Robustness assessment of steel frame structures with novel T-stub connections under lateral impact

The extent to which novel T-stub connections (NTC) enhance the collapse resistance of steel frame structures under lateral impact remains unclear, and there is a lack of a systematic quantitative evaluation approach. To address this issue, a component-based modeling methodology was employed, whereby the NTC was represented by an equivalent spring model, and a corresponding global structural model was subsequently developed. Building upon this, a robustness evaluation framework incorporating bearing capacity, generalized structural stiffness, and strain energy was established. Quantitative analyses were conducted for three column removal scenarios: side, penultimate, and corner columns. The results show strong consistency among the evaluation indices. Due to relatively weak boundary restraints, corner column removal induces the largest local deformation and highest strain energy concentration, with a comprehensive importance (CI) coefficient of 0.50, indicating the greatest collapse risk. Accordingly, the member importance ranks as: corner column, penultimate column, and side column. Compared with steel frames with conventional T-stub connections (TC), the NTC frame exhibits a higher safety and global stiffness, with an average increase of 16.35% in residual ultimate bearing capacity and a reduction of 13.84% in strain energy under identical impact conditions. Correspondingly, the robustness coefficients based on bearing capacity, generalized structural stiffness, and strain energy increase by 11.54%, 4.17%, and 2.30%, respectively, confirming that the proposed NTC enhances the collapse robustness of steel frame structures.