JPH0531620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a three-dimensional truss beam into which prestress is introduced.

(Prior Art) Generally, a three-dimensional truss beam is an extremely excellent beam for large-span buildings such as factory hangars, and is actually widely used in many large-span buildings.

(Problem to be Solved by the Invention) However, this type of three-dimensional truss beam is assembled by attaching many diagonal members between the upper and lower chord members, so the number of members and joints are large, and assembly is generally troublesome. It was hot.

In addition, when bending materials such as beams, steel resists tensile force to the full allowable tensile stress, but when it comes to compressive force, it will buckle laterally before reaching the allowable compressive stress, so the cross section must be increased. However, the same is true for three-dimensional truss beams, and the larger the span, the more important is the cross-sectional design that emphasizes buckling.

Therefore, in consideration of these points, conventional three-dimensional truss beams are vertically symmetrical with the neutral axis as a boundary, and have mainly rectangular cross-sections.

However, with such a configuration, tensile stress is generated at the inner lower end and outer upper end of the bending point at both ends where the bending stress is reversed, so the amount of steel used in these parts is considerably large, so the cross-sectional design may be wasted. I can't escape it.

Moreover, since there is a large amount of steel, assembly is complicated and material costs are high.

This invention was proposed in order to solve the above-mentioned conventional problems, and the purpose is to provide a three-dimensional truss beam that reduces the amount of steel material as much as possible and introduces prestress that allows for a significantly economical design. That is.

(Means for Solving the Problems) This invention provides a three-dimensional truss beam whose portions slightly inside from both ends are supported by fulcrums, so that the portions outside the bending points at both ends where the bending stress is reversed have a substantially triangular cross section. The above object is achieved by configuring the sections inside the recursion point to have a substantially inverted triangular cross section, and by installing tension members in a suspended manner between both ends of the three-dimensional truss beam to introduce prestress. be.

(Embodiment) Hereinafter, the present invention will be described with reference to an illustrative embodiment. A three-dimensional truss beam 1 is constructed by attaching a plurality of diagonal members 4 between an upper chord member 2 and a lower chord member 3, It is constructed between the left and right pillars 5, 5.

The upper chord seat 2 is composed of two chord members 2a, 2a, and the chord members 2a, 2a on the inner side of the recursion points C, C at both ends where the bending stress is reversed extend in parallel with a predetermined distance apart in the lateral direction. The chord members 2a, 2a at the portions outside the curved points at both ends are formed so as to gradually taper toward the tip, and a predetermined length portion at the tip is completely integrally formed.

A plurality of connecting members 7 are attached between the string members 2a, 2a at regular intervals in the longitudinal direction of the string members 2a, 2a.

In addition, the lower chord member 3 is composed of two chord members 3a, 3a in the same way as the upper chord member 2, and the chord members 3a, 3a on the inner side of the curved points C and C at both ends are completely integrated as a single member. In addition, the chord members 3a, 3a at the portions outside the curved points C, C at both ends are formed into two forks that gradually widen in the tapering direction. A plurality of connecting members 7 are installed between the string members 3a, 3a at regular intervals in the longitudinal direction of the string members 3a, 3a.

The diagonal member 4 is the chord member 2a of the upper chord member 2 and the lower chord member 3.
and 3a.

The three-dimensional truss beam 1 configured in this way has a substantially triangular cross-sectional shape at the outer side of the curved points C and C at both ends, and a substantially inverted triangular cross-sectional shape at the inner side from the curved points C and C at both ends. ing.

Further, the three-dimensional truss beam 1 is supported by the pillars 5 at a portion slightly inside from both ends, that is, at the ends of the chord members 3a, 3a of the lower chord members 3.

Moreover, between both ends of the three-dimensional truss beam 1, that is,
Tensile members 6 such as PC steel wires are suspended between the ends of the upper chord members 2 along the longitudinal direction of the three-dimensional truss beam 1, and both ends thereof are firmly fixed to the ground A.

In such a configuration, the lower end of the inner beam and the upper end of the outer beam at both end curve points C and C of the three-dimensional truss beam 1 can resist tensile stress caused by external force to the full allowable stress level, so the tensile stress It is sufficient if there is a cross-sectional area that can resist. Furthermore, the tension member 6 bears the tensile stress exceeding the allowable stress.

On the other hand, the upper end portion of the inner beam at both end recursion points C and C and the lower end portion of the outer beam at both end recursion points C and C are the upper chord members 2.
Since horizontal rigidity is increased by forming the lower chord member 3 in a double layer using two chord members, lateral buckling is less likely to occur, and compressive strength is significantly increased.

Note that the upper chord members 2 and the lower chord members 2a and 3
The diameter of a, the number of diagonal members 4, and the installation interval of the diagonal members 4 are determined as appropriate depending on the size of the beam span.

(Effects of the Invention) Since the present invention has the above configuration, it has the following effects.

Considering the parts that require consideration of lateral buckling and the parts that do not, the outer part of the recursion points at both ends is configured to have an approximately triangular cross section, and the inner part of the recursion points at both ends is configured to have an approximately inverted triangular cross section. Therefore, there is no wastage of materials, and it is possible to save a lot of steel and reduce the number of joints, making it possible to design economically.

Also, assembly work is extremely easy.

Furthermore, since tension members are installed in a suspended manner between the supporting points at both ends of the three-dimensional truss beam, the cross-section of the lower chord member inside the recursion points at both ends can be reduced as much as possible, which is also an economical design. is possible.

[Brief explanation of the drawing]

1 to 9 show one embodiment of the present invention, in which FIG. 1 is a perspective view of a three-dimensional truss beam, and FIG.
The figure is a side view, FIG. 3 is a plan view, FIG. 4 is a bottom view, FIG. 5 is a line a-a in FIG.
The figure is a cross-sectional view taken along line bb in Figure 2, Figure 7 is a line cc in Figure 2, Figure 8 is a sectional view taken along line dd in Figure 2, and Figure 9 is a cross-sectional view of the beam material at both end supports. It is a bending stress diagram. 1... Three-dimensional truss beam, 2... Upper chord member, 3... Lower chord member, 4... Diagonal member, 5... Column, 6... Tensile member, 7
...Connection member.

Claims (1)

[Claims] 1 In a three-dimensional truss beam whose portions slightly inside from both ends are supported by fulcrums, the portions outside the recursion points at both ends where the bending stress is reversed have a substantially triangular cross section, and the portions inside from the recursion points have a substantially inverted triangular cross section. 1. A three-dimensional truss beam introducing prestress, characterized in that the three-dimensional truss beam is constructed such that prestress is introduced by installing tension members in a suspended manner between both ends of the three-dimensional truss beam.