Local, Story, and Global Ductility Evaluation for Complex 2D Steel Buildings: Pushover and Dynamic Analysis

摘要

A numerical investigation regarding ductility evaluation of steel buildings with moment resisting steel frames is conducted. Bending ( μ L? ) and tension ( μ Lδ ) local ductilities as well as story ( μ S ) and global ductilities are studied. Global ductility is calculated as the mean values of story ductilities ( μ GS ) and as the ratio of the maximum inelastic to yielding top displacements ( μ Gt ). The ductility capacity is associated to drifts of about 5%. Ductility values significantly may vary with the strong motion, ductility definition, structural element, story number, type of analysis, and model. μ L? is much larger for beams than for columns. Even though the demands of μ Lδ are considered an important issue they are less relevant than μ L? . μ S is much smaller than μ L? for beams. μ GS for dynamic analysis give reasonable values, but μ Gt does not. μ L? , μ S and μ GS obtained from pushover are larger than those obtained from dynamic analysis and unlike the case of dynamic analysis, μ L? tend to increase with the story number showing an opposite trend. Considering that: μ Gt for dynamic analysis results in unreasonable values, pushover analysis does not consider energy dissipation, the strong column–weak beam (SCWB) concept was followed in the model designs, and μ Lδ is not relevant in framed steel buildings, the ratio ( R LG ) of global to local ductility capacity is calculated as the ratio of μ GS to μ L? of beams, for dynamic analysis. A value of 1/3 is proposed. Thus, if bending local ductility capacity is stated as the basis for the design, the global ductility capacity can be easily estimated.