JPS60228108A - Manufacture of steel pipe concrete composite hollow pile - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel tube concrete composite hollow pile.

An object of the present invention is to manufacture a steel pipe/concrete composite hollow pile that has a sufficient and rational function as an earthquake-resistant pile and has a high bending resistance.

Conventionally, the performance required for piles was to withstand the impact force during driving and to withstand the load of the superstructure.

When a bending force is applied to the pile, a pile with a large diameter must be used, or a large number of steel pipe piles must be used, which is not economical. By the way, in recent years, as structures have become larger and more and more are being constructed on soft ground, it has become a problem that in the event of an earthquake, a considerably large bending force is applied to the pile due to the force of the structure trying to topple, and the bending force is greater than that of steel pipe piles. There is now a demand for something that has bending strength and is inexpensive.

Incidentally, in order to increase the bending strength of conventionally used PC piles, PC piles, and AC piles, it is possible to increase the amount of reinforcing bars, but the spacing between reinforcing bars becomes narrow, and the filling properties of concrete are poor, making it difficult to put it into practical use. Therefore, the idea was to create a steel pipe concrete composite, which has been used in few cases in the past, and it was considered that the following two elements are essential to make it the most effective pile against bending force. Ta. In other words, it is necessary that the steel pipe and Funkrete behave as a complete unit, and that the concrete has the strength and thickness to withstand the bending compressive force ζ when subjected to bending force. In order to satisfy the above two factors, concrete is poured into a steel pipe, centrifugally formed to ensure a constant thickness of concrete, and high-temperature and high-pressure steam curing is used to increase the strength of the concrete to ensure its strength. Furthermore, by adding an expandable admixture, the concrete was expanded and the integrity of the steel pipe and concrete was ensured.

Through these synergistic effects, the performance is significantly improved compared to conventional piles.Furthermore, the force that acts on each pile during an earthquake is not only the bending force caused by the force that causes the structure to overturn, but also the Although axial compressive force due to weight acts repeatedly at the same time, we have succeeded in providing a pile that can deal with bending force and axial force most effectively.

The details will be explained below.

The steel pipe concrete composite hollow pile obtained by the manufacturing method of this invention has an annular cross section as shown in the drawing, the outer layer is a steel pipe 1, and the inner layer is a concrete raw material containing an expansive admixture, which is centrifugally formed and then cured in an autoclave.The compressive strength is BOOK.
y/cm2 or more unreinforced concrete layer 2, steel pipe 1
and concrete layer 2 are closely integrated. The outer diameter of the steel pipe 1 is 600 to 600 mm, the thickness of the steel pipe 1 is 4.5 to 16.0 mm, and the wall thickness (the sum of the steel pipe thickness and the concrete thickness) is 60 to 9 Q Ill. be.

Further, in the figure, 3 is a joint end plate.

By the way, the ingredients of the concrete are cement 200~
600 parts (hereinafter all parts by weight) Aggregate 1600-2100
It is economical to use crushed stone as the zero-aggregate inner aggregate consisting of 20 to 100 parts of a partially expansive admixture and water, and a pile with excellent performance can be obtained.

As the expandable admixture, used are dead-burned magnesia, dead-burned dolomite, calcium sulfoaluminate minerals, and finely pulverized materials mainly composed of these minerals.

The autoclave curing is performed at a temperature of about 180° C., a vapor pressure of about 10 Kg/Crn2, and a curing time of 8 to 10 hours.

The mixed expandable admixture exhibits an expansion effect when cured in an autoclave, and the expansion of the concrete is restrained by the steel pipes, resulting in complete integration and a compressive strength of 800 kg/cm2.
That's all.

Further, the outer diameter and thickness of the steel pipe of the pile obtained by the manufacturing method of the present invention, and the wall thickness of the pile were determined for the following reasons.

In other words, piles manufactured by combining steel pipes and concrete are used to support overburden loads, as well as to support earthquake forces and lateral forces that are difficult to apply when a structure built on a slope moves laterally. Developed to support the power of Incidentally, when supporting only overburden loads, conventional PC piles or concrete piles cured with high temperature and high pressure steam may be used. The reason for this is that when a lateral force is applied, a bending force is generated in the pile, but the above-mentioned PC pile and the like are extremely weak against bending force and cannot be used.

However, the pile obtained by the manufacturing method of this invention was developed for the purpose of increasing this bending force. That is, when a bending force is applied, a compressive force and a tensile force are generated inside the pile on opposing surfaces centered around the longitudinal axis of the pile.

Looking at the properties of concrete, the compressive force is 1, while the tensile force is 1.
Since the tensile force is extremely weak, ranging from /10 to 1/13, it is only necessary to reinforce this weak part, and this is solved by covering the outer shell with a steel pipe. In other words, it is unclear from which direction a lateral force will be applied to the pile, and the pile has a non-directional shape, ie, a circle, and requires non-directional reinforcement, ie, steel pipe coating. Now, when it comes to specifications for the outer shell steel pipe determined for the purpose of reinforcement, it is only necessary to determine the amount, or thickness, that is comparable to the bending force expected of the pile. As mentioned above, the pile can be set by considering the conditions under which overload and lateral force act simultaneously and determining the allowable stress of concrete and steel.One constraint here is the regulation of the pile wall thickness. be.

In other words, the pile obtained by the manufacturing method of this invention may be used alone, or when the pile is lengthened, and may be jointed with a conventional inexpensive concrete pile for economic reasons. In particular, the latter is often the case, and considering this, it is unnecessary to increase the wall thickness of this pile to measure the smoothness of load transfer, such as when it is poured during construction, or to increase the wall thickness of this pile only. Therefore, the specifications need to be as thick as concrete piles. Therefore, the outer diameter of the steel pipe is 3001R~600.
It was my friend. Among these, it is sufficient to set the thickness at which the steel pipe works effectively.

Among the above conditions, considering the bending force applied to piles, considering the case where a fairly large earthquake occurs in an area where earthquake forces occur frequently, the Architectural Institute of Japan has established architectural foundation structure design standards and The calculation method and magnitude of force are determined, and standards are determined to reflect this in settings. According to these, the lateral force is usually around 0.2 per overload load of 1, but depending on the ground conditions, the shape of the upper structure, etc.
Force will be generated on the pile at a rate of about 0.4.

Now, the standard load per pile for each pile diameter is as follows, and the lateral force is also as follows.

Pile outer diameter Overload load (W) Lateral force (wxO, 1~0.
4) 300mi 40ton 4~1 6ton400
mm 70tOn 7~28tOn500mm 100
ton 1.0~4 Q ton600mm 130t
on 13 to 52 tons When these lateral forces act on the pile, the bending force generated in the pile has the following formula according to the standards of the above-mentioned academic society.

β is a constant determined by the ground properties.

By incorporating the lateral force applied to the pile into the above equation, the bending force can be calculated. This is the bending force generated in the pile, and the pile must be able to resist this. Once the necessary bending resistance is determined, the only thing left to do is to decide on the design of the pile body, that is, the thickness of the steel pipe.

By the way, regarding practical products, it is necessary to consider corrosion of steel pipes. In other words, it is necessary to consider that the pile will normally last for 80 years, and add the amount that will corrode and disappear during this period (approximately 2 Ill).

Considering the above, from the graphs shown in Figures 6 and 4 when bending force and overburden load act simultaneously (permissible M-N diagram), the steel pipe thickness is required to be 4.5 to 16.0 IIZ. Anything else is not necessary in terms of design.

Figure 5 shows the conventional example of piles with the same diameter (φ50 g xx ) and the allowable M of piles obtained by the manufacturing method of the present invention (steel pipe wall thickness t = 911 mm, concrete wall thickness 71 mm).
-N diagram. By the way, when there is always a force acting on a pile, it is sufficient to consider only the axial force, but during an earthquake, in addition to the axial force, lateral force acts and a bending moment is generated.

Also, in the event of an earthquake, if the constant axial force is 1, it will be 0 to 2.
It is said that the axial force fluctuates within the range of . Since a pile with a diameter of 500mm is allowed to have an axial force of up to 100t in design, an axial force of 100t acts on each pile. During an earthquake, the axial force normally varies between 0 and 2 times the axial force shown on line X, that is, 0 to 200 t, and a bending moment of approximately 30 TM acts. Therefore, to determine whether it is acceptable to apply an axial force of 100 t to a pile with a diameter of 500 mm, it is sufficient to check whether the line segment X falls within the triangle shown in the figure. In contrast, the pile produced by the manufacturing method of this invention has the apex of the triangle in an ideal position, allowing the pile to utilize its full potential. In other words, it is possible to most effectively deal with the simultaneous effects of bending force and axial force.

Moreover, FIG. 6 is an M-deflection diagram of a pile obtained by the manufacturing method of the present invention and a conventional pile with a diameter of 400 IIm. This pile exhibits outstanding performance in both the elastic modulus, which is shown by the slope of a straight line rising from the origin, and the bending strength, which is shown by the curve extending to the right.

Furthermore, according to the manufacturing method of the present invention, since the steel pipe and concrete are integrated, there is no decrease in rigidity even when repeated loads are applied. In other words, if the steel pipe and concrete are not integrated, the bending of the steel pipe will cause the inner surface of the steel pipe to be partially pressed against the outer surface of the concrete layer, for example in a state close to line contact.
Unlike concrete, where cracks accumulate in the layers and gradually reduce the rigidity and bending strength, the present invention has no such fear.

By the way, in this invention, the composition of concrete manufactured through centrifugal force forming and high temperature and high pressure steam curing process is 200 to 600 parts by weight of cement, 1600 to 1,600 parts by weight of fine aggregate and coarse aggregate.
A formulation consisting of 2100 parts by weight and water is optimal.
If less than 200 parts by weight of cement is added, it is difficult to ensure sufficient concrete strength, and if more than 600 parts by weight of cement is added, the concrete strength will only increase slightly, which is very uneconomical. Further, if the fine bone or coarse aggregate is less than 1,600 parts by weight, it is uneconomical, and if it is more than 2,100 parts by weight, the moldability by centrifugal force molding is not good, and the strength is also reduced.

The above-mentioned coarse aggregate mainly includes river gravel and crushed stone, but the strength of concrete is higher when crushed stone is used than river gravel.

In addition, the pile obtained by the manufacturing method of this invention has the performance of an earthquake-resistant pile without the need for reinforcing bars in the concrete layer, so it not only reduces the cost of reinforcing bars, but also improves the manufacturing process and the construction of the pile product. can bring benefits. That is, in the manufacturing process, steps such as organizing the reinforcing bar basket, inserting the reinforcing bar cage into the steel pipe, and tensioning the reinforcing bar can be omitted. Furthermore, if reinforcing bars are present, there is a risk of creating voids on the back side of the reinforcing bars during centrifugal forming, which is undesirable in terms of strength, but since this invention does not use reinforcing bars, no voids are created in the concrete layer. Ideal compaction is possible, and since there is no escape for the expansion force, the force can be used effectively, and the steel pipe and concrete are strongly integrated.

In addition, in terms of product construction, the pile obtained by the manufacturing method of this invention does not require reinforcing bars, making pile head treatment very easy. When trimming the pile head, if it is reinforced, cut the steel pipe in two or more places, peel the steel pipe, expose the concrete surface, destroy and remove the concrete, leave only the reinforcing bars, and then cut the shaft bars. However, since the manufacturing method of this invention eliminates the need for reinforcing steel, it is possible to trim the ends, which would be difficult to do, by simply cutting the steel pipe with gas and then bending it.

The reason why it is possible to omit reinforcing bars in steel pipe concrete piles is because this invention uses an expansive material, and this is combined with technical elements such as high-temperature, high-pressure steam curing.

As mentioned above, this invention integrates steel pipes and concrete,
Ensuring sufficient concrete compressive strength and concrete thickness ζ This results in superior performance improvement over any conventional pile, especially when axial forces that vary in value in addition to bending moments act. In addition, its M-N diagram can utilize the full capacity of the pile, that is, it can be used rationally.

Furthermore, it was able to withstand repeated loads and achieve perfect performance as an earthquake-resistant pile.

This invention has the above-mentioned structure, and has taken advantage of the advantages of both steel, which is extremely strong in tensile force, and concrete, which is extremely strong in compressive force, and as a result of the numerical limitations mentioned above, it has been completed as a so-called "ready-made pile". It is a pile with excellent performance.

[Brief explanation of the drawing]

Figures 1 and 2 are a cross-sectional view and a partially sectional front view of a steel pipe concrete composite hollow pile obtained by the present invention, and Figure 5 is an allowable M-N diagram for a pile with a diameter of 3001 g.
FIG. 4 is an allowable M- and -N diagram for a pile diameter of 6001 m, and FIGS. 5 and 6 are an MN diagram and an M-deflection diagram showing a comparison with the conventional example. 1. Steel pipe, 2. Concrete layer, 3. Joint end plate. Figure 5 Bending Moment/To Figure 6

Claims (1)

[Claims] (1) A concrete raw material with an annular cross section, the outer layer is a steel pipe, the inner layer is 200 to 600 parts by weight of cement, 1600 to 2100 parts by weight of aggregate including crushed stone as coarse aggregate, and an expansive admixture is centrifugally formed. A method for manufacturing a steel pipe-concrete composite hollow pile, which is then cured in an autoclave to form an unreinforced concrete layer with a compressive strength of 8 o K17 cm2 or more, and in which the steel pipe and concrete are closely integrated into one.