Research On The Residual Deformation Control Of RC Step-Terrace Frame Structure After Earthquake Based On Self-Centering Braces

Different from the common frame structure embedded in the same plane,the Vertical components at the bottom of RC step-terrace frame structure have unequal height constraints,resulting in serious vertical and plane irregularities in the drop structure.Under the action of earthquake,the components on the grounded end of RC step-terrace frame structure will bear more seismic force,resulting in more serious damage.Previous studies mainly focused on the beam-column damage and the maximum displacement response of the structure under the action of earthquake,but there were few studies on the residual deformation and control measures of the structure after the earthquake.In this paper,the finite element analysis model of the RC step-terrace frame structure is established by Open Sees software,then the nonlinear time-history analysis of the structure is carried out using multiple ground motion records.The author studies the law of residual deformation of dropped structures under different seismic intensities.On this basis,the use of self-centering buckling-restrained brace(SCBRB)to improve the seismic damage and self-resetting performance of dropped-story frame structures is studied.Through the above research,the main conclusions were summarized as follow:(1)According to the statistical results of the maximum story drift angle and the maximum residual story drift angle angle of the dropped-story frame structure under different seismic intensities,the discreteness of the maximum residual story drift angle is significantly larger than that of the maximum story drift angle;In the case of the same number of floors in the superstructure,the more floors and spans under the upper embedding end,the greater the residual deformation after the earthquake of the frame structure with dropped floors under the action of strong earthquakes.(2)Under the action of strong earthquake,the distribution of the maximum value of the story drift angle and residual story drift angle of the step-terrace frame structure is basically the same among floors,mainly distributed in the 1st to 3rd floors of the superstructure;The residual deformation of the top floor and floors under the upper embedding end is small.(3)Judging from the structural residual deformation damage index,under the action of small earthquake,the frame structures with dropped floors are in an elastic state and will not produce residual deformation;The self-centering-repairability has little effect;under the action of strong earthquake,the self-centering-earthquake structure of the stepterrace frame structure needs to be repaired under the action of some ground motions;under the action of extremely rare earthquakes,the self-centering-earthquake structure of the step-terrace frame structure under the action of most ground motions Lost repairable value.(4)The influence of the SCBRB arrangement scheme on the seismic damage and reset ability of the step-terrace frame structure is studied.The analysis results show that the story drift angle of the upper ground layer will be increased only when the SCBRB is arranged on the dropped-story side of the step-terrace frame structure,and at the same time.It will also increase the damage of the upper ground end column foot;it is recommended to arrange the SCBRB symmetrically on the drop side and the upper ground side of the step-terrace frame structure.To save economic costs,a mixed support arrangement scheme of SCBRB and BRB can be used.(5)The control effect of SCBRB and BRB on the residual deformation of the stepterrace frame structure is compared and analyzed.The residual deformation control effect of SCBRB on the step-terrace frame structure is obviously better than that of BRB;by setting SCBRB reasonably,the seismic performance of the step-terrace frame structure can be significantly improved.The self-centering-earthquake residual deformation of the layer-removed structure is reduced or even eliminated.Compared with the uncontrolled structure,the maximum inter-story displacement angle of the SCBRB-step-terrace-frame structure is reduced by 38%～48%,and the reduction range of residual interlayer displacement angle is between 88% and 95%.