Electrochemical and mechanical aspects in solid oxide fuel cell stack must be understood to meet the reliability targets for market implementation. This study presents a stack modelling framework that combines thermo-electrochemical models, including degradation and a contact finite-element thermo-mechanical model. It considers rate-independent plasticity and creep of the component materials and proposes periodic boundary conditions to model the stacking of repeating units. This Part I focuses on the effects of the operating conditions and design alternatives. In the present conditions, the stresses in both the anode and the cathode contribute to the probability of failure (PO, which can be lowered by adjusting the operating conditions. The requirements for mechanical reliability are here opposite to those that alleviate electrochemical degradation. Gas-diffusion layers (GDL) and interconnect design alternatives and stacking have a lower impact on the P-f, but affect the contact pressure on the GDLs, which can cause electrical contacting challenges. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.