Seismic Response Analysis Of Multi-storey Steel Frames With Self-centering Energy Dissipative Braces

Traditional frame structure with anti-seismic performance could improve the seismic demand by increasing lateral force resisting system, such as brace system or shear walls, that are used to reduce the deformation response of structures. But there are still larger residual deformations in these frame structures after the earthquake, and these residual deformations will seriously affect the structural function and increase the maintenance costs to the structure after the earthquake. The occurrence of inter-story failure easily happens to frame structure with layer yield mechanism(or called column hinge mechanism)subjected to ground motion, the velocity pulse effect of near-fault ground motions makes it worse by adding the possibility of local failure, seriously restricting the frame structure of the overall seismic performance. The self-centering energy dissipative bracing(SCEDBs) is a new-type energy bearing member with both good energy-dissipation and re-centering capability. And it is compliance with the growing need for performance-based seismic design. This energy member applied in the building has a good energy dissipation effect for the frame structural system.The self-centering energy dissipative brace system can control the structural deformation mode effectively, because of its unique restoring role of self-centering system and its own rigidity provided to the frame structure. It not only reduces the possibility of emergence of a weak story in structure and controls the damage mode of structure, so that the structure have characteristic of ductile failure under severe earthquake, and also can be maintained bearing capacity of the structure and control residual deformation of structure to reduce the response of the structure after the earthquake.This paper main research content is as follows:(1)Introdicting the composition and assembly methods of the self-centering energy dissipative brace, the working process and reset principle of the self-centering energy dissipative brace are studied, and then the finite element of self-centering energy dissipative brace is modeled via Open Sees.(2)Nonlinear finite element fiber model of the structure with self-centering energy dissipative brace system are modeled by Open Sees. The self-centering energy dissipative braces(SCEDBs) were applied to 2-, 4-, 6-, 8-, 10- and 12-story steel frames in this paper, and the static pushover analysis and dynamic time-history analysis under ground motion ensembles corresponding to two hazard levels such as frequently-occurred level and rarely-occurred level were conducted via Open Sees software respectively. The comparable steel frame structures with buckling restrained braces(BRBs) were also analyzed for comparison. The different performance indexes were used to evaluate and analysis the effect on seismic response of self-centering energy dissipative brace system to the structures, then to evaluate the performance level of structures based on the performance indexes.(3)Analyze the structure from the elastic stage to failure with parameters of performance indicators, and apply fragility contrast analysis to the overall structure. And the incremental dynamic analysis of steel frame with self-centering energy dissipative braces and buckling restrained braces were performed by Open Sees under near-fault ground motion and far-field ones, then to analysis energy dissipation effect of each structure in different performance level. Then seismic fragility analysis was also performed based on the IDA results, to comparative analysis the fragility of the structure with self-centering energy dissipative braces and buckling restrained braces in different performance level under the near-fault and far-field ground motion.