord members 15 and 14 are
P _CR1 (string material 15) = π ² EI / (L ₁ ) ² (1)
P _CR2 (string material 14) = π ² EI / {(L ₂ ) ² + (H ₁ ) ² } (2)
However, this is not considered because the length in the depth direction is small.

Here, in order for the string members 14 and 15 to buckle at the same time,
π ² EI = P _CR1 (L ₁ ) ² = P _CR2 {(L ₂ ) ² + (H ₁ ) ² } (3)
Should be established.

According to the Cremona method (see Fig. 4), which is one of the truss solutions,
P _CR1 (string material 15) = PL ₂ (L ₁ + L _X ) / (LH) (4)
P _CR2 (string material 14) = PL ₁ (L _X −L ₂ ) {(L ₂ ) ² + (H ₁ ) ² } ^1/2 / {L (H ₁ L _X −HL ₂ )} (5)
It becomes.

Substituting equations (4) and (5) into equation (3),
{PL ₂ (L ₁ + L _X ) / (LH)} (L ₁ ) ²
= [PL ₁ (L _X −L ₂ ) {(L ₂ ) ² + (H ₁ ) ² } ^1/2 / {L (H ₁ L _X −HL ₂ )}] {(L ₂ ) ² + (H ₁ ) ² } (6)

When the equation (6) is reduced,
L ₁ L ₂ (L ₁ + L _X ) / H− (L _X −L ₂ ) {(L ₂ ) ² + (H ₁ ) ² } ^3/2 / (H ₁ L _X −HL ₂ ) = 0. 7)

therefore,
F = L ₁ L ₂ (L ₁ + L _X ) / H− (L _X −L ₂ ) {(L ₂ ) ² + (H ₁ ) ² } ^3/2 / (H ₁ L _X −HL ₂ ) = 0
L _X is calculated.

The calculation of L _X may be solved quadratic equation for L _X by multiplying the (8) formula _{(H 1 L X -HL 2)} , + the F, - L when the code is changed _You may ask for _X. Note that the calculation method of the shift distance L _X of the vertex D described above is one example when the chord members 14 and 15 are simultaneously buckled, and the shift distance L _X is determined based on other conditions. Can be changed as appropriate.

FIG. 5 is a model photograph of a bridge as a cantilever support structure using a truss structure in an embodiment of the present invention. The bridge 20 shown in FIG. 5 is a flat truss with the long side length L of the rectangle described in FIG. 3 set to 1000 mm, the short side H set to 300 mm, and the shift distance L _X of the vertex D is set to 50 mm. A plurality of triangular trusses 21a, 21b-1, 21b-2, 21b-3, 21c-1, 21c-2, 21c-3, 21c-4 are arranged in parallel to the vertex D-support point B.

  In the bridge 20 having the above configuration, a tensile force acts on the upper chord member 22 connecting the loading point C and the apex D and the upper chord member 23 connecting the support point A and the apex D. Further, lower chord members 24, 25 connecting the loading point C and the support point B, lower chord members 26, 27 connecting the support point B and the support point A, and triangular trusses 21a, 21b-1, 21b-2, 21b- A compression force acts on 3, 21c-1, 21c-2, 21c-3, and 21c-4. In this truss structure, the triangular trusses 21a, 21b-1, 21b-2, 21b-3, 21c-1, 21c-2, 21c-3, 21c-4 are inclined toward the support point A side. The length of the upper chord member 22 connecting the loading point C and the apex D is slightly longer than the length of the upper chord member 23 connecting the support point A and the apex D, and the lower chord member 26 connecting the support point B and the support point A, The compression force applied to 27 is reduced more than the compression force applied to the lower chord members 24 and 25 connecting the loading point C and the support point B.

  That is, by tilting the triangular trusses 21a, 21b-1, 21b-2, 21b-3, 21c-1, 21c-2, 21c-3, 21c-4 to the support point A side, the lower chord members 24, 25, The axial force applied to 26, 27 is balanced, and buckling of the lower chord members 24, 25, 26, 27 is prevented. Thus, the bridge 20 in the present embodiment is a combination of compression materials (lower chord materials 24, 25, 26, and 27) with an optimal length and number in a well-balanced manner.

  Further, in the bridge 20 in this embodiment, the lower chord members 24, 25, 26, and 27 on which the compressive force acts are set in two sets, and a plurality of triangular trusses 21a, 21b-1, 21b-2, 21b-3, 21c-1 , 21c-2, 21c-3, 21c-4 are arranged in parallel and connected to the upper chord members 22, 23, so that the lower chord members 24, 25, 26, 27 are prevented from buckling by the upper chord members 22, 23. In addition, since the upper chord members 22 and 23, which are tensile materials, can be reduced, the number of joints and members can be reduced, which is economically excellent. In particular, when wood is used as a material, the tension of the wood is stronger than the compression, so that the upper chord members 22 and 23 which are tensile materials are smaller than the lower chord members 24, 25, 26 and 27 which are compressive materials and have a cross section. The structure can be reduced in weight.

  Moreover, in the bridge 20 shown in FIG. 5, the chord material of the hypotenuse of the triangular trusses 21a, 21b-1, 21b-2, 21b-3, 21c-1, 21c-2, 21c-3, 21c-4 is used as the strip plate material. Since the plane truss of FIG. 3 can be considered as a plane, it is possible to prevent buckling of the lower chord members 24, 25, 26, and 27.

In this embodiment, L: H is 1: 0.3, but can be arbitrarily changed in the range of 0 <H ₁ / H <1, 0 <L ₁ / L <1. However, when considering the balance of the chord members 11, 14, and 15 to which the compressive force is applied, it is preferable that L: H is up to about 1: 0.888.

  The truss structure of the present invention is useful as a truss structure of a cantilever support structure such as a bridge.

A, B Support point C Loading point D Vertex 1a, 1b-1, 1b-2, 1b-3, 1c-1, 1c-2, 1c-3 Triangular truss 2b, 2c Upper chord material 3b, 3c, 4b, 4c Lower chord Material 11, 12, 13, 14, 15 String material 5a, 5b-1, 5b-2, 5b-3, 5c-1, 5c-2, 5c-3 Vertex of the base of the triangle 20 Bridge 21a, 21b-1 , 21b-2, 21b-3, 21c-1, 21c-2, 21c-3, 21c-4 Triangular truss 22, 23 Upper chord material 24, 25, 26, 27 Lower chord material

Claims (3)

Triangular trusses that are formed by placing chords on each side of a triangle that rises diagonally with the bottom side approximately horizontal, and the triangular trusses that gradually become smaller toward both sides of the largest triangular truss. A plurality of triangular trusses arranged side by side so that the triangular surfaces are substantially parallel;
Two upper chord members each connecting the pair of apexes of the triangles of each of the plurality of triangle trusses on both sides thereof, starting from the pair of apexes of the triangle base of the largest triangle truss;
Two lower chord members each having two sets of two lower chord members respectively connecting both ends of the triangle bases of the plurality of triangular trusses on both sides thereof, starting from both ends of the triangle base of the largest triangular truss,
The two upper chord members, the two sets of the two lower chord members, and the largest triangular truss are regarded as a plane truss each having one chord member, and one intersection of the upper chord member and the lower chord member is a support point A. A truss structure in which the other intersection is a loading point C, the base of the triangle of the largest triangular truss is a support point B, and the vertexes of the triangle bases of the plurality of triangular trusses are inclined toward the support point A.   The truss structure according to claim 1, wherein the chord material on the hypotenuse of the triangular truss is a strip plate material. The length of the long side of the rectangle surrounding the plane truss is set to L from the chord material connecting the support point B of the plane truss and the load point C described above on the long side, from the load point C to the support point B described above. the length L _1, when the length of the short side H, the length of the perpendicular drawn from the support point a to the straight line connecting the said loading point C and the support point B and the H _1,
0 <H ₁ / H <1, 0 <L ₁ / L <1
The truss structure according to claim 1 or 2.