JPH03183874A - Earthquake isolation device - Google Patents

Abstract

PURPOSE:To obtain a comprehensive energy absorption function by fixing one end of a steel bar to the foundation, connecting the other end to a building construction through a spherical member and, at the same time, forming a cross sectional area of the steel bar into a taper shape along it from the foundation side. CONSTITUTION:An earthquake isolation device is provided between a building construction 5 and the foundation 6, a load of the construction 5 is born, and the response control device is constituted of an elastic body having an elastic deformation for absorbing a shock caused by horizontal earthquake force and a steel bar 7 having an elastic and plastic deformation for absorbing a shock caused by horizontal earthquake force. After that, in the steel bar 7, the lower part 7a thereof is only inserted into the lower foundation 6 like a cantilever beam, the steel bar has a taper shape along it from the upper part 7b to the lower part 7a, and the upper part 7b is connected to a damper receiving steel holder 9 through a spherical sliding bearing 8. According to the constitution, a sectional area of the steel bar 7 is gradually reduced in correspondence with moment to generate, so that plastic strain can be equalized over the whole of the steel bar.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a seismic isolation device constructed by arranging an elastic body and a steel rod in parallel between a building structure and a foundation.

(Prior Art) Conventionally, as shown in FIG. 2, this type of seismic isolation device uses a bow 111 that is elastically deformed by horizontal seismic force while supporting vertical loads between the building structure 1 and base W2. A structure in which a steel rod 4 of a constant cross-sectional area that undergoes elastic deformation and then plastic deformation due to horizontal seismic force is installed side by side has been proposed.
(See Japanese Patent Application Laid-Open No. 60-223576). In this proposal, both upper and lower ends 4a and 4b of the steel rod 4 are loosely fitted into the structure 1 and the foundation 2, so that they are simply supported.

(Problem to be solved by the invention) By the way, in the above-mentioned seismic isolation device, since the cross-sectional area of the steel rod 4 is set to be the same along the axial direction from the foundation 2 side to the building structure 1 side, In response to the moment distribution that occurs during an earthquake, a high stress is generated in the bar 4 approximately at its center in the axial direction, and as a result, a large elastic strain is concentrated only in the center, not in the entire steel bar 4, and eventually plastic strain is generated. For this reason, the range of seismic force in which the steel rod 4 can absorb energy through elastic-plastic deformation is relatively narrow, limited by the rigidity, proof strength, etc. of the central portion. There was a problem that it was not possible to respond to a wide range of earthquakes, from small to large earthquakes.In other words, the rigidity of the central part,
If the steel rod 4 is designed with a large constant cross-sectional area in consideration of the strength, etc., it will exhibit a favorable energy absorption effect against large seismic forces, but the rigidity of the steel rod 4 will decrease against small seismic forces. If the steel bar 4 is designed with a constant cross-sectional area, it will exhibit an appropriate seismic isolation function against small seismic forces. However, there was a problem in that they easily fractured and destroyed in response to large seismic forces, and in either case, a wide range of energy absorption functions could not be obtained.

Therefore, generally, the steel rod 4 is designed with a certain cross-sectional area that corresponds to earthquakes that occur frequently, in order to exhibit an effective energy absorption effect against such earthquakes. In some cases, the deformation could not be followed and there was a risk of breakage.

Considering that a large relative movement occurs between the foundation 2 and the building structure 1 due to the action of a large seismic force, a large allowable deformation amount corresponding to this relative movement should be set for the steel rod 4. It is possible to increase the length of the steel rod 4, but this will widen the elastic deformation range of the steel rod 4, and in the range of small and medium earthquakes, only elastic deformation will occur, making it impossible to obtain sufficient seismic energy absorption capacity. It turns out you can't do it.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a seismic isolation device that can be applied over a wide range from small earthquakes to large earthquakes.

(Means for Solving the Problems) The present invention provides an elastic body that is elastically deformed to buffer horizontal seismic force while supporting the load of the building structure, and a horizontal seismic force between the building structure and the foundation. In a seismic isolation device in which steel rods that are deformed elastically and plastically to absorb force are installed in parallel, one end of the steel rod is fixed to the foundation and the other end is connected to the building structure via a spherical member. It is characterized by being formed into a tapered shape so that its cross-sectional area gradually decreases along the axial direction from the foundation side to the building structure side.

(Function) To describe the function of the present invention, one end of the steel rod is fixed to a foundation and the other end is connected to a building structure via a spherical member, and the steel rod is arranged like a cantilever. By forming the bar into a tapered shape so that the cross-sectional area of the bar gradually decreases along the axial direction from the foundation side to the building structure side, the stress distribution that occurs along the axial direction of the steel bar during an earthquake is made uniform. As a result, the generated elastic strain, and eventually plastic strain, can be made uniform over the entire steel rod. This results in
It can be expected to function as a damper in a wide range of situations, from small to large deformations, by suppressing the occurrence of large local plastic strains in the steel rod.

(Example) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a seismic isolation device according to the present invention.

The present invention basically includes: between the building structure 5 and the foundation 6;
A seismic isolation device in which an elastic body that is elastically deformed to support the load of a building structure 5 and buffer the horizontal seismic force, and a steel rod 7 that is deformed plastically to absorb the horizontal seismic force are arranged side by side. , one end 7a of the steel rod 7 is fixed to the foundation 6 and the other end 7b is connected to the building structure 5 via the spherical member 8, and the cross-sectional area of the steel rod 7 is changed from the foundation 6 side to the building structure 5 side. It is formed into a tapered shape so as to gradually decrease along the axial direction of the navel.

The seismic isolation device of this embodiment is interposed between the upper base 115 on the building structure side and the lower base 1i11i6 on the ground side,
It is composed of an elastic body (not shown) that supports a vertical load and deforms elastically in response to a horizontal load such as an earthquake force, and a steel rod 7 that undergoes elastic deformation and plastic deformation in response to a horizontal load.

The lower part 7a of the steel rod 7 is formed with a uniform cross section, and the lower part 7a is connected to the middle part 7 by a first tapered part 7e formed so that the diameter gradually decreases upward.
Connected to C. This intermediate portion 7C is formed with a uniform cross section smaller in diameter than the lower portion 7a;
C is connected to the upper part 7b by a second tapered part 7d that is formed so that its diameter gradually decreases upward. This upper part 7b is formed with a uniform cross section having a diameter smaller than that of the middle part 7c.

The steel rod 7 is fixed by inserting only the lower part 7a into the lower foundation 6 like a cantilever beam, and as described above, the lower part 7a is inserted into the lower foundation 6 and fixed.
It has a tapered shape in the axial direction from a to the upper part 7b, and has a structure in which the upper part 7b is connected to a damper receiving steel frame 9 fixed to the lower part of the upper foundation 5 via a spherical sliding bearing 8. There is.

The steel rod 7 of the full length example is a steel rod with a circular cross section, for example, the diameter of the lower part 7a is 160 nus, and the diameter of the middle part 7c is 14 ns.
The upper part 7b has a tapered shape with a diameter of 70 mm. This cantilever-like installation of the steel rod 7 is due to the structure and lower part 7.
By adopting a tapered shape from a to the upper part 7b, the cross-sectional area of the lower part 7a is increased in accordance with the generated moment, and as the moment becomes smaller, the cross-sectional area of the steel bar 7 is set to be gradually smaller. Therefore, plastic strain is not concentrated locally, but is generated approximately uniformly from the lower part 7a to the upper part 7b of the steel rod 7. As a result, the steel rod 7 can sufficiently follow deformations in a wide range from small to large earthquakes, and functions as a damper in a wide range from small to large deformations.

Furthermore, a reinforcing member 10 is provided between the lower portions 78 of the pair of left and right steel rods 7 to increase rigidity.

On the other hand, the above-mentioned elastic body has the same structure as the conventional structure, in which elastic sheets made of neoprene rubber or the like are formed into a flat plate, and metal sheets formed into the same shape are alternately laminated with an adhesive interposed. , flat plate-like end plates are attached to both ends of the plate, and each end plate is attached to the upper foundation 5.
and the lower foundation 6, respectively.

Furthermore, although the steel rod 7 can be replaced after a major earthquake, the lower part 7a of the steel rod 7 that supports the moment is embedded in the lower foundation 6, so it cannot be attached or removed with bolts. Therefore, follow the steps below for installation and removal. First, when removing the damper bearing 8, the spherical slide bearing 8 is removed from the steel frame 9, and then the steel rod 7 is shifted upward. For this purpose, the upper foundation 5 is provided with an upwardly extending hole 5a which accommodates the displacement of the steel rod 7. Further, the hole 5a is formed with a wide mouth toward the outside so that the steel rod 7 can be drawn out. Next, the lower part 7a of the steel rod 7 is lifted upward and extracted from the lower foundation 6, and then pulled out laterally, and in this way, the steel rod 7 is extracted from between the upper structure 5 and the lower base 116. This completes the removal work of the steel rod 7. In addition, when attaching the steel rod 7, the above procedure may be performed in reverse.

(Effects of the Invention) As explained above, according to the seismic isolation device according to the present invention, one end of the steel rod is fixed to the foundation and the other end is connected to the building structure via the spherical member, so that the steel rod cantilevers. By arranging the steel bars like a beam, and by forming the cross-sectional area of the steel bars into a tapered shape that gradually decreases along the axial direction from the foundation side to the building structure side, The resulting stress distribution is made uniform, and as a result, the generated elastic strain and eventually plastic strain can be made uniform over the entire steel rod.

As a result, the steel rod can be expected to function as a damper over a wide range of conditions, from small to large deformations, by suppressing the occurrence of localized large plastic strain, etc. in the steel rod.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing an embodiment of a seismic isolation device according to the present invention, and FIG. ff12 is a side sectional view showing an example of a conventional seismic isolation device. 5... Building structure (upper foundation) 6...
Foundation (lower foundation) 7... Steel bar 7a... One end of the steel bar (lower part) 7b... Other end of the steel bar (upper part) 8... Spherical member

Claims (1)

[Claims] Between the building structure and the foundation, there is an elastic body that is elastically deformed to support the load of the building structure and buffer the horizontal seismic force, and a steel that is elastically deformed to absorb the horizontal seismic force. In a seismic isolation device in which steel rods are arranged side by side, one end of the steel rod is fixed to the foundation, the other end is connected to the building structure via a spherical member, and the cross-sectional area of the steel rod is set on the foundation side. A seismic isolation device characterized in that the seismic isolation device is formed in a tapered shape so as to gradually decrease along the axial direction toward the building structure side.