| Although concrete is mostly used because of its properties under compressive loading, a knowledge of its tensile behavior is necessary in situations in which cracking, and the induced change in stiffness, are critical for the service and ultimate life of the structure. One important aspect of the tensile behavior of concrete is its performance under cyclic loading. The majority of past studies on the tensile fatigue performance of concrete have focused on the behavior under constant amplitude loads. However, in recent years, the effect of variable amplitude loading has also been emphasized.;In this work a model is developed for fatigue damage accumulation for concrete subjected to non-constant tensile cyclic loads. The model is based on concepts of Continuum Damage Mechanics and is able to account for the nonlinear propagation and accumulation of damage. Calibration of the model is done using existing experimental data, and its validity is checked against recently published tests.;The fatigue damage model is used to evaluate damage in concrete pavement systems. A comprehensive finite element model for rigid pavements is developed. Besides non-linear fatigue accumulation, the model also considers pavement cracking and change in subgrade support due to pumping. An improved representation for dowel bars is also proposed, which accounts for the relative deformation between the dowel and surrounding slab. Examples of the effect of using a non-linear damage accumulation rule are presented and discussed. |
