IMPACT BEHAVIOUR OF ROCKING RIGID BODIES SUBJECTED TO SEISMIC LOADS

摘要

Rocking of unanchored components (e.g. storage casks for spent fuel) is a highly nonlinear phenomenon, which cannot be completely described analytically. Therefore, the rocking motion of a rigid body under various conditions will be analysed with different models. The first model is an analytical model which is solved numerically by using the Runge-Kutta method. The other models are mostly plane finite element (FE) models. The FE models consider a rigid 2D (or in some cases 3D) block on a flexible ground without sliding. With the FE method it is possible to investigate the influence of the properties of the ground, the contact conditions, slight deviations from the ideal rectangular corner geometry and the use of anti-slip pads especially on the impact. The impact is described by the coefficient of restitution. The FE models, which take into account the above mentioned influences, lead to higher coefficients of restitution than those derived from the simplified model published by Housner (1963). For hard ground materials like steel or concrete the agreement between results from finite element analyses and the theoretical model with two rotation centres at the corners of the body is very good if the coefficients of restitution are based on best estimate values from FE analyses. For the model with the anti-slip pad the theoretical model is not usable. A classical resonance does not occur but a dynamic increase of the amplitude during the first cycles up to a factor of about 2.5 is possible.