Evaluation of the Robustness of Tall Buildings with Bundled Tube Resistant Skeleton using Fragility Curves

This research includes an analytical approach on the subject of vulnerability of structures with resistant skeleton consisting of multiple cells of moment frames, based on the seismic resilience approach. There are two considered studied structures consisting of a 24- and a 48-story bundled framed tube resistant skeleton. The results of this study have been obtained and evaluated through performing incremental dynamic analyses (IDA) and statistical evaluations of structural fragility curves. The seismic fragility analysis has been applied with respect to the assigned FEMA provisions in order to calculate the probability for the structure to exceed six performance levels. Then, by determining the damage coefficients according to the HAZUS 2005 instructions and applying the proposed formulation of the damage function in the report MCEER-09-0009, the seismic resilience strength index of the studied structures was calculated.Based on the results of nonlinear dynamic analyses, it was observed that the bundled framed tube structural systems have relatively good safety and resilience against collapse mode under strong near-field records containing velocity pulses. Also, based on the evaluation of the probabilistic values calculated for the occurrence of the assigned limit states, it was known that the studied bundled framed tube structures handle the gradual processes of stiffness deterioration and strength degradation, with a more comprehensive formation of the geometric nonlinear behavior. In accordance with the processed results of the fragility curves, it was known that the application of bundled framed tube structures in high-rise buildings can produce a high capability of dynamic stability .