異型拱橋相較於常規拱橋，在追求地形配合的同時，必然要犧牲一些結構受力的合理性。兩者之間如何圓滿共贏，實為一個值得探討的課題。本文旨在探討異型拱橋的拱軸線優化分析，文中所探討的是一種拱肋斜跨主梁的異型拱橋。拱肋跨徑 180 m，矢跨比 0.3451，主梁跨徑 190 m，平面半徑 600 m。探討的內容主要包括：

1.求解合理拱軸線：本文提出兩種合理拱軸線的近似解法包括二階微分方程式數值解法及桁架近似數值解法。

2. 優化拱軸線：本文應用修正的桁架近似數值解法，求解拱肋的近似合理拱軸線，且考慮最終成橋狀態及營運狀態下各荷載組合，在透過對拱肋某些點施加有限個集中力來調整拱肋內力分佈後，對拱肋軸線進行優化，使拱肋受力均勻合理。

The bridge, investigated in this paper, is a special-shape arch bridge with arch oblique cross the main girder. Its span is 180 m, rise-span ratio is 0.3451, main girder’s span is 190 m and plane radius is 600 m. The main contents, investigated in this paper, include:

1. Studying the method to solve the reasonable axis of arch. There are two methods in this paper. One is the second order differential equation method which solved by numerical method. The other is the modified approximate truss numerical method.

2. Optimizing the axis of arch bridge. The reasonable approximate axis of the arch was solved by using modified approximate truss numerical method. According to the final stage of bridge analysis, the axis of the arch was optimized by using several single node loads to let the arch’s stress be more reasonable.