Dynamically Loaded Foundations

The purpose of this study was to determine whether the closed form solutions used for the calculations of dynamically loaded foundations are sufficient to predict the actual behaviour of the foundation. The main limitation is that only impact loads are considered and this will limit the closed form solutions used for the study. A foundation was constructed and the actual behaviour of the foundation while exposed to an impact load was measured during an experiment. The experiment consisted of placing accelerometers and a LVDT on the foundation and then the foundation was hit with an impulse force hammer. Three parameters were tested namely the natural frequency of the system, the radiation damping of the soil and the displacement of the foundation. Closed form solutions to predict the behaviour of the foundation were obtained through numerous literature sources and these predictions was tested against the experimental values. From the data obtained through the experiment and the closed form solutions it was established that the prediction of the closed form solutions is over conservative. The natural frequency was the most accurately predicted with 5% difference between the predicted value and the experimental value. The damping was the worst parameter and because the damping was too high, the displacement was influenced. Nonetheless, there was some correlation between the value and conclusions can be made. There was a correlation between the predicted values and the experimental values. The overall prediction of the response of the foundation is over estimated, which will lead to a more conservative design.