JPH0477780B2 - - Google Patents

Description

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

[Prior Art] A filled steel pipe concrete structure is known as this type of structure.In the conventional filled steel pipe concrete structure, a simple right cylindrical steel pipe that also serves as a formwork is erected vertically, and the inside of the filled steel pipe concrete structure is It 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, in the conventional method, 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 may exceed the Mises yield condition. , local buckling may occur.

Therefore, even though there is plenty of margin in the circumferential stress and the confining effect of the steel pipe (the action of tightening the concrete to prevent it from expanding due to the circumferential stress of the steel pipe) can be expected to sufficiently increase the yield strength of the concrete, the increase in The steel pipe almost reaches yield due to the axial stress, and the confining effect cannot be fully exerted, resulting in a column or pile with a larger cross-sectional area than necessary.

An object of the present invention is to provide a filled steel pipe structure that can make full use of the confining effect of steel pipes, significantly improve compressive strength, and have a smaller cross-sectional area than conventional ones.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides one or more stages of ring-shaped grooves extending in the circumferential direction on the outer peripheral surface of at least a portion of the steel pipe in the axial direction. form,
In addition to filling the inside of the steel pipe with structural fillers such as concrete, mortar, and other grouting materials,
It is characterized by an unbonding treatment layer provided at the interface between the steel pipe and the hydraulic material to prevent adhesion between the steel pipe and the structural filler.

[Function] In the unbonded filled steel pipe structure with the above configuration, when compressive force in the axial direction is applied, the steel pipe can freely deform in the axial direction, and the deformation is absorbed by early buckling of the ring-shaped groove portion. Ru.

In particular, in this case, the steel pipe and the structural filler filled inside are in an unbonded state, so after the ring-shaped groove part buckles, the axial compressive force is applied to the structural filler inside the steel pipe. It only acts on steel pipes, and has almost no effect on steel pipes. That is, the axial stress acting on the steel pipe becomes close to zero. For this reason, only the ring tension acts on the steel pipe as a reaction that gives a confining effect. Therefore, if the Mises yield condition is applied, the confining effect of the steel pipe due to the circumferential stress can be fully exerted. As a result, the strength against compressive loads can be significantly improved,
Cross-sectional area can be reduced.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 show an embodiment in which the present invention is applied to a column H, in which numeral 1 is a steel pipe. Four stages of ring-shaped grooves 2 extending in the circumferential direction of the steel pipe are formed at predetermined locations in the axial direction of the steel pipe 1, and this portion constitutes a deformation absorbing portion 3 that absorbs axial deformation occurring in the steel pipe 1. .

The width and the number of steps of the ring-shaped groove 2 of the deformation absorbing section 3 are set appropriately according to the design conditions, and the thickness of the thin-walled part of the ring-shaped groove 2 is determined when the steel pipe 1 is assembled to the upper floor. The steel pipe 1 is set so that it has sufficient strength during construction and as a formwork when pouring concrete inside the steel pipe 1. In this case, unlike when the steel pipe is completely cut out at the ring-shaped groove part, there is no need to use a tack support jig during erection, and there is no need to take the trouble of intentionally attaching formwork to the ring-shaped groove part.

Further, on the inner surface of the steel pipe 1 configured as described above, a separation material (unbond treatment layer) 4 is applied in advance to prevent adhesion between the steel pipe 1 and the filling concrete. concrete 5
is poured and filled. As the separating material 4, 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.

Then, the column H of the unbonded type filled steel pipe concrete structure constructed in this way is erected as shown in FIG. 2. In this case, in the column H, the deformation absorbing portion 3 is provided at the intermediate portion between each floor, which is the point of reversal of the bending moment, and is adapted to absorb deformation occurring in the steel pipe 1 for each floor. Depending on the case, the deformation absorbing portion 3 may be provided throughout the section receiving compressive force. In addition, 6 is the joint part of the beam of each floor.

In such a filled steel pipe concrete structure, an axial compressive force acts on the concrete 5 inside the steel pipe 1, compressing the concrete 5, and when it exceeds a predetermined strength, the concrete 5 will undergo axial strain. At the same time, sudden lateral strain occurs in the radial direction.

However, the axial strain that occurs in the steel pipe 1 is absorbed by early buckling of the thin wall portion of the ring-shaped groove 2 of the deformation absorbing portion 3, and the transmission of axial stress between the upper and lower portions of the deformation absorbing portion 3 is eliminated. , steel pipe 1
Almost no axial stress occurs. In particular, in this case, the steel pipe 1 is in an unbonded state with the filling concrete 5, and the steel pipe 1 is not restrained by the concrete 5 in the axial direction at all. Therefore, although axial strain occurs in the concrete 5, no axial strain occurs in the steel pipe 1. 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 can be reduced. be able to.

Next, an example of construction of such an unbonded steel filled pipe concrete structural column will be described.

As a method for providing the ring-shaped groove 2 in the steel pipe 1,
An external type steel pipe cutting machine can be used to cut the steel pipes in the factory or on site after erecting the steel pipe columns or after pouring concrete inside the steel pipes.
The ring-shaped groove 2 can be cut. Further, the separation material 4 for unbonding treatment may be applied at any time before the concrete 5 is poured. In addition, for manufacturing the steel pipe 1 with the deformation absorbing part 3, prepare a short steel pipe in advance, cut it to form the ring-shaped groove 2 to manufacture the short pipe for the deformation absorbing part 3, and then cut it into the steel pipe. It is also possible to adopt a method of welding and fixing by intervening at the first joint. In this case, the short tube may be made thicker than the steel tube 1.

In the above embodiment, the steel pipe 1 is filled with concrete, but it may be filled with mortar, other hydraulic materials, soil, sand, metal powder, glass powder, plastic, viscosity, etc. A structural filler having a large compressive strength may be used instead. Furthermore, it is optional to increase the strength of the concrete by inserting reinforcing bars into the concrete or arranging prestressed steel.

[Effects of the Invention] According to the present invention, since the axial deformation occurring in the steel pipe is absorbed by the ring-shaped groove, almost no axial stress is applied to the steel pipe. 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 can be reduced.

In addition, in the present invention, by forming a ring-shaped groove without completely edge-cutting the steel pipe in the axial direction, a thin wall part that is easy to buckle but has a certain degree of strength is left, so that temporary joints can be used during erection. Using a support jig or purposely attaching a formwork to the ring-shaped groove part eliminates the need for troublesome work and has the advantage of saving labor.

[Brief explanation of drawings]

FIG. 1 is a half-sectional view of the main part of an embodiment of the present invention, and FIG. 2 is an overall sectional view of the same embodiment. DESCRIPTION OF SYMBOLS 1... Steel pipe, 2... Ring-shaped groove, 3... Deformation absorption part, 4... Separation material (unbond processing layer), 5...
…concrete.

Claims (1)

[Claims] 1. In a filled steel pipe structure used as a pillar or pile, at least a portion of the outer peripheral surface in the axial direction of the steel pipe is
A ring-shaped groove extending in the circumferential direction is formed, and a structural filler such as concrete is filled inside the steel pipe, and at the interface between the steel pipe and the structural filler,
An unbonded filled steel pipe structure characterized by being provided with an unbonded treatment layer for eliminating adhesion between the steel pipe and structural filler.