Assessment of Connection Imperfections in Seismic Response and Progressive Collapse in Steel Moment Frame Structures

Progressive collapse is a low probability event and requires abnormal loading to initiate initial collapse in a structure with a lack of sufficient cohesion and ductility to resist the spread of collapse. However, when collapse occurs, it can lead to significant human casualties. In this study, we will try to investigate the seismic vulnerability of one of the common building types in the country, namely steel structures with a medium-tension frame system with ۶ floors, and we will generate a fragility curve for these structures. The aim of this study is to determine the seismic vulnerability fragility curve of a steel medium-tension frame building system designed according to the ASCE۷-۱۰/IBC۲۰۱۲ design code on type D soil in a region with high seismic hazard. The models in question are a ۶-story steel medium-tension frame building with two cases, one with correct execution of connections and the other with ۱۰% error in connections. Modeling of these buildings was done by considering ۱۰ types of near-field earthquakes in OpenSeeS software and incremental nonlinear time history analysis was performed on the models. To achieve the goals of this paper, the models were modeled in ۳D in OpenSeeS software and subjected to nonlinear time history analysis under the influence of ۱۰ earthquake records, each of which was scaled from g ۰.۱ to g ۳.۵. Then, the values of demand and capacity in the structural components will be compared and the Drift component in presenting fragility in determining vulnerability will be examined and then by applying the necessary statistical techniques on the data, fragility curves will be generated for each of the models. The results obtained from comparing two buildings with two different failure curves show that the LS service level for a building modeled with ۱۰% execution error is ۲۱.۲۱% higher in terms of DCR and ۵۲.۹% higher for CP service level than the building modeled correctly.

کلیدواژه ها:

Nonlinear time history ، progressive failure ، failure curves ، steel frames