| Summary: | 碩士 === 國立臺北科技大學 === 土木與防災研究所 === 97 === For decades, structure health monitoring has been of great interest and many reachers have devoted to develop many methods to detect damage. In this paper, we simplify the steel frame as a 4-DOF system first of all, then used ARX model to identify the nature frequencies and mode shapes of the structure in numerical simulation. After obtaining the identification results very close to the exact solutions, we prove that system identification method is credible. Also, we find that the same system parameters are identified by the ARX model with or without inputs (external forces), as long as the correct model order is used.
However, when the ARX model is applied to the actual time-history data measured from a structure testing, good identification results can not be obtained. In order to obtain good results, besides increasing the model order, filtering and selecting the adquate range from data are also necessary. Based on the mode shapes from system identification results, inter-story drift mode shape (IDMS) and inter-story mode shape rotation angle (IDMSRA) are used to detecte damage locations for structure health monitoring. Both the results of the experiment and numerical simulation show that IDMS ans IDMSRA can correctly identify the damaged floors when the damage extent of the floors are similar. However, for other damage combinations, IDMS and IDMSRA may fail to detect all damage locations.
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