Abstract: The isogeometric thin-shell analysis based on CAD trimmed surfaces is progressively developing into an advanced analysis method that integrates high accuracy and computational efficiency. During the parameterized element attribute definition stage, the existing projection method still encounters significant robustness challenges under specific geometric features, such as numerical instability near adjacent points and difficulties in ensuring judgment accuracy for complex curves with inflection points or sharp corners. To address these issues, this paper proposes an integrated computational framework tailored to the STEP standard file format, enabling seamless CAD/CAE integration for complex multi-patch trimmed structures. The framework extracts and processes trimming and multi-patch coupling information. It employs an adaptive subdivision method for element preprocessing. For element attribute judgment, a novel boundary determination strategy integrating the projection method with the ray-casting method is proposed. The projection method retains its high efficiency for simple closed curves, while the ray-casting method is employed for complex ring domains formed by multiple curve splices. This forms a geometrically adaptive hybrid judgment strategy to achieve efficient element definition and partitioning. A series of numerical examples are utilized to validate the feasibility and applicability of this framework.