Abstract
In Japan, seismic design using components that absorb seismic energy has been approved. In fact, this design method has been applied to simple structures such as offices and distribution warehouses with dampers on all stories. We have proposed a design method for a structure of power plant facilities in which dampers are installed only in the lower story. In order to efficiently design such structures, it is important to understand their seismic response performance. Although many studies have been carried out on a structure with dampers installed on all stories, few studies have examined the seismic response characteristics of a frame with dampers installed on some stories of a structure. However, a recent trend is to retrofit some stories of high-rise buildings that will be hit by a major earthquake in order to improve their earthquake resistance while reducing the economic burden. From the viewpoint of improving the earthquake resistance of buildings, this trend is expected to spread to medium-to-low-rise buildings, and it is significant to understand their response characteristics.
This paper focused on medium-to-low-rise buildings with hysteretic dampers from the first story to the middle story. Based on the energy balance due to the earthquake, an equation was derived to give the yield story-shearing force of the damper, which minimizes the maximum story-shearing force of the story where the damper is installed. The yield story story-shearing force of the damper can be approximately calculated from the story-shearing force coefficient distribution of the main frame, the mass distribution of each story, and the yield story-shearing force of the damper of the first story. The derivation process was described in Chapters 3 and 4, and the prerequisites were described in Chapter 2.
Next, the effect of the number of stories in which dampers are installed on the seismic response characteristics of the building was discussed. It was found that when the maximum story-shearing force of the story in which the damper is installed is minimal, the maximum story-shearing force of the main frame of the first story is approximately equal to the yielding story-shearing force of the damper. It was also shown that dampers installed on more than 60% of the stories of a building can be expected to absorb roughly the same amount of energy as if they were installed on all stories. On the other hand, when the dampers are concentrated in the lower stories of the building, it was suggested that the elastic vibration energy of the story without the dampers increases. These were mentioned in Chapter 5.
Finally, in Chapter 6, a time history response analysis was performed using a multi degrees of freedom model that assumes a real building. A comparison of the results of the analysis with the theoretical values based on the equation showed that in most of the analysis cases, the results of the analysis tended to be generally similar to the theoretical values regardless of the difference in seismic motion, although there was some difference between the results of the analysis and the theoretical values when the neq was less than 2 and the interlaminar displacement of the damper differed greatly on both positive and negative sides.
