Seismic Response And Displacement-based Design Of Steel-Framed Building With Self-Centering Tension-Only Braces

With the development of society,the structures based on traditional ductile design have been difficult to meet the requirements of modern seismic requirements.In addition to the basic safety requirements,modern seismic structures should be able to recover from earthquakes and minimize the effects on the production and life after.Therefore,it has great theoretical value and engineering significance to develop a structure system with self-centering capacity.Steel frame with self-centering tension-only brace(SC-TOBF)is a new kind of flexible and self-centering,with a small seismic response and appreciated self-centering capacity.In this paper,nonlinear parametric analysis and dynamic time-history analysis considering the influences of near-and far-fault on seismic response of 9-and 16-story SC-TOBF are numerically conducted to study the pushover performance and dynamic performance of the structure,typical steel frames with buckling restrained braces are also designed and analyzed for comparison.In addition,a displacement-based seismic design method for SC-TOBF is proposedThe main works are as follows:(1)Parametric study.The 9-and 16-story steel-framed buildings with SC-TOBs is numerically conducted.Three key parameters,including the stiffness degradation factor,the activation strain,and the initial axial stiffness of the SC-TOBs,are investigated to explore the design space for the SC-TOB frames(SC-TOBF).Identical steel frames equipped with buckling restrained braces(BRBs)are also designed and examined for comparison purposes.The results indicate that increasing the stiffness degradation factor can improve the second stiffness of SC-TOBF and successfully make the distribution of inter-story drifts more uniform;an increase in the activation strain leads to a larger activation deformation of SC-TOBF,but it has a very limited effect on the inter-story drifts;increasing the initial axial stiffness appropriately is beneficial to reduce the inter-story drifts of the low stories.The lateral behavior of SC-TOBF is comparable to that of BRB frames when a lower activation strain and a higher initial axial stiffness are selected.Furthermore,when a higher stiffness degradation factor and a lower initial axial stiffness are selected simultaneously,the seismic action on SC-TOBF can be effectively reduced,and a relatively uniform distribution over the building height can be obtained.The SC-TOBF are considered to be a type of performance-tunable structure,and tuning can be achieved by varying a frame’s adjustable parameters(2)Dynamic time-history analysis of near-and far-fault ground motions.According to the Code for Minimum Design Loads of Buildings and Other Structures,10 near-fault ground motions and 10 far-fault ground motions are selected to carry out dynamic time-history analysis on 9-and 16-story models respectively.The results show that far-fault ground motions have great influence on SC-TOBF.SC-TOBF can realize good self-center characteristics and control the residual displacement angle within 0.1%with all earthquake levels.Compared with BRB frames,the base shear response of SC-TOBF under small earthquake is smaller,but the high-rise structure with longer period is greatly affected by far-fault ground motion.Because of higher second-order stiffness,Seismic response of SC-TOBF is more intense when suffering higher earthquake,but the distribution of inter-story drifts is uniform.(3)Displacement-based design method.By introducing appropriate residual inter-story drift angle to characterize the self-centering levels of the structure after earthquake,three performance levels for SC-TOBF are proposed.In addition,a displacement-based seismic design method of SC-TOBF is advised and the validity of the method is verified by dynamic time-history analysis of the numerical model.