JPH0354726B2 - - 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 steel pipe concrete structure,
When compressive force in the axial direction is applied, the steel pipe and concrete are distorted together, so if the pipe is significantly distorted, the pipe may exceed the Mises yield condition or cause local buckling due to the compressive force in the axial direction alone. or 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 support column, and furthermore, the range of elastic compression and tension of the edge stress of the steel pipe against bending is widened.
It is an object of the present invention to provide a bridge pier whose support section can have a smaller cross-sectional area than conventional ones.

[Means for Solving the Problems] The pier of the present invention includes a column made of filled steel pipe concrete on a footing, and an upper beam portion at the upper end of the column, in which the column is made of steel pipes. The steel pipe is constructed of unbonded filled steel pipe concrete in which the concrete filled inside the steel pipe is in a non-adhesive state, and a deformation absorbing portion is provided in at least a part of the steel pipe in the axial direction to absorb axial deformation occurring in the steel pipe. It is characterized by

[Operation] In the bridge pier configured as described above, the load applied to the upper beam portion is transmitted to the support portion, but at this time, deformation that occurs in the steel pipe due to the compressive load in the axial direction is absorbed by the deformation absorbing portion. In particular, in this case, since the steel pipe and the filling concrete are in an unbonded state,
The axial compressive force acts only on the filled concrete inside the steel pipe and has almost no effect on the steel pipe. 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. can be made,
As a result, the strength against compressive loads can be significantly improved, and the cross-sectional area of the support column can be reduced.

[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 5 constituting the support section 4 is erected on the upper part of the footing 2, with its lower end embedded in the footing 2. This steel pipe 5 is provided with a deformation absorbing portion 5a that absorbs deformation in the axial direction that occurs in the steel pipe 5 due to expansion and contraction of that portion. The position, number, and type of deformation absorbing portions 5a can be selected as appropriate.

As for the types, for example, there are those in which a ring-shaped gap is formed between the upper and lower edges of the steel pipe 5, those in which the ring-shaped gap is filled with a flexible material such as rubber, or those in which a ring-shaped groove is formed on the inner or outer surface of the steel pipe 5. such as those in which the steel pipe 5 is cut and actively used as a weak part to make it easy to buckle, and those in which a plurality of elongated holes extending in the circumferential direction are formed in the steel pipe 5 to give that part elasticity in the axial direction. In short, any material may be used as long as it has elasticity and local deformability so as to absorb the axial deformation that occurs in the entire steel pipe 5 at that location. Note that 7 is a temporary holding jig for setting up the steel pipe 5.

The inside of the steel pipe 5 thus erected is filled with concrete 6. In this case, the inner surface of the steel pipe 5 is coated with a separation material (unbonding layer) 8 in advance to prevent adhesion between the steel pipe 5 and the filling concrete 6, and then the steel pipe 5 is
Concrete 6 is poured inside. Therefore, the steel pipe 5 and the concrete 6 can be relatively freely displaced in the axial direction.

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 5, an unbonding treatment layer is formed.

Further, an upper beam portion 9 is provided at the upper end of the support portion 4 of the unbonded type filled steel pipe concrete structure configured in this manner. This upper beam portion 9 is integrally connected to the concrete 6 of the support portion 4. In this case, the upper beam portion 8 is made of cast-in-place reinforced concrete like the footing 2, and the upper end of the steel pipe 5 is fixed within the upper beam portion 9. 10 is a reinforcing bar in the upper beam portion 9. In addition to being made of cast-in-place concrete, the upper beam portion 9 may also be a precast concrete beam or a steel beam.

The steps for making the illustrated bridge pier are as follows: After constructing the piles 1, first, a formwork for the footing 2 is assembled, and at the same time, the steel pipe 5 is erected while being supported using a temporary support jig 7. A separating material 8 such as paraffin is applied to the inner surface of the steel pipe 5 in advance. Thereafter, the footing 2 is constructed by pouring concrete up to the upper end level of the footing 2.

Next, a formwork for the upper beam part 11 is constructed above the erected steel pipe 5, and concrete is poured into the steel pipe 5 and the upper beam part formwork to fill the 6 portions of the pillar part 4 with concrete. Then, the upper beam section 9 is constructed to complete the bridge pier. Incidentally, the concrete 6 for the column portion 4 and the concrete for the upper beam portion 9 may be cast separately.

In a pier with such a configuration, the load applied to the upper beam part 9 is transmitted to the support part 4, and the load applied to the support part 4 acts as an axial compressive force on the concrete 6 in the steel pipe 5, causing the concrete 6 to be compressed. compresses.
If it exceeds a predetermined strength, the concrete 6 will undergo axial strain as well as rapid radial transverse strain.

However, the axial strain occurring in the steel pipe 5 is absorbed by the deformation absorbing portion 5a, and no axial stress is transmitted between the upper and lower portions of the deformation absorbing portion 5a, and almost no axial stress is generated in the steel pipe 5. In particular, in this case the steel pipe 5 is in the unbonded state of the filled concrete 6, and the steel pipe 5 is not constrained by the concrete 6 in the axial direction at all. Therefore, although axial strain occurs in the concrete 6, no axial strain occurs in the steel pipe 5. Therefore, by applying the Mises yield condition, the effect of confining the steel pipe 5 due to circumferential stress can be fully exhibited,
As a result, it is possible to improve the strength against compressive loads. Furthermore, by expanding the range of elastic compression and tension of the edge stress of the steel pipe against bending,
The cross-sectional area of the support portion 4 can be reduced.

In addition, although the above description explained the case where there is one support|pillar part 4, this invention is applicable also to the case where there are two or more. 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 steel pipe, 25a is a deformation absorbing portion, 26 is a concrete column, 27 is a separating material, and 28 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.

[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...Strut part, 5, 25...Steel pipe, 5a, 25a...Deformation absorption part, 6, 26...Filled concrete, 8, 27
... Separation material, 9, 28 ... Upper beam part.

Claims (1)

[Claims] 1 In a bridge 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 an unbonded type in which the steel pipe and the concrete filled inside the steel pipe are not attached. 1. A bridge pier constructed of filled steel pipe concrete, and characterized in that a deformation absorbing portion is provided in at least a portion of the steel pipe in the axial direction to absorb deformation in the axial direction occurring in the steel pipe.