Study On Seismic Performance Of CFST Frame-Core Wall Structure With Dissipation Devices

The concrete filled steel tubular (CFST) frame-core wall mixed structure has beenadopted widely in the high-rise buildings in China recently. However, the seismicperformance of CFST frame-core wall structure should be improved for itscomplicated force mechanism and fuzzy cooperative working mechanism. Accordingto these problems, the dampers can be set in the CFST frame-core wall structure, andthen the CFST frame-core wall structure with dissipation devices is established, whichhas excellent seismic performance and more reasonable cooperative workingmechanism, whilst the seismic fortification lines of this mixed structure have beenadded. The related researches on the CFST frame-core wall structure with dissipationdevices in this paper had been carried out as follow:1. The1:4reduced scale structure models of CFST frame, CFST frame withdampers, CFST frame-shear wall structure and CFST frame-shear wall structure withdampers were designed and made, and the comparison experiments under low cyclicloading for these models had been done. Combined with experimental data, theperformances of hysteresis curve, skeleton curve, stillness, strength, energydissipation and the strain of the structure model had been analyzed, and the resultsshow that: the mechanical behavior and the structural failure mode have been changedby installing the buckling-restrained brace (BRB) in the structure, whilst thedevelopment process of plastic hinge has been delayed. Compared with the CFSTframe and the CFST frame-shear wall structure, the seismic fortification lines ofstructure are added and the seismic capacity is enhanced because of dampers, whilstthe seismic performances of the CFST frame and the CFST frame-shear wall structurehave been improved effectively.2. The nonlinear finite element simulation analysis had been done for the aforesaidexperimental models using the software of ABAQUS, and the skeleton curves of thestructures with dampers, stress of the CFST column and shear wall and the workingperformance of the dampers had been analyzed, whilst the comparative performanceanalysis of the structure with and without dampers had been performed, so themechanical performances of the CFST frame with dissipation devices and CFST frame-shear wall structure with dissipation devices were studied. By changing the initialstiffness and the yield force of the dampers, the effects of the parameters of BRB onthe seismic performance of CFST frame with dissipation devices and CFST frame-shear wall structure with dissipation devices had been analyzed and studied inthe paper. The results show that: the mechanical behavior of the CFST frame andCFST frame-shear wall structure have been improved by setting the dampers instructure. With increasing the initial stiffness and the yield force of the BRB, the yieldload and ultimate load of the CFST frame with dissipation devices and CFSTframe-shear wall structure with dissipation devices have been increased certainly, andthe total dissipation energy of the BRB and the additional damping ratio have beenalso increased.3. Based on the30-storey typical CFST frame-core wall mixed structure,120dampers were set with different connection with structure and different location instructure. Four damping scheme were formed according to the BRB and viscousdampers, and the nonlinear dynamic time history analysis of each scheme under theEL-Centro、Kobe and NR waves action had been performed by using the software ofperform-3D. The influence of the dampers on the seismic performance of the CFSTframe-core wall structure with dissipation devices had been analyzed in the aspects ofthe story drift, story shear force, base shear force, dissipation energy of damper andstructure. The influence of the aspect ratios on the seismic performance of structurehad been studied based on the calculation results of a40-story CFST frame-core wallstructure with same dampers. The results show that: compared with the structurewithout damper, the seismic performance indexes of CFST frame-core wall structurehave been improved obviously by setting viscous damper in structure, and thedamping effect of structure with BRB is determined by the location and connectionmode of the dampers. The control effect and the seismic performance of structurewith viscous dampers are more excellent than that of structure with BRB. Dampingeffect of structure is more obviously when the dampers are set uniformly along thestructure height and between the CFST frame and the core wall.4. Based on the nonlinear dynamic time history analysis results of the30-storeyCFST frame-core wall structure, the cooperative working mechanism of the mixedstructure with dampers had been preliminary analyzed according to the shear forcedistribution ratio of the frame and the elastic-plastic working state of structuralmembers. The analysis results show that: for the CFST frame-core wall structure withBRB and viscous dampers, it is no influence on the cooperative working between theCFST frame and the core wall under the frequent earthquake action, however,compared with the structure without damper, the shear force distribution ratio of the frame under the rare earthquake action would be decreased, whilst the cooperativeworking ability of the CFST frame and the core wall is enhanced and the degree ofplastic working state of structure member has been delayed, and the number ofstructural members that the stress of member has reached the ultimate stress aredecreased. Improvement effect of structure in cooperative working ability is moreexcellent when the dampers are set uniformly along the structure height and betweenthe CFST frame and the core wall.5. The1:35reduced scale model of CFST frame-core wall structure with23viscousdampers had been tested on shaking table under EL-Centro wave, Taft wave andartificial wave action. The accelerations, displacements and strains of key points inthe structures with and without dampers had been analyzed according to the66testconditions. The test results show that: under frequent, design and rare earthquakeaction, the relative displacement, the acceleration, the story drift, the torsion angle andthe strain of the mixed structure with dampers had been decreased obviously. Theviscous dampers in the structure have excellent working performance and play goodrole in energy dissipation.6. Combined with the characteristics of the BRB and viscous damper and the storydrift limits of the CFST frame-core wall structure in code, the calculating formula ofelastic stiffness for BRB and viscous damping coefficient for viscous damper of theCFST frame-core wall structure with dampers had been derived based on thedisplacement calculation method of frame-shear wall structure and response spectrumtheory. The simplified design method of this structure has been established, and themethod was adopted to design the typical CFST frame-core wall structure withdampers using ETABS analysis software, so the feasibility of the method is verified.