Column Effective Length Of Semi-Rigid Frames

This paper studies the stability of semi-rigid frame column, analyzes the influence of semi-rigid connection to the frame and presents the approaches of calculating the column effective length. Based on the theoretical analysis, the general buckling equation of semi-rigid frame column is deduced. The validity of the buckling equation is verified and the column effective length factor under random restriction is obtained by the finite element method. Considered the influence of semi-rigid connection, the traditional effective length is revised and the modified coefficient y to the semi-rigid frame column is deduced. In light of story-based buckling, that is, the structure is lapsed when the story stiffness is vanished, two kinds of calculation method are derived. To simplify the theoretical deduction and the actual application, the concept of end-fixity factor r is introduced and lateral stiffness S of the sway-permitted semi-rigid frame column is expressed by the end-fixity factor r and parameter Φ(Φ =kl) .Based on the assumption of proportional loading, a practical formula of the effective length factor is presented.By the story buckling theory, the analysis results of the prototypes are very close to the finite element analysis . Compared with the theoretical results, the errors is very small. This paper studies the semi-rigid connection classification and reveals the rationality of Eurocode 3. In Code(GB50017-2003),the calculation and classification of semi-rigid frame column are not definitely regulated, so the study offers references for the designers.