JPH11264134A - Construction method of CFT timber pillar - Google Patents

Abstract

(57) [Summary] [Problem] To provide a method of constructing a CFT timber column that can reasonably be constructed at a high quality and at low cost by using a CFT as a tall column, thereby making it possible to rationally construct a reverse construction method or a new underground method. . SOLUTION: The construction method of the CFT timber pillar according to the present invention comprises:
After placing the CFT steel pipe filled with concrete at the tip into the pile hole, pile concrete is cast to secure the vertical accuracy as a straight pillar, and then the remaining concrete is filled into the hollow inside of the CFT steel pipe. Specifically, in order to fill concrete in a predetermined range from the front end of the CFT steel pipe in advance, a partition plate for determining a concrete filling range is provided at a predetermined position from the front end. Further, the distal end is closed by a convex end plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a CFT structural pillar using CFT as a structural pillar.

[0002]

2. Description of the Related Art In recent years, as a pillar of a structure, a concrete filled steel pipe concrete (C
FT) has been increasingly used. This is a large bend in a small cross section compared to the conventional RC and SRC,
This is because it is a member that can ensure the shear strength and is rich in toughness. In underground structures, so-called filled-coated concrete in which RC is coated on the outside of the CFT is often used. On the other hand, as a method of constructing on a narrow site in a short construction period, a reverse construction method and a new underground construction method are attracting attention, and the construction employing this method is increasing.

[0003] However, if the above-mentioned construction methods developed to satisfy the needs of the industry are combined to promote more efficient construction, the above-mentioned methods are employed from the design point of view because of the following problems. Was in a difficult situation to do. (1) The H-shaped or cross-shaped straight columns used in the normal reverse-casting method have an open steel cross-section, so all the concrete in the permanent part can be constructed by post-casting. In the case of a straight pillar, how to cast concrete inside the steel pipe has not been solved.

(2) When the tip of a steel pipe is opened so that the concrete adheres to the entire surface of the steel frame in the same manner as a normal H-shaped or cruciform straight pillar, concrete of the pile (in-water concrete) is placed inside the steel pipe. Will come up. Since this underwater concrete contains a bentonite solution, there is a problem in that it is not only reliable in terms of quality but also hard to guarantee in terms of strength. Furthermore, since the concrete inside the steel pipe cannot be processed by the latence treatment or the extra pile at the pile head, there is a problem that the joint portion processing with the later-constructed concrete cannot be sufficiently performed. Therefore, as shown in FIGS. 8 and 9, the tip of the steel pipe is covered with a closing plate 32 so as to prevent the concrete 31 of the pile from entering the inside of the steel pipe 30 for CFT, and the hollow part inside the steel pipe is formed. It was conceived to suppress the buoyancy of the steel pipe by adding water 33 to the steel pipe.

However, in this case, as shown in FIG.
Bending stress is generated in the closing plate by the supporting force at the bottom surface according to the cross-sectional area of the end of the steel pipe 30 for the straight beam, and the blocking plate cannot withstand a normal thickness, and the pile concrete 31 closes because the closing plate 32 is a flat plate. A new problem has arisen such that the bottom central portion of the plate 32 is not sufficiently filled. In particular, since the specific gravity of the unconsolidated concrete 31 at the pile concrete portion at the tip of the timber column is 2.3, which is considerably larger than the specific gravity of the water 33 in the steel pipe 30 for timber column, it will be described with reference to FIG. As described above, the buoyancy obtained by adding the buoyancy 34 due to the pile concrete and the buoyancy 36 due to the muddy water 35 in the pile hole is equal to the buoyancy 3
In some cases, even if the center of gravity 37 is lowered by the water 33, the vertical accuracy of the shaft is difficult to be secured. (3) It is conceivable that CFT may be constructed by placing concrete over the entire length of the steel pipe before building, but the weight is too large and it is difficult to lift, so a very slight construction is required. It is difficult to adopt except for pillars.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a CFT capable of rationally constructing a reverse beating method and a new underground method at high quality and at low cost by making it possible to employ CFT as a pillar.
It is intended to provide a method of constructing a trussed pillar.

[0007]

According to the present invention, there is provided a method for constructing a CFT column having a CFT structure, wherein the tip is filled with concrete.
After placing the steel pipe into the pile hole, pile concrete is cast to secure the vertical accuracy as a straight pillar.
The concrete inside the hollow portion of the steel pipe for filling is filled with the remaining concrete. Specifically, in order to pre-fill concrete in a predetermined range from the front end of the CFT steel pipe, concrete is placed at a predetermined position from the front end. A partition plate for determining the filling range is provided, and the front end portion is closed with a convex end plate.

[0008]

FIG. 1 is a sectional view of a CFT timber column constructed by the method of constructing a CFT tall pillar according to the present invention. In FIG. 1, a CFT column 1 is supported by a pile concrete 2 and stands upright in a ground 3 while maintaining an accurate verticality. The inside of the CFT column 1 is filled with concrete 5 at the tip 4 and filled with permanent concrete 6 that has been poured into the remaining space.
Accordingly, since the weight of the tip portion of the CFT column 1 is increased by the preload concrete 5, the restoring force by the moment acts on the buoyancy acting at the time of placing the pile concrete, and the vertical accuracy is improved. It can be easily secured. In addition, since the front end portion 4 of the trussed pillar is plugged with the filling concrete 5, the axial force of the column is effectively transmitted to the pile concrete 2 over the entire bottom surface of the CFT trussed pillar 1. Furthermore, since the steel pipe of the CFT column 1 is continuous into the pile concrete 2, there is no decrease in the cross-sectional performance of the CFT, the treatment of the column stress can be performed smoothly, and the toughness is superior. In the pile hole 7, crushed stone 8 backfilled by a construction method described later in detail is filled on the pile concrete 2 in order to prevent buckling of the timber column in the backlashing work, and furthermore, The excavated soil 9 at the site, which has been similarly backfilled above, is filled.

FIG. 2 shows the CFT constituting the CFT column 1
FIG. 2 is an enlarged partial cross-sectional view of the steel pipe 10 for use. A convex end plate 11 is welded to the distal end portion 4 of the CFT steel pipe 10 to close the opening surface at the distal end. The partition plate 12 is fillet-welded at a predetermined interval from the tip 4 to determine the filling amount of the pre-filled concrete 5 to be filled in advance at the tip, and the main concrete 6 to be cast later is removed. It plays the role of receiving. The tip 4 further includes a concrete filling hole 13 for filling the tipping concrete 5 into the tip 4 of the CFT steel pipe 10 and a filling concrete 5.
An air vent hole 14 is provided at the position shown in the drawing so as to be smoothly filled without being disturbed by the air in the T steel pipe 10.

FIGS. 3 and 4 show a state before the concrete is filled in the tip portion 4 of the CFT steel pipe 10 in advance. To fill the concrete, the steel pipe 10 for CFT, the tip of which has been processed as described above, is placed horizontally on the support base 15 as shown in FIG. Filling is performed from the concrete filling hole 13 with the steel pipe 10 kept horizontal. The filling is continued until the concrete overflows from the air vent hole 14. At this time, C should be filled so that the filled concrete is sufficiently filled without creating a void in the entire tip.
If a vibrator is applied from the outside of the FT steel pipe 10 to apply vibration, it is possible to ensure extremely good filling. FIG. 4 is a partial cross-sectional view of the front end portion of the CFT steel pipe 10 in which the front end portion 4 has been filled with the concrete 5 filled therein. The CFT steel pipe 10 is sufficiently filled with the concrete for filling 5 between the end plate 11 of the end portion 4 and the partition plate 12, but most of the main body side has a void 17 left. As described above, since the tip plate of the CFT steel pipe 10 has a convex shape, the CFT steel pipe 10 is used when the pile concrete 2 is cast.
The lower part of the steel pipe 10 can be sufficiently filled. or,
When the pile concrete 2 is cast, since the underwater concrete in the pile hole 7 does not enter the steel pipe 10 for CFT, the quality of the permanent concrete 6 to be filled including the joint portion of the concrete can be ensured. In the method according to the present invention, since water is not poured into the CFT steel pipe 10, drainage is not required before the concrete 6 is cast, which is advantageous in terms of process and cost. Further, since the CFT steel pipe 10 is lifted with the tip filled with concrete, the weight is reduced as compared with the case where concrete is filled in advance over the entire length, so that the lifting plan can be easily performed. This is advantageous in terms of cost.

FIGS. 5 to 7 are construction process diagrams for specifically explaining the construction method of the CFT column according to the present invention. Hereinafter, description will be made in order. FIG. 5 shows a process from the excavation of a pile hole to the installation of a reinforcing cage. In order to excavate the pile hole 7, a stand pipe 20 is erected. Excavate to form the pile shaft. When the pile bottom 21 is reached, an enlarged bucket 22 is installed. Start of pile bottom excavation. Excavation to form the widened part 23 is started. Raise the bottom of the pile. Measurement of pile hole wall 24. A reinforced basket 25 for piles is built. FIG. 6 shows a process from erection of a straight pillar to pulling out of a stand pipe. A steel pipe 10 for a straight pole, which is pre-filled with concrete at its tip, is built. The weight of the concreting concrete 5 and the convex end plate 11 work to ensure smooth verticality against small buoyancy and fix the position with the underwater jack 26. Set tremy tube 27 for pile. Handle slime. Pile concrete 2 is cast. As in the case of (1), it is possible to sufficiently cope with the buoyancy of the pile concrete and the supporting force for the tip portion, and the verticality can be maintained. Backfill of crushed stone 8. Backfill of excavated soil 9 on site. Pull out the stand pipe 20. FIG. 7 shows a step of forming a CFT column. The concrete 6 is poured into the steel pipe 10 for the trussed pillar. Completed construction of CFT timber pillar 1. As described above, according to the method of constructing a CFT straight pillar according to the present invention, it is possible to adopt CFT as a straight pillar very smoothly. Therefore, CFT, which has many advantages such as large bending and shear strength with a small cross section and high toughness, can be installed on a narrow site in a short period of time. This allows for a new construction method that makes effective use of both advantages by being able to rationally adopt it at a low cost while ensuring sufficient. In the above-described embodiment, the pile concrete is cast after the steel pipe for CFT is erected, but the pile concrete is cast and then the steel pipe for CFT is erected as in the case of general straight pillar construction. Is also possible, CF
It is not always necessary to perform the casting of the permanent concrete inside the steel pipe for T immediately after the timber column work, but it may be performed at an appropriate time in the process according to the progress of the underground work. Further, although the shape of the steel pipe has been described as being circular, it is needless to say that a square or the like can be adopted as long as it does not deviate from the gist of the present invention.

[0012]

According to the present invention, the method of constructing a CFT column is as follows.
After placing the CFT steel pipe filled with concrete at the tip into the pile hole, pile concrete is cast to secure the vertical accuracy as a straight pillar, and then the remaining concrete is filled into the hollow inside of the CFT steel pipe. Specifically, in order to fill concrete in a predetermined range from the front end of the CFT steel pipe in advance, a partition plate for determining a concrete filling range is provided at a predetermined position from the front end. Further, since the distal end is closed by a convex-shaped distal end plate, the following effects can be exhibited. Due to the heavy weight of the tip, the momentum acts on the buoyancy that is applied when the pile concrete is driven, and the vertical accuracy is easily secured. Since the end of the trussed pillar is plugged with the filling concrete and the end plate, the axial force of the column is effectively transmitted to the pile concrete on the entire bottom surface of the trussed pillar, and no excessive stress is generated on the tip plate. Since the CFT steel pipe is continuous into the pile concrete, there is no decrease in the cross-sectional performance of the CFT, the treatment of column stress can be performed smoothly, and the toughness is superior. Since the end plate is formed in a convex shape, the pile concrete to be cast is sufficiently filled to the lower part of the steel pipe for CFT. Underwater concrete is CFT when placing pile concrete
Since it does not enter the steel pipe for use, it is possible to ensure the quality of the filled concrete including the joint. Since water is not put into the CFT steel pipe, drainage is not required before placing the post-cast concrete, which is advantageous in terms of process and cost. Since the weight is reduced as compared with the case where concrete is previously filled over the entire length of the CFT steel pipe, it is advantageous in terms of lifting plan and cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a CFT column.

FIG. 2 is a partial sectional view of a CFT steel pipe.

Fig. 3 Concrete filling work of steel pipe for CFT

Fig. 4 Completed concrete filling of steel pipe for CFT

Fig. 5: Construction process diagram of pile cage excavation to rebar cage

FIG. 6 is a drawing showing a process of pulling out a stand pipe from a built-in pillar.

FIG. 7 is a process diagram of forming a CFT column.

FIG. 8 is a partial view of a conventional CFT steel pipe tip.

FIG. 9 is a diagram showing a conventional CFT steel pipe installation state.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 CFT straight pillar 20 Stand pipe 2 Pile concrete 21 Pile bottom 3 Soil 22 Expansion bucket 4 CFT straight pillar tip 23 Expanded bottom 5 Precast concrete 24 Pile hole wall 6 Permanent concrete 25 Reinforcing cage 7 Pile hole 26 Underwater Jack 8 Crushed stone 27 Toremy pipe 9 Site excavated soil 30 Steel pipe for straight pillar 10 Steel pipe for CFT 31 Pile concrete 11 Tip plate 32 Closure board 12 Partition plate 33 Water in steel pipe for straight pillar 13 Concrete filling hole 34 Buoyancy by pile concrete 14 Air vent hole 35 Mud in pile hole 15 Support base 36 Buoyancy by mud in pile hole 16 Concrete bucket 37 Center of gravity 17 Void

Claims (5)

[Claims] 1. Filling the tip of a CFT steel pipe with concrete, embedding the CFT steel pipe in a pile hole and placing pile concrete to secure vertical accuracy as a straight pillar, A method of constructing a CFT structural pillar for filling the remaining concrete into the hollow interior of the CFT steel pipe. 2. The method according to claim 1, wherein the concrete is preliminarily filled in a predetermined area from the tip.
Construction method for FT timber pillars. 3. The method according to claim 1, wherein a partition plate for determining a concrete filling range is provided at a predetermined position from the tip. 4. The method for constructing a CFT column according to claim 1, wherein the tip is closed by a tip plate. 5. The method according to claim 1, wherein the end plate has a convex shape.