The Federal Aviation Administration (FAA) developed a two-dimensional model of its full-scale, indoor, reflection cracking test equipment at the National Airport Pavement Test Facility (NAPTF), William J. Hughes Technical Center, Atlantic City International Airport, NJ. The analytical model represents two jointed concrete slabs and a continuous hot mix asphalt overlay with a single, preexisting vertical crack centered on the joint. Mode II stress intensity factors (SIF) were derived from superposition of the linear elastic solutions of two separate problems having different domains. The first problem considers the uncracked domain with the same prescribed vertical displacements at the bottom as the original problem. The second problem considers the cracked domain, where vertical displacements at the bottom boundary are prescribed to be zero. The sum of the solutions of these two problems in the linear elastic domain gives the desired Mode II solution at the vicinity of the crack tip. By applying Schapery’s theory of crack propagation in viscoelastic materials, this model can be used to determine the energy release rate (ERR) in and asphalt overlay subject to Mode II cracking caused by repeated aircraft traffic loads. The model was used to compute Mode II SIFs at the crack tip for a series of incremental crack lengths, using assumed properties. Computed SIF values showed good agreement with SIF values computed by a finite element model (ABAQUS).
Author: Kairat Tuleubekov