摘要
本研究目的在於透過試驗與模擬分析，針對圓形單柱式鋼橋墩的耐震能力進行探討。首先以兩座實尺寸中空薄殼鋼橋柱進行循環載重試驗，透過試驗結果比較有、無填充混凝土對鋼橋墩耐震性能之影響。試驗結果顯示，無填充混凝土之鋼橋墩最大側推力接近800 kN左右，內填充混凝土之鋼橋墩則為900 kN，最大側推力提升了12.5%。此外，無填充混凝土之鋼橋墩柱底會呈現明顯的外鼓挫屈，並在側向位移比達4.0 %後強度逐步降低，強度最終下降約1/3。而內填充混凝土之鋼柱試體則在DR (%) 達8.0 % 時挫屈程度仍不明顯，強度也尚未折減 ，但由於柱體本身強度相對高於試體底部固定螺栓的強度，導致試驗過程中會發生螺栓拉伸嚴重、與混凝土基礎破壞，因此無法發揮試體應有的強度，但試驗仍證明鋼橋墩內部加入混凝土可明顯提升其耐震性能。 數值模擬方面，本研究使用商業有限元素軟體SAP 2000建立梁-柱元素之模型，並將「公路橋梁耐震評估與補強設計規範」律定之塑鉸性質輸入至M3彎矩塑鉸設定，接著進行非線性靜力側推分析以及循環載重分析，並將模擬與試驗結果進行比較，用以探討規範對於鋼橋柱耐震性能之適用性。模擬結果顯示，以規範計算之塑鉸性質進行空心之鋼橋墩的側推模擬結果尚屬合理；而內填充混凝土之鋼橋墩則因試體無法發揮應有的強度，因此目前無法確認規範的正確性。此外，規範將混凝土極限壓應變限制在0.005可能低估鋼橋墩實際強度。 參數分析結果顯示不同鋼材強度與不同螺栓強度皆會影響螺栓拉伸程度，而螺栓拉伸程度將影響試體受循環載重作用的初始勁度，亦會影響遲滯迴圈之束縮情形，因此本研究建議在設計上須考慮螺栓強度與試體強度之比例。另一方面，不同軸力比與不同徑厚比為影響鋼橋墩整體強度與韌性的關鍵參數。最後，本研究提出集中式塑鉸的方法來簡化鋼橋柱的耐震分析，利用分佈式塑鉸所得到的塑性發展長度，搭配斷面彎矩與轉角關係，可以簡單、正確模擬出鋼橋柱在側推與循環載重下的行為。
並列摘要
The purpose of this study is to investigate the seismic behaviors of circular single-column steel bridge piers through experimental and simulation analyses. First, two full-scale thin-walled steel tubes were used to perform cyclic loading tests. The test results were used to compare the effects of concrete filling and non-filling on the seismic performance of the steel bridge piers. The test results show that the maximum lateral force of the steel pier without concrete filling is close to 800 kN, while that of the steel pier with concrete filling is 900 kN. The maximum lateral force increased by approximately 12.5% with the concrete filling. In addition, the bottom of the steel bridge pier without concrete filling shows obvious local buckling, and the strength of the specimen gradually decreases after the drift ratio (DR) reaches 4.0%, and the strength finally decreases by about 1/3. When the DR (%) of the concrete-filled steel column specimen reaches 8.0%, the local buckling is still not obvious and the strengthof the specimen has not been reduced. The addition of concrete inside the steel tubes increases the overall strength of the specimen, which exceeds the strength of the fixing bolts at the bottom of the specimen. As a result, the bolts are severely stretched and damaged during the test, abd the test soecimen cannot develop the strength it should have. However, cyclic loading tests have shown that adding concrete to the inside of the steel pier can significantly improve its seismic performance. In terms of numerical simulation, we use the commercial finite element software SAP 2000 to construct numerical models with beam-column elements. The setting of M3 bending moments plastic hinge which are defined in the design code is used to simulate the nonlinear behaviors of the steel piers. Nonlinear static pushover analyses and cyclic loading analyses were performed. The simulation results were compared with the experimental results to verify the applicability of the design code to the seismic performance of steel bridge piers. The numerical results of the pushover analyses and cyclic loading analyses of the thin-walled steel tube without concrete filling are in good agreement with the experimental results, indicating that the plastic hinge properties defined by the design code are reasonable. On the other hand, since the concrete-filled steel pier cannot develop its potential strength due to the severely stretched and damaged of the bolts, the current concrete specification in the design code could not be verified by numerical simulations. In addition, the code limits the ultimate compressive strain of concrete to 0.005, which may underestimate the actual strength of steel piers. The results of the parameteric analyses show that different steel yield strengths and different bolt strengths affect the bolt tension. The bolt tension affects the initial stiffness of the specimen under cyclic loading, and also affects the shrinkage of the hysteresis loop of the specimen. Therefore, we suggest that the ratio of bolt strength to specimen strength should be considered in the design process. On the other hand, different axial force ratios and different diameter-thickness ratios are key parameters affecting the strength and toughness of steel bridge piers. Finally, a simple method is proposed to simplify the seismic analysis of steel bridge piers with the concentrated plastic hinge. Using the plastic development length obtained from distributed plastic hinges, combined with the bending moment and rotational angle relationship, it is possible to simulate the behaviors of steel bridge piers under pushover and cyclic loading tests simply and correctly.