Extension Of Stress-Based Finite Element Model Using Resilient Modulus Material Characterization To Develop A Theoretical Framework for Realistic Response Modeling of Flexible Pavements on Cohesive Subgrades

Pavement design methodologies have over the past decades seen philosophical evolutions and eventually practical implementation of new postulates. As more contributions are made by pavement researchers to the State-of-the-Art in pavement design, there exist a chasm between pavement engineers and state-of-the-art pavement research in terms of incorporation into pavement design guidelines. In developing countries such as Guyana in South America, as well as several departments of transportation, municipalities and townships in the United States, pavement engineers still use the American Association of State Highway and Transportation Officials (AASHTO) Pavement Design Guide (1993). This empirical pavement design guide and its previous iterations were based primarily on data that was collected and processed from the then American Association of State Highway Officials (AASHO) Road Test conducted between 1958 and 1960. The limitations with continued use of this method are obvious since the data was gathered under specific environmental conditions, a specific subgrade type, and with specific materials as well as specific pavement cross-sections. The continued use of this guide does not account for advances in material technology, different types and volumes of vehicular traffic, changing climatic conditions and also can be costly in expanding road networks. To solve this dilemma pavement researchers started working toward a more mechanistic approach for design and through the work of National Cooperative Highway Research Program (NCHRP), culminated in the publishing of the Mechanistic-Empirical Pavement Design Guide (MEPDG) in 2004. The finite element model used in the MEPDG is premised upon a displacement based theory. These theories are capable of making good predictions regarding global responses such as displacements and sometimes in-plane stresses but not the transverse stress distribution. To predict transverse stress distribution, stress based theories are more suitable for use in formulations. At The Ohio State University, Chyou (1989), Schoeppner (1991) and Butalia (1996) worked on different versions of the stress based model for composite laminates. This model was initially extended by Tu (2007) to good effect for analyzing the responses in pavement systems. In this research effort, this response model is being further extended to incorporate a material characterization model into the stiffness matrix for more accurate structural response predictions. The material characterization model (Kim 2004) allows the pavement designer to make predictions of Resilient Modulus, Mr, for cohesive subgrades without the need for conducting the test which can be both costly and complex. This approach renders a cost effective way of obtaining one of the most important parameters for employing a mechanistic approach which is also a major prohibition for many developing countries to move closer to the State-of-the-Art. This new synthesis allows for good predictions of global responses as well as transverse stress distribution which is critical for overcoming pavement layer debonding that can reduce pavement life significantly. Considering the results of the analysis compared to ABAQUS 3D Finite Element Models, this new synthesis forms the basis of a good pavement response model which can be used to further a more mechanistic approach for relatively small design agencies.