Analysis and Vibration Control of Stayed Cable

由於經濟省成本與造型美觀，在過去的三十年斜張橋日益普及。然而，斜張橋上的鋼纜具有較低的固有阻尼特性。這種極其低阻尼易受外力引起振動，造成斜張橋的不穩定，長期下來可能會導致斜張鋼纜本身及其錨定端點的金屬疲勞。當斜張橋跨度長度增加，斜張鋼纜的長度也跟著愈來愈長，如果只安裝黏滯性阻尼器，阻尼器所能提供的阻尼比也會相對減少。近年來，有研究學者提出以有勁度與阻尼變化的磁流變阻尼器來代替黏滯性阻尼器並可以有效降低斜張鋼纜的振動。 本研究實際架設一組斜張橋的縮尺的模型於國家地震工程研究中心，斜張鋼纜長約9公尺，一端連結水平擺放長約12公尺懸臂可擺動的剛性橋面板，另一端鉸接於反力牆，並加裝磁流變阻尼器配合被動控制及半主動控制理論抑制斜張鋼纜受不同頻率的正弦波外力振動。 實驗控制策略除了被動控制使用被動式固定電壓以外，本研究使用半主動控制理論包含Decentralized Sliding Mode Control 、Max Energy Control與Modulated Homogeneous Control，半主動控制理論為配合更接近實務上的應用與經濟性，均採用阻尼器上下相對位移訊號和阻尼器力量作為回饋判別輸出的半主動控制理論。實驗測試項目，包含未安裝磁流變阻尼器、磁流變阻尼器(被動模式)輸入固定電壓及半主動控制理論決定輸入電壓等測試，由比較被動控制與半主動控制的實驗結果，證明加裝磁流變阻尼器配合半主動控制理論可以有效抑制斜張鋼纜的振動，也證明了磁流變阻尼器應用在斜張鋼纜控制系統中的適用性。Because of economic advantages and aesthetic qualities, cable-stayed bridges have been increasing popularity over the last three decades. However, the stay cables are prone to vibration due to their low inherent damping characteristics, and this characteristic will even make cable-stayed bridges unstable. The vibration of cable may cause the failure of the cable anchorage due to metal fatigue. Therefore, researchers have proposed to use different control devices, either passive or semi-active, to reduce the cable motion. To study the vibration suppression of stay cable interacted with deck , a scaled-down cable-deck specimen is designed and constructed in NCREE, Taiwan. The length of the cable is about 9.0 meter with one end on the reaction wall and one end at the cantilever beam (simulate the bridge deck).A shaker which can generate sinusoidal force on the cable was used and installed in the middle point of the cable to generate the sinusoid excitation with various amplitudes and frequencies. One MR damper was attached at the end of cable (at 1/10 length of the cable) and the deck to mitigate the vibration of stay cable. The upper end of the suspended cable(about 9 meters) is anchored to the reaction wall and lower end anchored to the steel deck(about 12 meters).Besides the passive control study, three different semi-active control algorithms are use in this study which include: Decentralized Sliding Mode Control, Max Energy Control and Modulated Homogeneous Control. Only local measurement is used to evaluate the control command(with damper Stroke and damper Force Feedback).A series of test are carried out to investigate the control performance. Comparison among the uncontrol case passive-on control test and semi-active control test are made. Through the experimental test results, the performance of MR damper and the control effectiveness are examined