Linear Elasticity

In CalME, pavement structures are simplified as multilayer elastic systems. All materials are assumed to be linear elastic when calculating the critical responses of the pavement. This is true even for rate-dependent materials such as asphaltic materials and stress-dependent materials such as unbound materials. This is possible because all of the models in CalME that affects layer stiffness are non-iterative. In other words, if layer stiffness is affected by certain factor, that factor cannot in turn be affected by the same layer stiffness.

To characterize a linear elastic material in CalME, the user needs to provide the layer stiffness and Poisson’s ratio. Stiffness refers to the apparent Young’s modulus of a material under a given loading condition, such as loading rate, temperature, age, confinement, or stress state.

For in-service pavements, the layer moduli are determined from backcalculation using FWD data.

Even though it can significantly affect the calculated pavement responses, Poisson's ratio is fixed for each material type during model calibration. As a result, Poisson's ratio is fixed for each material type for design too.