عنوان مقاله [English]
The braced tube structure is one of the most efficient lateral load resistant skeletal systems under seismic loads. This high-rise mega frame has desirable aspects in terms of seismic response. Also, this system increases the resistance potential of high-rise structures in comparison with three-dimensional steel rigid frames. The present study denotes the seismic response properties of four mega braced tube structural systems of 20-story with different bracing configurations, which are the same in plan and loading arrangements, subjected to strong near-field records. The two studied structures have skeletal configuration of centralized braced panels. Moreover, the two other studied models were designed based on mega braced tube system considered as the resistant structure. In order to assess dynamic response parameters of the studied structures, several nonlinear time history analyses were performed. The selected earthquake records contain a variety of wave-like characteristics such as long period pulses and high amplitude spikes in the ground velocity and acceleration time histories. The analytical evaluation of seismic response parameters indicates the desirable performance of mega braced tube structural systems under powerful near-fault records.
The aforementioned seismic performances were investigated in terms of maximum lateral displacement, inter-story drift as well as absolute acceleration, relative velocity of floors and total base shear along with the integrated formations of skeletal nonlinear hinges. It was obtained that the concentrated configuration of a limited number of aligned braced panels in high-rise framed skeleton is not relatively suitable. Also, dynamic response parameters of the 20-story models with the configuration of centralized braced panels are influenced more while being subjected to near-field ground motions in comparison to the mega braced tube systems. The application of centralized braced panels would lead to the more intensive variation in seismic response parameters. It should be noted that the application of single elements as well as concentric aligned braced panels cannot be effective in controlling the maximum lateral displacement and drift demands. The structural vulnerability assessment indicated that mega braced tube structures have better seismic performance than the other type of resistant skeletons under influencing of large coherent velocity pulses which displayed in the time history of strong earthquake records.