Efficient ground motion intensity measures can significantly reduce the variability in predicting structural response, making the selection of appropriate measures a critical step in seismic vulnerability analysis. Th...
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Efficient ground motion intensity measures can significantly reduce the variability in predicting structural response, making the selection of appropriate measures a critical step in seismic vulnerability analysis. This study conducts vulnerability analyses on a six-story reinforced concrete column-steel beam (rcs) frame under three damage limit states: immediate occupancy (IO), life safety (LS), and collapse prevention (CP). The structural model is developed in the open-source software OpenSees, simulating both shear deformation and vertical bearing failure at beam-column joints. To account for the characteristics of seismic motions, two sets of ground motions-far-field and near-field-are selected. The efficiency of 22 chosen intensity measures (IMs) is evaluated and compared using the log-normal standard deviation beta RTR in vulnerability analysis. Results indicate that velocity-related measures, specifically Housner Intensity (HI) and Velocity Spectrum Intensity (VSI), perform well. To further enhance the HI measure's effectiveness across damage states, an optimized ground motion intensity measure, HIIMP, is proposed using the global optimization capabilities of a genetic algorithm (GA). As the damage limit state deepens, the proposed HIIMP measure achieves higher upper integration limits, increasing the influence of the softening period. Finally, the applicability of HIIMP to rcsstructures is demonstrated from the perspectives of sufficiency and scaling robustness.
Most of the vertical progressive collapse failure of structures is caused by central-column removal. When the lateral stiffnesses on the two sides of a removed column are different, the structure fails in an asymmetri...
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Most of the vertical progressive collapse failure of structures is caused by central-column removal. When the lateral stiffnesses on the two sides of a removed column are different, the structure fails in an asymmetric manner. Thus far, studies on asymmetric progressive collapse have been limited in the existing literature. In this study, an asymmetric double-half-span single-column structure was taken as the research object, and a type of through-column-type beam-column connection substructure was designed with a fully bolted connection in reinforced concrete (RC) column and steel (S) beam (rcs) framestructure. The entire process of the asymmetric collapse and the failure of the structure under the failure of a penultimate column was simulated by a static loading test. The difference between the lateral stiffness of the columns on the two sides of the removed column in the substructure was simulated by the unequal span. Additionally, the mechanism and the failure mode of the connections under progressive collapse were simulated using ABAQUS. The results were compared with those of a traditional symmetrical double-half-span substructure. It was found that the top flange of the beam on the side with smaller lateral stiffness first exhibited local buckling when the fully bolted connection substructure failed. Moreover, the rotational capacity of the connection was less than that under the central-column-removal scenario. The catenary action of the connection could not be fully exerted, which caused the ability of the progressive collapse resistance to be lower than that under the central-column-removal scenario. However, the ultimate rotation angle of the connection obtained from the test and the finite element analysis was higher than the allowable limit in the DoD (Department of Defense) guidelines, indicating that the use of the DoD criteria was conservative in evaluating the progressive collapse resistance of the fully bolted connection of the throughcolumn-type
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