Design Internal Forces of Non‐Dissipative Members in CBFs With Regular and Irregular Brace Configurations

ABSTRACT Steel Concentrically Braced Frames (CBFs) are widely used in seismic regions, with chevron and split‐X configurations commonly adopted for their structural efficiency and architectural flexibility. Although extensive research has been carried out on these systems, the effectiveness of the formulations available in the literature for estimating the internal forces of non‐dissipative members (i.e., beams and columns) has often been evaluated assuming that braces are located within the same span at each storey. In practice, instead, braces are frequently arranged in different spans to reduce the axial force demands on columns. This study aims to improve the prediction of internal forces in non‐dissipative members of chevron and split‐X CBFs. Particular attention is devoted to the estimation of the unbalanced vertical forces transmitted by the braces to the braced beams, the axial compressive and tensile forces in columns, and the bending moments in columns. To this end, two sets of steel buildings with different bracing layouts and soil conditions are designed in accordance with the second generation of Eurocode 8 and analysed through multiple stripe analyses using refined numerical models that explicitly account for material uncertainties. The results are used to assess existing formulations and to propose and validate more accurate predictive models.