1. Field of the Invention
The present invention relates to a metal joint connected between a pair of subject members and exhibiting energy absorbing performance with relative displacement between the subject members, a damping structure using the metal joint, and an architectural construction adopting the damping structure. This application is a national stage application of International Application No. PCT/JP2010/001759, filed Mar. 11, 2010, which claims priority to Japanese Patent Application No. 2009-059393, filed Mar. 12, 2009, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, an architectural construction such as a house or an apartment building adopting a damping structure suppressing vibration generated by earthquakes using a vibration damper has been increasingly utilized due to increased attention to disaster prevention. As a vibration damper of this type of damping structure, for example, a steel damper using hysteretic energy absorption with yielding of steel has been widely used in many architectural constructions since the damper exhibits excellent damping properties at a low cost. In the steel damper, a brace damper resisting an axial force is widely used since the mechanism thereof is simple and is easily designed.
For example, the technique disclosed in Patent Document 1 proposes a damping structure in which a base plate damper is interposed between a base and a leg of a pillar. Flexural yielding or shear yielding occurs in the base plate when a tensile force is applied to the pillar, and the tensile force generated at the leg is absorbed by the hysteretic energy absorption, such that damping properties may be exhibited.
Further, Patent Document 2 discloses a technique in which a steel sheet for a damper causing flexural-shear yielding is adopted, so that an increase in shear bearing force is suppressed even when a load is repeatedly applied to the steel sheet for the damper subjected to shear yielding.
In all techniques of Patent Document 1 and Patent Document 2 using a single thin body as a vibration damper, the energy absorbing properties are exhibited using the above-described shear yielding through a single thin plate. However, such a single thin plate has a problem in that in-plane rigidity and out-of-plane rigidity are not sufficient or the energy absorbing amount is reduced due to the occurrence of buckling.
When the plate thickness of the steel sheet used as a vibration damper is increased to improve the in-plane and out-of-plane rigidity and improve the buckling resistance, there is a problem in that the constructability at the time of connection assembly is degraded or the material cost increases with an increase in weight. Further, there is a need to increase the dimensions of the damper portion in order to ensure the vibration energy absorbing amount, but there is a problem in that basically says that increase in size prevents a decrease in size and high energy absorbing properties.
In addition, when the plate thickness of the single plate is increased, there is a need to increase the thickness and the size of the attachment portion so as to prevent the yielding of the attachment portion receiving a reaction force of a bending stress or a shear stress at the end of the damper. Furthermore, when the damper with a large plate thickness is used, there are problems in that the degree of fixation at the end of the damper with respect to the flexural deformation or shear deformation becomes relatively smaller and the rigidity of the damper is degraded.
Further, a vibration damper absorbing vibration energy by contracting a folded plate has been proposed. In the vibration damper, for example, a damping device is proposed which is bent toward the inside or the outside of a groove surface of a framework as shown in Patent Document 3 and absorbs displacement by being deformed toward the inside or the outside of the groove surface of the framework.
However, in the technique disclosed in Patent Document 3, the vibration damper is attached to the inside of the connection portion between a pillar and a beam intersecting each other. For this reason, the energy to be absorbed by the vibration damper having a folded plate shape proposed in the technique is not large, and therefore, the rigidity thereof may be low. Further, since the vibration damper is attached to a connection portion having a narrow gap, a folded plate is formed in which two or three hill and valley portions are alternately and continuously formed.
Furthermore, since the deformation absorption occurs by the contraction of the folded plate, the technique is a barrier to improving the vibration energy absorbing amount. Further, the rigidity of the vibration damper comes small.
Patent Document 4 discloses a technique in which a gap between plate members formed of Zn—Al alloy facing and separating from each other is partitioned into multiple spaces by a wavy partitioning plate formed of Zn—Al alloy to form a honeycomb structure.
However, in the technique disclosed in Patent Document 4, since the energy is not absorbed by the plastic deformation of the partitioning plate, it is not possible to absorb the large energy caused by a heavy earthquake.
Furthermore, the vibration to be absorbed by the disclosed technique is, for example, a comparatively small vibration generated in daily life such as the footsteps of a resident. Such the vibration generated in daily life may be suppressed by the elastic deformation and the damping effect of the partitioning plate; however, a large vibration such as an earthquake vibration may not be suppressed in such a configuration. That is, in Patent Document 4, it is not supposed that the earthquake vibration energy can be absorbed.