以子結構時間序列模型診斷剪力構架之損傷

Abstract

本研究最主要的目的是提供簡單、有效的研究法方來偵測建築物哪一層樓的系統特性改變。藉由損傷前後子結構頻率的改變量判斷可能發生損傷的樓層；透過未損傷構架之子結構之動力反應建立子結構之ARX模型求得預測反應，比較量測反應與預測反應的改變量亦可判斷損傷之樓層。利用加速度和速度之動力反應建立剪力構架之子結構ARX模型，透過連續小波轉換識別ARX模型之系統參數以估算子結構頻率及阻尼比。數值模擬六層樓剪力構架之地震及微動量測反應，藉一個或兩個樓層發生不同程度的損傷驗證本研究方法之可行性，並探討含雜訊的影響。經模擬結果證明相較於COMAC及FRFCM，使用本研究之評估方法較能準確診斷系統參數改變的情形。將本研究方法應用至五層樓鋼構架之震動台試驗，皆能準確地判別三種構架系統特性差異的樓層。

The main purpose of this work is to propose simple and efficient approaches to locate the stories whose properties may change in a building. The stories that are possibly damaged are determined by comparing natural frequencies of sub-structures in different stages (undamaged and damaged stages). The damaged stories can be also located by comparing the differences between the measured sub-structural responses and the responses predicted by the ARX model constructed using the dynamic responses of an undamaged building. ARX models for sub-structures of a shear building are established from sub-structural dynamic responses in term of one of acceleration and velocity. The parameters of an ARX model are identified through the continuous wavelet transform, and natural frequencies and damping ratios of sub-structures can be estimated directly through the identified parameters. The validity of the proposed procedure is confirmed using numerically simulated earthquake responses and ambient vibration responses of a six-story shear building having one-site or two-site damages with different levels. The effect of noise on the accuracy of the proposed approach is also investigated. It is also demonstrated that the proposed approach is superior to COMAC and a frequency response function curvature method in locating damaged stories. The proposed procedure is further applied to process the dynamic responses of three five-story steel frames, which are certainly not shear buildings, from shaking table test. The stories with different material properties in three frames are accurately located.