Abstract: | 對於外部預力預鑄節塊箱型橋而言,由於 預力鋼鍵配置於混凝土斷面外,且結塊間採用 乾接縫方式,因此本研究發展一種四點的連接 元素來模擬混凝土結塊間剪力榫之連接行為。 在勁度的推導過程分為開裂、半開和閉合三種 狀態,來模擬混凝土承受壓力和張力之情形,使 其能符合接縫真實的力學行為,並採用現有的 板殼元素模擬混凝土斷面,鋼鍵元素模擬預力 鋼鍵,以此三元素建立整體橋梁之有限元素分 析模式,進而預估整體橋梁之極限強度。本研 究以一簡支的外部預力箱型梁的試驗來驗證程 式和分析模式的正確性,並以三跨橋梁作為實 例分析,以確立此種分析模式對於連續且多跨之外部預力箱型橋之適用性。由結果顯示,連 接元素可以明確地表現出接縫的開裂情形,數 值上亦可得到良好的收斂效果,在橋梁極限強 度方面比AASHTO規範極限載重時之強度超過許 多,且接縫之開裂載重亦遠大於工作載重,顯示 此種橋仍具有相當之安全性。 A four-node link element is developed to model the key joints between the precast segments in externally prestressed concrete bridges. Three states of link elements are introduced to simulate the fully contact, partially contact and opening conditions of the joints. A finite element model, including the link element, flat-shell element and the tendon element, is established to analyze the bridges with external prestressing. Two examples are presented to verify the validity and applicability of the elements. The effects of the key joints on the ultimate strength of the bridge are also discussed. |