第五章 台北 101 大樓應用 TLCD 系統之抗風減振性能評估
5.4 台北 101 大樓安裝 TLCD 系統之參數研究
5.4.1 TLCD 設計參數
⎢ ⎥⎢ ⎥
=⎢ ⎥
⎢ ⎥⎢ ⎥
⎣ ⎦
為系統樓層扭轉向之擾動力向量。
5.4 台北 101 大樓安裝 TLCD 系統之參數研究
本節將針對結構於順向風力擾動下,探討風力擾動偏心距(ey) 及TLCD 距離形心位置(eT)對於TLCD 減振效能之影響。
5.4.1 TLCD 設計參數
台北101 大樓之結構系統參數整理如表 5.2 所示。本研究將考慮 TLCD 系統之頻率比
γ
=1 之設計條件進行分析。由於台北 101 大樓之 第一振態頻率為0.14Hz(X 向),第三振態頻率為 0.21Hz(扭轉向),因此由式(2.17)可知,控制水平振動之 TLCD(中心位置)有效長度 為Le=24.5 m;控制扭轉振動之 TLCD(Y 軸正向及負向)有效長度 為Le=11.4 m。TLCD 系統之尺寸設計整理如表 5.3 所示。此外,吾人 設定偏心距ey=1.0 m、1.5 m 及 2.0 m 等情況進行分析,而 TLCD 距 離形心位置則為eT=3 m 至 21 m 之間,並以 3 m 為增量進行數值模 擬分析。TLCD 系統之截面積比(
λ
)設計為 1.0(等斷面 TLCD)。5.4.2 分析結果
圖 5.4 及圖 5.5 分別為作用於結構樓層之順向風力擾動歷時及其
富氏頻譜,其結果顯示,隨機擾動風力最大為 120 ton,且其頻率內 涵主要分佈於1 Hz 以內。
圖5.6 及圖 5.7 分別為風力擾動偏心距與 TLCD 距離形心位置與 TLCD 系統扭轉向之結構角位移及角加速度均方根值折減關係圖。其 結果顯示,風力擾動偏心距(ey)愈大(即扭轉擾動力愈大),TLCD 系統對於結構扭轉加速度反應之減振效果愈好,且隨著 TLCD 距離形 心(eT)愈遠,TLCD 對於結構扭轉反應之減振效果則有增加的趨勢。
圖5.8 及圖 5.9 為風力擾動偏心距與 TLCD 距離形心位置與 TLCD 系 統 X 向之結構位移及加速度反應之均方根值折減關係圖。其結果顯 示,風力擾動偏心距愈大,TLCD 系統對於 X 向之減振效果愈好(即 控制扭轉向之TLCD 對於 X 向亦有減振貢獻),惟隨著TLCD 距離形 心愈遠,TLCD 對於結構 X 向反應之減振效果影響不大。由於改變擾 動偏心距僅會增加扭轉擾動外力,對於 X 向擾動力則完全無影響,
故本分析之結果合理。
表 5.4 與表 5.5 分別為扭轉向及 X 向於在eT=21 m 的條件下,
TLCD 系統之結構反應均方根值折減率。其結果顯示,扭轉向結構角 位移與角加速度之均方根值及峰值折減率分別為64 %、66 %、65 % 及66 %;X 向結構位移與加速度之均方根值及峰值折減率分別為 26
%、29 %、29 %及 43 %。
圖5.10 及圖 5.11 為ey=2 m 及eT=21 m 之條件下,結構扭轉向 控制與未控制結構之角位移及角加速度歷時比較;圖 5.12 及圖 5.13 為ey=2 m 及eT=21 m 之條件下,結構 X 向控制與未控制結構之位 移及加速度歷時比較。其結果顯示,TLCD 系統對於結構之扭轉振動
具有良好之減振效果。圖 5.14 為中心位置 TLCD 之水柱激盪位移歷 時圖,水柱激盪位移峰值可達25 cm。圖 5.15 及圖 5.16 分別為 Y 軸 正向及負向TLCD 之水柱激盪位移歷時圖,其水柱激盪位移峰值分別 為4 cm 及 5 cm 。
本節探討TLCD 系統應用於台北 101 大樓受扭轉擾動作用之抗風 減振性能評估,綜合上述之分析結果,吾人歸納以下幾點結論:
1. 風力擾動偏心距 (ey)愈大,TLCD 系統對於結構扭轉反應之 減振效果愈好,且隨著 TLCD 距離形心(eT)愈遠,TLCD 對於 結構扭轉反應之減振效果則有增加的趨勢。
2. 風力擾動偏心距愈大,TLCD 系統對於 X 向之減振效果愈好,
惟隨著 TLCD 距離形心愈遠,TLCD 對於結構 X 向反應之減 振效果影響不大。
3. 於ey=2 m,eT=21 m 之條件下,X 向結構位移及加速度之峰 值折減率分別為 29%及 43%。因此 TLCD 系統可降低結構之 加速度至4.1 ㎝/s2 <5 cm/s2(未加裝TLCD 系統,結構物加速 度為7.1 ㎝/s2),滿足我國規範規定半年回歸期之風力作用下,
頂樓加速度不得大於5 cm/s2之上限值。
第六章 結論與建議
本文除了針對變斷面VTLCD 系統進行理論分析與參數研究外,
並實際製作一組VTLCD 模型進行元件測試及 VTLCD 系統之結構減 振性能測試(振動台試驗),俾便充份掌握 VTLCD 元件之設計參數及 評估其減振效益。此外,吾人亦針對氣密式 TLCD 系統應用於結構防 震的可行性進行模擬分析,探討密閉氣室之初始壓力對於結構減震效 能的影響。本文最後則以世界第一高樓「台北101 大樓」進行 TLCD 系統之抗風減振性能評估分析,同時考慮結構水平向及扭轉向之振動 控制。根據本文所進行之理論模擬分析與試驗驗證之結果,吾人歸納 幾點結論與建議如下:
1、 根據 VTLCD 系統之液體有效長度估算公式所得之理論振 動頻率與 VTLCD 元件試驗所得之頻率十分吻合,顯示以 有效長度計算變斷面 VTLCD 系統之振動頻率相當精確可 靠,吾人可藉由調節液體的有效長度充份掌握 VTLCD 元 件之動力特性。
2、 結構共振簡諧擾動試驗之結果顯示,本案所進行之三種不 同孔口板開孔面積比之 VTLCD 設計(
φ
=1.0、φ
=0.64 及φ
=0.36)均有良好的減振效果,且由 VTLCD 系統之性能測 試可知,本案採用長度比β=0.54 之設計已具有十分良好之 減振效果。3、 簡諧波擾動試驗之結果顯示,擾動頻率與結構頻率之比值
0 .
=1
γ
s 時,VTLCD 系統(自然振動頻率與結構之頻率比為 1.0)之減振效果最佳,惟擾動頻率比γ
s ≤0.75時,VTLCD 系統之結構振動反應則有放大的現象。4、 本文根據系統識別分析所得之水頭損失係數進行非線性數 值模擬分析與試驗之結果相當契合,驗證本文所提非線性 理論分析模式之合理性及精確性。
5、 氣密式TLCD 系統可藉由調整密閉室內之初始壓力進而延 長水平段之長度(增加系統的質量),使得其振動周期可與 中低樓層結構之周期一致。此外,結構安裝氣密式 TLCD 系統(自然振動頻率與結構之頻率比為 1.0)具有減震效果,
於相同質量比及孔口板開孔面積比之下,水平段長度比 β 愈長,結構位移及加速度均方根之折減效果愈好。
6、 TLCD 系統可有效降低台北 101 大樓之水平向及扭轉向之 振動反應,當風力擾動偏心距(ey)愈大,TLCD 系統對於結 構扭轉反應之減振效果愈好,且隨著TLCD 配置距離形心 (eT)愈遠,TLCD 之減振效果則有增加的趨勢。
7、 本文之分析結果為VTLCD 系統與結構之頻率比設定為 1.0 之條件下所得,未來可將 VTLCD 系統與結構之頻率比亦 作為參數進行分析,俾便求得 VTLCD 或 TLCD 系統之最 佳設計參數,尤其是氣密式TLCD 系統應用於結構防震之 分析,因地震的頻率內涵較為寬廣,VTLCD 系統與結構之 頻率比亦可能影響減震的效果。
8、 未來可針對氣密式TLCD 系統應用於中高樓層之減震進行
相關深入研究,並評估進行試驗驗證的可行性(壓力計的規 格、加壓設備的選用、氣密室TLCD 試體之製作等)。
9、 台北101 大樓應用 TLCD 系統進行抗風減振之模擬分析僅 考慮順風向之風力作用,未來可將橫風向風力亦納入分析 模型,以期更詳實模擬結構受雙向風力作用之減振效益評 估。
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