Seismic Fragility Analysis of Steel Frame Structures Containing Initial Flaws in Beam-Column Connections

The objective of this paper was to evaluate the influence of initial flaws in the beam-column connections on the seismic performance of steel frame structures. The finite element models were constructed with different initial flaw lengths by ABAQUS. The initial flaw length was 0, 8, and 16 mm, respectively. The dynamic elastic-plastic time history analysis and the pushover analysis were conducted to obtain the probabilistic characteristics of seismic demand and seismic capacity. Seismic demands are quantified in terms of the maximum drift angle (RDA) and the displacement ductility ratio $\left({\mu }_d\right)$. Moreover, the peak ground acceleration (PGA) was used for the pushover analysis. Formulas considering the influence of initial flaws on failure probability of a structure were derived for each length using different design basic acceleration of ground motion. The fragility curves were further constructed based on the data of seismic demand and capacity. The results show that the fragility of steel frame structures is similar across different seismic demand parameters. In addition, the analyses of fragility curves obviously indicate that the seismic fragility of steel frame structures increases as flaw length increases. Finally, the fragility of steel frame structures with initial flaws is consistent using different design basic acceleration of ground motion.