Evaluation of seismic response characteristics of buildings by ambient vibration test

本研究的目的是通过环境振动试验评价建筑物的地震反应特性。研制了一种用于环境振动或微动测量的便携式系统。该系统的硬件由便携式传感器、小型放大器、A/D转换PC卡和移动计算机组成。在0.05~1s的周期范围内，系统的响应特性与地面速度成正比。为评价场地特征，研制了一套重量仅为5公斤的三通道系统。为评价建筑物的振动特性，研制了一套重量为12 kg的12通道系统。该系统的软件包括：a)监测和数据采集程序；b)频谱分析和结果显示程序。后者是用C++Builder开发的，可以在Windows操作系统下运行，可以方便地以任意比例显示时程数据，以便选择适合分析的截面。利用该系统对横滨和马尼拉的地面微动进行了测量，并在横滨和马尼拉测量了建筑物的环境振动。实践证明，该系统使快速高效的测量成为可能。例如，微震测量需要10分钟，建筑物环境振动测试大约需要2小时。利用测量的数据，研究了评价场地特征的方法。

The objective of the study is to evaluate seismic response characteristics of buildings by the ambient vibration test. A portable system is developed for the ambient vibration or microtremor measurement. The hardware of the system consists of portable sensors, a small amplifier, a PC-card of A/D converter and a mobile computer. The response characteristics of the system is proportional to ground velocity in the period range of 0.05 to 1 second. A 3-channel system whose weight is only 5 kg is developed for evaluation of site characteristics. For evaluation of building vibration characteristics a 12-channel system with weight of 12 kg is developed.The software of the system consists of a) the program for monitoring and data acquisition and (b) the program for spectral analyses and display of the results. The latter is developed wit.h C++ builder to be operated under the Windows OS.The time history data is easily displayed with arbitrary scale in order to select the section suitable for the analysis. The Fourier spectra and the spectral ratio are computed and displayed with arbitrary scale to understand the results in the field measurement.Using the system, microtremors of ground are measured in Yokohama and Manila, and the ambient vibration of the building is measured in Yokohama. It is confirmed that the system makes possible the very quick and efficient measurement. For example, it takes 10 minutes for the microtremor measurement and about 2 hours for the building ambient vibration test. Using the data measured the methodology for evaluation of the site characteristics is examined.