JPS6344894B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention facilitates fitting a part of a steel pipe to the outside of a concrete head for reinforcement.
The present invention relates to a method for reinforcing concrete pile caps with the aim of ensuring firm attachment.

Conventionally, piles with steel pipes fitted to the outside of the pile to reinforce the pile cap are known, but when manufacturing these piles, they are installed in a formwork together with reinforcing bars in advance, and concrete is poured into the formwork. Steel pipes are fitted and fixed, but for example, if the concrete pile cap is broken during footing, there is no way to fit the steel pipe back in, and it is used as is even though the strength has decreased. It was the current situation. Therefore, in order to reinforce this, construction methods such as crushing part of the pile cap to expose the reinforcing bars and burying them in the footings were used.

However, in this invention, since the steel pipe to be fitted to the concrete pile cap is heated and pressurized, fitting is easy, and the inner diameter of the steel pipe shrinks due to cooling contraction, making it possible to fit the pipe tightly to the pile cap. It can further strengthen the gender.

In this invention, the heating temperature of the steel pipe is preferably about 300°C. For example, when a steel pipe with an inner diameter of 500 mm is heated to 200°C, the inner diameter expands to approximately 501.1 mm, and when heated to 300°C, the inner diameter becomes approximately 501.6 mm, making it relatively easy to deform (increase in diameter) by applying pressure. However, since the temperature at which concrete is affected by heat is 300°C or higher, there is no risk of adverse effects on concrete even if the steel pipe is locally heated to 300°C and press-fitted. Also, although the pressure value is proportional to the amount of deformation of the steel pipe, for example, when heating a steel pipe with an inner diameter of 500 mm to a concrete pile cap with an outer diameter of 500 mm and fitting it to 300℃, it is easy to fit it with a pressure of about 20 kg. It can be fitted into.

That is, to explain this invention with reference to an embodiment, a concrete pile 1 having an outer diameter of 500 mm and an inner diameter of 500 mm is attached to the head of the concrete pile 1.
Fitting the lower end expanded portion 2a of the steel pipe 2 with a thickness of 7 mm,
(The maximum inner diameter of the expanded part is 515 mm) If the annular burner 3 is loosely fitted concentrically to the outside of the steel pipe 2 and the gas outlet of the annular burner 3 (inner diameter 600 mm) is ignited, the steel pipe 2 will be heated by the gas flame. heated. Therefore, P in Figure 1
If the steel pipe is pressurized from above, the steel pipe will easily descend and be fitted due to thermal expansion due to heating and deformation due to pressurization. In this case, care should be taken to keep the heating temperature at around 300°C on the heating surface of the steel pipe. In actual construction, there is no problem if the heating time and temperature for the wall thickness of the steel pipe and the amount of ejected gas are measured in advance, and the heating area is moved at predetermined intervals (to match the pressure fitting speed).

The above-mentioned press-fitting of the steel pipe may be performed by impact or by static pressure, but it is determined depending on the site situation and the required pressure value. Further, regarding the relationship between the inner diameter of the steel pipe and the outer diameter of the concrete, the inner diameter of the steel pipe is set to be equal to or slightly larger than the outer diameter of the concrete. Even if the inner diameter of the steel pipe is increased, the concrete head and the steel pipe must be tightly fitted in consideration of the shrinkage rate due to cooling.

By welding reinforcing bars 4 to the steel pipe and burying them in the footing, the connection between the concrete pile and the footing can be further strengthened. When the head of a concrete pile that was originally cast is destroyed over a predetermined length and the reinforcing bars are exposed, the strength of the top end of the pile decreases significantly (for example, there is no stress at all).
In such a case, fitting the steel pipe according to the present invention not only provides reinforcement, but also makes the connection between the pile and the footing even stronger.

That is, according to the present invention, since the steel pipes are fitted under pressure while being heated, the steel pipes can be fitted very easily and efficiently on site. Cooling after fitting also has the effect of making the fit between the pile and the steel pipe even stronger.

[Brief explanation of drawings]

Figure 1 is a sectional view just before implementing the invention, Figure 2 is a plan view, Figure 3 is a sectional view after fitting, and Figure 4 is a front view of a steel pipe with reinforcing bars welded to it. be. 1... Concrete pile, 2... Steel pipe, 3... Gas burner, 4... Rebar.

Claims (1)

[Scope of Claims] 1. A steel pipe expanded in a tapered shape so that the fitted end becomes larger in diameter toward the tip is brought into contact with the head of a concrete pile in order to be fitted therein, and while the steel pipe is heated, , a concrete pile cap reinforcement method characterized by applying pressure in the axial direction of the concrete pile and inserting a steel pipe to a predetermined depth. 2. The concrete pile cap reinforcing method according to claim 1, wherein the inner diameter of the steel pipe is equal to or slightly smaller than the outer diameter of the concrete pile. 3. The concrete pile reinforcing method according to claim 1, wherein the steel pipe is heated evenly over the entire circumferential surface of the steel pipe at a position immediately before fitting from the outer circumferential side.