| The primary-secondary structural system is a new structural system composed of the primary structure which provides the main bearing capacity and lateral resistance and the secondary structure which only bears its own load,and the primary structure and the secondary structure can work together efficiently.The components in the new primarysecondary structure have the characteristics of multiple categories and complex functional attributes,which leads to significant differences between the mechanical properties,yield failure mechanism and failure mode optimization of the primary-secondary structure and the conventional structure.The seismic design concept of the conventional structure is not fully applicable to the primary-secondary structure,which limits the popularization and application of this new structure system.Therefore,it is necessary to determine the reasonable seismic failure mode based on the analysis of the mechanical characteristics of this structural system and provide active regulation methods and means to achieve the reasonable seismic failure mode,so as to provide theoretical methods and basis for the seismic performance design of the primary-secondary structure.This paper conducts research from the aspects of mechanical characteristics,stiffness formation mechanism,seismic failure mode,concept of structural seismic design,brace optimization design and seismic failure mode regulation methods of primarysecondary structures.The main research work of this paper is as follows:In the aspect of mechanical characteristics,considering the differences in the types and functional attributes of components in primary-secondary structures,the mechanical concepts of primary-secondary structures were discussed from the perspective of structure composition and force transmission.Through the numerical simulation,the mechanical characteristics and deformation laws of the primary-secondary structures were studied.The influences of brace arrangements,connection forms and secondary column connections on the internal force and deformation of primary-secondary structures were clarified.The significant two-level mechanical characteristics of primarysecondary structure and the periodicity and reproducibility of internal forces of the secondary structure were revealed.In terms of stiffness formation mechanism,through the analysis of variable parameters,the main mechanical parameters affecting the lateral stiffness of primary-secondary structures were discussed,the mechanism of stiffness formation of primary and secondary structures was revealed,and the calculation method of bending and shear stiffness of primary-secondary structural modules and simplified calculation method of structural lateral displacement were deduced.Based on the mechanical concept and stiffness formation mechanism of the primarysecondary structure,a reasonable seismic failure mode for the primary-secondary structure was planned.Through elastoplastic analysis of typical primary-secondary structure models,the paper focuses on the influence of the change of component section parameters on the yield order,verified and clarified the reasonable component yield order of primary-secondary structure.This paper studied the plastic distribution characteristics of the outer tube components and the internal force distribution process between the inner and outer tubes,clarified the internal force redistribution characteristics of the inner and outer tubes and the multiple seismic fortification lines of the structure,and put forward that the key to realize multiple seismic fortification lines is the degradation of brace.The influences of various component parameter changes on lateral stiffness and energy consumption were studied.The key structural lateral stiffness components and the main plastic energy dissipation components were established,and the seismic concept of primary-secondary structural systems was proposed.Based on the reasonable seismic failure mode of primary-secondary structures,the optimization principle of tension-compression degradable brace was established,and the design concept of degradation controllable brace was proposed based on the buckling principle of local components.By analyzing the force mechanism of the degradation controllable brace,a simplified constitutive model of degradation controllable brace was proposed.Based on this design concept,a structure form of degradation controllable brace was developed.The effects of parameters such as the thickness,initial deflection,and material of the degradation controllable brace core plate on the degradation characteristics and energy dissipation capacity of the brace were demonstrated through pseudo-static test research.The rationality of the degradation controllable brace structure was verified,and the failure mechanism and the regulation mechanism of mechanical properties of the degradation controllable brace were revealed.Based on the controllable characteristics of the mechanical properties of the degradation controllable brace,through dynamic elastoplastic analysis,the effects of the degradation controllable brace on the structural plasticity development process,structural ground motion input,and key component failure modes were clarified,and failure mode regulation mechanism of the primary-secondary structure was revealed.By actively adjusting the buckling critical load and the post-buckling bearing capacity of the degradation controllable brace,the regulation and effects of the parameter adjustment on the primary-secondary structural seismic failure modes were analyzed and clarified.Finally,in order to achieve the reasonable seismic failure mode of primary secondary structures,seismic failure mode regulation method of primary-secondary structure based on degradation controllable brace was proposed.The effectiveness of the failure mode regulation method was verified by the typical engineering application,which provides the method and basis for the seismic design and realization of reasonable failure mode of primary-secondary structure. |
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