Abstract
The fragility of concrete-filled steel tubular (CFST) frame structures with buckling-restrained braces (BRBs) subjected to multiple earthquakes is studied in this paper. First, a fiber beam element model with rate-dependent concrete and steel material properties is developed for CFST members and, then, the effect of the strain rate on the seismic response of the CFST frame structure is investigated numerically. The influence of BRBs on the seismic response of the CFST frame structure is then comparatively analyzed. The seismic responses of the CFST frame structure with BRBs under single mainshocks and earthquake sequences are investigated, and the fragility curves are generated using probabilistic seismic demand analysis. The obtained roof displacement and inter-story drift ratio (ISDR) of the structure decreased by 10.2% and 6.9%, respectively, when obtained while considering the strain rate effect, compared with those obtained without consideration of the strain rate effect. BRBs can effectively improve the seismic performance of the CFST frame structure in that the maximum roof displacement and ISDR can be reduced by 45.1% and 43.9%, respectively. Compared with those under single mainshocks, the maximum roof displacement and ISDR of the structure with BRBs under earthquake sequences significantly increase. The fragility of the BRB structure under earthquake sequences is more severe than that under single mainshocks. Therefore, the influences of the strain rate effect and earthquake sequence should be considered to realistically evaluate the seismic fragility of CFST structures.
Highlights
Earthquakes are among the most destructive natural hazards
Realistic and reasonable evaluation of the seismic performance of the Concrete-filled steel tubular (CFST) frame structures with buckling-restrained braces (BRBs) is of great importance for the seismic design and structural safety of such systems
BRBs are systematically investigated investigated in this paper
Summary
Earthquakes are among the most destructive natural hazards. In the past few decades, there have been frequent occurrences of earthquake disasters worldwide. The severe damage and collapse of building structures under seismic actions leads to heavy casualties and property losses. Concrete-filled steel tubular (CFST) frame structures installed with energy-dissipating buckling-restrained braces (BRBs) have the advantages of being light weight, high strength, and possessing high lateral stiffness. They have been widely applied in the seismic design of high-rise and super-high-rise buildings [1,2,3,4,5,6]. When subjected to an earthquake, BRBs dissipate seismic energy by yielding and reducing the damage to the main structure, which results in good energy dissipation capacity and ductility of the whole structural system. Realistic and reasonable evaluation of the seismic performance of the CFST frame structures with BRBs is of great importance for the seismic design and structural safety of such systems
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