دانلود رایگان مقاله انگلیسی ارزیابی عملکرد لرزه ای ساختمان های فولادی مورب - اشپرینگر 2018

Abstract

In this study the seismic performances of axi-symmetric steel building structures with circular plan shape were evaluated based on the ATC-63 approach. For analysis models, thirty-three-story vertically convex, concave, and gourd-type axisymmetric buildings were designed using diagrid structure system, and their seismic performances were compared with those of the cylinder type regular steel structure. Seismic fragility analyses were carried out using twenty-two pairs of earthquake records to obtain the probability of failure for a given earthquake intensity. The validity of the response modifcation factor used in the seismic design of the model structures was also investigated. Based on the analysis results it was concluded that the response modifcation factor of 3.0 used in the design of the model structures is acceptable for the ATC-63 methodology. It was also observed that the seismic safety margin for a specifc level of earthquake decreases as the vertical irregularity of the structure increases.

6 Conclusions

In this study the seismic performances of axi-symmetric diagrid building structures with various vertical irregularities were evaluated based on the procedure recommended in the ATC-63. Seismic fragility analyses were carried out using twenty-two pairs of earthquake records to compare the probability of failure for a given earthquake intensity. The thirty-three story analysis model structures with diferent elevations were designed to have similar total foor areas, the aspect ratios of the model structures range from 2.0 in the case of the concave structure with low center of mass and to 6.2 in the case of convex structure with high center of mass.

According to the incremental dynamic analysis and fragility analysis of the model structures, the adjusted collapse margin ratios of the model structures turned out to be higher than the acceptable values specifed in the ATC-63. The collapse margin ratio of the cylinder-type structure with no vertical irregularity turned out to be larger than those of the other structures with vertical irregularity. The gourdtype structure with longest natural period and highest vertical irregularity showed the smallest collapse margin even though it was designed with the largest steel tonnage. The collapse margins of the structures with low center of mass were generally larger than those of the structures with high center of mass. The collapse margins for the convex structures are slightly larger than those of the concave structures. The structures with high aspect ratios such as the convex type with middle or high mass center showed relatively large adjusted collapse margin ratio. The structures with relatively longer natural period such as the gourd type structure and the structures with higher location of mass center showed relatively small adjusted collapse margin ratio. Based on the adjusted collapse margin ratios of the model structures obtained from fragility analyses, it was concluded that the seismic safety decreased as the vertical irregularity of the structure increased, and that the response modifcation factor of 3.0 used in the design of the model structures was acceptable.