JP2000206016A - Method and apparatus for manufacturing concrete specimen for estimation of strength of filled concrete in cft pillar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus in which the strength of filled concrete in a concrete filled steel tube(CFT) pillar can be estimated accurately by a method wherein the concrete which is poured into a form is cured while an axial compressive force is being given in an airtight state. SOLUTION: The surface of concrete 10 is pressed by the rear surfaceof a male screw body 4a, and an axial compressive force is introduced to the concrete 10. The magnitude of the axial compressive force is set at a magnitude which corresponds to an axial compressive force which acts on filled concrete in a CFT pillar as an object to be tested. While the display of a graduation is being observed, an upper-part lid body 4 is turned, and the axial compressive force is set at a prescribed magnitude. This manufacturing apparatus 1 in a state that the prescribed axial compressive force is applied to the concrete 10 inside a form body 2 is put into a styrene foam container, and the sealed-up concrete 10 is cured. The concrete 10 is cured while it is being subjected to the compressive force inside the sealed-up manufacturing apparatus 1. Thereby, the concrete is cured under a condition which is identical to, or close to, that under which it is cured inside a steel tube as the CFT pillar. Then, after the concrete reaches a prescribed material age, a concrete specimen inside the manufacturing apparatus 1 is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for manufacturing a concrete specimen for estimating the strength of CFT column-filled concrete.

[0002]

2. Description of the Related Art For example, a concrete-filled steel pipe (hereinafter referred to as "CFT") column in which concrete is filled in a steel pipe is sometimes used as a pillar which is a structural material of a building structure. Since this CFT column receives the axial compressive force in a shared manner between the filled concrete and the steel pipe, it is possible to reduce the axial load burden of the steel pipe material, to prevent local buckling of the steel pipe by the filled concrete, There is an advantage in that the concrete can be brought into a triaxial stress state by restraining the steel pipe, and the confined effect can increase the strength of the filled concrete.

The strength of the concrete filled with CFT columns is estimated based on the results of a strength test such as compression performed on a concrete test piece. Has conventionally been RC
In the same manner as in the case of SRC and SRC structures, concrete specimens manufactured by driving into steel formwork are cured in standard water or in-situ water.

[0004]

However, the actual strength of concrete filled with CFT columns is significantly different from the strength of concrete specimens manufactured as described above for the following reasons. That is, since the filled concrete of the CFT column is sealed in the column steel pipe without being exposed to the outside air, the curing conditions are significantly different from those in the case of on-site underwater curing. Moreover, since most of the structures using CFT columns are high-rise buildings, the filled concrete in the lower layer receives a high axial compression force due to the weight of the concrete, and the compressive strength increases due to the compaction action. That is not taken into account in the fabrication of

[0005] Therefore, CFT estimated from the strength test results of the concrete specimens manufactured as described above.
As for the strength of the concrete filling column, the strength of the concrete filling concrete of the actual CFT column will be underestimated. Therefore, the design supervision requires that the concrete for the CFT column should be mixed much more than the concrete design standard strength.
There is a problem that the strength of the actual concrete filled with CFT columns is unnecessarily increased, and the cost of CFT concrete, which is expensive in the first place, is increased by increasing the flow rate of fresh concrete.

The present invention has been made in view of the above-mentioned conventional problems, and can provide a more accurate estimation of the strength of concrete filled in a CFT column. It is an object of the present invention to provide a method and an apparatus for manufacturing a concrete specimen for estimating the strength of a CFT column-filled concrete or the like that can form a CFT column.

[0007]

The object of the present invention is to provide a concrete for estimating the strength of concrete filled with CFT columns or the like, which is characterized in that concrete poured into a form is cured while applying an axial compressive force in a sealed state. It is solved by the method of manufacturing the specimen.

[0008] That is, in this manufacturing method, the formwork functions as a steel pipe of the CFT column, and the poured concrete is cured in the sealed formwork under the same curing conditions as those that are cured in the steel pipe of the CFT column. It is cured under. Moreover, during this curing, an axial compressive force is applied to the concrete in the formwork, so that the compressive strength of the concrete filled in the CFT column is increased by the consolidation action, as well as the compressive strength of the concrete in the formwork. Is raised by the consolidation action. As a result, a concrete specimen having the same or similar strength as that of the actual concrete filled with CFT columns can be obtained. Therefore, it is possible to more accurately estimate the actual strength of the concrete filled with CFT columns based on the results of the strength test of the test specimen, and to use concrete of a mix that does not greatly exceed the concrete design standard strength. In addition, it is possible to form a reasonable CFT column that is economically efficient.

There is no particular limitation on the specimen manufacturing apparatus used for carrying out the above method, and various manufacturing apparatuses may be used. For example, the following manufacturing apparatus may be used. That is, a form body having both ends open for molding the outer peripheral surface of the concrete specimen, a first lid body detachably attached to one end of the form body, and screwed and attached to the other end of the form body. A second cover for introducing a compressive force to the concrete placed in the form during the screwing, and the cured concrete specimen inside the second cover in a state where the first cover is removed. An apparatus for manufacturing a concrete specimen for estimating the strength of CFT column-filled concrete or the like, characterized in that the lid is pushed out of the form body by further screwing of the lid.

In this manufacturing apparatus, the first lid is attached to one end of the mold body, concrete is driven into the mold through the other end opening, and the second lid is screwed to the other end of the mold body. By combining and screwing, it is possible to easily introduce a predetermined compressive force into the cast concrete in the formwork. In addition, when the mold is released after reaching a predetermined age, first, the second lid is removed from the mold body, and then the first lid is removed.
By further screwing the lid, the specimen in the mold body is extruded from the mold body and taken out, and the specimen can be easily taken out from the manufacturing apparatus.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a specimen for estimating the strength of CFT column-filled concrete is manufactured using the manufacturing apparatus shown in FIGS. 1 and 2.

In the manufacturing apparatus 1 shown in FIG. 1, 2 is a mold body, 3 is a lower lid as a first lid, and 4 is an upper lid as a second lid.

The form body 2 is a cylindrical member having both ends open, and the outer peripheral surface of the concrete specimen 5 is formed on the inner peripheral surface. Flanges 2a and 2b having a predetermined thickness project outward from upper and lower ends of the form body 2 so that the form body 2
It is provided integrally with. The lower flange 2a is provided with a mounting hole 7 through which the screw rod 6 from the lower lid 3 passes. A female screw 8 for screwing the upper cover 4 is formed on the inner peripheral surface of the upper end of the form body 2, and the upper flange 2 b is positioned on the outer peripheral side of the female screw 8. Thus, the periphery of the female screw 8 is made highly rigid by the upper flange portion 2b.

The lower lid 3 is bolted to the lower flange 2a of the form body 2 to close the lower end opening of the form body 2 in a sealed state. Bolt joining is performed by passing a screw rod 6 projecting upward from the lower lid 3 through a hole 7 in the lower flange 2a of the mold body 2, and a nut 9 is inserted into the screw rod 6 projecting upward from the lower flange 2a. Is screwed and tightened. By screwing and tightening the nut 9 to the screw rod portion 6, the lower lid 3 can be integrally attached to the formwork body 2. By loosening the nut 9 and removing it from the screw rod portion 6, the lower lid 3 can be removed. The body 3 can be removed from the form body 2.

The upper lid 4 closes the upper end opening of the form body 2 and the concrete 1 which is driven into the form body 2.
And a male screw 4a having a predetermined length screwed into the female screw 8 on the inner peripheral surface of the upper end portion of the form body 2, and an upper end surface of the male screw 4a. A disk 4b having the same diameter as the upper flange portion 2b of the form body 2 is integrally and continuously provided in a concentric state. The disk 4b is integrally connected to the upper surface of the disk 4b concentrically with the body 4a.

The inner diameter of the form body 2 is designed to be somewhat larger than the diameter of the female screw 8 portion, and the male screw 4a of the upper lid 4 is screwed with the female screw 8 of the form body 2. By screwing the male screw body 4a, the distal end surface of the male screw body 4a is projected beyond the female screw 8 and inward of the formwork body 2, whereby The upper surface of the concrete 10 driven into the formwork body 2 is pushed so that an axial compressive force can be introduced into the concrete 10. The length dimension of the male screw body 4a is designed to be longer than the distance dimension between the upper surface height position of the concrete driven into the form body 2 and the height position of the upper end opening of the form body 2, The male screw 4a starts pushing on the upper surface of the concrete 10 in the middle of screwing the male screw 4a into the mold body 2.

As shown in FIG. 2, a scale mark 11 for setting the axial compression force is provided on the outer peripheral surface of the upper flange portion 2b of the form body 2, and the outer peripheral surface of the disk 4b of the upper lid 4 is provided. The surface is provided with a reference scale mark 12 serving as a reference for setting the axial force by the scale mark 11, and the upper lid 4 is screwed into a rotation so that the position of the reference scale of the reference scale mark 12 can be determined. Depending on the position of the scale,
The magnitude of the compressive force of the axial force applied to the concrete 10 driven into the formwork body 2 can be set.

[0018] The concrete specimen is prepared by using the above-described production apparatus 1
It is manufactured as follows by using. That is, first, using the concrete used in the air volume test performed in the concrete acceptance inspection, the unit volume weight of the collected concrete is obtained, and the weight per specimen is calculated from the unit volume weight. Then, as shown in FIG. 3 (a), the lower lid 3 is attached to the lower end of the formwork body 2, placed on a weighing machine, and as shown in FIG. 3 (b), the weight per specimen 1 Is poured into the mold body 2 through the upper end opening of the mold body 2.

Thereafter, as shown in FIG. 3 (C), a rubber packing 13 is placed on the upper surface of the poured concrete 10, and the upper cover 4 is screwed into the form body 2,
By rotating the projection of the upper lid 4 with a wrench, the male screw body 4a of the upper lid 4 is screwed into the mold body 2, and FIG.
As shown in FIG.
Pressing the upper surface of 0, an axial compressive force is introduced into the concrete 10. The magnitude of the axial compression force to be introduced depends on the CF to be tested.
It is a size corresponding to the axial compression force acting on the filled concrete of the T column. By rotating the upper lid 4 while visually checking the scale marks 11 and 12, the axial compressive force can be easily set to a predetermined magnitude, and the axial compressive force between a plurality of test specimens can be set. The difference can be made as small as possible.

Thus, the concrete 10 in the form body 2 is
The manufacturing apparatus 1 in a state where a predetermined axial compressive force is applied to the container is sealed in a styrene foam container (not shown), and the concrete 10 is cured. The concrete 10 is cured while receiving a compressive force in the hermetically sealed manufacturing apparatus 1, so that it is cured under the same or similar conditions as the curing in the steel pipe of the CFT column.

After reaching a predetermined age, the specimen 5 in the manufacturing apparatus 1 is taken out. Extraction is performed as follows. That is, as shown in FIG. 4D, first, the lower cover 3 of the manufacturing apparatus 1 is removed by loosening the nut 9. By loosening the nut 9, the screwing state between the male screw 4 a of the upper lid 4 and the female screw 8 of the form body 2 is also loosened. Next, as shown in FIG. 4E, the upper lid 4 is further rotated in the screwing direction. As a result, the specimen 5 is pushed by the male screw body 4a of the upper lid 4 and is pushed out of the form body 2, and the specimen 5 is taken out from the manufacturing apparatus 1 to obtain the specimen 5. Can be

Using the specimen 5 thus obtained, a strength test is performed. As described above, the test specimen 5 is given an axial compressive force during its manufacturing process and is cured under the same or similar conditions as the curing in the steel pipe of the CFT column. The strength is the same as or approximate to the strength of the actual CFT column filled concrete. Therefore, based on the strength test results of the specimen 5, the actual strength of the concrete filled with CFT columns can be more accurately estimated, and the strength of the concrete using the mixed concrete that does not greatly exceed the concrete design standard strength can be obtained. It is possible to form a reasonable CFT pillar that is economically efficient.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the invention. For example, as a modified example of the above-described manufacturing apparatus, the form body 2 is vertically divided into a plurality of parts, for example, divided into two parts, and the form body 2 is attached to the tip of the male screw body 4a of the upper lid 4. It is good also as a structure provided with the large diameter part which slides in contact with an inner inner peripheral surface. Also, if you want to set more accurate axial force,
A hole for installing a pressure gauge is provided on a side surface of the formwork body 2, a lateral pressure of the internal concrete 10 is measured with the pressure gauge installed in the hole, and an acting axial force is obtained from the measured value by a predetermined formula to obtain an axial force. The setting may be performed. In the above-described embodiment, a screw tightening mechanism is used to compress the concrete 10 in the manufacturing apparatus 1. However, the present invention is not limited to this, and various axial compressive force introducing mechanisms such as hydraulic pressure are used. Good. The production of the specimen 5 may be performed using various production devices capable of curing concrete poured into a mold while applying an axial compression force in a sealed state. Also,
The present invention is not limited to the concrete filled with CFT columns.
It goes without saying that it may be widely used for producing concrete specimens for estimating the strength of various types of concrete similar or similar to the concrete filled with T columns.

[0024]

As described above, the method for producing a concrete specimen for estimating the strength of CFT column-filled concrete or the like according to the present invention provides a method of curing concrete poured into a form while applying axial compression force in a closed state. Therefore, it is possible to obtain a specimen having the same or similar strength as that of the actual concrete of the CFT column, and to reduce the strength of the actual concrete of the CFT column based on the strength test result of the specimen. It is possible to accurately estimate, and to form a reasonable CFT column with no waste in terms of strength and economy.

Further, since the manufacturing apparatus of the present invention has the above-mentioned configuration, a predetermined compressive force can be easily applied to the concrete placed in the formwork by the screwing operation of the second lid. In addition to the introduction, the specimen can be easily removed from the manufacturing apparatus by the further screwing operation of the second lid.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a manufacturing apparatus used in the method of the present invention.

FIG. 2 is an exploded perspective view of the manufacturing apparatus.

FIGS. 3 (a) to 3 (c) are FIGS.
(D) It is a longitudinal cross-sectional view which shows the method of this invention sequentially with (e).

FIGS. 4 (d) and 4 (e) are FIGS. 3 (a) and 3 (b), respectively.
It is a longitudinal section showing a method of the present invention together with (c).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus 2 ... Form body 3 ... Lower lid (1st lid) 4 ... Upper lid (2nd lid) 10 ... Concrete

Claims (2)

[Claims] 1. A method for producing a concrete specimen for estimating the strength of CFT column-filled concrete or the like, characterized in that concrete poured into a mold is cured while applying an axial compressive force in a sealed state. 2. A mold body for forming an outer peripheral surface of a concrete specimen, an open-ended form body, a first lid detachably attached to one end of the form body, and screwed to the other end of the form body. And a second lid for introducing a compressive force into the cast concrete in the form during screwing, and the cured concrete specimen inside is removed with the first lid removed. A concrete specimen for estimating the strength of CFT column-filled concrete or the like, characterized in that the second lid is pushed out of the form body by further screwing of the second lid.