鋼床鈑由於其輕質量的特性，常作為長跨度或高架橋梁之橋面板，如高屏溪斜張橋、關渡大橋等；鋼床鈑結構的上半部為面鈑、下半部則是由互相垂直之肋梁與橫梁組成，因此一般亦稱為「正交異向性鋼床鈑」。位於鋼床鈑上方之鋪面層的力學承載行為與一般道路鋪面之行為有著極大不同，一般道路的鋪面結構係承受土壤的均勻支撐，但是鋼床鈑之肋梁與橫梁則造成非均勻支撐的狀態，所以當載重位置改變時，鋼床鈑鋪面承受反力的情形也會改變。由於車輪載重會在鋪面表面及內部產生裂縫、並蔓延到下層，讓鋼床鈑與空氣、雨水直接產生接觸，造成鏽蝕使得強度下降，因而影響橋梁整體安全。然而，目前在國內外探討鋼床鈑柔性鋪面的相關文獻中，以破壞力學為基礎的分析仍相當有限，因此其相應的破壞行為仍待進一步之研究。本研究擬採用三維有限元素分析法，針對鋼床鈑柔性鋪面含有由上至下之頂部裂縫的情況進行破壞參數分析。首先，擬在無裂縫的鋼床鈑鋪面上嘗試多個具有代表性的載重位置，分析其得到的最大主張應變發生之位置及分佈範圍，以觀察裂縫可能產生之位置與機制；其次，擬依此觀察結果，建置鋼床鈑鋪面裂縫結構之三維破壞分析模型，並藉系列之數值實驗確認模型之可行性；繼而，擬以迴圈積分之型式計算對應之混合模態應力強度因子，並將探討多種不同影響因子作用下的影響效應，包括材料性質、載重加載、邊界條件、網格尺寸等相關參數，觀察應力強度因子相應的變化。研究成果期能對於鋼床鈑柔性鋪面之破壞行為提供進一步的了解，以作為及相關設計之參考依據。 ;The top-down crack (TDC) is one of the critical damage mechanisms that significantly reduce the life expectancy of asphalt pavement layer in an orthotropic steel deck (OSD) system. The fracture behavior associated with TDCs in OSD pavements appears to be more complicated than that in road pavements. In this research, the major types of TDCs are to be developed by cautious examination of the strain fields in an uncracked OSD pavement system. A three-dimensional finite element fracture model is then to be constructed to study fracture responses in cracked OSD pavements with possible appearance of these types of TDCs. The associated stress intensity factors are to be predicted by implementing a specific contour integral and feasibility of the calculation is to be verified by a series of deliberate demonstrations based on a number of numerical features. The verified fracture model is to be applied to conduct a number of sensitivity analyses to investigate the influence of complicated geometric, loading, and environmental effects in an OSD pavement system subjected to heavy mixed-mode vehicular loadings.
