JPH11141176A - Over damping structure - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a structure capable of significantly improving the seismic performance of a structure. SOLUTION: An over-damping is set by setting a damping coefficient Cn so that a damping force of a structure is larger than a restoring force. That is, the damping rate hn is set to be larger than 1.00, and the structure is made such that the structure can hardly vibrate naturally. As a damper for obtaining a damping force, a viscous shear wall having a structure in which a viscous body or a viscoelastic body having a large viscous resistance is sandwiched between steel plates is used. Structural members such as columns and beams have only the proof stress against long-term loads, and their cross sections are reduced, thereby reducing the spring constant Kn and further increasing the damping rate hn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an effective structure capable of improving the seismic performance of a structure.

[0002]

2. Description of the Related Art As a well-known structure for ensuring the seismic performance of a structure, a structural structure that is strong enough to increase the resistance to seismic force has been long and generally used. Seismic and damping structures have been proposed and put into practical use. The seismic isolation structure reduces the response by supporting the entire building with seismic isolation devices such as laminated rubber to reduce the seismic motion input to the building. The seismic isolation structure uses the seismic energy input to the building. Is controlled by a damping device such as a damper to absorb response.

[0003]

By the way, in a conventional general load-bearing structure which does not use a damper or the like, in order to increase the resistance against seismic force, the cross-section of the structural members such as columns and beams is inevitably increased, resulting in high rigidity. The structure becomes a short-period type structure, and as a result, a vicious cycle occurs in which the seismic force input to the structure increases and the cross section of the member further increases.

On the other hand, in the conventional seismic isolation structure, the seismic input to the structure is greatly reduced, and the acceleration response is sufficiently reduced. On the other hand, the displacement response is increased. Since the foundation needs to have a double structure for installation, an increase in construction costs cannot be avoided, and there is a problem that long-term maintenance is required for the seismic isolation device.

Further, the vibration control structure is to install various dampers such as an oil damper, a viscous damper, a steel damper, and a friction damper at important points of the structure to absorb vibration energy and attenuate vibration. Conventionally, there is no large-capacity damper capable of overdamping, and the conventional damping structure only absorbs a small part of the seismic energy, so that the deformation of the structure can be sufficiently suppressed. Although it is not a structure, it is basically a precondition for securing the structure's resistance to seismic force even though it is a seismic control structure.

In view of the above circumstances, the present invention is intended to provide an effective structure capable of significantly improving the seismic performance of a structure, instead of the conventional load-bearing structure, seismic isolation structure, and vibration control structure. .

[0007]

In general, a structure can be modeled as a vibration system having a mass, a spring, and a damper (damping mechanism). However, in the present invention, the damping force of the damper in such a vibration system is converted into a restoring force by a spring. By making it larger than that, that is, by making it overdamped, an overdamped structure in which the structure can hardly vibrate naturally is realized. That is, the present invention relates to a structure in which the n-th layer counted from the uppermost layer has a mass Mn, a spring constant Kn, and a damping coefficient Cn.
The damping coefficient Cn is set so that the equivalent effective gross mass ま で Mn, its natural period T ₁ , and its damping rate hn up to the first hierarchical level satisfy the following relationship.

(Equation 4)

[0008] The equivalent effective total mass 良 い Mn may be obtained by any of the following.

(Equation 5) Here, the above natural period T ₁ is the first natural period of the vibration system including the mass Mn and the spring constant Kn obtained assuming that there is no damping coefficient Cn, or the first natural period of the vibration system in consideration of the damping coefficient Cn.

(Equation 6)

In the present invention, since it is necessary to employ a damper having a large damping force, it is preferable to provide such a function as a damper to the earthquake-resistant wall. That is, if the earthquake-resistant wall itself provided at a key point of the structure is configured as a viscous earthquake-resistant wall that functions as a damper by sandwiching a viscous body or a viscoelastic body having a large viscous resistance (for example, 60,000 pois or more) between steel plates. It is possible to naturally obtain a large damping coefficient Cn and to freely set the damping coefficient Cn to a desired value.

Generally, when the cross section of a structural member such as a column or a beam is reduced to reduce the spring constant Kn of the structure, the damping rate hn naturally increases according to the above equation, which is more advantageous in increasing the damping force. . In the overdamped structure according to the present invention, since the structure can hardly vibrate even during an earthquake, the structural member hardly needs to withstand the seismic force. The member can be of a small cross-section having only a proof stress against a long-term load, which is preferred.

[0011]

Embodiments of the present invention will be described below. FIG. 1 shows a model of the overdamped structure of the present invention as a vibration model of a multi-mass system. In the present embodiment, as shown in FIG. 1, in the structure having the mass Mn, the spring constant Kn, and the damping coefficient Cn, the equivalent effective gross mass from the top layer to the n-th layer counted from the top layer, as shown in FIG. The attenuation coefficient Cn is set so that ΣMn, its natural period T ₁ , and its attenuation rate hn satisfy the following relationship.

(Equation 7)

Although there are various methods for obtaining the above-mentioned equivalent effective total mass ΣMn, it is preferable to use one of the following. However, it is not limited to this.

(Equation 8)

(Equation 9)

Satisfying the above relationship for all levels of the structure means that the damping force of the vibration system is greater than the restoring force, and therefore that the vibration system cannot vibrate. means. In other words, the over-damped structure modeled in this manner does not resonate even if subjected to seismic force only by performing the same motion as the ground motion with a predetermined phase difference. All of acceleration, velocity, and displacement are reduced as compared with the structure, and the input energy to the structure is almost zero.

The damping rate h in a conventional general structure
The value of is about 0.02 for a steel structure and about 0.05 for a reinforced concrete structure, and is a conventional vibration control structure incorporating oil dampers and other vibration control dampers at key points. Is about 0.10 to 0.3 even in the case of.

Incidentally, in order to realize the above overdamping, it is necessary to employ a damper having a large damping coefficient Cn. As such a damper, for example, a viscous shockproof wall as shown in FIGS. 2 and 3 is used. It is preferable to adopt 1.

The seismic control wall 1 includes a column 2 and a beam 3 (3a, 3a).
b), and a small gap is formed between the steel plate 4a fixed to the lower beam 3a and the steel plate 4b fixed to the upper beam 3b. And laminated alternately, and a viscosity of 6 between the steel plates 4a and 4b.
The viscous body 5 having a high viscous resistance of 10,000 pois or more, such as rubber asphalt, is sandwiched between the steel plates 4a and 4b in a state where the viscous body 5 is adhered to the steel plates 4a and 4b. Reference numerals 6a and 6b denote mounting plates fixed to the steel plates 4a and 4b, and reference numeral 7 denotes a mounting plate 6.
An anchor for fixing each of the steel plates 4a, 4b to the beams 3a, 3b via a, 6b.

The viscous earthquake-resistant wall 1 having the above-described structure has high rigidity and high toughness while being thin as a whole, and is nondestructively large-deformable and can be restored. is there. For example, steel plates 4a, 4 having a thickness of 16 mm
b are alternately superposed on each other, and rubber asphalt having a thickness of 2 mm (viscosity of 60,000 to 100
With a total thickness of only 88 mm, it can have the same level of rigidity as a 500 mm thick reinforced concrete earthquake-resistant wall, and has the undesirably high toughness of reinforced concrete Things. Of course, the damping force can be freely set by adjusting the type of the viscous material, the number of laminated steel plates, the size, and the like.

Therefore, by appropriately arranging the above-mentioned viscous earthquake-resistant wall 1 at a key point of a structure, a large damping force that satisfies the above equation is given to this structure, and the overdamped structure is easily formed. realizable. With such an over-damping structure, when the upper and lower beams 3a and 3b undergo interlayer displacement during an earthquake, the viscous shear wall 1 exerts an extremely large damping force and the two steel plates 4a and ,
4b is only slightly displaced in the plane (about 2 to 4 mm), and almost no vibration can be generated. FIGS. 4 and 5 show a specific example in which the above-mentioned viscous earthquake-resistant wall 1 is arranged at four corners of a low-rise large-span structure and overdamped.

As is apparent from the above equation, it is advantageous to increase the damping coefficient Cn and decrease the spring constant Kn in order to increase the damping rate hn in order to realize overdamping. It is preferable to reduce the spring constant Kn by making the structural members small in cross section.
And, as described above, since the structure can hardly vibrate even in the event of an earthquake in an overdamped structure, it is not necessary for structural members such as columns and beams to take into account the seismic resistance. The structural member can have a small cross section enough to ensure the proof stress against a long-term load. In other words, in such an overdamping structure, almost all of the seismic load is borne by the damper such as the viscous shear wall 1, and therefore, structural members such as columns and beams need to bear only a long-term load. In other words, this structure is a new type of structure in which the structure is sufficiently softened so that the ratio of seismic energy flowing to the viscous shear wall 1, which is a large-capacity damper, approaches 100%. As a result, in this structure, it is possible to significantly reduce costs by increasing the cross section of the structural member and to expand the effective indoor space.

It should be noted that the present invention is not limited to the form, scale, application and structure of the structure,
It can be applied to SRC structures and other arbitrary structures, and can be widely applied from low-rise buildings including single-story buildings (in the case of n = 1) to high-rise buildings. Of course, it is also possible to implement it for the purpose of seismic reinforcement of objects.

[0021]

As described above, the overdamping structure of the present invention
Since the damping rate hn of the structure is set to be larger than 1.00, that is, the damping force is set to be larger than the restoring force, it hardly vibrates even in the event of an earthquake, so that the seismic performance is remarkably excellent. A structure can be realized. In particular, by providing a viscous earthquake-resistant wall that functions as a damper, it is possible to easily obtain an extremely large damping force and easily adjust the damping force. It is possible to make the cross section as small as possible, and by doing so, the attenuation rate can be increased, which is more advantageous.

[Brief description of the drawings]

FIG. 1 is a diagram showing a vibration model of an overdamped structure of the present invention.

FIG. 2 is a side sectional view showing an example of a viscous shear wall applied to the overdamping structure of the present invention.

FIG. 3 is a front view of the same.

FIG. 4 is an elevation view showing an example of a structure to which the overdamping structure of the present invention is applied.

FIG. 5 is a plan view of the same.

[Explanation of symbols]

Mn mass Kn spring constant Cn damping coefficient ΣMn equivalent effective total mass T ₁ natural period hn attenuation factor 1 viscous shear wall 4a, 4b steel 5 viscous body

Claims (5)

[Claims] 1. An n-th layer counted from the top layer has a mass M
n, a spring constant Kn, and a damping coefficient Cn, the equivalent effective gross mass ΣMn from the top layer to the n-th layer, its natural period T ₁ , and its damping rate hn satisfy the following relations. An overdamping structure characterized by setting a coefficient Cn. (Equation 1) 2. The overdamping structure according to claim 1, wherein said equivalent effective gross mass ΣMn is obtained by the following equation. (Equation 2) 3. The overdamping structure according to claim 1, wherein said equivalent effective gross mass ΣMn is obtained by the following equation. (Equation 3) 4. The overdamping structure according to claim 1, wherein said damping coefficient Cn is set by providing a viscous shear wall functioning as a damper on said structure. 5. The overdamping structure according to claim 1, wherein said spring constant Kn is set in consideration of only a long-term load of said structure.