The dynamic response of ground anchorage systems
This thesis describes the development of the lumped parameter model and the results obtained from it. In order to fully utilise the response signatures obtained from GRANIT, it is essential to understand the effect of the various components of the 'complete ground anchorage system' such as protruding free and fixed length of the anchorage, anchorage head assembly, affected and non-affected rock mass. In order to monitor each subsystem and its dynamic response to potential changes/failures, the anchorage system, in its simplest form, is represented by the model which comprises seven masses and a number of spring/damper systems replicating the components described earlier. Ordinary differential equations for mass/spring/dash-pot elements were then configured and the model was implemented in software form and then solved for both time and frequency domain. The acceleration response was examined at a number of points in the anchorage system i.e. at the protruding length as well as at the anchorage head, along the free length, along the fixed length and even within the rock mass itself. Several laboratory and field anchorage applications were simulated using the lumped parameter model and the results obtained from the model. A parametric study was then undertaken with regard to addressing mechanisms which are generally present in anchorage applications such as changes of material properties of the resin and concrete, the introduction of defects, such as gaps along the fixed anchorage length or debonding at the proximal fixed anchorage length, and the influence of changes in post tension load on the dynamic response of the anchorages. Furthermore, an investigation of the impulse load was conducted with the aim of further development of the current impact device in order to be able to assess anchorages regarding the mechanisms mentioned earlier.