Service life design for bonded anchors - A rheological approach

The short-term performance of bonded anchors can be precisely described using appropriate models. In contrast, insufficient attention has been paid to their long-term performance, in particular the time-to-failure. An exact prediction of the time-to-failure is imperative for service life estimation. In this contribution, a model is presented which accurately describes the deformation behavior of bonded anchors under permanent load up to failure. The model consists of elastic and damping components which possess nonlinear material properties. The input parameters for the model can be determined using three simple tests: 1) a tensile test to determine the initial stiffness, 2) a 1000-h-creep-test to determine the evolution of viscosity, and 3) a degradation test to determine the loss of stiffness of the bonded anchor which enables the prediction of creep-failure. This contribution focuses on the interpretation of this test based on the dissipation of deformation energy. It is thus possible to characterize the real performance of bonded anchors, not just their behavior at loads below the creep rupture strength.