JPH0428062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an unbonded filled steel pipe structure used for columns, piles, etc.

"Conventional technology" Filled steel pipe concrete structures are known as this type of structure, but in conventional filled steel pipe concrete structures, a simple right cylindrical steel pipe that also serves as a formwork is erected vertically. The pipe is simply filled with concrete, and the steel pipe and concrete are in a bonded state and behave mechanically as one.

``Problems to be Solved by the Invention'' However, with conventional pipes, when compressive force in the axial direction is applied, the steel pipe and concrete are distorted as one, and if the steel pipe is significantly distorted, the steel pipe exceeds the Mises yield condition. or local buckling may occur.

Therefore, even though the circumferential stress has a margin and the confining effect of the steel pipe (the effect of tightening the concrete when it tries to expand due to the circumferential stress of the steel pipe) can sufficiently increase the proof stress of the concrete, The steel pipe almost reaches yield due to the increased axial stress, and the confining effect cannot be fully exerted, resulting in a column or pile with a larger cross-sectional area than necessary.

The present invention was made in view of the above problems, and
To provide a filled steel pipe concrete structure that can make full use of the confining effect of steel pipes, significantly improve compressive strength, and make the cross-sectional area of columns and piles smaller than conventional ones.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention provides a mechanism that acts on the steel pipe by being fixed to at least one location inside the steel pipe in a state that projects inside the steel pipe. An axial force transmitting part is provided to transmit axial force to the structural filler filled inside the steel pipe, and a notch is provided in the axial force transmitting part as a deformation absorbing part to absorb axial deformation occurring in the steel pipe. The present invention is characterized in that an unbonding layer is provided on a part of the steel pipe in response to the above, and an unbonding layer is further provided between the steel pipe and the structural filler to prevent adhesion between the steel pipe and the structural filler.

In this invention, the axial force transmitting part is a ring-shaped bearing plate extending in the circumferential direction with an outer peripheral part fixed to the inner peripheral surface of the steel pipe, and the deformation absorbing part moves the steel pipe up and down. It may be a ring-shaped gap formed by cutting edges, or it may be a plurality of long holes arranged in a staggered manner extending in multiple rows in the circumferential direction of the steel pipe. desirable.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 3 show one embodiment of the present invention, and Figure 1 shows a column (hereinafter simply referred to as a "column") H having an unbonded filled steel pipe structure and a beam K of several stories. , K, .

In these figures, numeral 1 is a steel pipe, and 2 is a steel pipe.
is concrete filled in the steel pipe 1.
A predetermined location in the axial direction of the steel pipe 1 (in this example,
(one location per 3 floors), beams K, K, ......
An axial force transmitting part 3 for transmitting the axial force applied to the steel pipe 1 from the steel pipe 1 to the concrete inside is fixed and protrudes inside the steel pipe 1.
The axial force transmission section 3 includes a ring-shaped bearing plate 4, a rib 5,
5. It consists of... A ring-shaped bearing plate 4 is enclosed in concrete inside the steel pipe 1 and is provided almost horizontally, and its outer circumferential surface is welded to the inside of the steel pipe 1, and the ribs 5 are provided on the upper part of the bearing plate 4 at almost right angles. The bottom part is the bearing plate 4 and the side part is the steel pipe 1.
are welded to each other. In addition, the axial force transmission section 3
A deformation absorbing portion 6 is formed in the lower steel pipe 1 at approximately the middle portion between the floors (moment recursion point). The deformation absorbing portion 6 consists of a ring-shaped gap 7 formed by cutting the steel pipe 1 so as to edge it in the axial direction, and is configured to absorb axial deformation occurring in the steel pipe 1 at this portion. The ring-shaped gap 7 of the deformation absorbing portion 6 may be filled with a flexible material so that its inner surface is flush with the inner surface of the steel pipe 1. Asphalt, rubber, lead, aluminum, etc., which are softer than the steel pipe 1, can be used as the softening agent.

Note that the shape of the deformation absorbing portion 6 is not limited to a ring-shaped groove, and for example, by making a cut to form a ring-shaped groove on the inner or outer surface of the steel pipe 1, the shape of the deformation absorbing portion 6 is not limited to a ring-shaped groove. The steel pipe 1 has a weak part that is easy to buckle, or the steel pipe 1 has a plurality of long holes extending in the circumferential direction arranged in a staggered manner so as to have axial elasticity in that part. In short, any material may be used as long as it has elasticity and local deformability to absorb the axial deformation that occurs in the steel pipe 1 at that location. Furthermore, on the inner surface of the steel pipe 1 configured as described above, a separation material (unbond treatment layer) is provided to prevent adhesion between the steel pipe 1 and the filling concrete.
8 is applied in advance, and then concrete 2 is cast and filled inside the steel pipe 1. As the separating material 8, paraffin, asphalt, oil, grease, vaseline, etc. are used, and by applying this to the inner surface of the steel pipe 1, an unbonding treatment layer is formed.

Next, the function of the filled steel pipe concrete structure configured as described above will be explained using FIGS. 1 to 3.

First, the shearing force applied to the beams K, K, and K for three floors is transmitted to the steel pipe 1 at the part where they are welded. However, the steel pipe 1 and the concrete 2 inside are separated by an unbonding treatment layer 8, and the steel pipe 1 is mechanically divided in the axial direction by deformation absorbing sections 6 provided every three floors. Since the axial shearing force is not transmitted to the steel pipe 1 below, the shearing force transmitted to the steel pipe 1 is not directly transmitted to the concrete 2 inside, and the axial force generated at the bottom of the steel pipe 1 is It is transmitted to the concrete 2 below via the bearing plate 4 of the transmission part 3. next,
When an axial force is transmitted to the concrete 2 below, the concrete 2 is compressed, and when it exceeds a predetermined strength, it causes strain in the axial direction. Accordingly, the steel pipe 1 also shifts downward, but since a ring-shaped gap 7 is formed below the axial force transmitting part 3 as a deformation absorbing part 6, the upper steel pipe 1 is moved downwardly.
The shearing force from the beams K, K, and K is reliably transmitted only to the concrete 2 (here, the ring-shaped gap 7 does not contact the steel pipe 1 below even if the upper steel pipe 1 moves). (Set the dimensions so that they do not touch each other.) In addition, the concrete 2 below is distorted in the axial direction and undergoes rapid transverse distortion in the radial direction. However, the lower steel pipe 1 is 3.
Since only the load for one story is borne, the stress in the axial direction generated in the steel pipe 1 is small. In particular, in this case, the steel pipe 1 is in an unbonded state with the filled concrete 2, and the steel pipe 1 is not restrained by the concrete 2 in the axial direction at all. Therefore, although axial strain occurs in the concrete 2, almost no axial strain occurs in the steel pipe 1. These actions similarly occur between the upper steel pipe 1 and the internal concrete 2.

Therefore, by applying the Mises yield condition, the confining effect of the steel pipe 1 due to circumferential stress can be fully exhibited, and as a result, the strength against compressive loads can be improved, and the cross-sectional area of the column H can be reduced. Can be made smaller.

Here, the second embodiment shown in FIGS. 4 and 5 will be explained. In this second embodiment, the deformation absorbing section 6 of the first embodiment is replaced with a steel pipe above the axial force transmitting section 3. The other configurations are completely the same as those of the first embodiment, and the same components are given the same reference numerals. Therefore, this second embodiment also has the same effects as the first embodiment.

Next, regarding the construction example of such a column H, the method of providing the deformation absorbing portion 6 in the steel pipe 1 is to cut the steel pipe 1 directly and provide the ring-shaped gap 7, or to cut a short steel pipe in advance. Prepare,
In addition to the method of cutting this to create a short length of pipe for the deformation absorbing section, intervening it at the joint of the steel pipe, and welding and fixing it, there is also a method of pouring concrete into the steel pipe on site and then cutting the specified part of the steel pipe. It is possible to form a ring-shaped space 7 by cutting it into a ring shape.

Further, the ring-shaped space 7 may be filled with a flexible material from the viewpoint of appearance and to serve as a formwork during concrete pouring. Further, when a short steel pipe is retrofitted, there is an advantage that the wall thickness of the short steel pipe can be increased.

In the above embodiment, the steel pipe 1 is filled with concrete, but it may be replaced with a structural filler such as mortar which has sufficient compressive strength when consolidated. Furthermore, it is optional to increase the strength of the concrete by inserting reinforcing bars into the concrete or arranging prestressed steel materials.

"Effects of the Invention" As explained above, the present invention provides an axial force transmitting part that transmits the axial force applied to the steel pipe to the concrete in the steel pipe at a predetermined location of the column, and also provides a structure that corresponds to the axial force transmitting part. A deformation absorbing section is provided to allow for deformation in the axial direction of the steel pipe, and an unbonding layer is provided to prevent the steel pipe from adhering to the structural filler. Only small axial stresses occur. Therefore, by applying the Mises yield condition, the effect of confining the steel pipe due to the circumferential stress can be fully exhibited. As a result, the strength against compressive loads can be significantly improved, and the cross-sectional area of the columns can be reduced.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a partially sectional side view showing the entire embodiment, and FIG. 2 is a main part (parts) of the embodiment. A side sectional view of section A in FIG. 1, and FIG.
The sectional view, FIG. 4, and FIG. 5 show the second embodiment. FIG. 4 is a side view with a partial cross section showing the entire embodiment, and FIG. 5 is a main part of the same embodiment. (4th
FIG. DESCRIPTION OF SYMBOLS 1... Steel pipe, 2... Concrete, 3... Axial force transmission part, 4... Bearing pressure plate, 6... Deformation absorption part, 7...
...Ring-shaped space, 8... Separation material (unbond treatment layer).

Claims (1)

[Claims] 1. In a filled steel pipe structure used as a pillar or pile, the steel pipe is fixed to at least one location inside the steel pipe in a state that projects inside the steel pipe, thereby reducing the axial force acting on the steel pipe. An axial force transmitting portion is provided to transmit the force to the structural filler filled inside the steel pipe, and a cut serving as a deformation absorbing portion for absorbing axial deformation occurring in the steel pipe is made to correspond to the axial force transmitting portion. An unbonded filled steel pipe structure, characterized in that an unbonded treatment layer is provided in a part of the steel pipe and further provided between the steel pipe and the structural filler to prevent adhesion between the steel pipe and the structural filler. 2. The unbonded filled steel pipe according to claim 1, wherein the axial force transmitting part is a ring-shaped bearing plate extending in the circumferential direction and having an outer peripheral part fixed to the inner peripheral surface of the steel pipe. structure. 3. The unbonded filling according to claim 1 or 2, characterized in that the deformation absorbing portion is a ring-shaped space formed by cutting the steel pipe so as to edge it up and down. Steel tube construction. 4. The unbond according to claim 1 or 2, wherein the deformation absorbing portion is a plurality of elongated holes extending in plural rows in a circumferential direction of the steel pipe and arranged in a staggered manner. Filled steel tube structure.