Modeling Flexural Fatigue Behavior using Viscoelastic Continuum Damage Mechanics Principles

Fatigue cracking is one of the major distresses in asphalt pavements. The AASHTO protocol for fatigue characterization using third point loading of a beam is popular in the engineering community due to its simplistic nature. This protocol requires testing different samples for fatigue performance at several strain levels and subsequent development of an empirical model through regression analysis. The behavior of asphalt concrete is dependent on factors like loading rate, loading history, testing temperature, healing and aging. To consider all these factors in the AASHTO fatigue model, considerable amount of time and resources is required. In this research, an existing uniaxial constitutive model has been applied to the flexural mode of loading. The testing methodology involves dynamic modulus testing to obtain viscoelastic properties and subsequent fatigue testing. One 12.5 NMAS mixture and four 19.0 mm NMAS asphalt concrete mixtures with different grade binders were tested according to the proposed methodology. The analysis of data indicates that there exists a unique relationship between the flexural pseudostiffness and amount of damage in the specimen. Similar observations under uniaxial mode of loading were made by previous researchers. A point of inflection was found in this damage characteristic curve beyond which the material loses its structural integrity at faster rate. Also, it was observed that normalized pseudostiffness at this inflection point is dependent on mixture properties. 1 PhD Candidate, University of New Hampshire, Durham, NH 03824. (aravind.kswamy@unh.edu) 2 Associate Professor, University of New Hampshire, Durham, NH 03824. (jo.daniel@unh.edu)

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