JPH0468140A - Construction of beam - Google Patents

Abstract

PURPOSE:To reduce construction cost and facilitate execution of work by forming a lower chord member into a steel framed reinforced concrete construction and applying bending moment to the structural steel in said member in the direction opposite to the deflection of the beam, wherein an upper chord member, vertical member and diagonal member have a steel frame construction. CONSTITUTION:A beam 10 is formed into a trussed structure comprising lower chord members 11, upper chord members 12, vertical members 13 and diagonal members 14. A structural body comprising columns 18, 18 and a large space 20 as far as a floor surface is constructed and a structural steel 15 is assembled. Next, the steel 15 is provided between the upper ends of the columns 18, 18. Each of the members 13, 14 and 12 is foxed to the steel 15 to form a truss. Reinforcing bars 16 are arranged outside the steel 15 and forms are installed and concrete is placed inside the steel 15, while concrete is placed outside the steel 15, to form the member 11 of steel framed reinforced concrete. In this case, bending moment is applied to the steel 15 in a direction opposite to that of the deflection of the beam 10. Further a load is applied to the beam 10 in advance through a wire 41 to keep the beam 10 approximately horizontally when structures are installed on the beam 10.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to the structure of beams with long spans and large cross sections that constitute the framework of buildings.

"Prior Art" In recent years, so-called megastructures have been studied as a structural form of buildings. Figure 10 shows an example of a building in which a megastructure was adopted.A huge gate was constructed using four steel-framed pillars and steel-framed lath beams 1 to 2 installed between their upper ends. It consists of a megastructure, which is a type frame, and the upper floor is constructed using ordinary columns 3 and beams 4 on the top of the megastructure, and the lower part of the megastructure has a large space with a high degree of freedom. It was designed to obtain the following.

In the building shown in Figure 10, the span of the truss beams 2 making up the megastructure is long, reaching several tens of meters; When constructing such a building, the IJ1 truss beam 2 is curved upward in advance, and during the construction stage,
As shown in the figure, by tensioning the wire 5 strung in a chevron shape using jacks installed at both ends of the truss beam 2, a downward preload is applied to the center of the truss beam 2, and the truss beam 2 becomes almost horizontal. At the same time, as the construction of the upper floor progresses, the wire 5 is loosened to release the preceding load, and when the upper floor is completed, the load causes the 1-lath beam 2 to become horizontal by itself. I am trying to make it so that

"Problem to be Solved by the Invention" By the way, in the above building, since the steel truss beam 2 is used as the long span and large cross-section beam composing the megastructure, the truss beam 2 requires a huge amount of steel, and the number of welded or bolted parts is huge, which increases construction costs and takes time.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a structure suitable for application to beams that require a long span and a large cross section, such as beams constituting a megastructure.

"Means for Solving the Problems" The present invention is directed to a structure of a beam with a long span and a large cross section constituting the frame of a building, which consists of a lower chord member, a lower chord member, and a vertical member and diagonal member connecting them. The lower chord has a truss structure, and the lower chord is made of steel reinforced concrete, and the steel frame itself in the lower chord is given a bending moment of 1- in the direction opposite to the direction of deflection of the beam, and the upper chord,
Both the vertical members and the diagonal members are made of steel, and the lower chord members and the upper chord members each serve as the beams of this building, and the vertical members and the diagonal members each serve as the beams of this building. It is characterized by being said to double as a pillar and brace.

``Example'' An example of the present invention will be described below with reference to FIGS. 1 to 9.

FIG. 1 is a partial elevation view showing the frame of a building constructed using a beam 10 having the structure of this embodiment.

=3 This beam 10 is basically of a truss structure consisting of a lower chord member 11, an upper chord member 12, a vertical member]3, and a diagonal member 14, and its cross section is shown in Fig. 2. The lower chord member 11 is a steel-framed reinforced concrete structure (more precisely, it is formed by filling concrete inside a box-shaped steel frame 15, placing reinforcing bars 16 on the outside, and pouring concrete 1). It is said that the filling and coating chamber is made of steel pipe concrete. In addition, the above upper chord member J2, vertical gain 1
3. The diagonal members 14 are all made of steel.

As shown in FIG. 1, this beam 10 is constructed such that both ends of the lower chord member 1] are joined to large-section columns 18 and 18 made of steel-framed reinforced concrete, and the beam 10 is constructed between their upper ends.
A pillarless large space ``40'' is formed below the beam 10 and the pillar 18, which has a width spanning four spans of this building and has five floors. .18 constitutes a megastructure, which is a gate-shaped frame for forming such a large space 20 and supporting the framework of the upper floor.

The floor of the floor directly above the large space 20 is formed at the upper surface of the lower chord 1 of this beam 10, and the floor of the upper chord 12 is formed.
The floor of the upper floor is further formed at the position of the second side, and the lower chord member 11 of this beam 10 also serves as the floor beam of the floor immediately above the large space 20, and the vertical member 13 and The diagonal members 14 each serve as columns and braces for this floor, and the upper chord members 12 serve as floor beams for the floor above.

Note that in FIG. 1, reference numerals 30 and 31 indicate columns and beams that are the building blocks other than the megastructure, and these are made of normal steel structures.

An example of the procedure for constructing the beam 10 will be described with reference to FIGS. 3 to 9.

As shown in FIG. 3, after constructing the frame up to the columns 18, 18 and the floor of the large space 20, the steel frame 15 that will become the lower chord member 11 of the beam 10 is assembled on the floor of the large space 20.

As shown in the figure, this steel frame 15 is composed of three pieces, a central part 15a and both side parts 15b, which are bent so that the central part 15a is displaced upward. The cutout dimension d1 is set so that it will be approximately horizontal when the beam 10 finally receives the load of the building, taking into account the rigidity of the truss, the weight of the concrete, etc., as will be described later. , a vertical moon 13 provided at the center of the beam 10 is attached to the center portion 15a of the steel frame 15 in advance.

Then, the steel frame 15 assembled in this way is attached to the column 18.1.
The reaction force is removed from column 1848 to lift it up, and the column is installed between the two ends of column 1848 as shown in FIG.

Next, a downward preliminary load is applied to the steel frame 15 constructed as described above, and the bulge is reduced until the bulge dimension becomes d2 (d2<a+). To do this, as shown in Figure 5,
A hydraulic jack 40 is attached upward along the vertical wall 13 provided in the center of the steel frame 15, and the column 1
5. Fix both ends of the wire 41 to the joint part of 18 and the beam 10, engage the center part of the wire 41 with the hydraulic jack 40, and operate the hydraulic jack 40 to push up the middle* part of the wire 4J. It is preferable to apply the reaction force downwardly to the central portion 15a of the steel frame 15 via the vertical member 13 by applying tension to the steel frame 15. Note that a lifting type hydraulic jack may be provided facing downward, and the central portion of the wire 41 may be pulled up by the hydraulic jack.

In this state, as shown in FIG. 6, the other vertical beams 13, diagonal members 14, and upper chord members 12 are respectively attached to the steel frame 15 to form a truss.

Thereafter, the preceding load applied to the steel frame 15 is temporarily released. As a result, as shown in FIG. 7, the bulge of the steel frame 15 increases, but the bulge dimension d3 becomes smaller than the original bulge dimension d1, which takes into account the rigidity of the formed truss.

After that, reinforcing bars 16 are arranged outside the steel frame 1!1H and a formwork is assembled, and concrete is filled inside the steel frame 15 and concrete is poured on the outside, and the lower chord member 11 of the steel-framed reinforced concrete construction is installed. Form. As a result, as shown in FIG. 8, the beam 10 is formed with less bulge, but the bulge dimension d of the beam 10 at this stage is equal to the above bulge dimension d3 by the weight of the concrete.
It becomes smaller, and of course becomes smaller than the exposed dimension d1 originally given to the steel frame 15. The exposed dimension d at this stage corresponds to the load of the upper floor frame and other various building components that will be applied to the beam 10 after this, and that load will eventually be applied to the beam 10. The beam 10 is set so that it is naturally almost horizontal.

Therefore, after the strength of concrete 1 is ensured, the concrete is constructed on the floor above the beam 10 to a level slightly higher than the level at which the beam 10 is expected to bend (until it becomes almost horizontal as shown in Figure 9). A preload is applied to the beam 10 via the wire 41 in order to reduce the bowing. After that, the upper floor frame is constructed on top of beam construction 0, and various building components are attached, and the wires 41 are gradually loosened according to the load, thereby reducing the preceding load in stages. Beam 1
0 is always kept almost horizontal.

As described above, if all the preceding loads applied to the beam io are released when the upper floor is completed, the beam 10 will automatically become horizontal due to the loads of the upper floor frame and various building members.

In the above beam 10, the lower chord member 11 and the upper chord member 12 ensure sufficient beam dimensions as a whole, and sufficient rigidity is obtained. Not only can a large space 20 be secured, but also the lower chord 1
1 is a steel-frame reinforced concrete 4 structure, and this lower chord material 1
] Since a bending moment is applied to the steel frame 15 in the direction opposite to the deflection direction of the beam 10, the steel frame 15 is It is possible to reduce the amount of steel and simplify the steel processing, which is advantageous in terms of construction costs and labor.

Moreover, the lower chord material 11. Upper chord member 12, vertical member 13, diagonal member 1
4 also serves as beams, columns, and braces of this building, so there is also the advantage that the frame of the entire building can be simplified.

In addition, in the construction procedure of the above embodiment, when forming a truss, the vertical members 13, diagonal members 14, and upper chord members 12 are assembled after applying a preliminary load to the steel frame 1.5 to reduce the bulge, so this work is This is something that can be done easily.

In other words, when assembling a truss with the steel frame 15 still having a large bulge (the bulge dimension dI), the vertical members 13 will tilt outward, making it difficult to erect the truss. However, in the above case, the truss is assembled after reducing the bulge until the bulge dimension becomes d2, so the vertical members 13 can be erected vertically without any hindrance. The truss can be easily assembled.

In addition, when pouring concrete to the steel frame 15 to form the lower chord member 11, the preceding load applied to the steel frame 15 is temporarily released to return it to a state with a bulge greater than d2, and in that state, the concrete is poured into the steel frame 15. Since we decided to pour
The rigidity of the beam 1o can be further increased compared to the case where the lower chord member (1) is formed by pouring concrete while the steel frame 15 remains reduced to d2.

In addition, in order to apply a preliminary load to the steel frame 15 and the beam 1o, an appropriate method can be adopted without being limited to the second embodiment.

In addition, in the above embodiment, the lower chord member 11 of the beam 1o was made of a filled-covered steel pipe concrete structure, but this is a steel frame J.
It may be a filled steel pipe concrete structure in which only the inside of the tube 5 is filled with concrete, or it may be a general steel reinforced concrete structure using not only a box-shaped steel frame but also a steel frame with an arbitrary cross-sectional shape. In addition, the upper chord material 12,
The vertical members 13 and diagonal members 14 are also suitable not only for steel frame structures but also for steel reinforced concrete structures and steel pipe concrete structures, and the positions and formats of the vertical members 13 and diagonal members 14 may be changed as appropriate according to design requirements. Needless to say, it's a good thing. moreover,
Rigidity can be further increased by forming a beam with a composite truss structure in which a truss is further integrally formed at the upper and lower portions of the beam 1o.

Further, in the above embodiment, the column 1 on which both ends of the beam 1o are supported
8 is made of steel-framed reinforced concrete construction, but it is not necessarily limited thereto. Further, even when the column 18 is made of steel-framed reinforced concrete, the concrete placement for the column 18 may be performed simultaneously with the concrete placement for the lower chord member 11 of the beam 10. Of course, the beam 10 can be provided not only at the upper end of the column 18 but also in the middle thereof. Furthermore, in the above embodiment, the steel frame 15 serving as the lower chord member 11 of the beam 10
However, in cases where the span is relatively small, etc., the lift-up method is not necessarily used.

Further, the above embodiment is an example in which the beam of the structure of the present invention is applied to a building in which a large column-free space is provided below and a frame of an upper floor is provided above. It goes without saying that the structural beam of the present invention can be applied not only to such types of buildings, but also to various types of buildings in general.

"Effects of the Invention" As explained in detail above, the structure of the beam of the present invention is such that the lower chord is made of steel-framed reinforced concrete. The steel frame in the bottom chord itself is given a bending moment in the direction opposite to the deflection direction of the beam, and the top chord, vertical members, and diagonal members are made of steel, so it is possible to obtain sufficient rigidity. Of course, compared to the case where the entire beam has a simple truss structure, the amount of steel can be reduced and the processing is simplified, which is advantageous in terms of construction cost and construction time. , vertical members, and diagonal members serve as the beams, columns, and braces of this building, respectively, so they have the advantage of simplifying the frame of the entire building, and are suitable for use as beams constituting a megastructure. .

[Brief explanation of the drawing]

Figures 1 and 2 show an example of the structure of a beam according to the present invention; Figure 1 is a partial elevation view showing the frame of a building constructed using the beam; The figure is a cross-sectional view of the beam (a view taken along the line ■-■ in FIG. 1). Figures 3 to 9 show an example of the construction procedure for the above-mentioned beam in the order of steps on 8F! This is a diagram for A. FIG. 1O is a perspective view showing a conventional example of a building using a megastructure. 0... Beam, l 1... Lower chord, 1... Top chord, ■ 3... Vertical member, 4... Diagonal member, 5... ...steel frame, 6 ...reinforcement, 1 ...column.

Claims (1)

[Claims] A beam structure with a long span and a large cross section that constitutes the frame of a building, and is a truss structure consisting of an upper chord member, a lower chord member, and vertical members and diagonal members that connect them, and the lower chord member is a steel frame. It is made of reinforced concrete, and the steel frame itself in the lower chord is given a bending moment in the direction opposite to the direction of deflection of the beam, and the upper chord, vertical members, and diagonal members are all made of steel, and, The lower chord member and the upper chord member each serve as a beam of the building, and the vertical member and the diagonal member each serve as a column and a brace of the building. The structure of the beam.