| As precast shear wall structure combines the characteristics of prefabricated technology and shear wall structure,it has become one of the fastest-growing and most widely used precast structural systems in China.The design concept of "cast-in-place emulation" is often adopted in the precast shear wall structure.However,in the traditional concrete shear wall structure,the self-weight,lateral stiffness and load capacity are often large,and the ductility and energy dissipation capacity are weak;moreover,the plastic hinges will appear at the bottom of shear walls and at the ends of coupling beams under the earthquake action,and the plastic deformations of reinforcement and concrete are permanent and difficult to be repaired.To improve the seismic performance of traditional shear wall and meet the application requirements of precast concrete structures,two aspects were studied in this thesis.On the one hand,the new-type concrete sandwich wall was proposed,the sandwich plates were placed inside the concrete shear wall to achieve a better match of the stiffness,lateral load capacity,ductility and energy dissipation of the shear wall.On the other hand,to improve the seismic performance of cast-in-situ or "cast-in-place emulation" concrete shear wall structures,new-type connectors in precast structures were proposed to form the precast sandwich wall structures with rigid connectors or energy dissipators.The concrete sandwich walls and precast concrete sandwich wall structures were systematically investigated through the quasi-static tests and numerical simulation,and the seismic design procedures were proposed in this thesis.The main contents and conclusions are as follows:(i)The elastic mechanics analysis of concrete sandwich wall was completed.Based on elastic theory,the internal forces and deformations of concrete sandwich wall were derived.The results showed that the responses were significantly affected by the material properties and dimensions of each part;in the middle section,the normal stress was very small,while the shear stress was large;the sandwich plate can be used to reduce the lateral stiffness of shear wall and lead the plastic development to occur firstly in the sandwich region,and then the embedded columns would mainly share the loads.(ii)The study of seismic performance of concrete sandwich walls was carried out.Five cast-in-situ sandwich walls(including one regular concrete shear wall,one concrete shear wall with double vertical concealed seams and three concrete sandwich walls with different characteristics)were designed and subjected to the quasi-static tests.The results show that the regular concrete shear wall undergone shear failure with poor ductility 2.2 under lateral loads;in the concrete shear wall with double vertical concealed seams,the integrity of the shear wall was weakened by the vertical concealed seams,the lateral load capacity was about 7% lower than that of the regular shear wall,the energy dissipation capacity was almost the same,but the ductility was improved to 3.0;in the concrete sandwich wall with short and thin sidewalls,the lateral load capacity was about 10% lower than that of the regular shear wall,but the ductility was improved to 3.8,the reasonable sandwich plate was conducive to achieve the reasonable match of the stiffness,lateral load capacity,ductility and energy dissipation;in the shear wall with double sandwich regions,the failure of the end embedded columns of was serious,the lateral load capacity and energy dissipation were lower than those of the regular shear wall,but the deformation capacity was significantly improved.(iii)The numerical simulation and parametric analysis of the concrete sandwich walls were analyzed.The numerical simulation of the five tested sandwich walls was completed,and parameters affecting the seismic performance of the sandwich walls were made and suggestions were proposed.The results showed that the three-dimensional finite element models can effectively simulate the lateral performance and failure mode;the larger the axial load ratio,the higher the lateral load capacity and the worse the ductility of the sandwich wall,compared with the sandwich wall with axial compression ratio 0.1,the lateral load capacity of the wall with the axial compression ratio 0.4 was increased by about 40%,but the ductility was reduced from 6.5 to 3.0;with the span ratio increase,the lateral load capacity and initial stiffness were decreased,compared with the sandwich wall with shear span ratio 1.0,the lateral load capacity of the wall with shear span ratio 1.5 was decreased by about 25%,and the initial stiffness was reduced by about 40%;the reasonable length and width of sandwich plate was conducive to achieve the reasonable match of the stiffness,lateral load capacity,ductility and energy dissipation.It was suggested about the numerical specimen that the length ratio and the width ratio of the sandwich plate were selected at 0.2?0.6 and0.3?0.45 to achieve the reasonable match of the stiffness,lateral load capacity and ductility.(iv)The quasi-static tests of the precast concrete sandwich walls and structures were carried out.The precast concrete sandwich walls and structures with new-type connectors were designed and the cyclic loads were applied to study the seismic performance.The results showed that welded steel plates used as connectors can effectively transmit forces and achieve the role of rigid connectors;the mild steel connectors used in the horizontal joints and the frictional connectors used in the vertical joints can be used as energy dissipators;the seismic performance of the structures with wet connections and dry rigid connectors was basically the same,and the energy dissipation relied on plastic deformation;the structures with energy dissipators remained elastic at the end of the tests,and the energy dissipators can effectively dissipate energy;compared with the rigid connected structures,the damping ratios of the structures with energy dissipators were larger,when the lateral displacement ratio was 1/50,the damping ratios of the structures with energy dissipators were about 0.20?0.25 and that of the rigid connected structures were about 0.15;the energy dissipation and lateral load capacity can be increased by increasing the frictional force of horizontal or vertical connectors reasonably;the self-centering capacity and lateral load capacity can be increased by increasing the prestressing force reasonably.(v)The numerical simulation and mechanical evaluation of the precast concrete sandwich walls and structures were completed.The numerical simulation of the tested precast concrete sandwich walls and structures were carried out and compared with the tests;the parameters affecting the seismic performance of the precast concrete sandwich walls and structures were studied by simulation;the mechanical evaluation of precast concrete sandwich wall structures with energy dissipators were also analyzed.The results showed that the three-dimensional finite element models and the layered shell models can effectively simulate the lateral performance;the energy can be effectively dissipated and the stiffness can be decreased by the reasonable design of connectors in the precast concrete sandwich walls;the energy dissipation,damping ratio and lateral load capacity can be increased by the reasonable increase of frictional force of horizontal or vertical connectors in the precast concrete sandwich wall structures;the self-centering capacity and lateral load capacity can be increased by the reasonable increase of the prestressing force,but the damping ratio was decreased at the same time;the mechanical analysis proposed in this thesis,which was suitable for precast concrete sandwich wall structure with energy dissipators,can effectively predict the hysteretic responses with an error not exceeding 15%.(vi)The seismic design method of precast concrete sandwich wall structures was proposed.Based on the analysis method in coupled shear wall,the stress and deformation of the sandwich wall were studied,and the force-based seismic design method of concrete sandwich wall structure was proposed;based on the mechanical analysis,the displacement-based seismic design method of precast concrete sandwich wall structures with energy dissipators was proposed;nonlinear displacement ratio spectrum and residual displacement ratio spectrum were obtained through dynamic time history analysis of 120480 bilinear single-degree-of-freedom models with energy dissipation,based on this,the repairability-based seismic design method of precast concrete sandwich wall structures with energy dissipators was proposed;all the proposed design methods were verified by the designed structures,respectively. |
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