鄰近活動斷層耐震能力評估與補強－以嘉南大圳北幹一號橋為例

Seismic Evaluation and Retrofit of the Isolated Bridge near Active Faults:Chianan Irrigation, Beigan No. 1 bridge

10.6849/SE.202103_36(1).0005

高墀修(Chih-Siou Gao)；蕭天任(Tien-Jen Hsiao)；吳明興(Ming-Shing Wu)；彭康瑜(Kang-Yu Peng)；陳國隆(Guo-Long Chen)

隔震橋 ； 近斷層效應 ； 耐震能力評估與補強 ； 液態黏滯性阻尼器（FVD） ； Isolated bridge ； Near-fault effect ； Seismic Evaluation and Retrofit ； Fluid Viscous Damper

結構工程

36卷1期（2021 / 03 / 01）

75 - 92

繁體中文

隨著隔震技術的發展推廣，國內部分橋梁開始採用隔震支承作為其抗震的選擇，從早期第二高速公路的部份橋梁，到1999年921集集地震後遭到破壞的一些公路橋梁重建，隔震技術在國內橋梁工程的應用已將近三十年。交通部頒「公路橋梁設計規範」（97年）亦新增「隔震與消能設計」章節。由於鄰近活動斷層之地震，通常具有較長週期的脈衝震波，隔震橋亦具有較長振動周期特性，隨著經濟部中央地質調查所公告第一類活動斷層的增加，位於鄰近活動斷層之既有隔震橋，在近斷層地震波作用下，可能造成共振現象，產生超出原設計預期之較大變位。本文以位在國3白河新化段的嘉南大圳北幹線一號排水橋為研究案例，利用隔震支承原型試驗結果，建立隔震橋梁分析模型，以探討一般遠域地震及近域地震對此隔震橋梁的影響與可行補強方法。研究結果顯示，因耐震規範地震力的改變，在一般遠域地震下，隔震支承即可能超出原設計位移量，而在近域地震下，當脈衝震波週期接近隔震橋梁振動週期時，位移將更加放大。經檢討研究，該橋之耐震補強方法，採用保留既有隔震支承，加裝液態黏滯性阻尼器（FVD），增加整體橋梁系統阻尼，以降低隔震支承位移反應。

With the development of the seismic isolation technology in Taiwan, Seismic isolation bearing has been used in some bridges to resist earthquakes. Since the construction of freeway NO.3 and the reconstruction of the bridge damaged by Chi-Chi earthquake, isolation technology has been used in three decade. MOTC also added a chapter ＂Seismic Isolation and Energy Dissipation Design＂ to ＂Specification for Seismic Design of Highways and Bridges＂ (2008).But the pulses in the near fault ground motion have a large displacement response which is exceed the design displacementon isolated bridges due to their long-period property. Take ＂Chia-nan Irrigation Channel No.1 Bridge＂ for example. We studied the effects of earthquakes near and far fault region on seismic behavior of isolated bridge, and suggest the retrofit method. This research shows that resultant displacement of the existing seismic isolated bearings may exceed the design displacement under the far-fault earthquake due to the seismic force increased. Furthermore, the resultant displacement will be much larger under the near-fault earthquake when the period of the isolated bridge is closed to the pulse period. Finally, we install fluid viscous damper (FVD) to increase the overall bridge system damping and to reduce the displacement response of the seismic isolated bearing.

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