JPH0621491B2 - Prestressed truss beams - Google Patents

Description

TECHNICAL FIELD The present invention relates to a truss beam structure using an X-shaped cross-section material in which a PC steel material is placed on the side where tensile stress acts and prestress is introduced. .

[Conventional technology]

In concrete structures, it is common practice to pre-stress PC steel materials on concrete beams, concrete slabs, etc. to introduce prestress to compensate for the weak points of concrete that is weak in tension.

However, in steel structures, the idea of introducing prestressing in the same way as in concrete structures has not been adopted because steel materials are relatively strong in tension.

By the way, when considering a truss beam that constitutes a structure, a large tensile stress and bending due to bending occur in the lower chord member. Therefore, methods such as coping with the amount of steel material and performing camber processing have been adopted.

[Problems to be solved by the invention]

However, when the amount of steel material increases, not only the cost increases but also the weight increases, which hinders design and construction. Further, the camber processing is troublesome, and it is also inconvenient to connect the members of the truss beam.

In view of the above problems, members having an X-shaped cross section are used for the upper and lower chord members, and prestress is introduced into the lower chord member on the tension side of the truss beam, so that tension due to bending stress generated in the member of the lower chord member is applied. A structure has been proposed in which the force is reduced, the amount of steel is reduced, the workability is improved, and the cost is reduced (Japanese Patent Laid-Open No. 62-37449).

The present invention is an improvement of the above invention and proposes a configuration in which the upper and lower chord members use X-shaped cross-section members, and the PC steel member can be easily arranged on the pulling side in either direction.

[Means for solving problems]

According to the present invention, a PC steel material is arranged in a groove of a tensile side member of a truss beam in which upper and lower chord members having an X-shaped cross section are connected by a lattice member, and a PC steel member is provided at a required position on the tensile side of the truss beam. Is a truss beam having a prestress, characterized in that a bearing plate for fixing the above is attached, and a tension force is introduced into the PC steel material.

〔Example〕

 Next, the illustrated embodiment will be described.

FIG. 1 shows an example in which the truss beam 1 is used as a simple beam. A PC steel material 5 is placed along the longitudinal center portion of the lower chord member 3 which is a portion subjected to a large tensile stress, and after tension,
Both ends are fitted and fixed to the rectangular pressure bearing plate 6 which is fitted and fixed in the groove portion of the lower chord member 3. FIG. 2 shows a cross section perpendicular to the axial direction of the truss beam 1. The upper chord member 2 and the lower chord member 3 are each a pair of angle members 2a, 3a which are back-to-back to form a substantially X-shaped cross section. The upper chord member 2 and one lower chord member 3 and the lattice member 4 connecting them together form a truss beam 1 having a triangular cross section. The PC steel material 5 is arranged along both side grooves of the lower chord member 3, and the lateral buckling of the lower chord member 3 due to the introduction of prestress to the truss beam 1 is about 45 ° in FIG. The lattice member 4 attached at an angle works effectively, prevents lateral buckling, and facilitates introduction and management of prestress.

The embodiment of FIG. 3 is also a case of a simple beam, and for the introduction of prestress, an overlapping portion (section indicated by a in the figure) is provided at the central portion in the longitudinal direction of the beam. There is a merit to change the amount of prestress introduced.

When applied to a continuous beam or an overhanging beam, a tensile stress is generated on the upper side of the beam, and therefore PC steel may be placed on the upper chord.

4 (a), (b), and (c) show an example of the arrangement of the PC steel material 5 in the groove portion of the lower chord member 3, and as shown in FIG.
There may be a case where the above is arranged above the lower chord member 3, a case where it is arranged above and below as shown in (b), and a case where it is arranged horizontally to the left and right as shown in (c).

The ones shown in (a) and (b) are suitable for placing the PC steel material 5 on the upper chord member, and those shown in (c) are placed on the lower chord member of the embodiment of the simple beam shown in FIGS. 1 and 3. Suitable for cases.

FIGS. 5 and 6 show an example of the bearing portion, that is, the fixing portion of the PC steel material 5. The lower chord member 3 is composed of two angle members 3a.
Are connected to each other with a reinforcing plate 3b at predetermined intervals to form a cross shape. The end portion of the PC steel material 5 penetrates the bearing plate 6 welded in the inner angle of the angle member 3a so as to be orthogonal to the material axis, and is fixed to the bearing plate 6 by the nut 7 in a tensioned state. In the figure, 8 is the angle member 3
It is a bearing portion reinforcement member welded to both ends of a.

[Effects of the Invention] By making the upper and lower chord members of the truss beam have an X-shaped cross section, it is possible to easily fit the PC steel material to the groove portion from the outside, and by introducing prestress to either the upper or lower tension side as necessary. The tensile stress generated on the tensile side can be reduced, the amount of steel can be reduced, and economical design and construction can be performed.
In addition, the bearing plate can be placed at a desired position by fitting it into the groove of the chord member.

Since the main material of the truss beam is deformed by the introduction of prestress, there is no need for camber processing.

The length of the PC steel material also changes according to the deformation of the main material of the truss beam, but as described above, the length can be made to be the required length because it is fitted into the groove portion from the outside. A small pre-stress acts on the load. In other words, the prestressing force is applied according to the load change, and it is possible to design with a smaller main material in which the main material proportional to the load increment is arranged.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a sectional view perpendicular to the axial direction of a truss beam, FIG. 3 is a front view showing another embodiment, FIG. 4 (a), (b) and (c) are sectional views showing the positional relationship between the upper and lower chord members and PC steel, Fig. 5 is a sectional view perpendicular to the axial direction showing the details of the bearing portion, and Fig. 6 is also the bearing portion. FIG. 1 ... Truss beam, 2 ... Upper chord material, 2a ... Angle material,
3 ... Lower chord material, 3a ... Angle material, 3b ... Reinforcing plate, 4 ... Lattice material, 5 ... PC steel material, 6 ... Bearing plate, 7 ... Nut, 8 ... Bearing supporting material ..

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Mashima 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Hiroshi Ogawa 1-2-7 Moto-Akasaka, Minato-ku, Tokyo No. within Kashima Construction Co., Ltd. (56) Reference JP 58-200806 (JP, A) JP 56-139292 (JP, A) JP 62-37449 (JP, A) JP 50- 35740 (JP, B1)

Claims (1)

[Claims] 1. A PC steel material is arranged in a side groove on the tensile side of a truss beam having a triangular cross section in which two upper chord members having an X-shaped cross section and one lower chord member are connected by a lattice member. A bearing plate for fixing the PC steel material is attached to a groove portion of a required portion on the pulling side of the truss beam, and a tension force is introduced to the PC steel material to fix the PC steel material to the bearing plate. Truss beam with prestressing.