細長い平面形を有する研究棟の応答挙動に関する実測的研究

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Since the end of 1960's, several experimental studies have been tried concerning response of building of long and huge configuration in plan based upon earthquake observations and microtremor measurements. Some of these studies described that high frequency components of the earthquake records on the base of the building were decreased when comparing them with those on the free surface. As for the superstructure, they described that torsional vibration was excited in symetrical building under the ground motion with a fair amount of high frequency components. However, in the above studies, it is hard to find clear explanation about relationship between the dynamic behavior and exciting ground motion. In this paper, authors describe the characteristics of dynamic behaviors of this type of bilding and exciting ground motions based upon the earthquake records and those of microtremors obtained at a reinforced concrete research building with 116 meter length, 16 meter width and 16 meter height in Hatoyama campus of Tokyo Denki University. In the transversal direction of the building, the response spectra of accelerograms observed, at the top show two different tendencies. Namely one group of the spectra has a peak that can be attributed to higher mode vibration of the structure with remarkable slab deformation as well as a peak to the fundamental one when comparing it with mode shapes obtained by means of full-scale structure analysis. In this case, the ground motions at both ends of the building estimated from filtered accelerograms on the base have similar shapes each other with time difference in time domain. Here, time phase delay between two accelerograms can be expressed as time difference which gives the maximum correlation coefficient between them. On the other hand, another group of the spectra has a peak that can be attributed to the fundamental natural period of the structure. In this case, the above time phase delay in two ground motions there has different meaning. According to the analytical results this time, time phase delays which exist in filtered accelerograms on the base are proportinal to the distance between observation points. However, the later case shows average time delay of each phase that exists in the time history of the accelerogram while the former case does constant time difference of travelling wave. In the longitudinal direction of the building, the response spectra of accelerograms at the top have a peak that can be attributed to lower mode vibration of the structure and have no remarkable peak in high frequency domain. As for the response spectra of accelerograms on the base of the building, decrease of high frequency components can be observed in several records twords longitudinal direction of the building when comparing them with those on ground surface. Adding to this, signiticant characterestics that certain components of the spectra are amplified by the vibration of the structure in both transversal and longitudinal directions can be observed. This can be thought to show that response effect caused by the vibration of the structure should, be considered when treating the dynamic behaviors of the base of this type of building. In order to investigate the basic characteristics of the building and to compare them with the results obtained from earthquake records, measurement of microtremors was carried out at the building and its near ground surface. According to the comparison of the records on the base with those on the ground, it can be thoght that the boundary condition between foundation and its sustaining soil is approximately continuous. And natural periods of the building estimated from power spectra of microtremors are from 10 to 15 percent less than those from earthquake records. Finally authors summarize the consideration presented here and conclude that higher mode vibration of this type of building with remarkable slab deformation can be excited as well as fundamental one when subjected to travelling wave.
社団法人日本建築学会の論文
1989-02-28

細長い平面形を有する研究棟の応答挙動に関する実測的研究

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