JPS62178647A - Prestressed truss girder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to the structure of a truss beam in which prestress is introduced by disposing a PCtm material on the side where tensile stress acts.

[Conventional technology]

In concrete structures, it is common practice to install prestressing steel materials in advance on concrete beams, concrete slabs, etc. to introduce prestress and compensate for the weakness of concrete, which is weak in tension.

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

By the way, when considering truss beams that make up a structure, large tensile stress and deflection occur in the bottom chord due to bending, so methods such as adjusting the amount of steel or applying camber processing are adopted to deal with this. .

[Problem that the invention seeks to solve]

However, when the amount of steel increases, not only does the cost (-) increase, but also the weight increases, which causes problems in design and construction.
Camber processing is troublesome and is also inconvenient for interconnecting the members of the truss beam.

In view of the above-mentioned problems, this invention introduces prestress on the tension side of the truss beam, thereby reducing the tensile force due to bending stress generated in the tension side member, reducing the amount of steel material, and improving workability. We are working to improve this and reduce costs.

[Means for solving problems]

The truss beam 1 in this invention has an upper chord member 2 and a lower chord member 3.
The parts are connected by a lattice material 4, and each member is made of, for example, angle material, other shaped steel, steel strip, or a combination of these.

This invention arranges the PC steel material 5 on the side of the truss beam 1 on which tensile stress is applied due to overload or self-weight, and introduces tension to the PC steel material 5, so that the truss beam 1 is This is intended to reduce the tensile stress generated on the tension side by applying compressive stress to the tension side. In order to introduce such prestress, the bearing plate 6 or guide member is fixed by welding or the like to both ends or multiple locations of the prestress introduction section on the tension side, and the P is tensed due to jacking, etc.
This is done by fixing the end of the O2 material 5 to the bearing plate 6.

〔Example〕

Next, the illustrated embodiment will be described.

FIG. 1 shows an example in which a truss beam 1 is used as a simple beam. A PC steel material 5 is placed along the longitudinal center of the lower chord member 3, which is the part that receives large tensile stress, and after tensioning,
It is fixed to a bearing plate 6 whose both ends are fixed to the lower chord member 3. FIG. 2 shows a cross section of the truss beam 1 perpendicular to the axial direction, and the upper chord member 2 and the lower chord member 3 are each a pair of angle members 2a.

3a are combined back to back to form a substantially cross section, and a truss beam 1 with a triangular cross section is formed by two upper chord members 2, one lower chord member 3, and a lattice member 4 connecting them. The PC steel members 5 are arranged along both sides of the lower chord member 3, and are set at an angle of about 45″ in FIG. The lattice material 4 attached in this way works effectively to prevent lateral buckling and to easily manage the introduction of prestress.

The embodiment shown in Fig. 3 is also a case of a simple beam, and an overlapping part (section indicated by a in the figure) is provided at the center of the beam longitudinal direction for introduction of the press 1-less. There is an advantage in changing the amount of prestress introduced.

The embodiments shown in FIGS. 4 and 5 are applied to continuous beams or overhang beams. In other words, in a continuous beam, etc., tensile stress is generated on the upper side of the beam at the supporting position, so the PC steel material 5 is
It has a perpendicular polygonal line arrangement. FIG. 6 shows an example of the arrangement of the PClH material 5 when used as a continuous beam.

Figure 7 (a), (bL (c) shows the lower chord 3 and PC
This shows an example of the arrangement of steel materials 5. (a) As shown in the figure, PC
Possible options include arranging the 1i material 5 above the lower chord material 3 (b) arranging it vertically as shown in the figure, and (c) arranging it horizontally from side to side as shown in the figure.

The ones in (a) and (b) are suitable for the embodiments shown in Figures 4 and 5 above, and the ones in (C) are suitable for the simple beam embodiments in Figures 1 and 3. .

FIGS. 8 and 9 show an example of the bearing pressure part, that is, the anchoring part of the PC steel material 5, and the lower chord material 3 is composed of two angle members 3a.
are connected by reinforcing plates 3b arranged at predetermined intervals, forming a cross shape. The end of the PC steel material 5 is passed through the bearing plates 1 and 6 welded within the inner angle of the angle material 3a so as to be orthogonal to the material axis, and fixed to the bearing pressure plate 6 with a nut 7 under tension. be. Note that reference numeral 8 in the figure indicates support reinforcement members welded to both ends of the angle member 3a.

〔Effect of the invention〕

■ By introducing stress on the tension side of the truss beam, the tensile stress generated on the tension side can be reduced, the amount of steel material can be reduced, and economical design and construction can be achieved.

■ Since the main material of the truss beam is deformed by introducing prestress, camber processing is not necessary.

■ As the length of the PC steel material changes according to the deformation of the main material of the truss beam, large prestress acts, and small prestress acts for small loads. That is, the press 1-less introduction force corresponds to the load change, and it is possible to design with a smaller main material than by disposing the main material proportional to the load increment.

[Brief explanation of drawings]

FIG. 1 is a front view showing one embodiment of the present invention, FIG. 2 is a sectional view perpendicular to the axial direction of the truss beam, FIGS. 3 to 5 are front views showing other embodiments, and FIG. The figure is a front view showing the arrangement of PC steel materials when applied to a continuous beam, Figure 7 (a). (b) and (c) are cross-sectional views showing the positional relationship between the lower chord member and the prestressing steel member, Figure 8 is a cross-sectional view perpendicular to the axial direction showing details of the bearing pressure part, and Figure 9 is also a cross-sectional view of the bearing pressure part. FIG. 1...Truss beam, 2...Top chord member, 2a
...Angle material, 3...Lower chord material, 3a
...Angle material, 3b...Reinforcement plate, 4...Lattice material, 5...PC steel material, 6...Bearing play 1・, 7... Nut, 8... Support reinforcement material. Fig. 1 3,,' ) j a Fig. 3

Claims (2)

[Claims] (1) Introducing prestressing, which is characterized by arranging a PC steel material on the tension side of a truss beam formed by connecting the upper and lower chord members with a lattice member, and introducing tension force into the PC steel material. truss beam. (2) The truss beam is equipped with bearing plates for fixing the prestressing steel material at required locations.Claim 1
Truss beam with prestress introduced as described in section.