Equivalent Circuit Model for Thick Split Ring Resonators and Thick   Spiral Resonators
  A simple theoretical model which provides circuit parameters and resonance frequency of metallic thick resonators is presented. Two different topologies were studied: the original Pendry's SRR and spiral resonators of two and three turns. Theoretical computations of resonant frequencies are in good agreement with values obtained with a commercial electromagnetic solver. The model could be helpful for designing thick frequency selective surfaces (FSS) based on this types of resonators, so called metasurfaces. 
Laura Maria Pulido Mancera, Juan Domingo Baena Doello
physics.optics