JP7500265B2 - Truss structure - Google Patents

Description

The present invention relates to truss structures, for example, steel-framed or wooden structures.

Traditionally, long-span truss structures such as lattice beams (see Fig. 3(A)) have a bridge 4 in which the upper chord 1 and the lower chord 2 are connected by multiple connecting members 3 so that multiple triangles (triangles with at least a part of the upper chord 1 or lower chord 2 as one side) are lined up from one end of the upper chord 1 or the lower chord 2 to the other end. In such a truss structure, if a distribution is taken in which the shear force increases from the center of the bridge 4 toward the end where the support is located (see Fig. 3(B)), the axial force borne by the connecting members 3 closer to the end of the bridge 4 will be greater, and so the cross section of the connecting members 3 must be designed taking this force into consideration.

However, generally speaking, the cross section of only the connecting material 3 at the end of the bridge 4 is not enlarged as in Figure 3(C), and from the standpoint of design and ease of production, the shape of each triangle of the bridge 4 and the cross section of the connecting material 3 are standardized (see Figure 3(A)). In this case, the cross section required for the connecting material 3 at the end of the bridge 4 that bears the greatest axial force is also applied to the other connecting materials 3, which increases the total amount of material used for the connecting materials 3.

The present invention was made with the above in mind, and its purpose is to provide a truss structure that makes it easy to reduce the total amount of material used for the connecting members.

In order to achieve the above-mentioned objective, the truss structure of the present invention has an upper chord and a lower chord connected by a plurality of connecting members so that a plurality of triangles are lined up from one end of the upper chord or the lower chord to the other end , has bridges with upward triangles whose bases are part of the lower chord and whose base lengths are not uniform, and has upward triangles whose bases are part of the lower chord and whose bases are shorter at both ends than at the center of the bridge, and has a plurality of triangles with the same bases at the center of the bridge, and has a plurality of triangles with the same bases at each end of the bridge, and the bridge does not have bundle members as connecting members but only diagonal members (Claim 1).

In the above truss structure, the bridge may have a shear force distribution in its longitudinal direction, in which the shear force is small at the center and large at both ends of the bridge (claim 2).

The present invention provides a truss structure that makes it easy to reduce the total amount of material used for the connecting members.

In other words, in the truss structure of the invention according to each claim of this application, compared to a conventional truss structure (see FIG. 3(A)) that standardizes the multiple triangles formed by the connecting materials and the cross sections of each connecting material, the truss structure does not standardize the multiple triangles formed by the connecting materials, making it easier to reduce the total amount of material used for the connecting materials, not only when standardizing the cross sections of each connecting material is attempted, but also when not.

The truss structure of the invention according to claim 1 is suitable for use in a general parallel chord truss (lattice beam) in which the shear force is small at the center of the bridge and large at both ends of the bridge (around the supports).

1 is an explanatory diagram illustrating a schematic configuration of a truss frame according to an embodiment of the present invention; FIG. 2 is an explanatory diagram illustrating a schematic configuration of a main part of the truss structure. (A) is an explanatory diagram showing the configuration of a conventional truss structure, (B) is an explanatory diagram showing the shear force distribution that occurs when a design load (uniform load) is applied to the conventional truss structure shown in (A), and (C) is an explanatory diagram showing a hypothetical truss structure in which the cross-section of the connecting material near the end of the bridge is enlarged.

The following describes an embodiment of the present invention with reference to the drawings.

As shown in Figures 1 and 2, the truss structure of this embodiment has a bridge (truss frame) 4 that forms a parallel chord truss, in which the upper chord 1 and the lower chord 2 are connected by multiple connecting members 3 so that multiple triangles are lined up from one end of the upper chord 1 or the lower chord 2 to the other end. The truss structure of this example is a long-span truss structure (e.g., five or more triangles are formed) whose both ends are supported by supporting members (supports) such as columns.

In this example, the lengths of the bases 5, 7 are not uniform between the downward triangles 6 whose base 5 is a part of the upper chord 1, or between the upward triangles 8 whose base 7 is a part of the lower chord 2. Note that in the illustrated example, the lengths of the bases 5, 7 are not uniform between the downward triangles 6 or between the upward triangles 8.

In the truss structure of this example, compared to a conventional truss structure (see FIG. 3(A)) that standardizes the multiple triangles formed by the connecting members 3 and the cross sections of each connecting member 3, the multiple triangles formed by the connecting members 3 are not standardized, making it easier to reduce the total amount of material used for the connecting members 3, not only when standardizing the cross sections of each connecting member 3 is attempted, but also when not.

In addition, as shown in Figure 2, in the truss structure of this example, the bases 5, 7 of the triangles 6, 8 at both ends are shorter than the bases 5, 7 of the triangles 6, 8 at the center of the bridge 4 between the downward triangles 6 or between the upward triangles 8.

In this example, the bases 5, 7 of the triangles 6, 8 at both ends are shorter than the bases 5, 7 of the triangles 6, 8 at the center of the bridge 4, both between the downward triangles 6 and between the upward triangles 8. That is, in FIG. 2, the length L5S of the base 5 of the triangle 6 at both ends of the bridge 4 is shorter than the length L5C of the base 5 of the triangle 6 at the center of the bridge 4, and the length L7S of the base 7 of the triangle 8 at both ends of the bridge 4 is shorter than the length L7C of the base 7 of the triangle 8 at the center of the bridge 4.

The truss structure of this example is suitable for use in, for example, a general parallel chord truss (lattice beam) in which the shear force is small at the center of the bridge 4 and large at both ends of the bridge 4 (around the supports). This is because the connecting members 3 are arranged at a higher density at both ends where the shear force is large than at the center of the bridge 4 where the shear force is small, making it easier to suppress the variation in the axial force N borne by each connecting member 3.

In other words, in the truss structure of this example, the lengths of the bases 5, 7 of the triangles 6, 8 are made different according to the shear force distribution in the longitudinal direction of the bridge 4 (for example, this is the shear force distribution that can be assumed when the bridge 4 is considered as one beam (simple beam), and is not an equal load distribution). Specifically, in areas where the shear force is relatively small (areas relatively far from the fulcrum, in this example the center of the bridge 4), the bases 5, 7 of the triangles 6, 8 are made relatively long (the slope θ of the connecting material 3 is made small) and in areas where the shear force is large (areas relatively close to the fulcrum, in this example both ends of the bridge 4), the bases 5, 7 of the triangles 6, 8 are made relatively short (the slope θ of the connecting material 3 is made large) according to the shear force distribution.

Here, there is a relationship of Q = N × sinθ between the shear force Q, the axial force N generated in the connecting member 3, and the gradient θ (the angle between the bases 5, 7 and the connecting member 3 in each triangle 6, 8), so for the same value of shear force Q, the greater the gradient θ of the connecting member 3, the more the axial force N generated in the connecting member 3 can be reduced. Therefore, when the bridge 4 is a typical parallel chord truss, by making the gradient θ of the connecting member 3 closer to vertical in the areas where the shear force on both ends of the bridge 4 is relatively large, and closer to horizontal in the areas where the shear force on the center side of the bridge 4 is relatively small, it is possible to suppress the variation in the axial force N generated in the connecting member 3, minimize it while making the cross section of the connecting member 3 uniform, and reduce the total amount of material used.

In the example of FIG. 1, the lengths of the bases 5, 7 are different in only two stages, the center side and both ends of the bridge 4, but they may be different in three stages or more. For example, if the shear force is divided into three stages, large, medium and small, from both ends of the bridge 4 to the center, it is conceivable to divide the bases 5, 7 into three types, a long region, a medium region and a short region, from both ends of the bridge 4 to the center.

In this case, the gradient θ can be calculated by optimizing the solution using a genetic algorithm with the quantity of connecting members 3 as the evaluation conditions and the stress, deformation, and vibration frequency as the constraints.

The truss structure of this example makes it easy to realize a rational structure that corresponds to the shear force distribution. It also makes it easy to standardize the cross section of the connecting members 3 of the long-span bridge 4, giving the bridge 4 a unified look while creating a structure that is easy to manufacture.

The present invention is not limited to the above-described embodiment, and can of course be modified in various ways without departing from the spirit of the invention.

The truss structure of the present invention can be applied to truss structures such as steel-framed structures (steel truss) and wooden structures (wooden truss).

Figures 1 and 2 show a case where the bridge 4 is a Warren truss that does not have any beams (vertical members) and only includes diagonal members as the connecting members 3, but the present invention can also be applied to other truss structures that include beams and diagonal members as the connecting members 3, such as a Warren truss, Howe truss, and Pratt truss.

Although Figures 1 and 2 show a parallel chord truss in which the upper chord 1 and the lower chord 2 extend parallel to each other, the present invention can also be applied to other truss structures in which the upper and lower chords 1, 2 are not parallel, such as an angle truss in which the upper chord 1 extends in an arc (e.g., a king post truss or a curved chord Pratt truss).

Although Figures 1 and 2 show a planar truss, the present invention can also be applied to a space truss.

It goes without saying that the above modifications may be combined as appropriate.

1 Upper chord 2 Lower chord 3 Connecting member 4 Bridge 5 Base 6 Downward triangle 7 Base 8 Upward triangle L5C Length of the base of the downward triangle at the center L5S Length of the base of the downward triangle at both ends L7C Length of the base of the upward triangle at the center L7S Length of the base of the upward triangle at both ends N Axial force Q Shear force θ Gradient

Claims (2)

The upper chord and the lower chord are connected by a plurality of connecting members so that a plurality of triangles are lined up from one end side of the upper chord or the lower chord to the other end side, and a bridge having an uneven base length is provided between the upward triangles having a base of a part of the lower chord ,
The bases of the triangles at both ends of the bridge are shorter than the base of the triangle at the center of the bridge, and multiple triangles with the same base are provided at the center of the bridge, and multiple triangles with the same base are provided at both ends of the bridge.
A bridge is a truss structure that does not have beams as connecting members and only includes diagonal members . 2. The truss structure according to claim 1 , wherein the bridge has a shear force distribution in the longitudinal direction thereof such that the shear force is small at the center and large at both ends of the bridge.