JPH0458855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a joint structure between a hollow pile head such as a precast concrete pile and foundation concrete.

(Problems to be Solved by the Invention) Recently, cases of damage to piles have been reported as one of the damages caused by earthquakes. Among these, damage often occurs at the pile head of precast concrete piles. There are several causes for this damage, one of which is the bending moment of the pile head. Normally, pile heads are designed to be free from bending restraints, but looking at the actual damage situation, it is estimated that a fairly large bending moment was generated at the pile head, and this was a contributing factor to the failure of the pile head. .

Conventionally, in order to join the pile head and the foundation concrete, as shown in Fig. 4, a reinforcing bar cage 3 with fixed reinforcing bars 2 protruding upward is inserted into the hollow part of the head of a hollow pile 1 built underground. After inserting, fill concrete 4
and set the anchoring reinforcing bars 2 into the foundation. Thereafter, the foundation reinforcing bars 5 are arranged across the anchoring reinforcing bars 2, and the foundation concrete 6 is poured and constructed.

In this conventional joint structure, the pile head and foundation concrete are joined by filling concrete and anchoring reinforcing bars. Therefore, against bending moments, the filling concrete restrains the rotation of the pile head, and is also restrained by the pile head being swallowed into the foundation concrete (swallowing height h). Therefore, in the conventional joint structure, the bending restraint conditions do not fully realize the state of freedom from bending restraint, which is a design assumption.

This invention was made in view of the above circumstances. The purpose is to free the pile head from bending restraint, i.e.
The combination of the pile head and the foundation concrete is such that almost no resistance acts against the bending moment of the pile head, and the load of the superstructure can be safely and reliably transmitted from the foundation to the pile head and then to the supporting ground at the tip of the pile. We propose a joint structure.

(Means for Solving the Problems) The present invention will be described below with reference to illustrated construction examples.

In Fig. 1, a disk-shaped precast concrete cap 8 is attached to the head of a hollow pile 1 built underground, with a U-shaped fixing fitting 7 protruding from its upper surface.
is placed, foundation reinforcing bars 5 are arranged on the upper surface of the anchor metal fittings 7, and foundation concrete 6 is poured. In this configuration, the cap 8 has a truncated cone-shaped fitting portion 9 on its lower surface with an enlarged opening facing downward, which covers the head of the hollow pile 1 and is loosely fitted with the pile cap.

In addition, in the drawing, gravel 10 and waste concrete 11 are laid under the foundation concrete 6, and a water-stopping filler 12 is filled in the gap of the fitting part 9 that is loosely fitted with the pile head. ing.

The anchoring fitting 7 acts only on transmitting the shearing force between the pile and the foundation, and in addition to the one made by bending the reinforcing bar 13 in a U-shape and protruding from it as shown in Figures 1 and 2 a, it is also the one shown in Figure 2 b. The reinforcing bars 13 and steel pipes 14 can be fixedly assembled in a cross-shaped structure and protruded from the cap 8, and various other shapes can be made. The U-shaped and cross-shaped fixing fittings 7 are used when lifting and handling the cap 8. It is convenient and easy to hook.

The cap 8 is placed on one pile, has a size that covers the pile head, and has a disk shape or a square disk shape. The fitting part on the lower surface has a truncated cone-shaped fitting part 9 as shown in Fig. 1 and Fig. 3c, as well as a fitting part 9 with a size that fits loosely into the opening edge of the hollow pile 1 as shown in Fig. 3a. A fitting part 9 consisting of an annular groove with a trapezoidal cross section, or a truncated conical protrusion that fits loosely into the opening of the hollow pile 1 as shown in Fig. 3b, is cut out at the periphery of the lower surface of the cap. It may be the fitting part 9 or the like. Each of the fitting parts 9 must be loosely fitted and placed on the head of the hollow pile 1, and must be able to be joined in a state where the pile head is free from bending restraint without restricting its rotation.

(Function) This joint structure consists of the above-mentioned structure, in which the cap placed on the pile head is integrated with the foundation concrete via the fixing metal fittings protruding from the top surface, and the fitting part provided on the bottom surface connects the cap to the pile head. It fits loosely with the part. Therefore, the foundation concrete exhibits almost no resistance to the bending moment at the pile head. This prevents damage to the pile and ensures that the load of the superstructure is transmitted from the foundation to the pile cap, and from the pile cap to the supporting ground at the tip of the pile.

(Effect of the invention) This invention consists of the above configuration. This joint structure between the pile head and the foundation concrete provides the following effects.

Since it can be joined using precast concrete caps, construction labor can be reduced. Since the caps are manufactured according to the dimensions of the piles, they can be supplied in large quantities and at low cost, resulting in low costs. The bending restraint on the pile head is reduced, and the strength of the pile material can be lower than that required in conventional construction methods.
Pile cost is low. It is easy to check whether the construction has been completed properly. The protrusion length of the anchoring fittings into the foundation concrete is shorter and simpler than in conventional construction methods, so it is advantageous for storing foundation reinforcing bars, engaging with column main reinforcements, or interfering with foundation beams, improving workability. do.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view showing the joint structure between the pile head and the foundation concrete in the example, Figures 2a and b are sectional views of the cap with the fixing fittings protruding, and Figure 3
Figures a, b, and c are cross-sectional views of the pile head on which a cap is placed, and Figure 4 is a longitudinal cross-sectional view showing a conventional joint structure between the pile head and foundation concrete. 1...Hollow pile, 2...Fixed reinforcing bars, 3...Reinforcement cage, 4...Filled concrete, 5...Foundation reinforcing bars,
6...Foundation concrete, 7...Fixing metal fittings, 8...
...Precast concrete cap, 9...
Fitting part, 10... Gravel, 11... Waste concrete.

Claims (1)

[Claims] 1. A precast concrete cap with a fixing fitting protruding from the top is placed on the head of a hollow pile built underground, and foundation reinforcing bars are placed on the top of the cap to span over the fixing fitting. 1. A joint structure between a pile head and foundation concrete, characterized in that the cap has a fitting portion on the lower surface thereof and loosely fits into the pile head.