JPH0354724B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bridge pier used for railways, roads, etc., and specifically relates to a pier that employs a filled steel pipe concrete structure for its support portion.

[Prior Art] When adopting a filled steel pipe concrete structure for a support column, in the conventional filled steel pipe concrete, the steel pipe and the concrete filled inside adhere to each other and behave as one, so axial force, When calculating the strength such as bending and shear force, the concrete cross section + steel pipe cross section is used as the basis for calculation.

[Problems to be Solved by the Invention] In the above-mentioned filled concrete structure, when compressive force in the axial direction is applied, the steel pipe and concrete are distorted integrally, so if the steel pipe is greatly distorted, the compressive force in the axial direction The Mises yield condition may be exceeded or local buckling may occur. Therefore, although 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 proof strength of the concrete, the increased axial stress causes the steel pipe to There is a problem in that the confining effect is not sufficiently exerted because the yielding is almost reached, and the support portion has to have a larger cross-sectional area than necessary. The present invention significantly improves the compressive strength of the strut, and further widens the range of elastic compression and tension of the edge stress of the steel pipe against bending, making it possible to reduce the cross-sectional area of the strut compared to conventional ones. The purpose is to provide a bridge pier.

[Means for Solving the Problems] The pier of the present invention includes a column made of filled steel pipe concrete on the footing, and an upper beam section at the upper end of the column, in which the column is located on the footing side. It consists of a thick column part and a thin column part on the upper beam side that is installed on the thick column part through a step part, and the thick column part and the thin column part are each made of steel pipe concrete with separate steel pipes. It is made of steel, and is constructed of unbonded steel pipe concrete in which the steel pipe and the concrete filled inside the steel pipe do not adhere to each other, and the upper ends of the steel pipes in the thick columns are open, and the tops of the steel pipes in the thick columns are open. The feature is that there is a gap between the upper end of the steel pipe in the section and the lower surface of the upper beam section.

[Function] In the pier with the above configuration, the load applied to the upper beam is transmitted to the support column, but at that time, the compressive load in the axial direction is transmitted to the upper end of the steel pipe of the thin column, which is open.
In addition, since the steel pipe and the filling concrete are in an unbonded state, it hardly acts on the steel pipe and acts only on the filling concrete. That is, the axial stress acting on the steel pipe becomes close to zero. Therefore, only 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, and the cross-sectional area of the narrow column portions of the support columns can be reduced.
The same can be said of the thick column portion.

[Embodiment] FIGS. 1 and 2 show an embodiment of the present invention.

A plurality of piles 1 are lined up and buried in the ground S, and a footing 2 made of reinforced concrete is connected to the upper end of the pile 1. 3 is the reinforcing steel. A steel pipe 6 constituting the thick column portion 5 of the support portion 4 is erected above the footing 2, with its lower end embedded in the footing 2. 7 is a temporary holding jig for setting up the steel pipe 6.

The inside of the steel pipe 6 thus erected is filled with concrete 8. In this case, a separation material (unbonding layer) 9 is applied to the inner surface of the steel pipe 6 in advance to prevent adhesion between the steel pipe 6 and the filling concrete 8.
Concrete 8 is poured inside. Therefore, the steel pipe 6 and the concrete 8 can be relatively freely displaced in the axial direction.

As the separating material 9, paraffin, asphalt, oil, grease, vaseline, etc. are used, and by applying this to the inner surface of the steel pipe 6, an unbonding treatment layer is formed.

Further, at the upper end of the thick column part 5 configured in this way, a narrow column part 11 having a smaller diameter than the thick column part 5 is provided with a step part 10 interposed therebetween. This narrow column section 11 also has an unbonded type filled steel pipe concrete structure, and the lower end of the steel pipe 12 in this case is embedded in the upper end surface of the filled concrete 8 of the narrow column section 11.
The edges of the steel pipe 6 and the steel pipe 12 are completely cut off. This steel pipe 12 is also erected while being supported by a temporary holding jig 13 before concrete 8 is placed on the thick column portion 5 below it. Temporary holding jig 13 in this case
are fixed to reinforcing bars 14 that vertically pass through the support column 4. Note that 15 is filled concrete, and 16 is a separating material applied to the inner surface of the steel pipe 12. This is the same as the separation material 9 described above.

Further, an upper beam portion 17 is provided at the upper end of the narrow column portion 5 of the support portion 4 configured in this manner. This upper beam portion 17 is made of concrete 15 of the narrow column portion 11.
A gap 18 is formed between the upper end of the steel pipe 12 and the lower surface of the upper beam part 17 so that the upper beam part 17 does not come into direct contact with the steel pipe 12. During this time, the diameter 18 is set so that even if a load is applied to the upper beam part 17 and the concrete 15 of the pillar part 11 shrinks, the lower surface of the upper beam part 17 will not come into contact with the upper end of the steel pipe 12, so that the opening is not larger than necessary. Not yet. In this case, the upper beam portion 17 is made of cast-in-place reinforced concrete like the footing 2.
Reference numeral 19 indicates reinforcing bars in the upper beam portion 17. In addition to being made of cast-in-place concrete, the upper beam portion 17 may also be a precast concrete beam or a steel beam.

Next, the procedure for making the illustrated bridge pier will be briefly described. After constructing the pile 1, first, a formwork for the footing 2 is assembled, and at the same time, the steel pipe 6 is erected while being supported using a temporary support jig 7. A separating material 9 such as paraffin is applied to the inner surface of the steel pipe 6 in advance. after that,
The footing 2 is constructed by pouring concrete up to the upper end level of the footing 2.

Next, a temporary receiving jig 1 is placed above the steel pipe 6 that has been erected.
3, the steel pipe 12 for the thin column part 11 is erected with support, and on top of that, a formwork for the upper beam part 17 is assembled, and at this time, a formwork for securing the above-mentioned gap 18 is also assembled. .
Then, concrete is poured into the steel pipe 12 and the upper beam part formwork to construct the filling concrete 15 portion of the narrow column part 11 and the upper beam part 17, and the pier is completed. Note that the concrete 15 for the narrow column portion 11 and the concrete for the upper beam portion 17 may be cast separately.

In a bridge pier with such a configuration, the load applied to the upper beam portion 17 is first transmitted to the narrow column portion 11 of the column portion 4, but at that time, the compressive load in the axial direction is transmitted when the upper end of the steel pipe 12 Since the steel pipe 12 and the concrete filler 15 are not in contact with the lower surface of the steel pipe 12 and are in an unbonded state, it hardly acts on the steel pipe 12 and only acts on the filler concrete 15 inside the steel pipe 12. Therefore, only the ring tension acting as a reaction that gives a confine effect acts on the steel pipe 12.

Therefore, by applying the Mises yield condition, the confining effect of the steel pipe due to circumferential stress can be fully exhibited, and as a result, the strength of the thin column part 11 against compressive load can be significantly improved, Furthermore, the range of elastic compression and tension of the edge stress of the steel pipe against bending is widened, so that the cross-sectional area of the narrow column portion can be reduced.

The above can also be said to the thick pillar portion 5 as well. Therefore, when viewed as a whole, it is natural that the support portion 4
The cross-sectional area of can be reduced. Also, on this pier,
It also has the advantage of having a large bending strength because the support section 4 is structured in two stages and the lower portion has a larger diameter.

In addition, in the above embodiment, the case where the strut part 4 has two stages has been explained, but it is also possible to provide a further stage in the middle to form a medium-thin pillar part, and to form a pillar part with three or more stages. good.

Further, in the above embodiment, the case where there is one support column has been described, but the present invention can also be applied to a case where there are two or more support columns. Figure 3 shows an example in which there are two piles, 21 is the pile, 22 is the foundation concrete, 23 is the footing, 24 is the column, and 2
5 is a thick column part, 26 is a thin column part, 27 and 28 are steel pipes,
29 and 30 are concrete, 31 and 32 are separating materials, 33 is a gap, and 34 is an upper beam portion.

Further, in the above explanation, the cross-sectional shape of the support columns 4 and 24 was not particularly mentioned, but the present invention
The present invention is not limited to having a circular cross section as shown in the figure, but can be applied to various shapes such as an ellipse and a polygon.

[Effects of the Invention] According to the present invention, since the steel pipe has a structure in which almost no axial load acts on the steel pipe, almost no axial stress is generated in the steel pipe, and therefore the Mises yield condition cannot be applied. In this case, the confining effect of the steel pipe due to the stress in the circumferential direction can be fully exerted. As a result, the strength against compressive loads can be significantly improved, and the cross-sectional area of the support column can be reduced. Furthermore, this pier has the effect of having a large bending strength because the support section is configured in stages and the diameter of the lower portion is increased.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of one embodiment of the present invention, FIG. 2 is a sectional view taken along the - line in FIG. 1, and FIG. 3 is a side sectional view of another embodiment of the present invention. 2, 23... Footing, 4, 24... Pillar part, 5, 25... Thick column part, 11, 26... Thin column part, 6, 12, 27, 28... Steel pipe, 8, 15,
29,30...Filled concrete, 9,16,3
1, 32... Separation material, 17, 34... Upper beam part, 1
8,33….

Claims (1)

[Claims] 1. In a pier that has a column made of filled steel pipe concrete on the footing and an upper beam section at the upper end of the column, the column is connected to the thick column on the footing side and the thick column via the step. The thick column part and the thin column part are each of steel pipe concrete steel construction with separate steel pipes, and the steel pipes and the steel pipes are filled inside. The structure is made of unbonded filled steel pipe concrete with no adhesion to the concrete in which it is attached, and the upper ends of the steel pipes in the thick columns are open, and the gaps between the top ends of the steel pipes in the thin columns and the bottom surface of the upper beams are open. A bridge pier characterized by having a gap.