預鑄構件結構健康監測之初步研究─以樓梯振動模擬為例

Abstract

本文以一地上9層之預鑄鋼筋混凝土樓梯為研究標的，考量預鑄構件、場鑄構件接合部結構行為不同，兩者接合可能有變位較大之特性，研究以Abaqus軟體建置樓梯之有限元素模型，探討其動態特性，以及接合部破壞對應之自然頻率變化。

在數值模擬分析階段，透過模態分析求得自然頻率及模態振型，並為驗證有限元素模型是否可靠，將模型導入地震歷時分析，選擇接合部作為模擬配置之監測點位，採用R4SID系統識別法，識別模型經由監測點位提取之歷時加速度，萃取自然頻率與模態振型，並以誤差指標及模態保證準則（MAC）跟模態分析結果比較，驗證模型為準確可靠。再來本研究以有限元素模型模擬樓梯接合部破壞，透過破壞預埋件以及削減混凝土彈性模數，發現對應樓梯之自然頻率有下降趨勢。

最後本研究針對該實際存在之樓梯進行監測，透過模型振動模擬之資訊以選擇接合部作為有效監測點位，並設計兩種不同之測試方式，分別為微振量測及敲擊測試。經由現地實測所得之自然頻率結果顯示，監測樓梯之接合部可以有效反應動態特性，包括樓梯板與樓板接合部、樓梯板與中間轉台接合部皆獲得良好之頻率識別結果，與模型模態分析所得之自然頻率高度一致。本研究提供可資參考之以樓梯為例的預鑄構件結構健康監測的流程及方法，提供後續學術探討精進相關之結構健康監測流程設計。

This paper investigates a nine-story precast reinforced concrete staircase, focusing on the differing structural behaviors at the connections of precast and cast-in-place components, which may exhibit larger displacements. The study utilizes Abaqus software to construct a finite element model of the staircase to explore its dynamic characteristics and the corresponding changes in natural frequencies due to connection failure.

During the numerical simulation phase, modal analysis is performed to obtain natural frequencies and mode shapes. To verify the reliability of the finite element model, the model is subjected to seismic time-history analysis. The joints are selected as monitoring points for simulation configuration. The R4SID system identification method is used to extract natural frequencies and mode shapes from the time-history acceleration data obtained at the monitoring points. The results are compared with modal analysis outcomes using error indices and the Modal Assurance Criterion (MAC) to validate the model's accuracy and reliability. The study then simulates connection failure in the staircase finite element model by degrading embedded components and reducing the elastic modulus of concrete, revealing a downward trend in the corresponding natural frequencies.

Finally, the actual staircase is monitored based on information from the vibration simulation model, selecting the connections as effective monitoring points. Two different testing methods, ambient vibration testing and impact testing, are designed. The natural frequency results obtained from field measurements show that monitoring the connections of the staircase can effectively reflect the dynamic characteristics. Both the connections between the staircase slabs and floor slabs and the connections between the staircase slabs and intermediate landings yield good frequency identification results, highly consistent with the natural frequencies obtained from the model's modal analysis. This study provides a procedure and methodology for structural health monitoring of precast components using staircases as an example, contributing to the advancement of structural health monitoring process design in future academic research.