Seismic Performance And Design Of Precast Concrtet Frame With Replaceable Energy Dissipating Connectors

A series of earthquake damage studies show that the failure and ductility deficiency of the joints are the main reasons to limit the improvement of seismic performance of precast concrete frame.In recent years,the emphasis for seismic design of building structures is now being shifted toward the new systems with high ductility and good resilience.The application and development of precast concrete frame system is the requirement of industrial construction in China,and the function-integrated structure can improve the efficiency of the components.Based on the concept of damage concreation and energy dissipation dispreading,a high ductility replaceable energy dissipating connector(REDC)with function of bearing service load and dissipating seismic energy can be arranged at the potential plastic hinge of precast concrete frame.Hence,an innovative function-integrated precast concrete frame with the advantages of high ductility and repairable is proposed in this dissertation,which is called the precast concrete frame with replaceable energy dissipating connectors(REDC-PCF).This dissertation focuses on the seismic evaluation and design of REDC-PCF through theoretical derivations,experimental analysis and numerical simulations.The detailed research results are listed as follows:(1)To verify the design concept of REDC-PCF,three quasi-static loadings on a two-story REDC-PCF test specimen are conducted by replacing the damaged REDCs installed at the precast connections.The test results indicate that the plastic damages of the tested REDC-PCF can be controlled within the REDCs and only the REDCs yield to dissipate energy,which realized the expected the yield mechanism and energy dissipation mode.After replacing the damaged REDC,the tested REDC-PCF can still restore its bearing capacity and energy dissipation capacity to the level before repair.(2)To further investigate the mechanical characteristics and working mechanism of REDC-PCF,the skeleton model and hysteretic model that reflect the mechanical and hysteretic characteristics of REDC-PCF are developed.The mechanical model of REDC-PCF consist of two types according to the sequence of gap opening at the column bases and the REDC initial yielding at the beam ends.Equations to predict the base shear,stiffness and roof drift of the REDC-PCF are developed.The simulation method of the hysteretic model in Opensees is proposed,and the applicability of hysteretic model in nonlinear static analysis and nonlinear dynamic analysis is verified.(3)To simplify the design process of displacement-based seismic design method,an elastic displacement spectrum-based design approach for REDC-PCF is proposed.According to equal displacement rule,the control displacement of the selected performance target is determined directly as the target displacement,and the seismic design is carried out with the target displacement,so that the designed structure can achieve the performance level of the small,medium and large earthquakes of the performance target.During the design process,the target period is determined directly by using the elastic displacement spectrum with 5% damping ratio.Then,the REDC and the non-yield concrete element are designed according to the requirements of stiffness demand,capacity demand and damage concentration requirement under the performance target.The results of nonlinear time history analysis of the example structures with3,6 and 9 stories indicate that the displacement response of the REDC-PCF can be estimated accurately only using elastic response spectrum.(4)To improve the ability to resist collapse,the optimization method of REDC-PCF is carried out in delaying the fatigue failure of REDC and reducing the internal force demand under the action of strong earthquake.Incremental dynamic analysis is carried out to investigate the damage distribution of the structure and to find the weak parts to determine the collapse prevention capacity.The seismic performance of REDC-PCF and cast-in-place reinforced concrete frame(RCF)is compared,which proves the great advantage of REDC-PCF in damage control and collapse prevention ability improvement.Based on the incremental dynamic analysis,vulnerability analysis is carried out to evaluate the damage state of REDC-PCF under different intensity of seismic action.Furthermore,the hysteretic model has great advantages in improving computational efficiency and convergence.Hysteretic models of the designed REDC-PCF are established to carry out incremental dynamic analysis.The seismic response is compared between the hysteretic model with the actual structural numerical,including displacement response,acceleration response,REDC cumulative damage factor,to verified the applicability of the hysteretic model in incremental dynamic analysis.(5)To evaluate the economic loss and restoration capacity of the structures,seismic loss analysis based on FEMA-P58 is carried out.The effect of the possibility of structure being repaired,dismantled and collapsed on the post-earthquake loss is compared between the REDCPCF and RCF.Morever,the effect of damage of different components on post-earthquake loss is aslo investigated between the two structures.The economic benefit and resilience capacity between the REDC-PCF and RCF are evaluated according to their economic loss and restoration time.