  This paper examines the strain response of typical HMA overlays above jointed
PCC slabs prone to bottom-up reflective cracking. The occurrence of reflective
cracking under the combined effect of traffic and environmental loading
significantly reduces the design life of the HMA overlays and can lead to its
premature failure. In this context, viscoelastic material properties combined
with cyclic vehicle loadings and pavement temperature distribution were
implemented in a series of FE models in order to study the evolution of
horizontal tensile and shear strains at the bottom of the HMA overlay. The
effect of several design parameters, such as subbase and subgrade moduli,
vehicle speed, overlay thickness, and temperature condition, on the horizontal
and shear strain response was investigated. Results obtained show that the rate
of horizontal and shear strain increase at the bottom of the HMA overlay drop
with higher vehicle speed, higher subgrade modulus, and higher subbase modulus.
Moreover, the rate of horizontal strain accumulation increases with higher
overlay thickness. Although initial strain values were higher at positive
pavement temperature distributions, the corresponding rate of strain increase
were higher at negative pavement temperatures. Finally, an extrapolation of the
strain history curve for various pavement design parameters was used to
estimate the number of cycles for bottom-up crack initiation.
