JPH0517959A - Earthquake resistance reinforcing device for existing structure - Google Patents

Abstract

PURPOSE:To provide an earthquake resistance reinforcing device relating to an existing structure especially that a ground liquefaction counter measure can be effectively and rationally performed. CONSTITUTION:A plurality of extension piles 2 are driven in the periphery of an existing structure 1 to provide an extension footing 3 integrally formed with an existing footing 3 of the existing structure 1 in a head part of these extension piles 2. Further, a damping device is provided in the extension footing 3 to connect this damping device to the extension piles 2 so as to constitute a three-dimensional truss by a plurality of diagonals 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic retrofit device for an existing structure which is capable of preventing damage to the existing structure due to liquefaction of the ground during an earthquake.

[0002]

2. Description of the Related Art In general, looking at the collapsing damage of structures during past earthquakes, the cause is often due to the liquefaction phenomenon of the ground.

The liquefaction phenomenon of the ground can cause catastrophic damage, since it sometimes dramatically increases the dynamic response of structures during earthquakes. Therefore, it is necessary to take liquefaction measures for structures that are important for urban functions and social life, special structures such as oil tanks where safety is essential, or commercial and residential buildings. .

Conventionally, various methods have been carried out as a liquefaction countermeasure method for this structure. Particularly, for a new structure, design consideration and ground improvement at the stage of foundation construction are carried out. It is planned.

However, there are various restrictions and it is not easy to carry out such a countermeasure method by ground improvement for existing structures.

However, at present, since there is no other effective construction method, the same construction method as the liquefaction countermeasure construction method for a new structure is only taken.

When the typical liquefaction countermeasure method is increased by a few, firstly, the method for increasing the ground density by compaction such as vibration (for example, sand compaction pile method, vibroflotation method, etc.) Named
Secondly, there are construction methods (for example, gravel drain construction method, drainage construction method using artificial drain material) for the purpose of suppressing soil pore water pressure during an earthquake.

[0008]

However, all of these construction methods are limited to prevent the liquefaction of the ground around the existing structure, and it is almost impossible to improve the entire ground immediately below the structure. However, it is hardly applicable to a structure that is large in plan. In addition, a structure with a long extension such as a viaduct of a railway or a road requires a large amount of money and is practically impossible.

Further, generally, since the ground around the foundation is improved by applying vibration or the like, there is a possibility that the existing structure may be deformed. Therefore, the immediate improvement such as piles and footings cannot be performed. . Furthermore, there are some that cannot be implemented due to the structure or the surrounding environment.

The present invention has been proposed in order to solve the above-mentioned conventional problems, and it is possible to effectively and rationally take a liquefaction countermeasure for an existing structure, and to enhance the seismic resistance of the existing structure. The purpose is to provide a device.

[0011]

In the seismic retrofitting method for an existing structure according to the present invention, a plurality of additional piles are driven around the existing structure, and an additional footing is attached to the head of the additional pile. The additional footing is provided integrally with the existing footing of the existing structure, and a damping device is provided in the additional footing. The damping device and the additional pile are connected by a plurality of diagonal members so as to form a space truss.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an illustrated embodiment (see FIGS. 1, 2, and 3). A plurality of additional piles 2, 2 are installed at several locations around an existing structure 1 such as a storage tank. 2 are cast. Steel pipe piles are mainly used for the extension piles 2 and 2,
Three to four pieces are placed in one place in a triangular or quadrangular arrangement in plan view, and additional footing 3 is placed on the head of the piece.
Is built integrally with the existing footing 4.

The additional footing 3 is formed in a triangular or quadrangular shape in plan view corresponding to the layout shape of the additional piles 2 and 2. When it is difficult to integrate the existing footing 4 with the existing footing 3, 4 and RC beams or PC beams are connected to achieve integration (not shown).

The concrete of the approximately central portion of the extension footing 3
A space 6 made of an outer shell steel plate 5 is provided in the container. The space portion 6 is formed in a flat shape, and the resistance plate 7 is installed in the space portion 6 so as to maintain a minute gap with the outer shell steel plate 5,
Moreover, a highly viscous substance 8 such as silicon or isobutylene is filled between the outer shell steel plate 5 and the resistance plate 7.
That is, a highly viscous damping device is formed in the concrete in the substantially central portion of the additional footing 3.

The resistance plate 7 and the pile 2 of the high-viscosity damping device configured as described above are connected to each other by a diagonal member 9. The lower end of each diagonal member 9 is connected to the side of each additional pile 2, the upper end is pulled to the central portion, and is connected to the approximately central portion of the resistance plate 7, so that the diagonal members 9 and 9 are A three-dimensional truss is constructed in the ground. The connecting portion of the diagonal member 9, the additional pile 2 and the resistance plate 7 is a pin joint so that it can move freely.

Since the additional pile 2 does not need to support the vertical load, it may be shorter than the existing pile depending on the case. As a result, it is possible to further reduce vibration during the construction of the additional pile.

In such a structure, the operation at the time of an earthquake will be described.

When a relative displacement occurs between the outer shell steel plate 5 and the resistance plate 7 due to the seismic force, the viscosity of the highly viscous substance 8 and the viscosity substantially proportional to the velocity gradient between the outer shell steel plate 5 and the resistance plate 7 are generated. Resistance is exerted.

Considering the vibration of the pile at the time of an earthquake, generally, a displacement distribution in which the displacement of the head is larger than that in the underground part is shown (see FIG. 9). In addition, at a certain depth in the ground, there is a fixed point corresponding to a node of vibration. Therefore, the pile body 2 and the resistance plate 7 of the viscous damping device at a certain depth in the underground portion.
When the and are connected by a plurality of diagonal members 9 so as to form a space truss, the resistance plate 7 causes substantially the same horizontal displacement as the pile in the ground. As a result, a relative displacement (velocity) occurs between the outer shell steel plate 5 and a viscous resistance force corresponding to the velocity gradient is exerted. Therefore, a large damping force is added to the vibration of the pile foundation.

By the way, when the ground is liquefied, the spring action between the pile and the ground is extremely reduced, so that the pile head displacement tends to be very large, and a viscous damping device such as that of the present application is not usually installed. In the pile foundation, the head of the pile is temporarily close to the protrusion, so the vibration of the superstructure supported by the pile foundation becomes very large, which may cause an earthquake, and the pile foundation itself. Even in the case, excessive stress is generated in the pile body, which may cause damage.

However, such a situation can be avoided in the pile foundation of the present invention provided with the viscous damping device. In other words, the horizontal stiffness of the vibration system of the entire foundation sharply decreases with a decrease in the spring action between the pile and the ground, but the apparent damping constant of the viscous damping device greatly increases accordingly. It is possible to suppress the vibration of the entire foundation.

In the examples, the case of liquefaction has been described, but even if the ground is not liquefied at the time of an earthquake, even in the state of ground softening due to an increase in pore water pressure,
It is also effective in the ground where the ground surface is composed of soft soil layers.

Next, the construction method will be explained step by step.
(See Figures 4, 5 and 6).

Three to four additional piles 2 are placed adjacent to the existing pile foundation.

Subsequently, the upper end of the diagonal member 9 previously attached to the pile 2 is pulled to the center between the piles 2, 2. At this time, jet water is jetted from a large number of water jet pipe ejection ports provided on the diagonal member or a large number of water jet pipe ejection ports that can be mounted only when tilted to assist this work. Subsequently, the ends of the diagonal members 9 and 9 drawn out from the piles 2 and 2 are connected to form a space truss structure in the underground part.

Subsequently, a highly viscous damping device including an outer shell steel plate 5, a resistance plate 7 and a highly viscous substance 8 is installed on the top of the truss composed of the diagonal members 9, 9. Next, an additional footing is constructed by placing a concrete on the damping device.

Although FIGS. 7 and 8 show the case where the double-cylinder-shaped high-viscosity damping device is used, other high-damping rubber can be used.

[0028]

Since the present invention is constructed as described above, it has the following effects.

If the pile foundation is constructed by the low-vibration method, the existing structure will not be adversely affected during the reinforcement work.

With the conventional construction method, it is not possible to treat the ground directly under the structure and it cannot be applied to a structure having a large planar scale, but it can be dealt with only the outer periphery of the structure, and there is a restriction on the planar size of the structure. Absent. It is also effective for structures with long extension.

Since the effect is further enhanced with the softening of the ground due to liquefaction, so-called “stickiness” is obtained.
It can be said that it is a construction method with characteristics.

When the ground is liquefied, the vibration control effect does not largely depend on the ground conditions, so that the design conditions are not greatly affected by the unevenness of the ground.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing a structure of a base portion of an existing structure.

FIG. 2 is a plan view showing a structure of a base portion of an existing structure.

FIG. 3 is a vertical cross-sectional view showing a structure of a base portion of an existing structure.

FIG. 4 is a side view showing a method of constructing a foundation portion of an existing structure.

FIG. 5 is a side view showing a method of constructing a foundation portion of an existing structure.

FIG. 6 is a side view showing a method of constructing a foundation portion of an existing structure.

FIG. 7 is a partial perspective view showing a structure of a base portion of an existing structure.

FIG. 8 is a plan view showing a structure of a base portion of an existing structure.

FIG. 9 is an explanatory diagram showing a vibration mode of a pile during an earthquake.

[Explanation of symbols]

1 ... Existing structure, 2 ... Additional pile, 3 ... Additional footing, 4
... Existing footing, 5 ... Outer shell steel plate, 6 ... Space part, 7 ... Resistance plate, 8 ... High viscosity material, 9 ... Slanting material.

Claims (3)

[Claims] 1. A plurality of additional piles are driven around an existing structure, an additional footing is integrally provided with the existing footing of the existing structure at the head of the additional pile, and the additional footing is provided. A seismic reinforcement device for an existing structure, wherein a damping device is provided, and the damping device and the additional pile are connected by a plurality of diagonal members so as to form a space truss. 2. An additional pile is driven around an existing structure, the head of the additional pile is integrally connected to the existing footing of the existing structure, and the additional pile is installed between the additional footing. A seismic reinforcement device for existing structures, which is equipped with a damping device. 3. The seismic reinforcement device for an existing structure according to claim 1, wherein a high viscous damping device is used.