Design Demands on Columns of Inverted-V Braced Steel Frames

Seismic demands on columns that belong to 10-, 14- and 18-story buildings structured with ductile concentrically braced frames (CBF) in a chevron configuration are studied in this paper. Buildings were carefully designed following principles of the capacity design philosophy, and they were virtually located in a soft soil condition. The research explores a more realistic assessment of the axial and bending demands on the columns of braced bays for a safe and economical design. Based on the statistical results of detailed nonlinear analyses, a procedure for estimating the axial design load in the columns of braced frames is proposed for mid- and high-rise buildings to obtain a conservative prediction of the demand. The methodology depends on the story where the column is located and the expected capacity of the bracing system calculated from a participation factor. Furthermore, a relationship between the building height and the accuracy of the prediction is underlined. The study also provides some detailed background behind the design procedure of CBF from specialized codes and compares the efficiency of published methodologies to estimate the design demands.