Seismic performance of inclined CFT frame-core tube-outrigger truss structure system

In order to clarify the seismic performance of inclined CFT column frame-core tube-outrigger truss hybrid structures, the seismic performance of this structure system was analyzed using MARC finite element software, with the background of the Qingdao Haitian Center project. Elastic-plastic dynamic time-history analysis under the frequent earthquake, fortification earthquake and rare earthquake was carried out. The results show that the inclined CFT column can effectively suppress the top displacement of the structure by about 76. 6% reduction compared with that of straight CFT column frame-core tube-outrigger truss hybrid structures under a rare earthquake. The seismic shear-force transfers from core-tube to frame part due to inclined CFT columns, and the transferred seismic shear-force of the frame part is closer to the seismic design requirement for the dual lateral force resistance system, i. e., the frame part bears at least 20% of the total base shear-force of the structure under frequent earthquakes. Meanwhile, the change of the structural bottom overturning moment is opposite to that of the seismic shear-force. Subsequently, the seismic collapse fragility analysis of the structure based on incremental dynamic analysis (IDA) was carried out, then the plastic development path of structure was determined as coupling beam, bottom of core tube, bottom end of frame column, and outrigger truss. The fragility results show that the inclined form of CFT frame columns do not adversely affect the safety reserve of the structure and still showed excellent resistance to earthquake collapse. The plastic damage of the coupling beam and the surrounding bottom wall of the variable cross-section floor of the structure is the most serious, and these parts should be strengthened in the design. © 2023 Science Press. All rights reserved.