三維有限元素法於柔性路面之破壞分析研究

The Flexible Pavement Distress Analysis by the 3-D Finite Element Method

由於國內路面之交通量及車輛荷重有明顯增加的趨勢，而現有柔性路面厚度設計方法如美國AASHTO及AI等都未明確的由力學觀點探討不同型輪重對路面績效的影響。國內有些研究者以多層線性彈性理論或二維軸向對稱有限元素法用於路面之結構分析，但並未能考慮材料之非線性及不同型輪重因素。本研究採用能合理模擬瀝青混凝土之非線性模式與三維有限元素法結合，並探討一軸兩輪荷重之鋪面結構反應並與二維數值解作比較。接著將結構分析結果與破壞模式結合預測鋪面在車輛反覆荷重所造成之車轍與疲勞龜裂，其結果亦與觀測值作比較。最後則將所得之鋪面績效代入AASHTO之現在路面服務指標方程式，並比較二維及三維績效分析所得鋪面績效PSI之差異。

Even though the traffic flow of heavy vehicles has increased in Taiwan,the current flexible pavement design methods such as AASHTO and AImethods do not consider the effect of different vehicles, wheels on pavementperformance from the mechanics point of view. Some researchers inTaiwan have started to investigate the structural response of pavement byusing the multi-layer linear elastic theory, and the axisymmetric nonlinear finite element method. However, these approaches cannot consider thenonlinear behavior of material or the type of loading. In this study, anonlinear model, which can represent the behavior of asphalt concrete, isincorporated with the 3-dimentional finite element method to investigatethe structural response of pavement and the results are compared with theresults from 2-dimentional finite element analysis. The stresses from thestructural analysis are combined with the pavement distress models to predictthe rutting and fatigue cracking of pavement, and compared with themeasured distress. Finally, the distress from the 2-D and 3-D finite elementmethods are incorporated into the Present Serviceability Index equation tocompute the PSI by the number of vehicle exposures.