第五章 結論與建議
5.2 建議
1. 於進行移動荷重試驗過程當中,發現試驗載重車較多的時候,較難維持 試驗的一致性,因此未來在規劃類似的實驗時,建議盡量避免較難掌 控的試驗。
2. 由頻率識別結果可看出,以有限元素分析架構之模型與實際施工完成之 橋體,其結構特性有明顯之差異,可根據識別之結果進一步調整有限 元素分析模型之結構參數,以期能如實反映橋體之動態特性。
3. 本研究礙於量測系統之關係,無法對橋塔部份進行量測及模態識別,建 議日後可採用無線式感應子對橋塔進行量測及分析,並與本研究做一 比較。
4. 弦理論公式並未考慮鋼纜之撓曲剛度及中垂效應,中垂效應較大或撓曲 效應影響較明顯的鋼纜,可能產生較大的誤差;對於長度較長或撓曲效 應影響較明顯的鋼纜,還需進一步確認弦理論公式的適用性。
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表 2.1 SPC51 規格介紹
型號 SPC51
頻道數 16
A/D 轉換 16bit
最大輸出電壓 ±10V
取樣頻率 可調式(10,20,50,100,200,500,1000Hz) 放大倍率(Gain) 1、2、10、100
啟動方式 手動、自動、時間設定
高通濾波器 0.1Hz 或 1Hz
低通濾波器 1
3×取樣頻率
紀錄長度 可調式(最多 99999999 點/頻道)
記憶體 硬碟 9.34G
表 2.2 VSE15D 速度計規格 型號 VSE15D 頻率範圍 0.1~70Hz 量測範圍 ±10cm/sec(kine)
靈敏度 1V/kine 或 10V/kine 最大輸出電壓 ±10V
表 2.3 LVDT 規格介紹
型號 DDP-50A
量測範圍 50mm
輸出電壓 2.5mV V/ ±0.3%
(5000 10× −6strain±0.3%) 靈敏度
100 10× −6strain/mm
非線性現象 0.3%RO
感應子彈力 5.4N
頻率響應 1Hz
溫度範圍 0 ~ 60+ C
輸入/輸出 電阻 350Ω
最小激發電壓 Less than 2V
最大激發電壓 5V
重量 500g
表 4.1 微動試驗求取隨機遞減訊號之參考測站 Ambient test
mode f(Hz) damping(%) Impact test
mode f(Hz) damping(%)
表 4.4 有限元素軟體分析出之橋梁動態特性 Finite element method
mode f(Hz) 1 0.75 (x,z) 2 1.02 (x,z) 3 1.45 (x,z) 4 1.92 (x,z) 5 1.94 (y) 6 2.68 (x,z) 7 2.79 (y) 8 2.94 (y) 9 3.26 (x,z) 10 4.29 (x,z)
表 4.5 微動試驗、衝擊試驗、有限元素分析 MAC 值比較
frequency (Hz) MAC
mode
ambient impact FEM ambient VS. impact ambient VS. FEM impact VS. FEM
x-1 1.48 1.47 1.02 0.898 0.866 0.769
x-2 2.09 2.03 1.92 0.861 0.888 0.833
x-3 3.16 3.19 2.68 0.904 0.980 0.917
y-1 1.74 1.71 1.94 0.989 0.952 0.954
y-2 2.62 2.58 2.79 0.877 0.931 0.874
y-3 2.82 2.88 2.94 0.870 0.825 0.661
z-1 0.88 0.93 0.75 0.997 0.993 0.984
z-2 1.48 1.47 1.02 0.857 0.827 0.846
z-3 1.74 1.72 1.45 0.976 0.969 0.938
z-4 2.09 2.03 1.92 0.982 0.972 0.978
z-5 3.51 3.51 3.26 0.978 0.958 0.972
表 4.6 動態車流載重試驗之位移 DAF(一台卡車單向行駛)