Following a series of recent innovations, isogeometric shell analysis based on trimmed CAD surfaces is currently being developed into an accurate, efficient and mature design-through-analysis methodology. This work contributes to this emerging technology with respect to the following aspects. On the analysis side, we present a robust variationally consistent Nitsche-type formulation for thin shells at large deformations that weakly enforces coupling constraints at trimming curves. On the geometry side, we present a set of algorithms that enable automatic interaction of trimmed shell analysis with CAD data structures based on the STEP exchange format. We integrate these methodologies in a comprehensive framework for isogeometric trimmed shell analysis. We demonstrate that our framework is able to seamlessly perform large-deformation stress analysis of an industry-scale 76-patch surface model of a Dodge RAM hood, while delivering comparable accuracy with respect to Simulia’s commercial software package Abaqus. •We present a variationally consistent formulation for coupling isogeometric shells at trimming curves.•We also present algorithms that enable automatic interaction with CAD data structures based on the STEP exchange format.•We integrate these methodologies in a comprehensive framework for isogeometric trimmed shell analysis.•It enables seamless and accurate large-deformation stress analysis, illustrated with a 76-patch model of a Dodge RAM hood.