| Building industrialization and resilience-based design are the inevitable trends of China’s construction industry.In order to make better use of the advantages of self-centering concrete frame structure,a kind of low-damage self-centering precast concrete(LDSCPC)frame connection is proposed.The specially designed steel connectors can ensure the reliable transfer of the vertical shear force at the beam end under large deformation.The modular design of energy dissipation devices not only makes the damper easy to replace,but also can be upgraded to other types of dampers.In order to study the seismic performance and earthquake resilience of LDSCPC joints,experimental research,optimization design,theoretical research,and numerical simulation are carried out in this paper.The seismic performance and design method of the LDSCPC frame are studied based on three levels:energy dissipation device,frame joint,and single frame.In detail,this study includes contents as follows:Based on the characteristics of low damage and replaceable energy dissipation components of LDSCPC joints,10 cyclic load tests were designed for the seismic performance under earthquake,performance maintenance under aftershock,and performance recovery after damper replacement.The test results show that the performance of LDSCPC joints is well maintained after the earthquake,and can almost return to the original level after replacing the damper.LDSCPC joints have excellent low-damage characteristics and earthquake resilience.To study the influence of the design parameters of mild steel damper on the energy dissipation and mechanical properties of LDSCPC joints,mild steel dampers with different design parameters were replaced after initial loading,and the same cyclic load tests were carried out.A detailed Abaqus finite element(FE)model is established,which considers the plastic damage of concrete and the ductile damage of damper.The damage and stress distribution of dampers are further studied.The smaller bolt preload and screw-hole clearance together cause the weakening behavior of the damper in the test,and increasing the bolt preload can effectively improve it.Based on the FE analysis results,the preload of 155k N can increase the energy dissipation in one cycle of the joint by at least 40%.To improve the energy dissipation performance of LDSCPC joints,a series of FE analyses are carried out on the potential factors influencing the energy dissipation performance of the damper through the detailed Abaqus FE model.The analysis parameters include screw-hole clearance,bolt preload,the size of the energy dissipation strip,and so on.In addition,the contribution of the mild steel damper on the side of the rotation center to the overall energy dissipation capacity and bearing capacity is analyzed when the joint is open.By analyzing the influence law and degree of various factors on energy dissipation performance,three optimization schemes are proposed,and their mechanical characteristics and energy dissipation performance are verified by FE analysis.The optimization scheme 3based on three independent energy dissipation rings is more recommended because of its excellent robustness and performance reserve.To further study the mechanical properties of LDSCPC joints,the mechanical mechanism,hysteretic characteristics,and performance characteristic points of LDSCPC joints are analyzed theoretically.The theoretical model of LDSCPC joints under the ideal state and the theoretical model considering the weakening behavior are established,and the validity of the theoretical model is verified by comparing with the experimental results.The numerical model of the LDSCPC joint is established based on Open Sees.In Visual Studio2019,referring to the source code of Open Sees,the LCdamper material model corresponding to the M-θ_r simplified model of mild steel damper and the LCdamper P material model corresponding to the weakening model are developed with C++programming language.By comparing with the test results,the Open Sees numerical model considering weakening phenomenon can accurately simulate the stress state and opening and closing behavior of precast components in LDSCPC joints,and the hysteretic behavior of joints is in good agreement with the test results.Taking a single frame as an example,the seismic design method of the LDSCPC frame is proposed based on the direct displacement-based design method,and a design example is given.To evaluate the seismic performance of the LDSCPC frame objectively and effectively,based on the Open Sees numerical models of RC frames and LDSCPC joints which have been verified by experiments,the Open Sees numerical model of the LDSCPC frame is established.The nonlinear dynamic analysis and seismic fragility analysis are carried out.The results show that the failure probability of LDSCPC frames is low at all performance levels,and the contribution of mild steel damper is significant.In addition,the weakening phenomenon of mild steel damper on the overall response of the frame is not very obvious.LDSCPC frames have excellent and reliable seismic performance and earthquake resilience. |
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