JPH06146225A - Load resistant member - Google Patents

Abstract

PURPOSE:To enhance the strength by laying a pressure bearing plate at each of opposite ends of a steel pipe which are opened, by stretching an unbond type steel wire, steel rod or the like through the steel pipe in the axial direction of the latter, by fixing the steel wire or the like to the pressure bearing plates, and by filling concrete in the steel pipe. CONSTITUTION:When a load is exerted to a load resistant member 1, a steel pipe 15 holds concrete 15 which is therefore prevented from bulging out. Next, pressure bearing plates 12 restrain the concrete from coming out from ends of the steel pipe 11 upon loading, and since reinforcement 4 is added, the load resistance is increased by about 50% at maximum in comparison with a conventional steel pipe which no reinforcement is added. Further, the tension force is increased at the time when the load resistant member is deformed, and accordingly, the load resistance becomes substantially equal to the original value. Accordingly, it is possible to enhance the load resistance and the ability of deformation without an increase in the section modulus thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load-bearing material used for supporting columns such as rockfalls, avalanche prevention fences or beams.

[0002]

A rockfall prevention fence is used as one method for protecting a road from rockfalls.
This rockfall prevention fence is used for relatively small-scale measures against rockfall, and H steel is generally used for the columns at present. However, in many cases, the columns are actually bent, and the energy absorption by H steel does not occur. There are few and dangerous conditions. In order to compensate for such weak points of the support pillars, methods such as increasing the section modulus of H steel are currently taken, but if the support pillars become large, it is not possible to construct a preventive fence on the slope of a mountain. There are cases. Therefore, a strut structure having a large load bearing capacity with a small size is desired.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a large load bearing capacity and deformation with a small size without increasing the section modulus unlike H steel. An object is to provide a load bearing material capable of obtaining the capability. That is, according to the present invention, as shown in FIGS. A reinforcing member 14 such as an unbonded steel wire or a steel rod fixed to a pressure bearing plate 12 via a stopper 13 such as a nut, and a concrete 1 filled in a steel pipe 11.
The load-bearing material 1 is composed of

[0004]

The function of the present invention has the following functions. <a> Restraint by steel pipe When load is applied to load bearing material 1, internal concrete beam 1
5 can be restrained by the steel pipe 11 to prevent the concrete 15 from protruding.

<B> Restraining action by the pressure bearing plate It is possible to prevent the concrete 15 from attempting to come out of the end portion of the steel pipe 11 during loading.

<C> Reinforcing Material Strengthening Effect of Reinforcing Material By including the reinforcing material 14, the maximum proof strength is improved by about 50% as compared with the concrete-filled steel pipe without the reinforcing material 14.

<D> Effect of Improving Deformation Ability by Not Introducing Tension to Reinforcement When tension is introduced to the reinforcement 14, the strength of the load bearing material 1 becomes somewhat stronger. However, as proved by the following experiment, when a tension force is introduced into the reinforcing material 14, the load-bearing material 1 receives a compressive force, so that the deformability decreases. Therefore, when a large load is applied, there is a drawback that the compression side has a lower strength than the tension side, and the crushing occurs earlier, and the strength sharply lowers and cracks occur in the steel pipe on the tension side. Therefore, in the present invention, the tension force is not introduced into the reinforcing material 14. As a result, the load-bearing material 1 does not receive a compressive force, so that the deformability is increased. However, the reinforcing material 14 does not have any tension force. That is, when the load-bearing material 1 is deformed, the reinforcing material 14 on the tension side is stretched, so that the tension force is first introduced at this point. Therefore, as is clear from the following experimental results, the load bearing strength is almost the same as when the tension force is introduced from the beginning, and the same strength can be obtained. Therefore, the load-bearing material 1 of the present invention can exhibit excellent effects in terms of load-bearing capacity and deformability.

[0008]

[Experiment content] The test piece used for the experiment is a steel pipe (material STK40
0, outer diameter 165.2 mm, pipe thickness 4,5 mm, length 2000 mm), unbonded type PC steel rod (diameter 17 mm, C class No. 1 [SBPR 1078
/ 1225]) and ordinary concrete (compression test strength 59.6MP
Using a), 13 types shown in FIG. 5 were produced.
In the production, first, a steel pipe coated with a release agent for concrete form was fixed vertically, and four PC steel rods were placed at predetermined positions (diameter 100 mm inside the steel pipe at equal intervals). After the placement, a concrete was placed. The concrete beam having the PC steel rod pulled out from the thus-produced specimen is the specimen BC shown in FIG. 5, and only the steel pipe is the specimen BST. Although the initial tension is not introduced to the sample BC, a fixing plate is attached.

The maximum pulling force required during this work is 4 tf
And the maximum adhesive stress is about 40-50 kpa (0.4-0.
It is considered to be 5 kgf / cm ² ). In addition, specimen B00
-1, B00-2 and B00-P are concrete-filled steel pipes without a PC steel rod, and B00-P is a steel pipe in which steel plates (plate thickness 10 mm) are adhered to the concrete surface at both ends of the specimen. Welded all around. B00-X, B03, B1
2, B24 and B36 are concrete filled steel pipes having a PC steel rod. Of these, B00-X is the present invention,
Initial tension is not introduced, but a fixing plate is attached.
Tensile force is introduced to other specimens, but for the tension of PC steel rod, steel discs (diameter 146mm, thickness 32mm) at both ends of the specimen.
Was used as a fixing plate, and the predetermined amount in FIG. 5 was introduced immediately before the loading test in order to avoid the influence of relaxation.

The two-digit number following the symbol B of the specimen name represents the initial stress of the concrete calculated assuming that the concrete does not adhere to the steel pipe. FIG. 1 shows an outline of a two-point loading bending test. At the fulcrum and the loading point, the steel plate bearing 16 (100 x
30 × 200 mm), and the bottom face of the bearing has a curved surface of 80R in the plate thickness direction so that the steel pipe and the steel plate bearing 16 can be in surface contact even if a large bending angle occurs.

[0011]

[Experimental Results] FIGS. 6 and 7 show the relationship between the load and the deflection at the center of the span. Specimen B00 (NO3,4), B12 (NO
8,9), B24 (NO10,11) and B36 (NO12,13) were tested in duplicate, and are shown separately for easy identification. The experiment revealed the following.

<A> The specimen BC lost bending strength from the initial stage of loading, and lost its yield strength due to crushing between loading points.

<B> The specimen BST lost its proof stress due to the progress of local buckling deformation generated inside the loading point. In addition, yield point stress degree 319MP obtained from short column test of steel pipe
When the collapse load is calculated using a (0.2% offset method), 1
It is 1.6tf.

<C> Specimen B00-1 and B00-2
The concrete part started to come out of the steel pipe when the load was about 11 tf, local buckling deformation became remarkable outside the loading point, and the yield strength was lost due to the fracture of the steel pipe of the cross section. B00
It can be seen from FIG. 5 that the maximum load of is approximately the sum of BST and BC. The advantage of the deformability of concrete-filled steel pipe is remarkable.

<D> Specimen B00-P has its effect because the steel sheets welded to both ends of the steel pipe prevent the concrete from coming out, but the maximum yield strength is B00-1.
Is almost the same as. The local buckling deformation progressed inside the loading point because the concrete did not come out, and the proof stress was lost due to the fracture of the steel pipe on the tensile side of the cross section.

<E> Specimen having a PC steel rod (NO6 to 1)
Regarding 3), the curve gradient after the concrete cracks are different depending on the magnitude of the introduced tension force.
The greater the tension, the earlier the local buckling deformation will occur,
It can be seen that it lacks deformability. However, their maximum proof stresses are almost the same, and specimen B00 without PC steel bar
-1,2, P (NO3 ~ 5) compared to the yield strength is increased about 60%. In these specimens, local buckling deformation became remarkable between the loading points, and the yield strength was lost due to the fracture of the steel pipe.

<F> The yield strain corresponding to the yield point stress degree obtained by the 0.2% offset method from the short column test of the steel pipe is about 3550 μ. The center deflection of the span when the maximum tensile strain of the beam reaches this value is defined as the yield deflection, and the yield deflection of the specimens NO3 to 13 was calculated from the measured axial strain and deflection of the experimental beam to be 8.0 to 9.8 mm. . When the concrete-filled steel pipe loses its yield strength, the beam deflection is the smallest B36.
-1 is 11 times the yield deflection, and B00-X and B0
It can be seen that the specimen having a PC steel rod as in 3 and having a small tension is 20 times or more. As described above, by filling the steel pipe with concrete, the bending deformation capability is dramatically increased, and the concrete can be prevented from coming off by the PC steel rod, and the bending strength can be increased by the reinforcement.

[0018]

[Example of Use] FIGS. 3 and 4 show examples of use of the load-bearing material 1 of the present invention. FIG. 3 shows an example in which it is used as a pillar such as a rockfall or an avalanche prevention fence. In this case, a rope and a net are stretched between load-bearing materials 1 which are erected at predetermined intervals. Also,
FIG. 4 shows an example of use as a beam material for a lock shed.

[0019]

Since the present invention is as described above, the following effects can be obtained. That is, the load bearing material of the present invention can obtain a concrete restraint effect by the steel pipe or the pressure bearing plate, and can improve load bearing capacity and deformability by the reinforcing material that does not introduce tension force. Therefore, the strength as a load-bearing material can be increased, and a large load-bearing force and deformability can be obtained with a small size without increasing the section modulus unlike the conventional H steel. Therefore, when it is used for falling rocks, avalanche prevention fences, lock sheds, etc., the construction is easy and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a side view of a load bearing material of the present invention.

[Figure 2] Front view

[Figure 3] Example of use when used as a rockfall prevention fence

[Fig. 4] Example of use when used as a lock shed

FIG. 5 is an explanatory diagram showing a list of test specimens.

FIG. 6 is an explanatory diagram showing the relationship between the load and the deflection at the center of the span.

FIG. 7 is an explanatory diagram showing the relationship between the load and the deflection at the center of the span.

Claims (1)

[Claims] 1. A steel pipe having both ends open, pressure bearing plates arranged at both ends of the steel pipe, and an unbonded steel wire or steel rod axially housed in the steel pipe and having both ends fixed to the pressure bearing plate. A load-bearing material consisting of concrete filled in a steel pipe.