Advanced multi-body modelling of DCCSS isolators: Geometrical compatibility and kinematics

The effectiveness of Double Concave Curved Surface Sliders (DCCSS), which initially spread under the name of Double Friction Pendulum (DFP) isolators, was already widely proven by numerous experimental campaigns carried out worldwide. However, many aspects concerning their dynamical behavior still need to be clarified and some details still require improvement and optimization. In particular, due to the boundary geometrical conditions, sliding along the coupled surfaces may not be compliant, where this adjective is adopted to indicate an even distribution of stresses and sliding contact. On the contrary, during an earthquake, the fulfillment of geometrical compatibility between the constitutive bodies naturally gives rise to a very peculiar dynamic behavior, composed of continuous alternation of sticking and slipping phases. Such behavior yields a temporary and cyclic change of topology. Since the constitutive elements can be modelled as rigid bodies, both approaches, namely Compliant Sliding and Stick-Slip, can be numerically modelled by means of techniques typically adopted for multi-body mechanical systems. With the objective of contributing to the understanding and further improvement of this technology, a topology-changing multi-body mechanical model was developed to simulate the DCCSS. In the present work, attention is focused on details regarding geometrical compatibility and kinematics, while the complete dynamics is presented in another work. In particular, for the sake of comparison, the kinematic equations are presented and applied not only for the proposed Stick-Slip approach, but also for the currently accepted Compliant Sliding approach. The main findings are presented and discussed.