熱浸鍍鋅在陽明山馬槽橋之應用

Application of Hot-Dip Galvanized Steels to Mao-Tsao Bridge

陽明山馬槽橋為大跨度之拱橋，主跨徑134公尺長，下弦拱採用鋼骨鋼筋混凝土構造，其他為鋼筋混凝土。由於地形關係，本工程附近經常雨霧彌漫，雨量豐沛，氣溫變化亦大，在地質上又受工址旁之馬槽地熱崩裂口硫氣影響，為一易腐蝕環境，而本工程之施工是採先吊裝下弦拱內之鋼拱構造，再以鋼拱構造做為支撑，分段灌築混凝土。使得鋼結構須暴露在潮濕大氣中甚久，為克服此高腐蝕環境，利於維修及增長橋梁使用年限。本橋為國內首座鋼料使用熱浸鍍鋅之橋梁。本文主要在說明使用熱浸鍍鋅之考量因素、鍍鋅方式、及在設計上因應熱浸鍍鋅之特殊事項，另外亦檢討本橋使用熱浸鍍鋅之初步情形，以供做為將來鋼橋使用熱浸鍍鋅之借鏡。

Mao-Tsao bridge, located in Yang-Ming-Shan National Park, is a long-span arch bridge with main span of 134 m. This bridge is a reinforced concrete structure except the arch rib which is a mixed struture of steelrame and reinforced concrete. Due to the topographic condition, the bridge is in the rainy and foggy area and daily temperature is changeable. In addition, the location of the bridge belongs to a sulfureous region of Yang-Ming-Shan Nation Parke All of these factors make the bridge subject to corrosion, especially during the construction stage of arch rib. The arch rib was constructed by concrete lapping method with pre-erected composite arch, in which the steel part would be exposed to the serious corrosion environment for a long time. To avoid the damage of the bidge caused by the corrosive environment and extend the life of the bridge, the steel parts of the bridge were coated by hot-dip-galvanization. This paper is mainly to present the state-of-art of the hot dip galvanized Mao-Tsao bridge. In addition, the working situation of zinc galvanized steel part of the bridge will be discussed. It will be a valuable reference for the construction of bridges surrounded by corrosive environment.