應用「希爾伯特-黃」於直接基礎搖擺橋梁之地震動力反應頻率分析

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Title:	應用「希爾伯特-黃」於直接基礎搖擺橋梁之地震動力反應頻率分析
Authors:	許誌斌;Hsu, Chih-Pin
Contributors:	土木工程學系
Keywords:	希爾伯特-黃轉換;單跨度簡支橋梁;直接基礎;搖擺效應
Date:	2018-06-21
Issue Date:	2018-08-31 11:22:57 (UTC+8)
Publisher:	國立中央大學
Abstract:	台灣因位於環太平洋地震帶上導致地震災害時常發生，為了防止或減輕地震災害發生，世界各國研究者已有研究出各種隔震機制，其中一種即為直接基礎搖擺機制。過往研究中證實直接基礎搖擺機制可以利用土壤的塑性使地震能量消散，並使傳遞到上層結構的地震能量減少，雖然會使結構頂端位移增加，但直接基礎搖擺機制依舊提供了良好的抗震性能。直接基礎搖擺機制在帶給結構良好的抗震性能的同時也會使結構自身週期上升，並使其由線性訊號轉變為非線性訊號。傳統使用的分析方法是快速傅立葉轉換(Fast Fourier Transform，簡稱FFT)，但FFT只能夠處理線性訊號，而其在處理非線性訊號的精確度不高。而希爾伯特黃轉換(Hilbert-Huang Transform，簡稱HHT)因能計算出訊號的瞬時頻率及瞬時能量，繼而使訊號經過HHT處理後能得出訊號的「能量-頻率-時間」分布。基於上述緣由，HHT時常被利用於非線性及非穩態訊號的處理上。本研究將使用HHT分析直接基礎單跨橋梁之搖擺效應，將以單跨度簡支橋樑為對象，藉由改變橋面板質量、柱高、模擬土壤之橡膠勁度和基礎尺寸的得到一系列實驗模型之振動台實驗資料，並將此資料透過希爾伯特黃轉換處理，觀察上述結構條件改變時，會對結構頻率及搖擺反應帶來何種影響。由研究成果可得知，搖擺反應愈大時，結構頻率下降的幅度會愈來愈多，而在相同的搖擺反應下，原先自然振動頻率較高者的頻率下降幅度又會比自然振動頻率較低者來得多。本研究中影響頻率變化最大的結構條件為柱高及橋面板質量，而基礎尺寸會影響到搖擺反應的大小而間接影響到結構頻率變化。雖然確定了搖擺反應與結構頻率變化之關係，但依舊無法確定其與加速度之關係。 ;Taiwan often occurs the earthquake disaster because located on Ring of Fire. In order to prevent or mitigate the earthquake disaster, researchers all over the world have studied a variety of isolation mechanisms, one of which is the direct foundation rocking mechanism. Previous studies had confirmed that the direct foundation rocking mechanism can dissipate the seismic energy by using the plasticity of the soil and reduce the seismic energy transferred to the superstructure. The direct foundation rocking mechanism provides effective seismic performance, although it will increase the displacement of the top of the structure. The direct foundation rocking mechanism brings effective seismic performance to the structure will also increase the period of the structure and transform it from a linear signal to a non-linear signal. The traditional analysis method is Fast Fourier Transform (FFT), but Fast Fourier Transform can only process linear signals, and its accuracy in processing nonlinear signals is not precise. Hilbert-Huang Transform (HHT) can calculate the instantaneous frequency and instantaneous energy of the signal, and then make the signal undergo Hilbert-Huang Transform process to obtain the "energy-frequency-time" distributed of signal. Based on the above reasons, Hilbert-Huang Transform is often used to deal with nonlinear and non-steady-state signals. This study will use the Hilbert-Huang Transform to analyze the rocking effect of direct foundation single-span bridges. The research of a single-span simply supported bridge is main subject. I will get a series of experimental models of shaking table experimental data by changing the mass of the bridge deck, the column height, the stiffness of rubber which simulating soil and the foundation size. Then taking Hilbert-Huang transform to dealing with these data to observe the influence on the structure frequency and the rocking reaction when the above structural conditions are changed. In the study, we can know that structural frequency will decrease more and more when the rocking reaction is greater. However, under the same rocking reaction, the higher natural frequency is, the higher magnitude of frequency reduction will be. In this study, the most influential structural factors affecting the change of frequency are the column height and the mass of the bridge deck, while the size of the foundation affects the magnitude of the rocking reaction and indirectly affects the change of structural frequency. Although the relationship between the rocking response and the change of structure frequency has been determined, I can’t determine its relationship with acceleration.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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