Variation of Ductility Capacity of Steel Beam‐Columns

This paper presents an investigation on the variation of ductility capacity of steel beam‐columns. First, experimental data obtained from previous tests are surveyed, and their ductility ratios are examined. It is found that experimental ductility ratios scatter over a wide range with their coefficients of variation ranging from 0.4 to 0.9. Next, nonlinear numerical analysis is carried out with slenderness, axial force, strain hardening, residual stresses, and initial out‐of‐straightness as variables. The analysis reveals that neither residual stresses nor initial out‐of‐straightness is a major factor affecting the ductility ratio, but strain hardening is very influential on the ductility ratio, suggesting that strain hardening is one of the major sources for the large variation in the experimental ductility ratio. A guideline is also presented for estimating ductility ratios of steel beam‐columns. Finally, problems associated with large variation in the ductility capacity of steel beam‐columns are discussed with reference to the reliability design format.