JPS63118420A - Fortifying of concrete pile - Google Patents

Abstract

PURPOSE:To obtain a foundation with fortified head at low cost by a method in which carbon fibers are wound around a driven pile from the embedded portion to the pile head, and a structure is constructed on the pile head. CONSTITUTION:The head of a hollow reinforced pile 2 being driven is crushed to expose main reinforcing bar 3, and long carbon fibers 4 impregnated with a resin are wound around the exposed portion of the pile 2 from the natural ground 1 and clamped. Soil 5 is embedded on the pile head portion, and a footing 6 is constructed on the top of the pile 2. The foundation with fortified pile head can thus be constructed at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for reinforcing ready-made concrete piles used for the foundations of civil engineering and architectural structures.

(Prior art) Conventional concrete piles constructed specifically for the purpose of reinforcement are made by forming hollow reinforced concrete inside a steel pipe that serves as the outer shell, and restraining the inner concrete with the steel pipe, making it extremely strong against bending moments. There is.

Alternatively, the cross-sectional shape of the main reinforcing bars buried in the concrete can be made larger.

(Problems to be Solved by the Invention) In concrete piles having a steel pipe as an outer shell, the wall thickness of the steel pipe is often thicker than the actual required wall thickness because a general-purpose standard product is used. Therefore, it was stronger than necessary and was disadvantageous in terms of cost.

Furthermore, if the cross-sectional area of the reinforcing bars is increased, the concrete cover thickness cannot be ensured, and if the reinforcing bars are made densely packed, problems tend to occur in the packing density of the concrete.

In past earthquake damage to prefabricated piles, the pile caps often suffered extremely brittle shear compression failures, which has been confirmed in various experiments. Pile failure causes tilting and movement of the superstructure, but brittle failure involves more than just tilting;
This may even lead to a fall.

Generally, when the bending capacity is about 2/3 of the shear capacity, the structure has excellent toughness, but with steel pipe reinforcement, not only the shear force but also the bending capacity of the pile increases, and the capacity against shear failure does not necessarily increase.

Furthermore, even with the method of increasing the cross-sectional area of the main reinforcement, the shear strength hardly increases, so there is a risk of shear failure. It is difficult to properly evaluate the magnitude of the seismic force applied to piles during a major earthquake, but simply increasing the bending strength of piles will cause the shear force generated in the piles to increase more than expected and cause shear failure.
Unexpected damage may occur. Therefore, the above method does not necessarily improve seismic properties.

The present invention was made in view of the above circumstances, and an object thereof is to provide a method for reinforcing concrete piles that easily ensures sufficient strength using ready-made concrete piles.

(Means for Solving the Problems) In order to achieve the above object, the method for reinforcing concrete piles according to the present invention involves winding long carbon fibers around the exposed parts of the piles that have been driven into predetermined positions, and then attaching them to foundation slabs and footings. This involves reinforcing the midway point from the top of the pile that connects to the ground to the ground, which has a binding force, and constructing a structure on top of this reinforced pile.

(Function) After the pile is driven, only the pile cap that is most strongly affected by the shear stress generated between the structure and the ground is reinforced, thereby ensuring sufficient required strength. The parts connected to the foundation slab and footings and the parts that pass through the strong ground are restrained by the surroundings, so the restraining force from the surroundings is weak, and reinforcement near the pile cap of the backfill part where strong shear stress is applied. That's enough.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

In Fig. 1, a hollow reinforced concrete pile 2 is driven into the ground 1, and after its tip is inserted into the supporting ground, the pile head is crushed to expose the main reinforcement 3, and then the pile 2 is removed from the ground 1. The exposed part is wrapped with resin-impregnated long carbon fibers 4 and tightened, and then the top is backfilled (backfilling soil 5), and the main reinforcing bars 3 exposed on the top surface of the piles 2 are overlaid with reinforcing bars, and concrete is poured. A footing 6 is formed on the top of the drag 2 by pouring it, thereby transmitting the load of the structure to the supporting ground.

Hereinafter, FIGS. 2 and 3 show other embodiments in which the troublesome work of winding carbon long fibers involved in the embodiment shown in FIG. 1 is avoided.

That is, as shown in FIG. 2, the carbon length J! Concrete cylindrical body 7 with 1I4a as reinforcement
Prepare. The inner diameter of this cylindrical body 7 may be slightly larger than the outer diameter of the pile 2. As can be understood from FIG. 3, the pile 2 is driven into the ground 1 and then inserted into the exposed part, and mortar 8 is placed between the inner circumferential surface of the cylindrical body 7 and the outer circumferential surface of the pile 2. etc. are filled in. This eliminates the need to perform the troublesome work of winding carbon long fibers on site.

Through the above construction process, the concrete is restrained evenly from the outside by the long carbon fibers 4 so that compressive failure of the concrete in that part does not occur due to the gg shear stress applied to the pile cap part directly near the bottom of the footing.

(Effects of the Invention) As explained in detail above, according to the method for reinforcing concrete piles according to the present invention, after the pile is driven into a predetermined position, long carbon fibers are wound around the exposed part, so that the required minimum A limited amount of reinforcement is sufficient. In other words, the largest brittle fracture is most likely to occur in the area slightly below the pile cap, which receives the load, and this area is only covered with backfill soil, and damage to the foundation is difficult to repair. , it is possible to effectively protect and strengthen the parts that require the most strength.

This is economical and does not increase pile driving resistance.

In addition, since it uses long carbon fibers, it is lightweight and easy to handle, and has good durability even in corrosive ground such as volcanic areas and industrial waste landfills. Because of this, it can withstand actual use sufficiently, and also has the effect of following plastic deformation well.

[Brief explanation of the drawing]

FIG. 1 is a sectional view explaining the present invention in detail, FIG. 2 is a perspective view showing a second embodiment, and FIG. 3 is a sectional view showing an example of its use. 1... Earth Mountain 2... Reinforced concrete pile 3...
...Main reinforcement 4...Carbon long fibers 5...Backfill soil 6...
...Footing 7...Cylindrical body
8... Mortar patent applicant
Mitsubishi Chemical Industries, Ltd. Obayashi Corporation Representative Patent attorney −
Iranijisuke Patent Attorney Masatoshi Matsuki No. 1
Figure 2

Claims (2)

[Claims] (1) A method for reinforcing concrete piles, which comprises driving the pile into a predetermined position, then winding long carbon fibers from the backfilling portion to the pile head, and constructing a structure over the pile head. (2) The long carbon fibers are embedded in a concrete cylindrical body previously formed to have an inner diameter larger than the outer diameter of the pile in a spiral shape concentric with the concrete cylindrical body, and the concrete cylindrical body is placed at a predetermined location on the pile. 2. A method for reinforcing a concrete pile according to claim 1, characterized in that the concrete pile is inserted into the concrete pile and the gaps are filled with mortar or the like.