高強度大號鋼筋混凝土橋柱耐震行為

Abstract

我國鋼筋混凝土橋梁受制於公路橋梁設計規範與公路橋梁耐震設計規範之規定材料強度上限，鋼筋 最高為fy=4200 kgf/cm2，抵抗地震力構材之混凝土fc'最高為420 kgf/cm2，而我國橋柱常需滿足景觀設計考量與結構勁度不宜過大等需求，進而導致鋼筋擁擠等問題，影響施工品質。為提升施工性，本研究使用SD550W D36與SD550W D43做為縱向主筋，與SD550W D16做為橫向箍筋與多螺箍筋(大螺箍)，一共設計五座矩形橋柱試體，並進行其中兩座試體(以SD550W D36與SD550W D43做為主筋、SD420W D16做為橫向鋼筋)之反覆載重試驗，以檢核高強度大號鋼筋之使用在提升施工性的前題下是否滿足足夠的耐震性能。 在橋柱反覆載重試驗中，C550D36在位移比5.0%時開始挫屈，7.0%時斷裂；C550D43在位移比6.0%時開始挫屈，8.0%時斷裂，由此顯示較粗的D43鋼筋挫屈時間發生較晚，具備更好的韌性。兩個試體的降伏位移比分別為1.15與1.22，極限位移比分別為5.92與6.66，韌性分別為5.14與5.46，均高於公路橋梁耐震設計規範要求的單柱式橋墩4.0韌性容量。能量消散方面，C550D43能量消散面積在位移比6.0%後明顯優於C550D36，在較高位移比下仍能有效消散能量，顯示出優越的耐震性能。

Reinforced concrete bridges in our country are limited by the material strength caps set by the highway bridge design specifications and the highway bridge seismic design specifications. The maximum yield strength for reinforcing steel is 4200 kgf/cm², and the maximum compressive strength for concrete used in seismic-resistant structures is 420 kgf/cm². Furthermore, bridge columns often need to meet aesthetic design considerations and structural stiffness requirements, which can lead to issues such as congestion of reinforcement and impact construction quality. To improve constructability, this study uses SD550W D36 and SD550W D43 as longitudinal reinforcement, and SD550W D16 as transverse ties and stirrups. A total of five rectangular bridge column specimens were designed, and cyclic loading tests were conducted on two specimens (using SD550W D36 and SD550W D43 as longitudinal reinforcement, and SD420W D16 as transverse reinforcement) to evaluate whether the use of high-strength, large-diameter reinforcement can meet the required seismic performance while improving constructability. In the cyclic loading tests on the bridge columns, the C550D36 specimen began to buckle at a drift ratio of 5.0% and fractured at 7.0%, while the C550D43 specimen began to buckle at a drift ratio of 6.0% and fractured at 8.0%. This indicates that the thicker D43 reinforcement buckled later and exhibited better ductility. The yield drift ratios for the two specimens were 1.15 and 1.22, respectively, and the ultimate drift ratios were 5.92 and 6.66, with ductility values of 5.14 and 5.46, respectively, all exceeding the seismic design specification requirement of a ductility capacity of 4.0 for single-column piers. In terms of energy dissipation, the C550D43 specimen showed significantly better performance than the C550D36 specimen after a drift ratio of 6.0%, effectively dissipating energy at higher drift ratios and demonstrating superior seismic performance.