JP2694881B2 - Seismic retrofitting method for existing structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for seismic retrofitting 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 sometimes causes a catastrophic damage because it dynamically increases the dynamic response of the structure during an earthquake. Therefore,
Liquefaction measures must be taken 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 type of structure, and especially for a new structure, design consideration and ground improvement at the stage of foundation construction are performed. And it is done systematically.

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 construction method similar to the liquefaction countermeasure construction method for a new structure is only taken.

When the typical liquefaction countermeasure method is increased by a few times, firstly, the method for increasing the ground density by compaction such as vibration (for example, sand compaction pile method, vibro flotation method, etc.) The second method is a construction method (for example, a gravel drain construction method or a drainage construction method using an artificial drain material) for the purpose of suppressing the soil pore water pressure during an earthquake.

[0006]

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, it takes a great deal of money for a structure with a long extension such as a viaduct of a railway or a road, which is practically impossible.

[0007] In general, since the ground around the foundation is improved by applying vibration or the like, there is a risk that the existing structure may be deformed. Therefore, it is not possible to improve the piles, footings, etc. in the immediate vicinity. . In addition, the structure,
Alternatively, there are things that cannot be implemented depending on 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 measures against liquefaction of an existing structure so that seismic reinforcement of the existing structure can be achieved. The purpose is to provide a method.

[0009]

According to a first aspect of the present invention, there is provided a seismic strengthening method for an existing structure, wherein a plurality of additional piles are driven around the existing structure and the heads of the additional piles are mounted. An additional footing is provided integrally with the existing footing of the existing structure, a damping device for stopping horizontal shaking of the existing structure is provided in the additional footing, and the damping device and the additional pile are provided in plural units. It is configured by connecting the three-dimensional truss with diagonal members to form a three-dimensional truss.

According to a second aspect of the present invention, the method of seismic retrofitting an existing structure comprises placing a plurality of additional piles around the existing structure and providing an additional footing on the head of the additional pile. A damping device that integrally connects the additional footing and the existing footing of the existing structure and that stops the horizontal swing of the existing structure between the additional pile and the additional footing. ing.

According to a third aspect of the present invention, there is provided an earthquake-proof reinforcing method for an existing structure, which is constructed by installing a high-viscosity damping device as a damping device in the earthquake-proof reinforcing device for an existing structure according to the preceding two aspects. ing.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on an illustrated embodiment (see FIGS. 1, 2 and 3), and a plurality of additional piles 2 are provided at several places 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, and 3 to 4 piles are placed in one place in a triangular or quadrangular arrangement in plan view, and the extension footing 3 is installed on the head of the existing footing 3. It is formed as one with 4.

The additional footing 3 is formed in a triangular or quadrangular shape in plan view according to the arrangement and shape of the additional pile 2. In addition, if it is difficult to integrate the additional footing 3 with the existing footing 4, the additional footing 3 is formed separately from the existing footing 4 and then connected integrally with the existing footing 4 by RC beams or PC beams, etc. 3 and the existing footing 4 should be integrated (not shown).

A space 6 made of an outer shell steel plate 5 is provided in the concrete in the approximate center of the additional footing 3. 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 approximate center 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 portion of each diagonal member 9 is connected to the side portion of each additional pile 2, the upper end portion is pulled to the central portion, and is connected to one substantially in the central portion of the resistance plate 7. Therefore, 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 an earthquake force, a viscous resistance force substantially proportional to the viscosity of the highly viscous substance 8 and the velocity gradient between the outer shell steel plate 5 and the resistance plate 7 is generated. To be demonstrated.

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 the viscous damping device as in 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, in the pile foundation of the present invention provided with the viscous damping device, such a situation can be avoided. 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 FIGS. 4, 5 and 6). 3-4 adjacent to existing pile foundation
Place additional pile 2 of books. Subsequently, the upper end of the diagonal member 9 previously attached to the pile 2 is pulled to the center between the piles 2 and 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, 9 drawn out from the piles 2, 2 are connected to form a three-dimensional truss structure in the underground part.

Subsequently, a highly viscous damping device made of 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, concrete is placed on the damping device to create an additional footing.
7 and 8 show the case where the double-cylinder-shaped high-viscosity damping device is used, other high-damping rubber can also be used.

[0024]

Since the present invention is configured as described above, it has the following effects. According to the method for earthquake-proofing reinforcement of an existing structure according to claim 1 of the present invention, a plurality of additional piles are driven around the existing structure, and an additional footing is added to the head of the additional pile. Of the existing footing, and a damping device for stopping the horizontal shaking of the existing structure is provided in the additional footing, and the three-dimensional truss is composed of the damping device and the additional pile with a plurality of diagonal members. Therefore, there is an effect that it is possible to effectively reduce the horizontal sway of the existing structure, particularly during an earthquake.

In addition, since the structure is constructed around the existing structure, there is an effect that it can be effectively applied to a structure having a large planar scale and a structure having a long extension. In addition, since horizontal shaking of existing structures is reduced by the damping device, the seismic control effect does not greatly depend on the ground conditions when the ground is liquefied. It doesn't really matter. Further, since the effect is further enhanced with the softening of the ground due to liquefaction, it can be said that the method has a so-called "strong" property.

The additional piles installed around the existing structure are not installed to receive a vertical load, but are installed to receive a horizontal force such as seismic force, and therefore need to be installed particularly deeply. Therefore, there is an effect that construction can be easily performed.

According to a second aspect of the present invention, the method of seismic retrofitting an existing structure comprises placing a plurality of additional piles around the existing structure and providing an additional footing on the head of the additional pile. A damping device for integrally connecting the additional footing and the existing footing of the existing structure, and providing a damping device for stopping the horizontal swing of the existing structure between the additional pile and the additional footing. Therefore, it has the same effect as the seismic retrofit method of claim 1.

[Brief description of the 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 (2)

(57) [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 damping device for stopping horizontal shaking of the existing structure is provided, and the damping device and the additional pile are connected by a plurality of slant members so as to form a space truss. Reinforcement method. 2. A plurality of additional piles are driven around the existing structure, an additional footing is provided on the head of the additional pile, and the additional footing and the existing footing of the existing structure are integrally connected. A method for earthquake-proofing an existing structure, characterized in that a damping device for stopping horizontal shaking of the existing structure is provided between the additional pile and the additional footing.